2006 Mercedes GL420 Coolant Leak

[v1k_10]

Hi all,

I bought a 2006 plate GL420 last year and on the way home a coolant warning came up on the dashboard.

I thought it was due to the car not having been driven much so topped it up again and thought that'd be the end of it. But it keeps happening.

It's been to various garages, had a new header tank fitted, 2 new header tank caps, a new water pump as well as going back to the dealer who I bought it from to have the attached part changed - what is this and where does it sit?

It came back but in the same way as before, the top up coolant light came on again on the way home. I was told that as the engine has run, this was expected, so I topped it up again.

The dealer I bought it from is washing his hands of the whole thing and has refused t help any further.

Unfortunately, it keeps happening though. If I drive a few miles, the top up coolant light comes on?

There are no visible water leaks, 4 garages have pressure tested it and they have all said that there is no problem with this.

Mercedes diagnosed a faulty engine and said it needed a new one.

From my own findings;

1. It happens when the car reaches 80C.

2. The car doesn't over heat though, the temperature of the engine stays between 80C - 90C.

3. I've checked and the fan seems to work - the one at the front of the engine bay, used to cool the radiator, although I can't see if any of the blades are broken as there is very little space.

4. The water seems to be leaking from the outlet on the header tank.

Has anyone seen this before and could anyone please help?

 

[joderest]

Ok, need a bit more info, Mercedes have said needs a new engine, did they say why ?, Is it some sort of internal water path failure.
How many miles has engine done?
Saying the dealer has washed his hands of it, as long as you reported the issue in first three months of ownership and have that logged, he cannot, he has to make the car fit for purpose. You may have to go via small claims to make a claim.
Have you tried a Mercedes Independant in your area to see what they make of it.
One last thing, is it using water, do you have to top it up, if not could be a sensor issue

 

[v1k_10]

Hi again - thanks for that. To be honest, I'm in no way mechanical at all and so will try my best to answer as much as possible.

its done 130,000 Miles, dealer has said that he is putting his company through liquidation and to be honest, I'm not holding my breath with getting him to fix it in any way.

When driving it for approx 10mins, it heats to approx 80C. At this point the top up coolant light comes on. on parking up, the coolant level has dropped in the header tank. Once cooled down, on opening the header tank cap, the level is lower than it should be and it then needs to be topped up again.

The area around the header tank is sometimes also 'damp' after driving the car - as if coolant has come out of the header tank and fallen around that area.

 

[joderest]

ok, but you say a Mercedes dealer has said needs a new engine, did they explain why ?, from what you are saying it sounds like a pressure issue, forcing water out of header tank.
130,000 is not that great amount of miles. you need someone to tell you what is going on.
out of interest, does the exhaust show a lot of steam ?

I am sure someone with greater knowledge than me will be along soon

 

[v1k_10]

Hi, Thanks for the reply, to be honest, MB didn't really explain very much. They said that it'd be easier and cheaper to replace the engine than to fix anything on it.

No steam coming from the exhaust.

 

[joderest]

you need to find and use the service of a local Mercedes independent garage, just ask them to find out what is wrong, and give them all the information you have. The Mercedes reply is typical of people who do not fix but replace.

 

[joderest]

Also perhaps putting it on STAR to see what comes up when light on.

 

[v1k_10]

STAR? Is that the diagnosis machine? It's been on that, just shows low collant level, not where it's been lost or how?

 

[joderest]

ok, and this is just an educated guess.
You say engine is fine until it hits about 80 on temp gauge, this would be the point of the thermostat opening, hence water circulating round engine, if the engine is somehow pressurising the system, it would blow back out the coolant tank. in this case i would suspect a head gasket failure of a crack somewhere in the head allowing compressed air into the system. You could take it to a garage and ask for a sniff test on the coolant, this would establish if there are combustion gasses in the water pointing to a failure. This should be a fairly inexpensive test. I know you can by kits and do it yourself, think they are called "doctor head gasket".
I cannot suggest anything else. If it is the head or gasket, its a repair job not a new engine.

 

[v1k_10]

Thanks for that, I'll deffo give it a go. As I understand it a Head Gasket change is a big job and will be pricey but in all honesty it'll be cheaper than buying a new car and so i dont mind it. Just as long as someone can diagnose it.

As it stands, it's been to 4 garages and none have managed to diagnose it correctly as yet.

Thanks again.

 

[v1k_10]

Sorry - If it is a faulty head gasket, would something like K Seal fix that or is it not really worth using that?

 

[LostKiwi]

Sorry - If it is a faulty head gasket, would something like K Seal fix that or is it not really worth using that?

Do not use chemical sealers.
At best they are a get you home solution. At worst they will create more issues with heater matrix blockages and do nothing to fix the problem.

A quick test for a pressurising system is to squeeze the top hose with the engine running. If it's rock hard it's pressurised.

Another test is to leave off the coolant cap.
If water pushes out it's pressurising.

Finally if it's pressurising it's not uncommon for the heater to stop blowing hot air.

 

[v1k_10]

Many thanks, when you say "a pressuring system" is that what it should or should not be doing?

The heater was blowing cold air just before it went back to the dealer to get fixed by his garage. They apparently replaced the pictured part above but this didn't help. It now blows hot air however.

Not sure if this means anything but when the car has been left standing and the header tank cap is opened, it seems to "suck" air back into the header tank. The coolant in the header tank "bubbles" if if it is cold. Is this normal?

 

[Crispian]

Just an idea.

Have you noticed any damp inside the car at all,carpets wet or Windows getting misted up?

Faulty heater matrix?

 

[v1k_10]

No wet carpets etc, 1 of the mechanics asked me that before too and so have kept an eye out for it.

 

[Crispian]

One other thing I'd do is leave it ticking over and keep an eye open for obvious drops under the car or in engine bay.

Had a classic that did this,had the heads off and all sorts trying to find it.

Turned out to be a weeping radiator core that wasn't evident until the thermostat opened up.

Good luck with it.

 

[v1k_10]

The drops always come from below the header tank area. On opening the bonnet, the area around the header tank is damp..... all other areas are bone dry.

I had the clips around the header tank replaced and that helped for a little while (in that it took the car 20mins to lose coolant rather than 5 - 10mins) but has since gone back to losing coolant within 5-10mins again.

 

[Crispian]

A small split in one of the hoses that isn't evident until warm?

 

[v1k_10]

nope, hoses have been checked by the garages and by myself too - bone dry.

 

[EXMERCTECH]

Sorry - If it is a faulty head gasket, would something like K Seal fix that or is it not really worth using that?

K Seal would if it worked would only be a temporary fix.
It could block the heater matrix causing ever more issues,

That part looks like it goes In between the inlet manifold's.

Get a dry cloth make a hole in the middle.
Place it over the header tank
Put the cap back on and run the engine.
If the cloth gets wet it pressurising the systen
Pointing towards possible head gasket.
Has the coolant ever been run very low,

Depends what the diagnosis from the garage was.

Shouldn't be any air/bubbles in the system.
You could try vacuuming the coolant system down to remove and coolant and air.
Then if this holds vacumn then refilled the system.

Specialists equipment not every garage has this.