Coolant!

[b16mak]

Hey guys

I wonder if you can help me, I have had this problem for about 2 years now but it seems to getting worse over the last few weeks.

I took my car for a cam belt change and water pump change at the VW Dealer and since then I remember the same day it flashed saying it needed me to top up the coolant. Called them up and they said it's probe air in the system and should sort itself out. Happened again 2 they said to up with a little water. Happened again a few months later they did a pressure test for me- all OK. Happened again a few months later- they did a overnight test and was OK no leaking. They changed one or two pipes which had slight kinks but they didn't think that would be causing the leaking. No obvious leaks or anything....But they just changed one or two little parts no big job done. Also took it to a guy I know in Kwik Fit who just could see no leaking either.

I have been told it could be the head gasket on its way out ??? I really hope not as I haven't had any problems with my car since I have had it 6 years now. Its a 2007 Golf Match 1.9 TDI with 98k and no issues ever!!

Every time I open the coolant it lets out air, the level of coolant goes above the max when I remove the cap, but when the cap is on it drops below the min a little. I topped it up on Thursday with a bit of water and done about 150 miles since then and its now just flashed again!!

Any help much appreciated!

Thanks!

[xjay1337]

The system is under pressure.

So opening the cap when it's hot is not only dangerous but it would cause the water inside the expansion bottle to expand. If you are finding that you get hissing when the engine is cold when you remove the expansion bottle cap then you have a problem and the system is not pressuring and depressuing properly. It is a self bleeding system so you wouldn't need to do any special processes normally.

The coolant level needs to be set when the car is completely cold. If it's dropping it is leaking somewhere. A failed head gasket is very rare on the 1.9 TDI engines and if you were having a headgasket problem your oil would be like a creamy mayonnaise and/or you would have oil in your coolant, or blue/white smoke from the exhaust on a regular basis when driving. 

[b16mak]

Hi

Thanks so much for the reply. I am glad you don't think its the Head gasket, I havent seen any oil in the coolant, it is very clear and clean pink.

Can you tell me what I should do to check what it is, as a few people have looked at it and they see no leak, no pressure loss anywhere on a pressure check and overnight pressure check at VW.

Thanks!

[MJ]

Sounds like theres an internal coolant leak within the engine. Usually water jacket to cylinder bore. Or possibly a distorted head leaking coolant into the exhaust track.

The behaviour of you coolant bottle is perfectly normal, these systems can and do hold pressure for some time, even when they cool down.

When the coolant starts going missing on 1.9 tdi pd engines it only tends to be one of a few things:

1.Head gasket (changed a handful so it does happen)
2.Cracked head (as above)
3.Exhaust gas cooler (again refer to point 1.)

You never get water to oil contamination on these engines so mayo on the oil cap won't occur and oil in the water is usually a failed oil cooler as oppose to the gasket.

[xjay1337]

Is there the seal on the underside of the coolant cap?

Have you checked around the water pump for leaks? Where it mounts to the block... If the level is being set correctly and it's not burning it internally then it must be leaking somewhere or evaporating out of the coolant cap.

I've never come across a cracked head on a 1.9 TDI! 

I very much doubt it's any of those things, if the problem only started following a waterpump change, then it would be reasonable to assume it's something to do with that.

[MJ]

Replaced 2 heads on 1.9s; one on a BKC and a BLS over the years. Both cracked in the exhaust ports. And done loads on the rev A and Bs fitted to the BKDs.

There is a rubber seal on the coolant cap.

If it started when the pump was changed I'd say it could be leaking from its seal, behind the timing cover but they usually leave a crusty red residue when it dries up on the crank cover/sump.

[xjay1337]

The question about the seal was aimed towards OP. If it was missing or fell out somehow following the coolant change then that could explain where the water is going, evaporating away.

Not doubting you of course but genuinely that is the first time I've heard of that happening on a 1.9 engine at all.

If the coolant is leaking slowly over a few weeks, and only really leaking when hot due to expansion of components then there's a good chance it would either evaporate fairly trace-free or blend in to the rest of the gunk that would naturally be an engine.

