Fuel filter O-rings -- important!

Creeble said:

But after reading all this, it sure seems like it could be the o-rings on the return valve. There's nothing obviously wrong there (except that I can't put the metal cover on any more because I have replacement hose clamps that are too large), but from what everyone says, this is the #1 place to look, no?

Just try some bigger o-rings?

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I'm not sure what replacement hose clamps you're talking about. Are they holding? Are the hoses under them cracked? Look in that whole area.

Also, the "t" may be cracked. Get reading glasses/magnifying glass (depending on age) and look carefully.

Could be from B100 use - these o-rings don't like it much.

get a new OEM set from the $dealer$ or tdiparts:

http://tdiparts.com/catalog/product_info.php?products_id=476

Make sure you contact the dealer and ask if they have them - the VW part number is on the tdiparts page above. I checked with my dealer and they didnt' have them in stock - it was going to be a few days to get them, but I guess if you are ordering them from tdiparts then you have to wait anyway. If you do get them from tdiparts, you can also get a backup fuel filter since it sounds like you just installed your backup ;-)

For B100 - I recommend replacing the fuel lines with polyurethane lines (clear) which can be bought from procycle:

http://procycle.us/main/fuel_hose.htm (the 5/16th ones)

and viton inter-injector lines which you can buy from greaseworks:

http://www.greaseworks.org/store/product_info.php?cPath=27_40&products_id=212

I replaced those clip-clamps (what's the special tool you need to remove these, anyway? Every pair of pliers I have slip) with regular screw-tighten hose clamps. This was recently, as I was trying to debug the problem. Yes, I know the T is plastic, so I was careful not to over-tighten.

I've got 40k mi on B100, and haven't had any trouble with the o-rings before -- I replace them with the fuel filter every time. All my hoses look fine, though thanks for the suggestion on polyu replacements - sounds like a great idea to be able to see everything. I've got some 5/16 viton that I used on my boat as well; unfortunately wrong size for the injector bypasses.

I'm becoming more and more convinced that the problem is the o-rings, or perhaps more correctly, the filter housing where the o-rings go. Is there any simple way to test -- like bypassing the tee with a coupler and sticking a rubber plug in the filter? Finding a rubber stopper might be harder than finding replacement o-rings...

Thanks; this is a great forum.

Try some petroleum jelly, in the area of the orings. Also inspect the ends of the lines for cracks on all sides of the hose. I like my polyu lines because it's very easy to see damage. tdiparts has replacement tees - if you find yours is cracked just make sure you order the right one. They're around $40. Also, there's a 3rd party replacement tee that someone sells- i think it's a few posts back. It actually has no thermostatic function, it's just a plug for the hole in the filter, and the fuel line just passes through it. It looks like a stainless version of the oem thermo tee.

With B100 use, I was noticing that the orings that came with the purolator filter were degrading - they actually were flaking. I thought of getting some viton orings, then saw that tdiparts had the oem orings, so i ordered those. I still had a massive air problem though. Finally replaced the purolator with a new filter and air problems vanished, so it was the purolator. The backup I had was also a purolator, so I expect to have the same problem once i start using b100 this summer.

Uh...just what IS the thermostatic function of the thermostatic T???

The thermostat directs the returning fuel to the tank if it is warm or back to the filter if it is cold. This promotes rapid warm-up of fuel that the manufacturer desires.

nylonoxygen77 said:

Try some petroleum jelly, in the area of the orings. Also inspect the ends of the lines for cracks on all sides of the hose. (snip)

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__. Yeah, I diagnosed a pinched O-ring on MzLauraLee's waggin using drugstore "mineral oil". A few drops around the T and O-ring area and the bubbles way reduced.

__. Then I pulled the T and found the pinched O-ring. I put in new ones (less than $3 for a pair from the stealer). I lubed them with the mineral oil before I put them in, then made sure that the O-rings were slipping into the bore smoothly -- one thing that's important is that the barrel on the T go straight in. If it's cocked to one side or the other, it will push a section of the O-ring out the 'high-side' and pinch it.

__. Then I put a CAT filter on both our cars and solved all our filter problems once and for all.

Ooh, I'll look for that s/s T replacement; should be fine here in sunny california. Thanks for the tip(s) on petroleum jelly / mineral oil on the port. I'll try that today.

CAT filter sounds like a good idea, but there's so little room for anything in the beetle's front end. I'd like to have the dual racors (with suction gauge) that I have in the boat...

Polyu lines, yes. Ordering now. Love that idea.

Will post results of experiments.

Others have said there are no unique fitment issues with the CAT filter in the new beetle.

