View topic - The "myth" about German cloth fuel lines
View topic - The "myth" about German cloth fuel lines
PSScoots
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Thu May 21, 10:24 am
I have a 66 bug that needs to have all its flex fuel lines replaced and I want to use the original style German cloth covered flex. I also want to use stock "spring clamps" at the ends, and not the screw-tight variety.
http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=
The "problem" is we have always had a VW in the family going back to , and my Dad's an aircraft mechanic, and he swears the German stuff is a fatal fire hazard.
I know this has probably been asked a zillion times, but I need to know if this is a good choice, and if so why. Specifically cause there's going to be words over this.
While I respect my Dad's opinions, he may have picked this tidbid up in the 70's.. or 60's... or God, even the 50's and never "updated" his opinion, and what was true back then may not be true of what's on the shelf 40 years later.
He also loves the screw claps but tends to tighten them down so hard, the rubber extrudes, and when it gets old, it cracks ... you guys see where I'm going with this, right??
fast Ed
Thu May 21, 10:30 am
Sounds like you shouldn't let your father work on the car ... :lol:
cheers
Ed N.
PSScoots
Thu May 21, 10:48 am
fast Ed Canuck wrote: Sounds like you shouldn't let your father work on the car ... :lol:
Yeah, you got the drift....
62_Maggiolino
Thu May 21, 11:09 am
the German fuel lines can actually get tighter (after installed and used)than a spring clamp would......
Michael Fischer
Thu May 21, 11:26 am
I have to cut them off sometimes. You really dont even need clamps. The American junk is to big doesnt fit tight and it swells up in no time. I have ripped apart many fuel filters trying to pull off the German line.
Harris
Thu May 21, 11:27 am
I understand where your coming from, but I don't see that you have any other choice unless your Dad can fabricate a metal line with fittings for and in the pump and carb. That takes some good garage engineering to do. If they need to be replaced it has to be done.
What does you Dad suggest?
I would not use rubber line out of the hardware store. Ethanol's effect on the lines is hard enough and I think the woven line is still your best bet. I do think the gray line, if you can find it, is better than the black that is available today.
Good Luck. If possible, you might casually remind Dad that the carb inlet nozzle and the fuel pump outlet nozzle coming out are usually the problems with a fire. Not the line itself assuming it is kept in good condition.
PSScoots
Thu May 21, 12:11 pm
Harris wrote: What does you Dad suggest?
That's part of the problem I didn't mention because I was looking for a thumbs up or down on the German stuff.
When he was working for the airlines, he had access to avionic quality parts, including fuel lines, and he used that in the cars. However, the "secret stash" is running low, and I am suspicious of it because of its age. I have a hard time getting across to him that "new" and "unused" are two different concepts. Yes, it may be unused, but it's still 10 year old avionic rubber.
Harris
Thu May 21, 1:03 pm
How has the avionic rubber been stored? If it been away from sunlight and and in a dry place, it just may be ok, but I also understand you dont' want to take a chance on a fire. You might ty it for a day or two all the while checking it. I assume the line on there now is avionic line too. If the present line on the car is not sticky or mushy, then it has done well with Ethanol running through it--- if that is the fuel your using.
I personally would be more comfortable with old avionic line than new aftermarket woven. I know they advertise it as German, but it's not the German line we've had in the past.
First choice would be the older gray woven line
Second would be old avionic line
Third would be the new stuff.
Above all make sure your carb inlet tube is tight. If at all loose, remove the carb. Pull the tube out and clean it with a fine grit paper. Tap it back in with tack hammer until you feel it bottom out. Then, take a sharp punch and lightly "ping" 3 or 4 places around the tube. This will slightly deform the carb body material against the tube. I even put a little JB Weld on mine, but I've never had one come in over 40 years.
akokarski
Thu May 21, 1:46 pm
when you pull German hose off the fitting it shrinks like Chinese handcuff. If you push it off it will come off a lot easier.
