Let's play name that engine part and help me identify my coolant leak!

[lardope]

So I have a slow, slow, very slow, coolant leak. I put stuff in my coolant tank that glows under UV light and found the culprit I think. See pictures. Now I just have to figure out what the heck I'm looking at and I'll see if I can find a youtube video explaining how to replace it!

Also, is there no way of embedding photos in these posts (Okay solved. Thanks Nero Morg!)

 

[Nero Morg]

There is, use the photo icon in the text box.

Also, that's the coolant flange. Probably just needs a new o ring.

Coolant Flange for Cylinder Head O-Ring (A4)(B5.5)

For Volkswagen Jetta, Golf and New Beetle TDI on the A4 chassis with the ALH or BEW. O-Ring Seal between 3-way cooling flange that attaches to the back of the cylinder head over the transmission. T...

www.idparts.com

Unless it's leaking around one of the glow plugs. If it is, take the glow plug out, apply thread tape, put back in.

 

[lardope]

Can you see the photos now?

Okay thanks a lot! That means I have to drain my coolant, right?

 

[Nero Morg]

Yes it does. Regardless if it's the o ring or the glow plug. Which is it leaking from?

 

[Diesel Fumes]

The oring is a common fail point there.

Off topic but what are those 3 sensor things? And why does one of alhs have them and the other doesn't? Is it because one was born an automatic?

 

[JB05]

Coolant glow plugs for manual equipped TDI's.

 

[Tdijarhead]

The automatic doesn't have them, as nero said if they are leaking pull them, use some thread tape and call it good.

 

[lardope]

After looking everything over again tonight, looks like the o-ring! Thanks everyone

 

[lardope]

Just getting around to this, but I am going to try and replace the O-ring coolant flange tomorrow. I see no youtube videos dedicated to this, so I am going in blind. If anyone knows anything please let me know. From just looking at it, I see two small bolts to remove. I'm hoping that's basically it!

 

[WolfgangVW]

Just getting around to this, but I am going to try and replace the O-ring coolant flange tomorrow. I see no youtube videos dedicated to this, so I am going in blind. If anyone knows anything please let me know. From just looking at it, I see two small bolts to remove. I'm hoping that's basically it!

Is that a BEW?? Looks like you made it 8 months!

I have an ALH, had a coolant leak a few falls ago. It was the coolant flange O-Ring. I would just replace any O-rings in general area while coolant is drained. For myself did the coolant flange ring to head, ring between that and glow plug flange and CTS o-ring, and might as well replace CTS as well but your call. Ha I think at the time I cheaped on the latter and ended up having to do a month later lol. Ya I think it was two bolts but watch your torque when re-installing I had a weird issue with a bolt stripping but got lucky and was ok. The bolt itself stretched and broke, check my threads if your interested. This all being said not sure what you car has as it looks different than mine hence the BEW question. Good luck!!

 

[lardope]

Is that a BEW?? Looks like you made it 8 months!

I have an ALH, had a coolant leak a few falls ago. It was the coolant flange O-Ring. I would just replace any O-rings in general area while coolant is drained. For myself did the coolant flange ring to head, ring between that and glow plug flange and CTS o-ring, and might as well replace CTS as well but your call. Ha I think at the time I cheaped on the latter and ended up having to do a month later lol. Ya I think it was two bolts but watch your torque when re-installing I had a weird issue with a bolt stripping but got lucky and was ok. The bolt itself stretched and broke, check my threads if your interested. This all being said not sure what you car has as it looks different than mine hence the BEW question. Good luck!!

BEW, yes! I did. The leak is almost negligible, but looks like it caused some corrosion and dealing with it means that I can stop carrying a jug of coolant in my trunk, lol. What is the CTS?

 

[Nero Morg]

Coolant Temp Sensor

 

[WolfgangVW]

^ yes Coolant Temp Sensor!

 

[pkhoury]

I don't envy you. I lost my coolant this morning testing out a new tune revision, and I lost my coolant somehow from the lower radiator hose... and doing the same driving conditions, can't replicate it now!

 

[03TDICommuter]

I don't envy you. I lost my coolant this morning testing out a new tune revision, and I lost my coolant somehow from the lower radiator hose... and doing the same driving conditions, can't replicate it now!

Check the radiator tanks and where they're clamped to the core. Mysterious coolant leaks where I can't find where they came from, ended up being there on three different cars. It'll hold pressure until the conditions get stressful, leak, and then seal right back up.

 

[Genesis]

Yep.

From experience: Water pump seal fails, coolant leaks, ok, that's a timing belt job.
Do it, don't change the CTS O-ring because its not leaking (so why, right) and as soon as you're done guess what leaks next? Uh huh.

 

[03TDICommuter]

Yep.

From experience: Water pump seal fails, coolant leaks, ok, that's a timing belt job.
Do it, don't change the CTS O-ring because its not leaking (so why, right) and as soon as you're done guess what leaks next? Uh huh.

I did have a water pump that leaked only when the engine was cold. Once some pressure built up, it would seal up tight. Different car though.

 

[pkhoury]

Yep.

From experience: Water pump seal fails, coolant leaks, ok, that's a timing belt job.
Do it, don't change the CTS O-ring because its not leaking (so why, right) and as soon as you're done guess what leaks next? Uh huh.

My water pump seal better not fail! I just did my timing belt under 300 miles ago!

 

[Diesel Fumes]

I'm ordering parts to fix a coolant leak in this area (coolant temp sensor). What other parts should I order? I have the larger coolant flame oring, CTS o ring. Is there another one? This is an alh with no coolant glow plugs (5 speed swapped auto alh)

 

[fatmobile]

I'm not sure wrapping teflon tape around the plug heaters is a good idea.
Current is supposed to flow through them to ground.
If tape insulated all but a small contact area that area could get hot.

 

[Fahrvegnugen]

Good point, that area does get hot and those can catch on fire even unmodified. The plugs look like mine, all cracked apart. I'd just replace all that stuff if it was me. Then you don't have to redo the job because the part you didn't fix let go when its freezing outside on your way to work. Though I haven't fixed mine because it hasn't yet caused a disaster.