[MJ]

Truth be told I never thought I'd see one crack, same with the head gaskets. I always thought these PD lumps were bullet proof but skoda went and ruined that rep with the late ASZs in the Fabia VRS that suffered with problematic head gaskets then VW AG introduced the BXE and BLS engines that are just a pile of crap - rep tainted.

[b16mak]

Hi

Thanks for the help guys. As You can probe tell I have no idea when it comes to cars :( 

I came to turn the car on again this morning, flashed coolant low. Checked the level it was the lowest ever, right at the bottom, so topped up with water to the max line (no longer flashing coolant low). Drove about less than 10 miles all together today and looked again just now and the coolant level is very high up, the tank is 3/4 full. Also, when I came to unscrew the blue lid, there was a lot of air coming out. It seems the fluid isn't leaking, there seems to continually be air in the system playing around with the coolant level? I dunno!

There is no seal as far as I could see, I took a pic of the cap can upload this for you if it helps?
Thanks Guys!

Mak

[th3_f15t]

Future safety tip, don't take your coolant cap off when the engine is hot! That "escaping air" is very high pressure steam, which is well over the 100 degree Celsius boiling point of water, as when a liquid is under greater pressure it boils at a much higher temperature. If that makes contact with your skin, you'll literally melt your hand.

As has been said, if it's a slow leek over a few weeks then traces of it being left are going to be slight, if any. I would probably go back to the dealer that fitted the water pump, explain that you're not happy and you suspect the water pump has been fitted incorrectly and see if they'll look at it or replace it again.

[xjay1337]

Hi

Thanks for the help guys. As You can probe tell I have no idea when it comes to cars :( 

I came to turn the car on again this morning, flashed coolant low. Checked the level it was the lowest ever, right at the bottom, so topped up with water to the max line (no longer flashing coolant low). Drove about less than 10 miles all together today and looked again just now and the coolant level is very high up, the tank is 3/4 full. Also, when I came to unscrew the blue lid, there was a lot of air coming out. It seems the fluid isn't leaking, there seems to continually be air in the system playing around with the coolant level? I dunno!

There is no seal as far as I could see, I took a pic of the cap can upload this for you if it helps?
Thanks Guys!

Mak

If you unscrew the coolant cap there is the threaded section around the outside and then around the center is a ring there should be a rubber seal on this ring as it seals around the radiator cap.

As mentioned before... you should not unscrew the coolant cap while it was hot. There should be no pressure if you unscrew the cap when cold.

[MJ]

It's not necessarily a bad thing if there's still pressure there when you open the cap when it's cold. It just means that A. The cap is holding pressure and B. That pressure is not exceeding the safe level of the cooling system.

[b16mak]

  Ouch! I have been unscrewing the cap when the engine is hot many times since this problem first began a couple of years ago. Luckily I still have my hands and face! 

I just checked this morning, engine cold, no air pressure when I unscrewed the cap.

It was a while ago, would VW really change that water pump now?

[xjay1337]

It's not necessarily a bad thing if there's still pressure there when you open the cap when it's cold. It just means that A. The cap is holding pressure and B. That pressure is not exceeding the safe level of the cooling system.

There should be no pressure when cold.

Did mention specifically not opening the cap when its hot. 

There is a 2 year parts and labour warranty from VW so if its within that timespan you're within your rights to go back and enquire.

[Shaw]

Coolant in a GTi (unless the engine has problems) is very rarely above 100'c. This doesn't mean it's safe to unscrew the coolant cap on a hot engine though, just because there's no super heated steam doesn't mean you can't burn yourself.

The system should pressurise as it gets hot, but should return to atmospheric pressure once the engine has cooled.

The only way you would see any considerable amount of pressure in the cooling system on a cold engine is if you have a leak between the combustion chamber and the water galleries.


I've head stories in the past of faulty coolant caps where the internal pressure release system is faulty, causing them to vent steam continuously. Over a period of time this would lose coolant.


Edit: have you had a sniff test done?


Edit2: another point to make. The lack of creamy oil doesn't really mean your HG isn't blown. A HG can fail in many ways, a small leak between a cylinder and water gallery will pressurise the cooling system without getting coolant back the other way.