Hi just wondering if anybody has had similar problems or able to point me in the right direction car currently losing 450ml of coolant over roughly 5 weeks and 800 miles noticed white smoke coming from exhaust also but unsure if it was due to the weather but car is still doing it when engine is warm.

the car was pressure tested and the mechanic said it only dropped very slightly but he thought that was due to his cap not being the best of fit any help is appreciated

 

head gasket
Do a compression test as the white smoke indicates coolant is in combustion chamber and burning.
This will ruin your cats if run too long

 

I’ll book it in for a compression test thanks I’ve checked the oil and it looks good and the car doesn’t overheat strangely I started it just and gave it a few revs and no exhaust smoke

 

The only way to get coolant into the exhaust is a leaky intercooler, cracked block, cracked head, leaky headgasket, or a cracked turbo center section. If you exhaust all the cooling system tests, try a borescope looking to see the intercoolers are dry inside. Or checking before and after the turbo for burnt coolant, traces will give you clues on what's failed. ie coolant on the sparkplug means it's getting into the combustion chamber, so intercoler, headgasket, block and head are still suspect. Or you see coolant residue only after the turbo, well pretty safe guess on where it's coming from.

The compression test will only show if you have a really bad mechanical issue in a cylinder. Pulling the plugs and looking for pink coolant on them is just as telling. Typically if the engine is running smooth a compression test will show normal.

The followup test to that is a leakdown test which can show bubbles in the coolant bottle, but only if the head gasket is bad enough.

I"ve had the best luck diagnosing head gaskets with a tailpipe sniffer. Any hydrocarbons in the cooling system means cracked head, block or headgasket.

You can try the colour changing fluid that detects hydrocarbons but I find it's not sensitive enough. The tailpipe sniffer is always right and picked up a positive even when the fluid test showed negative.

There's also more to the story, I would always ask. How long has this been happening? Is the car tuned? low octane/questionable fuel? Overheat?
Any other issues in the past year? Blown headgaskets under normal circumstances just aren't common.

As for the concern that your mechanic had about his tool leaking that could be proved by spraying the adapter with soapy water and verifying the leak.

You need a solid answer when considering a headgasket or major repair where the engine is consuming coolant. You could also buy your own quality pressure tester and do your own, followed by leaving it on with it not pumped up and watching the pressure build as the engine warms up. If the pressure goes up too fast, you have an issue. If the pressure goes up instantly when you rev it you have a problem. Pressure changes are slow in a cooling system. The other advantage to this type of test is it can be done when the engjne is actually running and at operating temp. I would also check the intercooler side of things as well.

Good Luck

 

I only purchased the car at the beginning of October as a private sale, car is standard and always runs on 99 since I’ve had it no overheating car warms up at a steady pace and stays the same temperature I did start it again after and there was no smoke even when giving it a few revs but I know the coolant is leaking as it’s stained the driveway so hoping it’s not the head gasket and just a split pipe/ pierced radiator, but also thankyou for the information you provided

 

Coolant on the ground is the first place to start.
It would have been good if you mentioned that in your first post.

You need to find out where it's coming from and fix it first.

I have seen a situation where a small coolant leak causes an overheat and that causes the the head to warp and the headgasket to leak.

Because you have no history of the car anything is possible.

 

Agreed. Residue buildup on the overflow tank? Residue on any of the coolant lines, intercooler/hoses, rad / rad hoses?

 

Had a look around the engine bay today at local mechanic while waiting to get in at a Mercedes’ specialist can see dried coolant underneath the turbo he suspects water pump?

 

Where on the garage floor relative to the car? Under engine? Left or right side? Center? Below one or both exhaust tips?

 

unsure of where it is coming from to be exact from the drips on the floor as the driveway is on a slope but there was dried coolant just underneath the turbos when looking directly at them it was under and to the right