Anton
hoghead
Thu May 21, 2:12 pm
i know where your dad is coming from. i was an aircraft mechanic for 10 years in the air force. the reasons that aircraft people don't like the braided fuel line is simple.
on an aircraft when the fuel lines become old/cracked they will drip fuel. that is a sign that they need replacing. they are checked very often. usually at least 3 or 4 times a week. jp4 or jp8 jet fuel is kinda like a high grade desiel fuel so it's kinda hard to get it to burn. the small drips are not really a safety hazard and a good warning.
now with braided fuel line, the rubber underneath can become cracked or torn and allow fuel to leak out. the braiding will absorb the small amounts of fuel till it becomes saturated. what this does is that it doesn't give an early warning (drip) that the fuel lines are bad. the braiding becomes so saturated and you can't see it that if a maintenance guy happens to lite up a lighter, or cigarette then it can become dangerous.
the catch is there is a huge difference between cars and planes. in a car (gas) it is much easier to start a fire. the normal drip from a plane is no big deal, on a car is a HUGE deal! the braided line adds a measure of insurance in a car keeping fuel from dripping on hot engine parts and igniting. with all this said, IF you run braided line, it MUST be checked regularly to insure it's not cracked or breaking down internally. if you don't check it, you might as well invest in a good fire extingusher!!!
EverettB
Thu May 21, 2:21 pm
I've never had a problem with the German braided fuel line.
As you stated, do not over-tighten the clamps, all this does is fatigue the ends faster and can cause a split. A lot of people here like the fuel injection style clamps. They are smooth and don't bite into the hose.
I usually take a look at the lines every time I change my oil. If the ends are cracking around the edge, I replace that piece. I'd say I only replace them once/year and usually only the ones in the engine compartment as they seem to break down faster.
Whenever I buy a car, I replace all the lines just so I know they are new. The small piece under the gas tank always seems to be about to snap off or is already moist with gas - no one ever checks that one.
PSScoots
Thu May 21, 2:41 pm
EverettB wrote: I've never had a problem with the German braided fuel line.
Thanks Everett, the answer is much appreciated.
[Insert emoticon here for "Worshipful Awe"]
Towel Rail
Thu May 21, 3:19 pm
In addition to replacing all the fuel hoses, whenever I buy an ACVW, I install some kind of fitting at the firewall tin to keep the edge from cutting into the fuel line. I can't recommend it enough!
- Scott
Dubbers Toy Box
Thu May 21, 5:55 pm
Harris wrote:
.... I know they advertise it as German, but it's not the German line we've had in the past.
There are a few different brands out there. CRP (continental rubber products) makes the best hose and it is made in germany. a few years ago it was grey but now it is coming in black. it says made in germany on the braid.
there is another german brand but im not sure of the name, but the hose is much harder even when new.
and then there are at least 2 brazil made hoses, one being premium quality (junk), the other is "top leather" thicker than the premium quality hose.
There is also fake german hose made in China. The funny part about the china hose is there is an occasional bump in teh cloth braid. It will leak there. it appears that they joined 2 pieces together there and thats what causes the bump.
Russ Wolfe
Thu May 21, 10:18 pm
I have had New German Conti braided fuel line fail within 6 months. On a car that was only driven about miles in that 6 months.
I will not use it any more.
And I have a 50 ft roll of it sitting here.
Hotrodvw
Fri May 22, 6:36 am
I think hoghead hit it dead on here. The thing is, people think that just because it's made in Germany, it's the shiz..... Not necessarily. What you really need to look for is a spec like 30R6, 30R7, or some sort of rating for fuel, and that it be made of a material suitable for fuels, like Nitrile/Buna N. A fuel hose with a 30R7 rating is specifically designed for engines with higher under the hood temperatures. I think in an A/C VW, this would be ideal to help prevent any vapor locking issues also.
Now, personally, I run the ss braided/Teflon lined hose. This is only practical though if you have threaded connections, rather than a clamp on situation. I wouldn't use any fuel line w/o a clamp, weather it's needed or not.....ever.
goswald79
Want more information on china black hydraulic hose? Feel free to contact us.
Fri May 22, 9:27 am
A little of topic, but where do you guys buy your fuel line? I am going to replace mine this weekend, and I was going to try O'Reilly's and Advanced. I have never bought the cloth line from these stores, and I'm wondering if they bother to sell it. I did buy some real nice cloth line from the Mercedes dealership, when I had a diesel benz, but it wasn't cheap.
Any recommendations would be good. I don't want to have to wait for it to come by mail, if it can be found local.
