thermostatic T question.

[redline808]

what is the thermostatic T in the fuel fiter. is there a 1 way valve in there? where can i buy a new one?

thanks.

 

[dweisel]

what is the thermostatic T in the fuel fiter. is there a 1 way valve in there? where can i buy a new one?
thanks.

The purpose of the thermostatic tee is to control the return fuel flow at the filter. In cold weather the tee opens and sends the return fuel flow thru the fuel filter to warm fuel within the filter to help prevent gelling. In warm weather the tee closes and return fuel goes straight thru the tee and to the fuel tank.

google vw thermostatic tee for sale

 

[DanG144]

There is a spring loaded one way valve in it and a diverter/check valve. The check valve (one way valve) prevents flow from coming out of the filter into the tee. The diverter/check valve prevents fuel from flowing backwards through the tee and also diverts cold fuel into the filter through the check valve causing it to recycle until it reaches a certain temperature, then it is directed to the tank.

You can buy one from BoraParts.com - he is closest to you - or IDParts.com or the dealer.

In Hawaii you could probably get by with out the thermo tee (many do here on the mainland). Filters are available without it, and you could use a 5/16" hose barb coupling (maybe 1/4" if you have a Mark III) in place of where the thermo tee used to be.

If your tee is broken at one of the top connections, then you can simply install the tee, use a hose barb to bypass it, and depend upon the spring loaded check valve portion of the tee to keep fuel from coming out of the tee ends. This may get you on down the road for a while.

 

[DanG144]

Look on page 38 in the pdf. Yours is 30 C or less. The rest of the training material is for a different engine and does not apply to you.


http://www.volkspage.net/technik/ssp/ssp/SSP_223.pdf

 

[whizznbyu]

Has anyone ever seen a bad thermostatic TEE cause an airlock in a B5? I'm trying to find a cause for fuel starvation/hard starting in this car when the nose is parked uphill.
Lift and tandem pumps have been changed out to brand new. Thank you.

 

[gatz]

We had that happen on our MK4 BEW (PD), and I believe its the same part number for your B5. The tee got damaged somehow and just blocked flow entirely. They can also crack and leak if you aren't careful.

 

[DanG144]

The problem you have can be caused by an air leak into the fuel line when it is depressurized. The air leak can be anywhere under the hood.

I take it you are not getting any fuel leakage anywhere? No drips or damp spots, no matter how tiny?

I had one from the tandem pump outlet fitting on my car that was very hard to detect. It was leaking out the bottom where it was not visible to me. The only reason I found it was it finally caused the coolant hose under it to develop a hole.

A new hose still leaked in the same spot. I finally had to put a very high quality 360 degree hose clamp on the hose from McMaster.com to stop the leak. The stock spring clips are very good, but were not sufficient. Maybe I had a scratch or surface defect in the sealing area.



If you have absolutely no drip of fuel from anywhere, then it is leaking only when under a vacuum. This is most likely at an 0-ring seal, which the thermo tee has.

The thermostatic tee is one potential source of leakage.

 

[hey_allen]

I had a thermo-T split along the joint where the body and the bottom portion are glued together. It was sucking a good bit of fuel into the fuel lines, through the no longer securely closed check valve in the base of the T.

I briefly got by with a hose barb joining the return hoses and a plastic plug secured under the remains of the T, to keep from sucking air through the filter.
I replaced mine with a cheap replacement from eBay, as the dealer wanted $65 and did not even have it in stock.

 

[whizznbyu]

I have never ever seen any fuel leak anywhere. I've also had the car up in a lift for oil changes and skidplate installation and never have been able to find a damp spot anywhere. If I had a leak, I doubt that it would never make it to the floor. But I have seen stranger things happen.

 

[drucifer]

Has anyone ever seen a bad thermostatic TEE cause an airlock in a B5? I'm trying to find a cause for fuel starvation/hard starting in this car when the nose is parked uphill.
Lift and tandem pumps have been changed out to brand new. Thank you.

You had fuel starvation then replaced tandem pump and lift pump? If the tee fixes it that was an expensive lesson.

 

[whizznbyu]

You had fuel starvation then replaced tandem pump and lift pump? If the tee fixes it that was an expensive lesson.

Living and learning.

 

[DanG144]

He had fuel drain back to the tank. His fuel lines empty overnight, when he does not park nose down. This is on a PD engine with electric in tank lift pump and cam driven mid pressure fuel pump (tandem vacuum and fuel.)

Whizz, Have you had any issues with your clutch slipping? That can be a sign that fuel is leaking down into your flywheel area, from something up near your tandem pump.

 

[whizznbyu]

He had fuel drain back to the tank. His fuel lines empty overnight, when he does not park nose down. This is on a PD engine with electric in tank lift pump and cam driven mid pressure fuel pump (tandem vacuum and fuel.)

Whizz, Have you had any issues with your clutch slipping? That can be a sign that fuel is leaking down into your flywheel area, from something up near your tandem pump.

Funny you should ask that.
It has a 5 speed manual. Transmission came from Franz.
1st and 2nd, it does not slip. On 3rd, 4th, and 5th, when I press hard on the accelerator upwards of 2500 it slips. BUT, it was doing that way before the fuel starvation issue. Maybe it is related. Having said that, the Tandem pump has been replaced, and it still does the same thing.

