Checking for air suction prior to fuel filter.

[AnotherPerson]

Anybody can help me out with what I would need to do this? At idle the car runs well. Under load it will start to miss and now I’m thinking I may have a hose letting a little bit of air in. Being at idle it doesn’t run bad I figure a mighty vac might not pull hard and fast enough to make it leak.


Also what’s the most common place it would leak. Seems to happen more since it’s cooling off.


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[AnotherPerson]

Just popped off the thermo tee with the car running and the filter is dry at the top. Never touched diesel yet after about 70miles. Dumped some power service in there to wet it but should this be normal? Maybe my tee is bad again? It’s got about 20k on it.


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[wonneber]

I wonder if the Tee was hot enough to return all the fuel back to the tank?

 

[Powder Hound]

That thermo-T and the (count 'em - 5) connections there (including the t insertion into the filter that needs 2 o-rings on its own) make for many places for air to leak. There's 3 more on the injection pump, and if the return lines from the injectors are old, they can introduce air while the engine is running as well.

Good luck tracking this down. Some people also coat the thermo-t's o-rings and that part with petroleum jelly (aka vaseline). I ended up using screw bands instead of the spring clamps for the hoses and cut down air incidence greatly.

Cheers,

PH

 

[UhOh]

I'd rule in/out possible filter issues by running fuel (directly to the IP, though I like to use an in-line filter) from a separate container (a good opportunity to run some Diesel Purge).

I am running Nicktane filter kits (w/CAT filters) on all three Golfs now. This eliminates any Thermo-T issue (though in colder regions one might stop and consider whether it's better to retain the Thermo-T, and thus the stock filter setup). But I had issues (long cranking after sitting) right away on one install; tightened down the fittings (amazed at how much more I could tighten) AND replaced one of the stock band clamps with a screw clamp and that's been the end of that story!

 

[Nevada_TDI]

IIRC, the Mk1 filters have just an in and out port without the thermo T. It has a fill hole with a lock down knob and a built in o-ring. Not as effective as the Locknard version micron-wise, but it won't leak air at 5 different spots...