2007 CL63 Loss of coolant - potential Headbolt failure, advice needed

[Knightrider69]

Hi guys I've owned my cl63 for 3.5 years now and it's been great but the other day I got the dreaded low coolant warning on my dash. I couldn't see any visible leak or puddle under the car and I think my oil level has gone up (I last topped up the oil a few weeks ago to 3/4 on the dipstick and now it's reading well over the max mark - I also checked the coolant at the same time and the level was fine then). The car has only done approx 90 miles since I last checked the levels.

After reading all the posts on various forums from other unfortunate owners who had this problem I'm fearing the worst in that there is Headbolt failure and head gasket failure.

I called the AA out yesterday and the patrolman first did a pressure test on the cooling system (5psi) for about 10 minutes with the engine off and he said the system was holding pressure. He then started the engine and let it idle till the coolant got to over 80 degrees and the cooling system still held the pressure. After this he performed a head gasket failure test using a coloured liquid in a tube placed over the coolant expansion tank and it passed that test - he said if the head gasket had failed the coloured liquid would have changed colour which it didn't.

There is no visible sign of coolant contamination on the oil dipstick or under the oil cap. The engine runs fine and there was no white smoke from the exhaust. The AA patrolman said he thinks the car is fine but I'm not convinced as there is still the unexplained loss of coolant and oil level rising.

I was hoping for some advice on where to go from here, the AA said they will flatbed the car to a garage if I need to. If it is the head bolts I don't want to hydrolock the engine by driving it with 1 litre of coolant in the oil. Equally if it isn't the head bolts I don't want to spend thousands on an unnecessary repair.

Can anyone tell me what the best way will be to check and confirm if it is actually Headbolt failure - would the car have passed the pressure and head gasket test if it had Headbolt failure?

Thanks in advance for any advice

 

[Steve84N]

Turn the car on from cold with the coolant cap off. Only run it for a minute or two like that but look in inside the expansion tank for bubbles.

 

[Knightrider69]

Turn the car on from cold with the coolant cap off. Only run it for a minute or two like that but look in inside the expansion tank for bubbles.

Hi I tried that today and there were no bubbles. The AA also did the head gasket test using the liquid that detects engine gases and none were detected

 

[Knightrider69]

I decided to suck some oil out today through the dipstick to get the level down and see the condition of the oil. I took out approx 1200ml to get the level down to half way on the dipstick so my level was approx 700ml over the max level. When I last checked the oil level a few weeks ago the level was 7/10ths on the dipstick so the oil level has gone up the same amount as the coolant that was lost.

The oil that removed looked ok, it looked like normal dark used oil and didn't have any obvious signs of contamination (it wasn't milky or mayonnaisey. I then took about 100ml of the oil that I had removed and mixed 30/40ml of coolant with it. I stirred it with a screwdriver and gave it a good shake and the coolant seems to have blended in with the oil - is that normal, I always thought oil and coolant don't blend and they change to a mayo type substance? The only thing I could say was the oil looked like it had thinned down a bit but apart from that it looked like normal used oil?

Is there anyone on this forum who has had headbolt/head gasket failure on their m156 Amg car before - I could really use some advice and info from anyone who has been through this?

 

[Steve84N]

Hmm, well it is difficult to get a consistent oil reading on the M156 in my experience. Therefore, I'd suggest it's possible your oil level hasn't actually risen.

It's not unheard of to have a coolant leak, possibly something simple like a crack in the expansion tank.

I'm no expert but you could be lucky and these two 'events' are an unfortunate coincidence. The coolant could have been slowly leaking for a long time until it finally tripped the low fluid warning. Something like a tiny crack in the expansion tank that only weeps when hot or a weak valve on the coolant cap.

What about sampling the coolant to see if it's dirty with oil?

 

[Will]

Head gaskets can leak and fail in different ways - you can have a leak from the combustion chambers (bores) into/out of the coolant passages, likewise from the oil ways into either of the above, and sometimes a leak externally.

Oil pressure is higher than coolant pressure. So if you had a leak from the oil side into the coolant you’d usually find oil in the coolant, but sometimes the pressurised coolant can enter the oilways when the engine is shut down.

If your oil level has risen, and the coolant has dropped by the same amount you have probably found your problem. It’s time to take a sample of the engine oil and have it checked for Glycol but that would explain why the performance hasn’t suffered as the combustion chamber seal may not be affected in this instance, you won’t see any white smoke or get combustion gases in the header tank etc. Having said that, with 500+bhp and eight cylinders you probably wouldn’t notice a slight running issue at the very beginning!

 

[Steve84N]

I believe the failure mode for the head bolts is often for the head to shear off so try and gain access to view them and look for any broken heads?

 

[E55BOF]

If the coolant stays blended in with the oil, that is not normal; it should separate out, with the the oil on top and the coolant beneath, fairly quickly. If you take measurements again with the same result, pound to a penny Will is right, and you have a head gasket leak between an oilway and a water passage. It doesn't necessarily follow that you have a head bolt problem, though. A glycol test of the engine oil is the first step to take.

 

[Knightrider69]

I believe the failure mode for the head bolts is often for the head to shear off so try and gain access to view them and look for any broken heads?

Wouldn't that mean pretty much taking the engine apart to get to see the head bolts? That's way past my skill level.

Is it possible for the head bolts to leak coolant but the head gasket to stay intact? The question is whether I can get way with just replacing the head bolts without taking the heads off and having a 2-3 times bigger bill? If the head gasket had been breached surely the engine would have failed the head gasket test, or is there some way it might Have passed on this engine?

