My 03 MCS is losing coolant. I have no leaks under the car and replaced the Coolant tank to no avail. Coolant is still escaping somewhere, but I have normal power and no smoke or moisture out the tail pipes. My oil looks fine and as long as I keep putting in coolant it doesn't overheat. I'm at a loss as to where this stuff is going! I cleaned the engine compartment and floor under the car and filled her with coolant. When I came out the next morning, there was no fluid in the reservoir and no leaks or stains to be found. It feels like a Head Gasket but I'm seeing none of the usual symptoms...

Any and all advise welcome

 

Thermostat gasket....the coolant blows back, so no drip....
Very common....
Or even the radiator on a car of that age...they seem to go around 10 years or so...

 

... wait a minute...
You cleaned the engine and floor, filled the reservoir left the car overnight (without running it?) and the coolant was gone?!?

WTF?

No drips or stains?

What are the chances you did some work recently and didn't bleed the coolant system fully/properly leading to massive air pockets (that's eating/using/replacing the fluid)?

 

If the coolant was low, and the tank was filled when warm, the coolant was likely sucked in as the coolant contracted.... The tank on a r53 is JUST an expansion tank...heck...if it was VERY LOW...it might have just flowed into the system and had a bit of self bleeding..not complete I bet....
Before jumping to a head gasket conclusion, there are a few things too look at....heck if it runs good...oil looks good, starts good...kinda doubt the headgasket is gone....just my take.

 

So after some deeper diving this car is getting real weird. The oil does look milky now that I've drained it to a pan. During teardown to get to the head gasket the cylinder 1 and 3 plugs were not completely installed and combustion gasses were escaping into the shroud that the spark plug sits in. I am running a compression test today at some point so those results should tell me more about whats going on with this thing. ALSO the water pump does have moisture around it so it will be replaced, but I am loosing more fluid then seems plausible from this leak point. Thanks of all the advice.

 

Just finished the compression test and all 4 cylinders are giving 150 kpa. That puts my mind slightly at ease that it may not be a gasket but still proves nothing in the way of a crack... the head and block were both cold.

 

I'm very curious to see what you find. Although I have an R56, I am having the same issue. No leaks or anything. Only symptom that I have that something is REALLY wrong is once the car reaches operating temp, after a decent drive if I get stuck in traffic or even at a light, I lose power and the 1/2 engine amber light pops up. Shut the car off and turn it back on and then all is well. My coolant level is the only thing that is giving me a headache at the moment, so I'm thinking the two are tied in together.

 

Instead of a compression test, try a leak down test. That will tell you A LOT more about whats going on with your engine / head than a compression test.

When you do the leak down test, 30% loss is industry standard "acceptable" on our cars though, anything over 7-10% I would find out where its going.

Good luck!

 

Does your oil level fluctuate?
Do you have heat in the car?

 

So I decided to bite the bullet and replace the head gasket. I pulled the dip and found milky oil so it seemed like the best option. During teardown I found pitting on my cam and the local machine shop recommends I replace it. Where can I find a plain-Jane STOCK cam? Everything I can find is performance street cams that I don't need the headache of.

As for the Headgasket swap - The head has been vacuum and pressure tested, valve seals replaced and resurfaced. I have bought a full gasket kit for the head/oilpan/timing/dome cover as well as a new timing chain and tensioners. New tstat is going in as well. Is there anything else you guys would recommend I do while I have the car pulled apart? I'm debating on fresh injectors

 

Look at the oil cooler...
they sometimes fail allowing oil/coolant to mix....especially on cars that have not gotten regular coolant flushes...
sounds like the head gasket was OK from the tests...and no cracks found in the head right?

 

There was no crack in the head

 

Pictures of the camshaft? May not even be worth the money to replace.

 

thought this would be good place to post this picture, i am not sure what this sensor is but, it is leaking coolant on my 2012 justa. if any one can help it would be greatly appreciated.<br/>