Thermostatic Tee - Failed

Jolly

Veteran Member
Joined
Jan 20, 2011
Location
Batavia NY
TDI
MKIV Golf 5
This is more of FYI, than a question... Regardless, maybe others can benefit from similar circumstances.
Went to leave work yesterday, and had a no start issue with my MKIV Jetta (5 speed, 293k miles). It was cold, but not cold enough to have a no start condition. I opened the hood and see air in the fuel lines (damn thermostatic tee!!!!). I seem to have repeatedly bad luck with the thermo-tee; the tee radomly fails, and then the pump and injectors loose prime. So, for the occasion, I carry a gatorade bottle of clean diesel and spare thermo-tees.
When I had the hunch that the tee failed on me again, I pulled the fuel lines off the filter, put them both in the gatorade bottle, opened the injector lines to push out any air, and then started cranking. After tightening injector lines, and getting a battery jump from my buddy because the battery ran down to NOTHING in the process, I got it to fire on fuel supplied by the gatorade bottle. While the engine was running, I quickly reconnected both lines to the fuel filter, and I saw that the supply line continued to pull air. I pulled them back off the filter, put them both back in the gatorade bottle, while the engine warmed up and so I could change out the thermo-tee. Finally, with the new tee, and the fuel lines reconnected to the filter; I was on my way home.
Not sure if I am the only one who has similar issues with these therm-tees or not... But for anyone who has a no-start issue because of air in fuel, this may be a place to start trouble shooting.
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Never had an issue with the actual "T", but went a couple rounds with the O-rings on the "T" for my CAT filter converter. Some heavy grease applied to the O-rings prior to inserting them seemed to solve that.
 

maxmoo

Veteran Member
Joined
Jan 19, 2011
Location
Lakefield, Ontario, Canada
TDI
2000 golf, 2001 golf, 2000 beetle, 2003 wagon, 2004 golf, 2004 jetta, all diesels
if the check valve in the in tank pickup/sending unit gets restricted or pluged the o-rings on the thermo T are the most likely spot to allow air in with the increased vacuum
 

greenskeeper

Top Post Dawg
Joined
Mar 10, 2003
Location
USA
TDI
1998 Jetta TDI
i got rid of that garbage at my first filter change many years ago. A 1.6 IDI fuel filter fits nicely and you can splice the return to eliminate any future problems. Good to -20F without the T.
 

Metal Man

Vendor
Joined
Sep 29, 2001
Location
Sunbury,PA 17801
TDI
1998 NB TDI, 2006 Jetta TDI, 2014 Tiguan gas, , 2019 E Golf X2
Are you using original VW tees? I got an aftermarket one here once that looked pretty rough, I think I threw it away. I only sell original ones and they aren't a huge seller.
 

dezeljunky

Veteran Member
Joined
Sep 18, 2010
Location
Richmond, BC
TDI
2003 Golf GLS TDI Silver 5spd
I just had this happen to me. A good idea I heard from another thread was to use some super thick grease (or wax) on the o-rings and where the bottom of the T mates with the horizontal part of the filter. I couldn't find any thick/wax at the hw store (Canadian tire) so I decided to use the wax from a toilet wax ring. It's super tacky and thick and the MK4 filter doesn't get so hot so we'll see how long that works... I'll keep the rest of the wax ring in the trunk in an emergency. Good seal so far and for $2. I had used Grade 2 bearing grease but it was too thin.

Another good alternative is to use the 1.6L IDI diesel fuel filter(eg. VW 1987 Jetta is a year) that doesn't use a thermostatic T. Then just connect the return line directly to the tank. This is fine if your area doesn't get too cold.
 

fossill

Veteran Member
Joined
Mar 22, 2008
Location
Canada
TDI
Golf
Thats what I've been using for the last 7 years and never had an issue, even in -45C. I always use additive.
 

turbovan+tdi

Top Post Dawg
Joined
Mar 23, 2014
Location
Abbotsford, BC.
TDI
2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
i got rid of that garbage at my first filter change many years ago. A 1.6 IDI fuel filter fits nicely and you can splice the return to eliminate any future problems. Good to -20F without the T.
I had two tees crack and one outright fail. Finally replaced with the Kerma Widget and it's been great. It's just a straight pipe, there's no innards to fail.

http://www.kermatdi.com/kerma-widget/
Nice fix's, never thought of that but haven't had a failure yet!
 

PGM jetta

Veteran Member
Joined
Dec 14, 2015
Location
Northern Alabama
TDI
05 Jetta BEW
I've been running a Nicktane filter set up with a 2 micron CAT filter for a couple of years. Never had any problems and hardly ever have to change the filter. And only cost $15 to change
 
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