Russ Wolfe
Fri May 22, 10:17 am
Hotrodvw wrote: I think hoghead hit it dead on here. The thing is, people think that just because it's made in Germany, it's the shiz..... Not necessarily. What you really need to look for is a spec like 30R6, 30R7, or some sort of rating for fuel, and that it be made of a material suitable for fuels, like Nitrile/Buna N. A fuel hose with a 30R7 rating is specifically designed for engines with higher under the hood temperatures. I think in an A/C VW, this would be ideal to help prevent any vapor locking issues also.
The Conti (as in Continental) I had was the right spec for Fuel. I worked in the fuel system industry for 29 years.
Also, the hose that I had fail was not in the engine compartment. It was under the gas tank. NO heat.
I will not use the external braided hose any more on customers cars. It exposes me to too much financial liability.
Michael Fischer
Fri May 22, 10:40 am
I have yet to have any Contitech line fail. Is it possible you got a defective piece. Germans are only human you know. Maybe it was damaged in shipping.
I wouldnt want old fuel line on my aircraft.
Harris
Fri May 22, 1:25 pm
Hoghead wrote:
Quote: it MUST be checked regularly to insure it's not cracked or breaking down internally. if you don't check it, you might as well invest in a good fire extingusher!!!
Best advice . I had a lady tell me the other day she owned 3 bugs years ago and had fires in two of them and that Vw's were proned to fire.
I corrected her statement and ask if she sued her mechanic. Well, she didn't have a mechanic and just drove it until it burned up. End of conversation.
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How Well Do You Know Hoses? - MOTOR
There are literally dozens of different types of hoses in modern vehicles, from windshield washer tubing to brake flex hoses, from intake air ducts to transmission cooler, radiator and heater hoses, and everything in between. Sooner or later, some of them will need to be replaced.
This article will tell you what you need to know about selecting the right hose for any given application. Let&#;s start with the basics. Molded hoses are used for many applications such as radiator, heater and other cooling system hoses. Straight hoses, often purchased and replaced as &#;bulk&#; items, may include some heater or bypass hoses as well as a few radiator hoses. Many transmission cooler hoses, fuel hoses, vacuum hose and the like are routinely replaced or repaired from bulk stock.
When replacement time comes, one of the first questions should be, What&#;s the correct hose material for this application? How many times have you seen, for instance, a piece of 5&#;8-in. heater hose drafted for duty as a fuel neck vent tube hose? According to every manufacturer I contacted, this is strictly prohibited. Even silicone heater hose, widely&#;although incorrectly&#;considered the most chemically resistant bulk hose available, is a very poor choice for such an application. You really need a hose specifically designed for this sort of use. And this is all the more critical in applications such as flex-fuel, diesel and biodiesel-fuel vehicles, where the wrong hose might not last even a week.
If you think hoses are one of the few remaining low-tech components on today&#;s vehicles, you don&#;t know hose.
Fuel Hoses
A few years back, Fred, one of my students, called me about a comeback his shop had gotten stung by. It was a mid-&#;90s car in which they had previously replaced the fuel pump. Now, several months later, it had been towed back in. The Schrader valve on the fuel rail showed no pressure, and the pump&#;s current draw was abnormally low. Thinking it might be a simple case of &#;out-of-gas-itis,&#; they added a gallon to the tank, with no improvement.
Now, with the tank on the floor and the pump and bracket assembly removed, the problem was clear: The small fuel outlet hose connecting the pump to the sender bracket was ruptured, and the hose material itself was mushy. Fred assured me that the hose had been changed when the new pump had first been installed, since the original &#;pulsator&#; had lost its elasticity and became too loose on the fittings. So, he wondered, what was the problem? After all, they didn&#;t want to wind up dropping the tank a third time.
It was a good question, and I asked one of my own. &#;What kind of hose did you use?&#; As near as I could remember, the answer came back &#;just regular injection hose.&#; They still had the same spool on the shelf. Did the customer use any kind of fuel additives? Reached after some time, he confessed to adding &#;three or four cans of dry gas&#; as part of his Thanksgiving ritual every year. Couple that with the mandated switch to oxygenated fuels in our area the previous year, and he had a pretty aggressive fuel mixture in his tank. Still, shouldn&#;t a good injection hose have been able to stand up to it?
A little further research solved the mystery. The roll of injection hose at Fred&#;s shop had been on the shelf there for several years by that time, and had not been formulated to withstand today&#;s oxygenated fuel blends. To compound the problem, it was not rated for continuous immersion in fuel.