Here is the Kerma Widget, referred to in this thread, which is Al no SS. This one is installed in my CAT filter and came with O-rings. No air issues for me.

I used a straight thru barb connector from a hardware store plus a well plug in the hole to eliminate the T- cost about $4. I had problems with the oring tearing. I don't miss the T and the line bubble is much smaller. I only have about a 3-4mm bubble in the line now. Cat filter change is now a little easier w/o the T. Unless you live in a frigid climate, I think you are better off w/o the T- IMO.

I agree with truman. If my widget had not been free to compensate for an inadvertant shipping issue I would have tapped the hole in the CAT head and used a threaded plug + barb connector. The A3s don't even have a thermostatic tee AFAIK.

truman said:

I used a straight thru barb connector from a hardware store plus a well plug in the hole to eliminate the T- cost about $4. I had problems with the oring tearing. I don't miss the T and the line bubble is much smaller. I only have about a 3-4mm bubble in the line now. Cat filter change is now a little easier w/o the T. Unless you live in a frigid climate, I think you are better off w/o the T- IMO.

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Well plug? Whassat? Rubber plug thingy? Seems like that's where I'm headed...

Well plug/expansion plug, should be available a your local hardware store. It's worked fine on mine- no leaks. The barb connector to eliminate the T can also be acquired there.

KS97Passat said:

Can someone report the size of these o-rings so that I can get some from my local "o-ring store" (I may hold out for viton material too)? For some reason, Caterpillar doesn't include these with the retrofit filter I buy from them.

I have a friend whose car I suspect has this sucky problem. He's getting lots of bubbles in his clear fuel line (A4 - manual transmission) and the car is a little slow to start.

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Did you ever find this to be true or false on your friends car? I have the same kinda thing but haven't check my fuel line for bubbles yet.

FWIW, here's how my problem (and solution) finally played out.

I tried using a well plug on the return side, bypassing the "T". Still had bubbles in the input side. Took out the sender from the tank, cleaned it (somewhat messy, but no obvious problems). Still had bubbles. Disconnected / reconnected the two fittings that go back to the tank, still couldn't find anything.

Finally, I just took it in to my mechanic (along with a roll of Viton hose that I already had) and told him to replace all the lines in the engine compartment. He did, along with a new "T" (and o-ring). Problem gone.

There weren't any visible leaks in the old lines, but something must have been letting air in somewhere. Kind of a bummer that there wasn't a definitive "aha!" moment, but I'm happy to have the Viton hose in there; one less thing to worry about.

r

ssullivan777 said:

Did you ever find this to be true or false on your friends car? I have the same kinda thing but haven't check my fuel line for bubbles yet.

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I don't remember what was done to his car. He is the kind of guy who does many car repairs by the seat of his pants. In his case, if smearing some goop around the tee made it better, that's probably where the work ended.

Recently I took a pair of o-rings as supplied with new factory fuel filters to the local business that specializes in selling sealing products to see what size they were and for comments about materials used. I was told that the pale blue one was probably covered with teflon, that I should not substitute and that the dealer price was fine. I plan to go with that advice.

My Filter is different???

Hey Guys, I checked mine at lunch today and my filter does not have a removable "T" fitting like every other one I have seen.

It is standard fittings. ( slide hose on & tighten clamp )

Went to check for bubbles to and no clear piece of hose from the filter to the engine???

Any thoughts??

ssullivan777 said:

Went to check for bubbles to and no clear piece of hose from the filter to the engine???

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Yeah, Beetles don't have the clear hose. I just put a piece of vinyl hose between the filter and the injection pump temporarily. I think it was there for about a week, and had already begun to melt down from the biodiesel; I wouldn't recommend leaving it there for more than a couple of days.

Weird that your Beetle's filter doesn't have a removable T. Never heard of that filter.

Eric.

Creeble said:

Yeah, Beetles don't have the clear hose. I just put a piece of vinyl hose between the filter and the injection pump temporarily. I think it was there for about a week, and had already begun to melt down from the biodiesel; I wouldn't recommend leaving it there for more than a couple of days.

Weird that your Beetle's filter doesn't have a removable T. Never heard of that filter.

Eric.

Click to expand...

Yep, I guess if I want to change it, I am gonna have to see the steeler, cause all the replacements I can find, take the T and micky mouse clip.

Does your filter look like this?

The 98, the first NB, did not have the thermostatic tee. TDIparts.com has the filter.

