Coolant leak on 2002 TDI wagon

It's getting worse. Not the bottle. Pressure release when unscrewing bottle cap.
Are their known parts that eventually fail on older cars?

If you have lots of tank pressure when the car is cold its most likely the head gasket. Coolant is probably coming out of overflow bottle under hi-boost. That is about the coolest leak that comes to mind .

I've had this happen on two of my ALHs, and both times, (not to downplay jayb79's suggestion), people suggested "head gasket - yikes.

Thankfully, both times it was not. In order of "easiest to check vs. less so":

1. Thermostat housing was leaking at the O-ring - tough to notice because it's kinda hidden. But if you position your phone just right and turn on the flash, you might notice something like this:


1.(a) Haven't had this issue on my cars, but in the same general area, the hard coolant pipe that runs horizontally directly in front of the block, right behind the injection pump - there's an O-ring in there that has been known to fail. Photo here shows no dampness in that area, so no issue here.


2. Sealing O-ring on the water pump started to go (about 20K miles before TB was due for change). So, swapped out the timing belt a bit early, but didn't have to pull off the head, so that was a win.

Awsome, Thanks. We'll look.

What photo? I don't see a link or photo. My 04 Jetta GL may have problem #1(a.) Thank you for any visuals offered.

Automatics have a plastic cool flange on the side of the head that will warp and leak.

And the bearing on the waterpump can fail and leak there, but it will look the same as when the waterpump's o-ring fails. That is, the coolant appears from the same location, and the fix is the same: replace the water pump.

My current coolant leak in my 4-dr is oozing at the heater core. This fix is a royal PIA to be sure. The symptoms are continuous fogging of the inside of the windscreen and the smell of coolant in the car.

Cheers,

PH

I just found a leak on mine, but can't figure out where it's coming from. It runs down rear of block and follows the seam where tranny meets engine block. Not much rust on car, as it was originally from the south and Maryland. I think it's originating somewhere on left side of engine block, can't see if hard pipe is rubbing on side, I tried tightening up the coolant glow plug mount bolts and they were tight. Any ideas??

Could be the o-ring on the coolant temp sensor (which is located behind the triumvirate of coolant glow plugs). I had that on my '00 bug (which also, at 14yrs old when it started leaking there, still had the blue coolant temp sensor).

It’s probably the o ring on the coolant GP housing that’s bolted to the head.
They tend to get hard and shrink.
Lately if I’m doing TB’s I just change that o ring .
I’ve had three of them leak on my cars before I started doing this.

Thanks for the tips, I wasn't sure if that housing had any orings behind it or not. How many items do you have to disconnect to do it?

timeline said:

It's getting worse. Not the bottle. Pressure release when unscrewing bottle cap.
Are their known parts that eventually fail on older cars?

Click to expand...

(Almost) Everything will fail on older cars. The hoses can last a long time unless they get fluids on them. My minor coolant leak was the radiator (on my '99.5). Nice thing about coolant leaks is you can almost always see them. Start underneath, cover removed. You can also pressurize the system to help find leaks.

Might have to remove the bracket that holds the vacuum hose that runs under the vacuum pump.
That’s all I remove and that’s so I can get to the two 10 mm bolt that holds the housing to the head.
Yes it’s obvious , but must be stated, coolant must be drained.
You will still dump what ever coolant that’s in the head, shouldn’t be too much but you will need to have some new mix to put back in.

I love that this thread has a (mildly humorous) typo in the title - yet everyone responding just jumped right past that and we went on to troubleshooting the "coolest" leak.

That's why this is the best message board I've ever come across.

The leak could also be the small coolant line that goes to the head behind the vacuum pump. It would leak down along where the transmission joins to the engine.

Eric

Nuje said:

I love that this thread has a (mildly humorous) typo in the title - yet everyone responding just jumped right past that and we went on to troubleshooting the "coolest" leak.

That's why this is the best message board I've ever come across.

Click to expand...

But it is the “coolest leak” , I noticed it but wasn’t gonna say anything.

csstevej said:

But it is the “coolest leak” , I noticed it but wasn’t gonna say anything.

Click to expand...

