Coolant Loss

[Alan_525i]

I posted about this at the beginning of fall and still haven't found a solution. I find the expansion tank empty after every 80-100 miles of driving. It's at my mechanics for the second time for this problem. There are no visible leaks and the system holds pressure. There is no white smoke at startup from the exaust, no driveability problems. Heater core was replaced at 70K (108K now). Where is my coolant going?

UPDATE:

Talked to my mechanic today. Blown headgasket. So, what things should i do to her while shes apart? Looking for both preventative maint. items and a little more power. M20 motor btw.

[kngpen]

I also have this same exact problem. Tested with good results (no leaks or anything) My radiator was replaced at about 95k miles and its had the slow loss ever since. I just fill it up with water whenever it is thirsty

[George Davis]

I suggest a cylinder leak-down test. Coolant disappeared from my chevy truck in much the same way. No smoke, no driveability problems, no leaks. It was a head gasket leak, allowed coolant to be sucked into one cylinder and blown out.

[chamilun]

if you are losing the coolant, but only the amount that would normally be in the expansion tank, the problem is your expansion tank.

whats happening is when the system builds pressure/heat, the small impossible to see cracks will leak. cold pressure test will NOT identify these leaks. if your expansion tank is older, buy one (around $50) and replace.

[Alan_525i]

bump

[Tiger]

Pressure test is the only definitive way to do the diagnosis.