&#;But it&#;s fuel line! How could it not be rated to be in contact with fuel?&#; Fred asked incredulously. It turns out that the fuel line that&#;s used under the hood (SAE Standard J30R9) has to have an outer layer that can resist the heat, oil, ozone and exhaust it&#;ll likely encounter there, but that particular outer covering&#;s formulation doesn&#;t withstand continuous submersion in fuel. Worse yet, the in-tank hose (SAE J30R10) can&#;t be used under the hood, either, because its outer covering can&#;t stand up to the underhood environment. And, of course, the SAE also has specs for other fuel lines, like J30R7 and J30R8, each different from, and incompatible in some way with every other! (The better solution might have been to buy the new upgraded pulsator from the dealer, but at the time there was still widespread debate about its long-term durability.)
Even today, there&#;s no single fuel hose rated for both underhood and in-tank service. I asked Richard Mirtz, Senior Product Manager Fluid Power Auto Sales for the Gates Corp. about it. &#;If we could build it, we would,&#; he said. But whichever layer you put on the outside will fail when exposed to the other set of conditions. And if you build it with both layers one on top of the other, it&#;s so thick you can&#;t even bend it or clamp it.
Of course, thermoplastic tubing can be used in both applications, and now often is, but again, there seem to be at least two types required. One, used in the tank, is a somewhat flexible spring-reinforced pleated tube with smooth cuffs at each end. The other, more familiar type used under the car and sometimes under the hood, is a semirigid, thick-wall nylon tubing usually equipped with metal or barbed-plastic fittings or connectors.
Fuel Line Hoses
Fuel lines are only the tip of the proverbial iceberg. There are further problems with other types of hoses. For instance, can you use an engine or transmission oil cooler hose in a power steering application? The answer is . . . maybe, but probably not. In any event, you&#;d need the right diameter hose, with a high enough pressure rating, a high enough temperature range and, last but not least, material compatibility. You may also encounter problems using these hoses in a power steering application because their relative inelasticity may not provide adequate pulsation dampening. So you can probably use power steering hose in a transmission oil cooler application, but not vice versa, at least not in a pressure line application.
Watch out, too, for higher temperatures due to close routing near the exhaust in some power steering applications. And, of course, some power steering systems use mineral hydraulic oils instead of more conventional power steering fluids, so you have to pay attention to each detail of the OEM&#;s specifications to assure compatibility. The more prudent course of action is obvious: Look for the SAE J-spec number&#;or in the case of some European nameplates, the DIN number&#;on the original hose, and match it on the replacement.
How about PCV hose and brake power booster hose? Can they be interchanged? Disregarding the slight size differences&#;most booster hoses are either 11&#;32 or 15&#;32 in. I.D., while PCV hoses usually run 3&#;8, 7&#;16 or 1&#;2 in.&#;PCV hoses are generally rated to withstand 10 to 24 in./Hg of vacuum, while brake booster hoses are rated for 30 in./Hg. Both should stand up to engine fumes readily, but PCV hoses may be more specifically resistant to continuous internal oil and fuel exposure, while the booster hose may be more resistant to internal brake fluid exposure.
You get the idea. A lot of the hose substitutions many of us have made over the years have probably fallen short of any best practices standard. You shouldn&#;t use fuel line for a transmission cooler application, nor a windshield washer hose for a purge line. Let&#;s get back to the question of using that silicone heater hose for a fuel fill neck vent tube. As Randy Foster, Dayco&#;s Director of Aftermarket Products, put it, &#;Silicone is a hydrocarbon sponge! It absorbs fuel, it doesn&#;t contain it.&#; And standard fuel or emissions hoses aren&#;t all rated for coolant usage either, so the next time you have to replace a 5&#;16-in. bleed hose, don&#;t just whack off a length of the nearest black tube you can find. Call the parts store for the right stuff. SAE J20R3 Class D2 would be adequate.
Hose Clips and Clamps
Even hose clamps (or clips, as our British cousins call them) are not quite as simple as they seem. Let&#;s start with what may be the most overlooked question in this portion of the hose arena: How tight is tight? Standard screw-type clamps with a 5&#;16-in.-wide band generally call for a tightening torque of 14 to 16 in.-lbs. A 1&#;2-in.-wide banded clamp gets only 25 to 35 in.-lbs. of twist, while a 9&#;16-in.-wide band is tight at 30 to 40 in.-lbs. If the clamp threads are cutting through the rubber, you&#;ve gone too far.
