Hi All,

I'm new to the forums and I won't be around much longer as I am about to sell my 2002 Mini as I will be moving overseas next week to start grad school.

My Mini started overheating in stop and go traffic several months back and I realized that the coolant level was low and there was fluid dripping off the A/C compressor. I took it to the shop to have them change the water pump and the thermostat while they were at it.

When I got the car back, it kept overheating. I took it in and they changed the radiator cap (no charge). It started overheating again so I took it back and they changed a bleeder valve (no charge).

Luck me, it kept overheating... I've bled the system myself (all THREE bleeder valves, including the hidden one near the thermostat housing), and at higher engine temperatures (and/or higher RPMs?) air makes its way into the system. Fluid gets pushed up into the reservoir by the air (well above the MAX line), eventually creating an air lock causing the engine to overheat. If I bleed out the air, I can get the coolant level back down around the MIN line, so I know I'm not losing nearly as much fluid as is being pushed into the reservoir. Both the low and the high fans come on. I replaced the radiator cap again and nothing changed. I took it back to the mechanic and they tried (for the second time) to test if the air bubbling into the reservoir was exhaust (symptomatic of a bad head gasket), but again they didn't see the fluid level rise (beyond standard expansion/contraction of the fluid due to heating/cooling) or observe any air bubbling into the reservoir (again, no charge).

Is it a pretty safe bet that I have a bad head gasket? I don't have any other symptoms - spark plugs are dry (they maybe smell a bit of carbon), oil doesn't have antifreeze, and antifreeze doesn't have oil. Is it possible that it's just a hairline crack in a hose or junction somewhere in the system that is causing air to be sucked in as the fluid flows past (hopefully not a crack in the engine block)? Is there something else that I'm missing here? Could the thermostat housing be causing this without leaking fluid?

I'm selling the car in a few days and I know I could get ~$5,000 if it's not the head (103,000 miles), but I can probably only get ~$2,500 if it is the head. Is it worth it to take it to the dealer to have them diagnose it (more $$$ down the drain if it is the head)? Should I try something else in the meantime?

Thanks for your advice!

 

I suggest a cooling system leak down test. This is done by using a small pump that attaches to the radiator and you pump preassure into the system. Once charged, you search for leaks. This can include opening the oil filler cap and listening for air and even pulling spark plugs and check each cylinder.

From what you wrote, my guess would be head gasket... Test this with a standard compression test and cylinder leak down test.

Best of luck.

Motor on!

 

When hot, the cooling system is under pressure... So no "sucking air in"....
For it to have low coolant....It is leaking out...or going into the oil, or out the tailpipe....
I'd take it to an independent shop...have it looked at...
Might be a minor issue, like a $100 radiator, or could be your worst case.....