Radiator?

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Ok this is an interesting one....

My ALH has a very slow coolant leak. Maybe 2oz over the space of a few weeks, but it's there. I've been chasing this since I had to replace the timing components early due to the water pump leaking (BADLY!)

I'm also chasing oil leaks which appear to be at the valve cover and that infernal joint between the vacuum pump and head. I've got another one vacuum pump gasket coming, along with a grommet for the breather (it is definitely leaking there) and I'll take a "Hondabond" sort of approach to the valve cover gasket and, if no joy there, a new valve cover.

But the coolant leak has me stumped. There is NO leak being deposited on the garage floor, and there's no indication of a head gasket problem; the coolant is clean and bright. I've got a black light; there is no illumination AT ALL around the hard pipe or thermostat housing (thought maybe it was there, it isn't.) Ditto on the heater core connections at the firewall -- clear. HOWEVER, there is a pretty decent amount of glowing on top of the transmission and also all over the *front* of the oil filter housing and a smattering (pretty even but more slanted toward the driver side) of glowing on the front of the engine itself.

The only thing I can come up with is a very slow leak in the radiator itself and with the system pressurized it leaks -- but not enough to deposit anything on the floor, and at the radiator hose connections as well -- no leak indicated.

Is the only way to go at this to do the lock carrier thing? I can't get this thing to leak VISIBLY as it won't drop anything on the floor; if I can avoid having to discharge the A/C that would be fabulous; I definitely would prefer to avoid that if at all possible. And I definitely do not want to throw parts at it and be wrong.

I'm going to hit the engine all over with degreaser and rinse it all off, then see if I can get it to leak for me enough to trace the source -- but given the diffusion I'm seeing it looks like it may well be the radiator and, of course, given airflow and the fans winds up depositing small amounts of coolant on anything that it can collect on (in other words the front-facing pieces of the engine/accessories/bell housing.)

Just tossing this out there to see if anyone else has had a similar experience.
 
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2many diesels

Veteran Member
Joined
Mar 20, 2011
Location
Nor Cal
TDI
rabbit pickup 1z swap Audi A4 Quattro ALH. 02 Beetle TDI. 99 Golf TDI. 03 Wagon TDI. 914 Porsche ALH t
if your car is an automatic, I would suspect the plastic coolant flange on the end of the head. They are known to crack an leak small amounts of coolant. Cheap to replace and should be done as a matter of coarse, also replace the oring for the temp sensor, If it is a manual car, the flange is aluminum, but the oring against the head coule be bad.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
It's a stick so the flange is metal, which is why I discounted that; I've changed a couple of them on automatics for friends in the past that started leaking. I'm wondering if the glow plugs THEMSELVES could be leaking....

Looks pretty easy to change that O-ring... I thought it was perhaps leaking at the temperature sensor (a sore spot that has happened to me before) but nope -- zero glow back there around the wiring and the hole where it goes, so that's not it. Wherever it's leaking it's a vapor sort of thing that's depositing on surfaces, but the worst of it is on the bell housing. What leads me to be cautious about yanking the radiator is that I don't see ANY glow on the fins, which I'd expect if one of the tubes was leaking.

Hmmm... I think it's time to get the degreaser out, clean it up real good, run it a bit and see if I can find some glow somewhere before I start throwing parts at this thing and wind up frustrated and pissed off. I can smell the coolant after it's gotten good and hot and then shut down and left for a while under the hood... just faintly, but there.
 
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Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Hmmm... I think it may be the EGR cooler leaking into the exhaust, which explains why I can't find a liquid leak. Small enough that it ultimately gets burned up and blown out the pipe.

Went for a run and got it good and warm so the system was pressurized, and I don't see anywhere it's leaking -- but I could, after shutting it down, hear a very, very small bubble back behind the engine where the cooler is. I didn't have the A/C on so it couldn't be residual pressure in the evaporator and the hose connections at the cooler aren't wet either. It's definitely not leaking at the heater core; there's no UV glow at all inside the vehicle in or around the vents or on the windshield.

If that's the case I may just bypass the connection; it sure looks like a 5-alarm pain in the butt to replace that thing, never mind being expensive. I suspect there's no real way to know other than bypassing it, is there?

That doesn't look like fun.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
I had a verrrrry slow leak at the cts O ring. It would leave the top of my transmission damp. I finally got around to changing the O ring and now the transmission is dry. I found it by putting my dry fingers on the cts housing where the cts sits. My fingers always came away damp.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
The "Ultra Gray" Permatex appears to work real well on that valve cover gasket. The jury is out in terms of durability but so far exactly ZERO seepage, and it was leaking like HELL before.

Take the cover off, remove the baffle, wipe down the baffle to get the oil out of there and clean up the valve cover REAL GOOD with brake cleaner to make sure ALL of the oil and debris is off the (now-hard) gasket and the channel it sits in, moisten shop towel with brake cleaner and do the same for the cylinder head surface (you want both surfaces absolutely clean and dry, NO OIL on either), put the baffle back in, lay a thin bead on the gasket, wait a few minutes, set the cover back on and run the screws in with your fingers (NO torque yet), wait an hour, torque 'em and then let it sit overnight. Then clean the bejeezus out of the engine with your favorite engine degreaser to get all the crap off of it, especially the back of the block, rinse it off and take it for a nice run to get it good and warm so you evaporate all the water off.

$8 for a tube of Permetex Gray .vs. $200+ for a new valve cover? And maybe I'll get lucky enough that the remainder of the tube won't harden up before I have occasion to use the rest of it doing ATX pans, differentials and other things. I'll take it if it holds up.

Now I get to leave the car with paper shop towels under it after running it good and hard, getting it nice and warm, with the belly pan and side skirts off in the hope that it will drip coolant from SOMEWHERE and give me a crack at figuring out where the in bejeezus that leak is coming from. If it's leaking into the EGR cooler, however, then it's probably going to be bypass-and-cap the holes time for that. I'd get a tune and "race pipe" it but it's my kid's car and if she moves in the future to somewhere that actually does emissions inspections that could turn into trouble.
 
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