 

[pruzink]

I replaced the thermostatic tee valve on my 2004 Jetta several years ago with a Kerma Widget (the Kerma widget is an aluminum straight through connector that blocks any flow from ever returning to the filter). I live in Texas now, but I had this valve installed for years when I lived in Connecticut & it made no difference in the winter. The reason that I replaced it was due to the speed at which fuel rail return fuel gets quite hot, I felt that 95% of the time that the valve would be in the full return to tank position. Because the valve was such a cheaply made piece of plastic, I didn't think that the reliability of the valve working correctly was likely.

 

[pruzink]

http://www.kermatdi.com/kerma-widget/

 

[TornadoRed]

http://www.kermatdi.com/kerma-widget/

Instead of spending $40 for the widget, I'd recommend switching to the Nicktane filter head that accepts the CAT 2-micron fuel filter. That will end all problems related to air entering the fuel filter via the thermostatic-T. And it will extend your fuel filter replacement interval to 60k or 80k miles or more. The 2-micron filters are much superior to the OE filters.

 

[Genesis]

I have one of the earlier incantations of this in my '03 (it was from someone else, and has a mounting point for the "T") and it's the shiz. The filter lasts darn near forever and it's the 2u common-rail rated CAT filter as well. I don't remember who made it; I may craft up a blocking plug for the T at some point (I do have a lathe and a piece of aluminum rod can easily be turned to take a couple of O-rings to seal the port) and be done with that.

 

[TornadoRed]

I have one of the earlier incantations of this in my '03 (it was from someone else, and has a mounting point for the "T") and it's the shiz. The filter lasts darn near forever and it's the 2u common-rail rated CAT filter as well. I don't remember who made it; I may craft up a blocking plug for the T at some point (I do have a lathe and a piece of aluminum rod can easily be turned to take a couple of O-rings to seal the port) and be done with that.

I had one of those, too, from Lubrication Specialist made by Greg Landuyt. It was an improvement over the OE filters, but it was awkward to swap the Cat filters, especially if you got the outside of the filter and the filter head wet with fuel. The shape of the Nicktane filter head is superior as it lets you get a really good grip on it. Not sure if I gave the old Lubrication Specialist head to someone else or if I still have it stashed away.

I recommend the kit for the Cat 2-micron filter, as replacements are easy to find everywhere. http://nicktane.com/osc/product_info.php?cPath=23_30&products_id=47

 

[IndigoBlueWagon]

I think these are solutions in search of a problem. In 15 plus years of owning more than a few TDIs I've never had a problem with a fuel filter tee. I've replaced some proactively, and at $13 it's not a big deal. Use a good tee and a good quality fuel filter and you'll not have a problem.

 

[TornadoRed]

I think these are solutions in search of a problem. In 15 plus years of owning more than a few TDIs I've never had a problem with a fuel filter tee. I've replaced some proactively, and at $13 it's not a big deal. Use a good tee and a good quality fuel filter and you'll not have a problem.

I'm not sure if you remember that GTG in Milwaukee about 6 years ago. I got a new set of nozzles and Frank Irving calibrated them and installed them. Maybe you had already headed for home, but I could not get my Golf started. Jason, Frank, and I think Jeff from Rocketchip were all there, trying to help. Jason was ready to drive to his shop outside Madison to get another IP, because they all figured I wasn't getting fuel because the IP had failed.

But it was the fuel filter -- air was leaking in past the thermostatic-T. Replaced the fuel filter, bled the air out of the lines, cranked it over for 20 seconds or so and it started.

 

[IndigoBlueWagon]

I remember that GTG but not your issues. Maybe I had left. But people can fault almost any part of any vehicle for an issue one time or another. I maintain the fueling systems on these cars are pretty reliable.

 

[DanG144]

For a while, some filter manufacturers or suppliers were providing O-rings for thermostatic Tees that were too small, and one particular brand had oversize holes for the thermo-tees, so even the right size O-rings would not seal. Sorry I don't know the makers.

I have had one thermotee fail from pulling on it too vigorously to pull it out of a very tight fitting hole on one filter.

The filters I got from IDParts.com never gave me any issues.

I still use Greg's filter housing with thermotee, and Caterpillar 2 micron filters.

 

[whizznbyu]

I maintain the fueling systems on these cars are pretty reliable.

I hope you are correct with this statement.
As far as having an algorithm, once the Tee gets replaced, and if the problem persists, tandem pump and lift have been replaced. Where else can the problem be? Which part/gasket/O- ring should I address next?

 

[IndigoBlueWagon]

I think DanG already answered your question. Air leak in a fuel line somewhere. Not sure of the best way to find it.

 

[Amine5]

Hi there, i think am witnessing a problem in that tee valve, i have a strange noise coming from hpfp after the engine warm up , no noises when starting cold , and the noise is pretty clear when driving up hill, this started after changing the fuel filter housing by a used one after i broke the original fuel filter housing cap , i think it was a bad idea, the noise is louder in hot weather, there is no loss in power no limp mode just noisy hpfp and rattling injectors only when warm , can somebody give me advice?

 

[compu_85]

A photo of your fuel filter setup would be helpful, since the thero T setup on the common rail cars I've seen is completely different than the 2000s cars.

 

[Amine5]

 

[Amine5]

I sent a picture of the fuel filter from google

 

[Amine5]

0774671C-D4BD-4A4D-89BD-916099579950.jpeg

• Amine5
• Jun 27, 2022

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• Amine5
• Jun 27, 2022

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• Amine5
• Jun 27, 2022

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• Amine5
• Jun 27, 2022

 

[Amine5]

That’s a broken one that i teared down