SAE J spells out the nitty-gritty details on the 32 (yes, 32!) most common types of hose clamps. Buried within the specs is the notion of durability torque, which is the maximum torque you can apply once to a given clamp when tightening it over a steel pin of the appropriate size without distorting the clamp. Then there&#;s installation torque, specified simply as half the durability torque, and ultimate torque, which is defined as the maximum torque that can be applied before the clamp becomes so distorted it can no longer perform its intended function.
I imagine we&#;ve all encountered clamps at their ultimate torque worst, and I&#;m willing to bet we&#;ve all exceeded installation torque thresholds more often than not. I know I certainly have!
There are some good alternatives available for many applications where a standard worm screw clamp isn&#;t enough. For truly heavy-duty applications, try a spring-loaded bolt constant-tension clamp.
For heater hose applications, you might want to try out one of Gates&#; PowerGrip SB clamps. NAPA markets something along the same lines, as well. These use familiar heat-shrink technology to produce a good seal even on out-of-round fittings. I bought a couple of boxes of these shrink clamps in a variety of sizes and have been quite pleased with the resultant sealing force. It&#;s impossible to twist the hose on the fitting once the clamp has shrunk in place, and the installation has a very clean look.
There are a couple of factors to consider here, though: Be sure there&#;s adequate access to allow your heat gun to get at the sealing area all the way around the fitting nipple (you can use a diffuser); if there&#;s any possibility that you might have to remove the clamp and salvage both the hose and the fitting, make sure the position of the clamp will allow access for the removal tool as well. And be sure you have the handy remover tool for just such an eventuality. While it might be possible to use a soldering iron or a razor blade, the dedicated tool is the better bet.
When selecting a metal hose clamp, look, too, at the formation of the band&#;s edge. A rolled edge is much gentler to the outer layer of the hose. Remember, it&#;s the compressive force of the clamp applied evenly around the entire circumference of the hose that makes a good, leak-free seal. Overtightening the clamp may damage not only the outermost layer of the hose, but even intermediate layers, including the fiber reinforcements that impart structural strength to the hose.
Smooth-bore nut & bolt type clamps provide a secure connection for high-pressure injection systems. Crimpable eared clamps are generally designed for one-time use, but hold very well. They&#;re particularly popular with some European marques, on both fuel and hydraulic transfer hoses. You probably have the needed crimping tool already from your CV boot repair kit.
There are also some very high-end clamps that use a detachable inner liner of spring steel which deforms, flattening slightly as the outer band is drawn tight. Depending on design details, this may either transfer the clamping force toward the edges of the band, allowing the hose&#;s natural resilience to create a sort of trapped O-ring seal against the underlying inner fitting, or concentrate the clamping force in a single bead centered under the clamp band.
What about one-piece, constant-tension spring clamps? If not rusted or damaged, spring clamps generally provide a consistent seal and automatically compensate for hose setting (a loss of hose wall resilience due to thermal cycling and aging). This reliability and reduced labor costs for installation account for their widespread use by virtually every major automaker over the last decade or so. Even so, these clamps are not failureproof in all instances. Signs of coolant residue near clamped connections usually indicate cold fluid leakage, and a new or different clamp may be required. From time to time, I encounter a leaking spring clamp that actually rusts through the center of its band opposite the ends.
You can reuse spring clamps that are still in good shape, provided the new hose is the same thickness as the original and the fitting is not distorted. Flex the clamp fully open a time or two to be sure it still applies adequate tension. If you&#;re reusing both a hose and its original spring clamp, try to align the hose exactly with the impressions it has already made in the hose wall.
Specialty Hoses
Power steering pressure hoses have to withstand seriously high pressures, and require crimped fittings. Brake hydraulic (flex) hoses are engineered with a significant margin of safety against bursting or leakage, and must be manufactured and assembled to meet very high standards. There&#;s simply no room for error, and these hose must have a minimum burst strength of psi.
Air conditioning hoses generally fall under SAE J51 for remaining R-12 systems, and under SAE J for R-134a systems. Automotive refrigerants are routinely subjected to relatively high pressures, and are notoriously difficult to contain. Subtypes range from A to F, with the higher letters generally corresponding to lower permeability and higher prices. In general, you want to use a hose rated at least as Type C, Class II. Again, specialized crimping tools are needed, especially for high-side applications, so tailor-made replacement assemblies may be the most cost-effective choice for low-volume shops.