Another thing to check if you're having problems with air bubbles and you use B100 or WVO - the injection pump seals. The three big ones are the main pump head seal (between the cast iron pump head and the aluminum body) and the two quantity adjuster seals. You don't have to take the IP out of the car to replace any of them, but it's a tricky job. I noticed that when I run B100, I don't have as much air in my lines as when I run diesel. The B100 causes the seals to swell, and the dino causes them to shrink. Furthermore, they will naturally shrink when it's cold out. I had a heck of a time this winter with cold starts. I haven't dug into the problem yet but I know my pump is losing prime when the car sits for 8 hours or more, so I can only assume the seals are in need of replacement. They can be purchased from Dieselgeek.com along with the triangle socket you need to get the pump covers off.

My next step is to do a vacuum test on the lines inside the engine compartment. I have massive air in my system now. It could be a combination of things. I have a greasecar kit and a FPHE, which really complicates the fuel system.

nylonoxygen77 said:

Does your filter look like this?

The 98, the first NB, did not have the thermostatic tee. TDIparts.com has the filter.

Another thing to check if you're having problems with air bubbles and you use B100 or WVO - the injection pump seals. The three big ones are the main pump head seal (between the cast iron pump head and the aluminum body) and the two quantity adjuster seals. You don't have to take the IP out of the car to replace any of them, but it's a tricky job. I noticed that when I run B100, I don't have as much air in my lines as when I run diesel. The B100 causes the seals to swell, and the dino causes them to shrink. Furthermore, they will naturally shrink when it's cold out. I had a heck of a time this winter with cold starts. I haven't dug into the problem yet but I know my pump is losing prime when the car sits for 8 hours or more, so I can only assume the seals are in need of replacement. They can be purchased from Dieselgeek.com along with the triangle socket you need to get the pump covers off.

My next step is to do a vacuum test on the lines inside the engine compartment. I have massive air in my system now. It could be a combination of things. I have a greasecar kit and a FPHE, which really complicates the fuel system.

Click to expand...

First time i looked i thought it was like it, but its not, on the right in the picture there is a ?? that is where my T is, and it is made on to the top of the filter like the other fiitings.

Now yet another thing to check on why 2000 A4 golf cranks, but does not light off. Air in the lines ???
So...When it comes to the "O" rings on the FF thermo fitting :
1. If they are different colors, witch one on top, which one on the bottom ?
2. What is the correct size ?, AND are they both the same size, or different sizes ?
3. If your running B.D. shouldn't they be of Viton material ?

I would think McMaster-Carr would sell the Viton "O" rings, if I knew the correct size OD, ID, and cross section. (most likely they are metric ???)

Thanks for the advice and comments.

Peter

They're (supposed to be) slightly different sizes... the blue one goes on first (sits at the top of the thermostatic "T" when in place)... You can get them from your friendly local VW dealer... P/N: 1JO 198 247.

Yuri.

I removed the "T" and now use the old style fuel filters. Ran great all winter.

my car is getting all kinds of bubbles so now I have to buy the O rings for the T.

The Bentley Manual on page 20-26 says the thermostatic "T" returns fuel to the filter when the fuel temperature is less than 15 degrees C (59 degrees F) and the fuel goes to the tank when the fuel temperature is greater than 31 degrees C (88 degrees F).

If you're going to replace the IP seals, (it's always a good idea, if you own a TDI, to also own the triangle socket) - you should also replace the fuel-temperature sender. That's a fault-code waiting to happen, so as long as you're in there, it's an easy swap.

'02 Jetta TDI which cranks but won't start. 100 degrees here so fuel is def NOT gelling. Have primed low pressure side of system but can't seem to get any fuel to injectors. Took intake line off IP (from filter) and attached vacuum gauge. Did not register any vacuum when cranking so does not appear to be capable of pulling fuel in from the tank.

Solenoid is getting power and can hear it click, so don't think relay is the problem.

Is bad IP seals the correct diagnosis here? Seems like it should create vacuum at intake line of IP if seals are OK.

Steve

Did you change the filter? If the filter is clogged, you won't get fuel. If you did change it, you could have an air leak from a damaged or poorly seated o-ring. This thread suggests several good ways to troubleshoot air leaks into the fittings on the filter (dripping mineral oil onto fittings, etc.).

franklp said:

Did you change the filter? If the filter is clogged, you won't get fuel. If you did change it, you could have an air leak from a damaged or poorly seated o-ring. This thread suggests several good ways to troubleshoot air leaks into the fittings on the filter (dripping mineral oil onto fittings, etc.).

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Yep, filter was changed, planning to bypass the T. But most curious why intake on IP is not producing vacuum.

Update: Got it running by priming at the T, which pulled fuel through the IP and injectors. Will investigate bypassing the T, or replacing the O-rings in the T. If neither work, will replace fuel lines in engine bay w Viton. Last item will be to replace seals in IP.

Thanks for all the tips in this forum, been great help!

Steve