Mod must've seen my comment and decided to fix the thread title - people are going to read this now and go "what are these fools talking about?!" ¯\_(ツ)_/¯

ahhhhh not it’s not as funny : (

Nuje said:

I love that this thread has a (mildly humorous) typo in the title - yet everyone responding just jumped right past that and we went on to troubleshooting the "coolest" leak.

That's why this is the best message board I've ever come across.

Click to expand...

If he thinks he has the coolest leak ever who are we to argue?

Ok,I think I found the problem. The metal flange that bolts to block(the part that has the nipples and coolant temp sensor) and that the coolant glow plugs bolt to, mine has 2 notches cut on opposite sides. Since oil was leaking around my valve cover, it looks like it worked it's way through the notch and deteriorated the o-ring in that spot. The dealer did have a coolant temp sensor(one I pulled out looked crappy) and the coolant glow plug flange o-ring (#037121687)in stock, but not the one that I needed-the flange to block head one(#037121688). After looking around various parts stores, I got one that was close, but it seemed a little too stiff to contour to the flange groove. After going into Advance last night, decided to stop into Harbor Freight. They have a 397pc. metric ring assortment, item #67580, for $8.99. I looked at the sizes listed, and one seemed close. I got the kit for just under $7 with the 20% off. The biggest one in set was a better fit than the size I found on ecs tuning. I put it in the flange groove, it worked into it nicely. I also bought some of the Permatex Water Pump and Thermostat Housing gasket maker(small tube). I filled the flange groove with the gasket maker,set the oring in, then put it on block. Waited the hour, tightened it down rest of way, needs 24 hours before adding coolant.I will update after I add coolant tomorrow. You get 11 of the o-rings in the Harbor Freight kit, haven't checked to see if the other o-ring needed is in kit or not, I already bought it from dealer...

What should it cost to replace this part or will new gaskits fix it?
038 121 133 A 121-075flangeI
manual
transmission
ALH,BEW$183.33

Metal Man said:

If he thinks he has the coolest leak ever who are we to argue?

Click to expand...

If you saw my garage floor you would have sympathy for me. :-D But that was funny. Spell check humor ...

Part number looks like the flange on the side of the head. Much easier than the hard pipe o-ring, but probably still a couple hours labor + coolant.
That hard pipe gasket near the thermostat is no fun. Will take a few hours labor at least for one tiny o-ring.

adjat84th said:

Part number looks like the flange on the side of the head. Much easier than the hard pipe o-ring, but probably still a couple hours labor + coolant.
That hard pipe gasket near the thermostat is no fun. Will take a few hours labor at least for one tiny o-ring.

Click to expand...

Thanks. The dealer in Janesville WI. said 500 bucks with the part. Wish some of you guys were in Wisconsin.

Take it to JasonTDI in Madison, good guy.

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adjat84th said:

Take it to JasonTDI in Madison, good guy.

Sent from my Pixel 2 using Tapatalk

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Yea he's the best but he doesn't service liberals. We had a falling out years ago I'm afraid. He installed the current used engine in my wagon. All good but it had a leaky valve cover gasket. I think thats why I'm at this point. Who knew. I don't blame anybody for this, just sayin. The info retrieved here has taught me allot about this leak issue though.

Ah, sorry to hear.
The Jetta in my signature belonged to Jason years ago. That picture was actually taken at his shop when I bought it. 307k miles and still trucking!

adjat84th said:

Ah, sorry to hear.
The Jetta in my signature belonged to Jason years ago. That picture was actually taken at his shop when I bought it. 307k miles and still trucking!

Click to expand...

Yep, I got about that on my wagon, 304k.



Thanks for the advise.

It will take maybe an hour, even if your having a bad day to change this.

Worse part is all the coolant coming out of the head when you take the 2 bolts out.
Go to the classifieds here and see who’s parting a manual car out.

You can get the whole flange assy with the coolant gps for about 45 bucks.
If the old one isn’t bad its about 7 bucks for the seal, I just picked up 2 of them from my local dealer.

If your doing just the seal maybe 20 minutes.

I'm being told now the leak is on the heater core exit pipe. This makes since as leaks occur when heat knob is turned on. Can this be a loose clamp or should all the houses and new clamps be replaced? This is an 02 so the life of these hoses could be compromised. I read the other post here on this and I understand there is a heat sensitive clamp. Is that a VW OEM part?