Hoses are more likely to seep when cold than when hot. More coolant hoses fail from internal electrochemical degradation than from external factors. Still, oil leaks or mechanical damage from abrasion or friction can and do cause premature hose failures. Kinks not only impede flow, but may also cause internal mechanical damage, leading to failure. Feel hoses for resilience, cracking and bulging, especially near their ends or where they&#;ve been subjected to external fluid leaks or heat.
When checking vacuum and vapor hoses, be sure to check for hose wall collapse under high-vacuum conditions. A warm-engine snap-throttle deceleration test will usually reveal any puckering.
To remove high-pressure hoses, first depressurize the system. Release any clamps and move them past the flare of any internal fittings. Crimped ear clamps are most easily removed using a pair of pincer pliers at right angles to the crimp, as shown in the photo at the bottom of this page. Mark one end of the hose so you can match up the new hose exactly.
Pulling a stuck hose off by brute force can easily damage underlying heater core tubes. Using a heat gun for a half minute or so may soften and release old hoses. You can also gently twist the hose, taking care not to damage the fittings. Sometimes you can work the rounded taper of your hose tool between the hose and the fitting to ease them apart. If not, slitting the hose lengthwise allows you to peel it back. This sacrifices the hose but saves the fittings. I know I&#;d rather replace the hose than the heater core! Try not to scratch the underlying tube with your cutter. There are a variety of useful tools that can make this task a bit easier.
Size matters, of course, but you already knew this. Still, it doesn&#;t hurt to review the lesson, if you&#;re contemplating a substitution: 7mm hose is sloppily loose on a 1&#;4-in. fitting; 10mm hose is slightly large on a 3&#;8-in. application. Half-inch hoses are bigger than 12mm hoses, while 17mm hose is loose on a 5&#;8-in. barb. When you use too large a hose, you run the risk of leaks. If you try to tighten your clamp to compensate, you may damage or distort the hose. You may also occasionally crush the fitting out of round in the process. The obvious solution is to find the right hose.
Can you safely use a 1&#;4-in. line on a 7mm fitting? There are (at least) two factors to consider. 1. How critical is flow rate in the given application? The reduction in cross-sectional area is a surprising 19%. 2. How resilient is the hose? You may damage any internal reinforcement braid by forcing the smaller hose over the larger nipple bead, or you may stretch the outer covering enough to damage it and accelerate its eventual demise. You&#;ll sleep better if you install the correct replacement hose size.
Hose Installation Tips
Now that you&#;ve selected the correct type and size of hose for the task at hand, you need to install it. First, check the condition of the fitting. Flattened, pitted or deformed parts may need to be replaced or repaired. Small pits on water outlet castings, for example, can often be filled in with a thin layer of a good RTV silicone.
If you&#;re cutting the hose from bulk stock, you can make a cleaner and squarer cut with a dedicated cutting tool or even a razor blade than with a pair of diagonal cutting pliers. Before making the final cut, make sure there will be no kinks in the installed position. Leave enough slack to allow for relative motion between the two ends of the hose, if necessary. For example, cutting a heater hose too short may unduly stress the heater core&#;s fittings as the engine rocks in its mounts. With molded hoses, make sure the replacement part is oriented the same way as the original and is the right length. (This is why you marked one end of the old hose prior to removal.) To consolidate part numbers and reduce inventory costs, many molded aftermarket heater hoses, and even some radiator hoses, are cut-to-fit items.
In some cases, it may be necessary to lube the fitting lightly in order to slide the hose in place. Use an appropriate fluid based on the application. Rubber assembly fluid is usually the preferred choice, but acceptable alternatives may include water or silicone grease. Don&#;t use any fluid for which the hose is not rated.
Position both clamps loosely over the ends of the hoses, not too close to the raised fitting bead. A good rule of thumb is to allow a space at least equal to the hose wall&#;s thickness between the clamp and the bead, except for shrink-band clamps, which are designed to be installed extending just over the sealing bead itself. Make sure the clamps are faced the right way for future service access, then gently snug them and reinspect the installation. Rotate either end as necessary to achieve a smooth layout, then tighten the clamps to spec.
