Jetta fuel filter “T”

[Gun-driver]

What is the purpose of the “T” in the top of the fuel filter.
I changed my filter and I’m having trouble keeping it from leaking.

 

[KLXD]

It's a thermostatic valve. Recirculates the fuel until it warms up then directs it back to the tank.

 

[Gun-driver]

Thanks guess I need it then. I was looking at bypassing with a straight barb fitting and using a different filter.
Any tips on getting it to seal.

 

[Genesis]

Replace the O-rings. If that doesn't do it odds are it's cracked and the only real fix is to replace it.

It's unlikely bypassing it will actually cause you material trouble in the real world; plenty of people have gotten tired of it and done exactly that.

 

[oilhammer]

It keeps fuel from gelling in the filter when it is really cold. In PA you'll want it.

New filter should have come with new o-rings, but sometimes the T gets a tiny crack or something from age. You'll just need to get a new one, not a big deal.

 

[Gun-driver]

I replaced the O rings. it’s missing the metal protector cap would that matter?

VW wants $80 that’s fricking crazy!!! Guess I’ll have to wait on the $12 one from IDparts

 

[Genesis]

The monkey clip is necessary, yes; it slots in the filter and holds it in place. IDParts has it or you can fashion something from coat-hanger style stock of the appropriate size (it's sort of obvious how it fits and holds it in place)

The seal is made with O-rings, not pressure, but if it backs out it will leak (usually air, which causes all sorts of bizarre hard-starting problems.)

 

[IndigoBlueWagon]

What brand filter do you have?

 

[ToxicDoc]

The monkey clip is necessary, yes; it slots in the filter and holds it in place. IDParts has it or you can fashion something from coat-hanger style stock of the appropriate size (it's sort of obvious how it fits and holds it in place)

The seal is made with O-rings, not pressure, but if it backs out it will leak (usually air, which causes all sorts of bizarre hard-starting problems.)

I don't think he's talking about the retaining clip. I think he's talking about a large T-shaped cover that is only used in some TDI models.

 

[oilhammer]

The metal cover is only used on the NB, and I suspect it is due to a difference in crashworthiness.

 

[WildChild80]

You can use zip ties in a pinch...but I got lucky and have 2 spares that I pulled from a salvage yard...I keep one in my wallet...ya never know...

Sent from my Pixel XL using Tapatalk

 

[Gun-driver]

I don't think he's talking about the retaining clip. I think he's talking about a large T-shaped cover that is only used in some TDI models.

Yes this https://www.idparts.com/fuel-filter-tee-protective-plate-a4-p-2607.html
i want to say it had one when I got the car but it had seen better days and it got discarded.
By the way she has 263,000 and still running good.

Update I ordered a new one from idparts but in the mean time I got it to stop leaking by using an Oring under the base.

 

[burn_your_money]

For what it's worth, my T is bypassed and I haven't had any problems. Given how far you can go on a tank, I suppose if you filled up 8 hours south and then drove back home without refilling you might have some issues if you let the car cool down and then tried to restart it.

 

[TornadoRed]

I disagree with the claim that the thermostatic-T is essential or even effective.

If the fuel is gelling, the thermo-T will recycle hot fuel back into the filter so the engine will run for 5 or 10 minutes. But when the T opens up to send that hot fuel back to the fuel tank, cold gelled fuel will enter the filter and the engine will die.

Personally, I would prefer that my engine not start at all, than have it run until I'm several miles from home before it dies and the car needs a tow.

 

[flee]

I disagree with the claim that the thermostatic-T is essential or even effective.
If the fuel is gelling, the thermo-T will recycle hot fuel back into the filter so the engine will run for 5 or 10 minutes. But when the T opens up to send that hot fuel back to the fuel tank, cold gelled fuel will enter the filter and the engine will die.
Personally, I would prefer that my engine not start at all, than have it run until I'm several miles from home before it dies and the car needs a tow.

There is a temperature when all diesel will gel, with or without the thermo-T.
I see it as a tool that addresses the zone where the fuel may be subject to gelling
unless there is a convenient heat source to prevent that from occurring.
I don't see the logic in assuming you will only experience extreme conditions where
the thermo-T is of limited or no value.

 

[oilhammer]

People who think preheated fuel filters do not work have never owned or driven a pre-1989 VAG diesel in the winter.

 

[IndigoBlueWagon]

People who think preheated fuel filters do not work have never owned or driven a pre-1989 VAG diesel in the winter.

Just dump a gallon of gasoline in the tank, it'll work fine.

 

[oilhammer]

Straight from my 1979 Rabbit's owner's manual!

 

[Genesis]

Oh they work, it's just that there's a certain boundary set of conditions under which they work and beyond that they don't.

If the fuel gels in the tank it matters not what the FILTER does because there's no supply. Once the engine is running and has been for a bit the returned fuel (which is materially warmer) starts to "fix" the problem, but that assumes it's running for a bit..... chicken and egg issue once again.

The real bug-a-boo is with a vehicle that can go from a warm place to a very cold place on a single tank of fuel and where the supply you got when you filled was not treated. Then you shut down overnight, outdoors, and..... These cars wouldn't go far enough on a load of fuel to get in trouble that way would they? Oh wait...

 

[oilhammer]

Fuel "gelling" occurs in the filter, because that is where the paraffins in the fuel collect. Which is why fuel gelling acts just like a clogged fuel filter, because that is what is happening.

 

[burn_your_money]

People who think preheated fuel filters do not work have never owned or driven a pre-1989 VAG diesel in the winter.

Or, we just buy the correct fuel and don't have issues. I drove a few Mk1 and Mk2s without the filter pre-heater and never had any sort of fuel gelling issues.

 

[oilhammer]

Perhaps in your neck of the woods they are/were more aggressive with fuel additives, but around here single digit temps brought many older diesels to a stand still. My friend and mentor showed me some tricks to thaw the screw on firewall mounted fuel filters, and some methods people used to counteract the problem. Starting in '89, we got the preheated ones, but Volkswagen sold kits to convert some of the older ones which was supposedly just to install the standard equipment used on cars sold in colder regions (perhaps Canada?).

I know my Vanagon does not have one, but the German military T3 my friend has, which is only one year newer, has one, which is actually a different filter mount... the actual screw on filter is itself the same. The return line from the pump doesn't go directly back up to the tank, but is a different line altogether that goes over to this different setup.

Once the fuel is warm enough back at the tank, and the engine is warmed up some, the issue generally goes away. It typically happens within 10 minutes or so of a cold start. Some of the older non-VAG diesels had the same problem. A coworker's 7.3L Powerstroke F250 did it one time.

I have had it happen to me several times on my old stuff, but never on the newer stuff. And oddly enough, I was more diligent about extra anti-gel additives on the older stuff. My TDIs I only ever worry if it gets down to around 0 F and I know it may stay that way, which is rare here but it happens.

 

[TornadoRed]

ugh, I was more diligent about extra anti-gel additives on the older stuff. My TDIs I only ever worry if it gets down to around 0 F and I know it may stay that way, which is rare here but it happens.

For me the worry/don't worry cutoff is around -8°F. That's when I start doubling the amount of extra anti-gel additive.

 

[burn_your_money]

Perhaps that's part of the reason why diesel is so much more expensive here (additives). It's currently 3.60 USD a US gallon. I don't think I've ever added anything to my tank for anti-gelling. I distinctly remember a few days stretch of -30c (-22f) and not having issues but that may have been in my 92 Jetta with the thermo t. Not to say I didn't have it disabled though. That's 10 years ago though so those types of details are no longer stored in my memory banks.