 

[Steve84N]

If you have got a leak it's too late to replace head bolts in situ. Best get a glycol test for starters as others stated.

 

[Knightrider69]

If the coolant stays blended in with the oil, that is not normal; it should separate out, with the the oil on top and the coolant beneath, fairly quickly. If you take measurements again with the same result, pound to a penny Will is right, and you have a head gasket leak between an oilway and a water passage. It doesn't necessarily follow that you have a head bolt problem, though. A glycol test of the engine oil is the first step to take.

Hi thanks for your message, I mixed the coolant and oil and have left them in the container overnight in the garage. I will check tomorrow to see if they have separated but they had mixed in completely within a few stirs of the screwdriver.

what's a glycol test, I've got the oil that I pulled out in a container so yes if there is some way of testing to see if there is coolant in there that makes sense

 

[Will]

Glycol is present in antifreeze (aka coolant), you can check for it’s presence (or lack of) in the oil sample that you have. It would confirm your suspicions if you found coolant had got into your engine oil, and explain the coolant loss and the engine oil rising up.

 

[Steve84N]

Something like this where you send off your oil for analysis:

https://onlineservices.sgs.com/uk/engine-oil-testing-kit-all-inclusive/OGOCEO?gclid=EAIaIQobChMImq23vriR6gIVFomyCh0pKwsYEAAYASAAEgKA1PD_BwE

 

[Knightrider69]

Glycol is present in antifreeze (aka coolant), you can check for it’s presence (or lack of) in the oil sample that you have. It would confirm your suspicions if you found coolant had got into your engine oil, and explain the coolant loss and the engine oil rising up.

Hi thanks for your reply, I did a quick eBay search for glycol testers and it's coming up with the kit where you suck coolant into the tube and wait to see how many of the coloured disks rise up - is that what you're saying I need to test to oil with?

I have one of those in my garage so if it's that I can try it

 

[Steve84N]

This one does glycol under the Bronze package for £30.

Car Engine Oil Analysis | Best Oil Testing Lab UK | The Oil Lab

Engine Oil Analysis can identify the four biggest engine killers before it’s too late! Routine testing can tell you where they come from and what they can do to your equipment.

www.theoillab.co.uk

The kit you have won't do this.

 

[Will]

If the head gasket had been breached surely the engine would have failed the head gasket test, or is there some way it might Have passed on this engine?

The AA guy was probably looking for hydrocarbons in the coolant to show the head gasket could have failed between the coolant passages and the bores. If it is just seeping a little coolant into the oil, that wouldn’t show up on that test.

Likewise 5psi may not be enough for leakage to show either. When hot and pressurised it’s more like 1 bar IIRC.

It sounds like you’ve caught this early, whatever the problem turns out to be, as it’s only lost a few hundred millilitres of coolant in 90 miles of driving.

 

[Knightrider69]

Hi tha

This one does glycol under the Bronze package for £30.

Car Engine Oil Analysis | Best Oil Testing Lab UK | The Oil Lab

Engine Oil Analysis can identify the four biggest engine killers before it’s too late! Routine testing can tell you where they come from and what they can do to your equipment.

www.theoillab.co.uk

The kit you have won't do this.

thanks for the link. I'm thinking to save time and get the same result I might drive the car for 10-20 miles and see if my oil level goes up again and my coolant level drops down again. I've sucked enough out so it's half way on the dipstick so that would be a faster way of finding out?

I keep reading about the danger of hydro locking the engine - can anyone explain how hydro locking happens - is it when the coolant leaks so much into the Engine oil that the sump level goes up so high it ruins the engine? Or is it the coolant leaking into the combustion chamber of the engine - if that was happening now would I not be getting misfiring and white smoke from the exhaust?

 

[Will]

Hi thanks for your reply, I did a quick eBay search for glycol testers and it's coming up with the kit where you suck coolant into the tube and wait to see how many of the coloured disks rise up - is that what you're saying I need to test to oil with?

I have one of those in my garage so if it's that I can try it

That kit you have is for checking the strength of the anti-freeze in the coolant system, no good for an oil analysis glycol check.

For £29.99 that link in Steve’s post above would do it. Maybe cheaper options out there but hassle free and would confirm what you think is happening!

 

[Will]

I keep reading about the danger of hydro locking the engine - can anyone explain how hydro locking happens - is it when the coolant leaks so much into the Engine oil that the sump level goes up so high it ruins the engine? Or is it the coolant leaking into the combustion chamber of the engine - if that was happening now would I not be getting misfiring and white smoke from the exhaust?

Hydro-locking usually means fluid has got into the combustion chambers/bores, and when the piston comes up to TDC there’s nowhere for that fluid to go.

Not a great deal of ‘squish’ room so even a cupful of coolant could bend your con rods etc or worse.

 

[Knightrider69]

The AA guy was probably looking for hydrocarbons in the coolant to show the head gasket could have failed between the coolant passages and the bores. If it is just seeping a little coolant into the oil, that wouldn’t show up on that test.

Likewise 5psi may not be enough for leakage to show either. When hot and pressurised it’s more like 1 bar IIRC.

It sounds like you’ve caught this early, whatever the problem turns out to be, as it’s only lost a few hundred millilitres of coolant in 90 miles of driving.

Hi yes either way this has definitely been caught early which is one plus at least. having owned this car for a few years I was fully aware of the risks of low coolant messages - it's approx 1 litre of coolant lost and 90 miles with it mixed in the oil