Take a minute as early as possible in the process to check for leaks. Cooling systems should be pressurized somewhat in excess of the cap rating and should hold pressure with no leakage for 20 minutes or more. Dry-testing the system is less messy than filling it first, and air is thinner than coolant, making for a more conclusive test. In the event of a leak, use a spray household cleaner in the suspect area. Bubbles will confirm the location. Most fuel systems will pressure up at initial key-on, though you may have to cycle the key several times to build adequate pressure if the lines have drained completely. Of course, it may not be possible to leak-test power steering or oil cooler lines until later in the repair process, but checking as early and as thoroughly as possible helps prevent subsequent hair loss.
There seem to be a number of widespread misconceptions about silicone hoses. While silicone is certainly suitable for a number of applications, it&#;s simply not rated for use as fuel, oil or fuel vapor hose. Coolant losses due to evaporative permeation are often 12 times or more greater with silicone hoses than with standard coolant hoses. In an apparent complication, these permeation losses preferentially involve the water portion of the coolant mixture, so antifreeze concentrations tend to increase over time, especially if you use a 50% or stronger mixture for topping off. Silicone hose does, however, have a much higher upper temperature limit than conventional heater hoses, usually about 350°F vs. 260°F for conventional hoses. This makes it a very good choice when it must run close to hot exhaust components.
Take extra care when clamping silicone hoses. Standard perforated-band clamps will cut into the hose&#;s soft surface, causing premature failure. Use only heat-shrink clamps or clamps with a smooth inner band and follow the recommended torque specs carefully.
Some secondary air injection repair kits utilize a very high-temperature silicone hose to attach to the catalytic converter air nipple. Experience teaches that high-temperature protection does not include any noticeable increase in structural integrity. Be sure the final installed hose position avoids any sharp angles or offsets, as these will inevitably rupture the hose sooner rather than later.
Finally, small-diameter, thick-wall silicone hose is routinely used in DPFE and EGR backpressure transducer applications. There&#;s often an ozone-resistant outer layer as well. It&#;s also the hose of choice where direct exhaust backpressure readings are needed for diagnostic purposes. At my shop, we stock several meters of 3mm and 4mm thin-wall and thick-wall silicone vacuum hose for general-purpose use, largely again for its superior temperature range and inherent flexibility. We find it a particularly good replacement for the fabric-covered OE vacuum hoses used by VW/Audi and others.
What about maintenance? Until about 15 years ago, radiator and coolant hose failures were a common enough occurrence that conventional wisdom recommended prophylactic replacement every four years or so. Much of the published marketing literature still repeats this advice. Yet virtually everyone in the replacement hose manufacturing industry admits that the advent of electrochemical-resistant (ECR) hoses has at least doubled hose longevity. So, replace every four years? Every eight years? My suggestion is to closely examine the interior of the upper radiator hose whenever you change the coolant. Any visible striations on the inside mean that the hose is beginning to suffer from electrochemical degradation and should be replaced. Replace any bypass hoses at that time, too, or whenever replacing the water pump at least, because these and upper radiator hoses generally suffer the highest failure rates.
Wrapping It Up
I thought I knew something about hoses, and hose selection, but in the course of my research for this article, it became clear just how little of what I thought I knew was right. I hope you can benefit from the information I&#;ve presented.
At my own shop, we now stock some of the shrink-band clamps I mentioned, for coolant hose applications. We&#;ve always had some excellent hose clamps on hand, primarily for injection hoses, but we&#;ve expanded our inventory to cover some new types as well.
We have long carried a couple of feet of SAE J30R10 in-tank fuel hose, plus a couple of 25-ft. lengths of J30R9 high-pressure hose in several diameters. We decided to use the high-pressure line wherever it fits (except in the tank), even though it&#;s substantially more expensive than the low-pressure stuff. Why? Both to cut evaporative emissions and to reduce the possibility of mistakenly substituting a low-pressure hose where we shouldn&#;t. Besides, with typical repair lengths on the order of a few feet or less, the price of the hose itself isn&#;t the issue it would be at the manufacturing level.
We also added some power steering return hose in addition to the transmission cooler hoses we already had in stock. We laid in some small-diameter coolant hoses that we&#;ll now use instead of generic fuel or vacuum. EPDM is the material of choice for coolant containment. Silicone heater hose was never a big item for us, and we&#;ll restrict its use to high-temperature coolant applications, as before.
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