Our of coolant regularly

[Riva811]

Hi I Had my radiator replaced by MB in January after it cracked. The car coolant goes low very often and it needs topping up every few weeks. I went back twice and they confirmed there is no leak. Wondering if the coolant ends up inside the engine

 

[Petrol Pete]

You would hope not , have you checked your oil level recently ? If it's rising that's where the coolant is going and will be disastrous for the engine . The cooling system pressure test is a straightforward procedure than any garage can do.

I find it odd - despite the evidence showing coolant loss - that an MB dealer is telling you all is OK

 

[Riva811]

You would hope not , have you checked your oil level recently ? If it's rising that's where the coolant is going and will be disastrous for the engine . The cooling system pressure test is a straightforward procedure than any garage can do.

I find it odd - despite the evidence showing coolant loss - that an MB dealer is telling you all is OK

Took it to MB Brentford and Chelsea and Brentford again after complaining to head office. MB Chelsea confirmed that they pressure tested it and there is no leak. Brentford wanted more cash to diagnose after I paid their diagnosis fee during the breakdown repair. They are so understaff that they almost refused to service the vehicle under the plan. Overall disappointed with Brentford, I questioned if they serviced it as they didn't even record the service on the car

 

[MJJ]

I had a very similar issue on a Peugeot recently. It turns out the coolant expansion tank cap had failed, and the pressure release valve contained within the cap was opening too early - letting coolant out of the top of the expansion tank. It would not do this when idling, only when the engine was under load so impossible to diagnose by sight.

What compounded the issue is that all coolant pressure tests I have seen involve removing this cap, and replacing with a screw on pressure fitting. Thus, you are removing the faulty item and the pressure test passes.

You could try wrapping a rag around the expansion tank cap, and see if it is soaked in coolant after a good drive. Alternatively, simply replace the cap with new as they are not expensive - may save another expensive garage visit.

Martin.

 

[Riva811]

I had a very similar issue on a Peugeot recently. It turns out the coolant expansion tank cap had failed, and the pressure release valve contained within the cap was opening too early - letting coolant out of the top of the expansion tank. It would not do this when idling, only when the engine was under load so impossible to diagnose by sight.

What compounded the issue is that all coolant pressure tests I have seen involve removing this cap, and replacing with a screw on pressure fitting. Thus, you are removing the faulty item and the pressure test passes.

You could try wrapping a rag around the expansion tank cap, and see if it is soaked in coolant after a good drive. Alternatively, simply replace the cap with new as they are not expensive - may save another expensive garage visit.

Martin.

Just had a look at the coolant tank, MB Brentford appear to have tighten it really really hard. Managed to open it and the tank is empty! If the coolant was coming out I am sure it would of ended up on the engine bay? I had a look at the engine oil, it is above the indicator and it appears to be quite clean. The case of the disappearing coolant - hopefully not overflowing the engine...

 

[Riva811]

Wondering if this is the problem

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Wouldnt the pressure test find this though?

 

[Petrol Pete]

Riva , I would be worried right now . You could try what MJJ has suggested first ^^^^^

 

[Petrol Pete]

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This is a M113 engine and I am not sure if it has the same/similar water pump set up as yours . but with this fault you end up with water in the sump as our German friend so eloquently explains.

Well I think that's what he's saying He has some good content and my German is improving by watching it (not) Fast forward button is your friend here

 

[Spider10]

I 2nd that it has to be going somewhere? Oil doesn't mix with water so that's pretty easy to check

 

[Spider10]

It might be an idea to do a headgasket check, it could off gone between 2 cylinders

 

[Riva811]

Called MB to pay to diagnose. The guy straight away said want to take it to Brentford? I said no they did a terrible job first time around. Since the coolant tank is empty they are sending road side assistance to take a look at it. If he cant figure it out I will take it over to Klasse, not paying premium price for sub-par customer service and engineering by MB.

 

[Riva811]

I 2nd that it has to be going somewhere? Oil doesn't mix with water so that's pretty easy to check

Me too, I might just put cooler in it and take it to webuyanycar and sell it for £12,000
If it was working perfectly I could get 14k privately but it seems like selling privately is lost cause

 

[Spider10]

I have a chemical kit which you replace the header tank cap with then run it up to temperature and if it turns green it has exhaust gases in the system

 

[Riva811]

I have a chemical kit which you replace the header tank cap with then run it up to temperature and if it turns green it has exhaust gases in the system

Sound interesting, link to buy?
Funny thing is the car performs like crazy acceleration-wise and no funny sounds. Besides "Top up Coolant See User's Manual" showing up on every startup and after a really good thrash.

 

[Spider10]

Yes I've had it where they run fine its annoying really ill sort the link now

 

[Spider10]

Here it is

Combustion Leak Tester Head Gasket Test kit Block Sniff Fluid PETROL DIESEL100ml | eBay

Works with PETROL/DIESEL/LPG engines (blue fluid for PETROL, red fluid for DIESEL). When combustion leak is present, a small amount of combustion gas goes into the cooling system which can be easily detected by this simple device.

www.ebay.co.uk

 

[Spider10]

Its abit different to mine but basically the same for next to no money

 

[markjay]

Coolant leak can be invisible, if the coolant leaks onto a hot surface (e.g. exhaust manifold).

But I would certainly start by replacing the pressure cap. Febi do OE caps for the fraction of the cost of the genuine ones.

Also, note that the cap has to be 'locked' in a certain way - there's a notch on the right hand side of the neck - and the image on top of the cap should be facing you straight when fully tightened. If you correctly lock the notch in place, it is not possible to 'overnighten' the cap.

 

[Riva811]

Coolant leak can be invisible, if the coolant leaks onto a hot surface (e.g. exhaust manifold).

But I would certainly start by replacing the pressure cap. Febi do OE caps for the fraction of the cost of the genuine ones.

Also, note that the cap has to be 'locked' in a certain way - there's a notch on the right hand side of the neck - and the image on top of the cap should be facing you straight when fully tightened. If you correctly lock the notch in place, it is not possible to 'overnighten' the cap.

On that's not how it looked like when I opened it. Sounds like mb Brentford tighten it the wrong way as well. Love having random monkeys working on the car at Mercedes

 

[MercedesDriver]

If the expansion tank cap is faulty there will be a coolant dried residue on the tank. My was faulty and changed it with MB genuine one. It was very cheap fix.