Mysterious coolant leak

[aps1231]

Back to the drawing board. The mechanic says he pressured tested the coolant system, let the engine run for 45' and didn't find any leak. He then replaced the thermostat, pressure cap and bleeder valve, but the car is still loosing coolant. Today, I just drove two miles and left a trail of coolant (~ one gallon) on the road. The temperature was perfectly normal. The coolant drips profusely from the bottom, next to the rear right axle. I checked the overflow plastic bottle and connections. There's a little bit of coolant there, but there's no way one gallon would have gone thru the cap.

The mechanic suspects a head gasket leak. Is there any way for the coolant to escape in that area, other than the pressure cap?

Again, your experience and advice would be welcome.

[aps1231]

Additional info. I started the engine with the expansion tank almost empty. In a couple of minutes, the level goes to the top and some coolant leaks thru the cap, while more coolant drips profusely from the bottom. Coolant temperature was about 185F.

[nola911]

Could it be overfilled? Mine definitely did that before I had over-heating problems. Im not totally familiar with the coolant systems, but I thought it had an overflow, or that the cap relieved pressure and fluid. I know I had a problem with water vs. coolant

I wish I could be more helpful, I just really don't know enough. Let me also recommend the forum at renntech for technical stuff.

[jjanari]

also, I would check your oil level to make sure you're not getting coolant in the oil, though I doubt that's what's happening from you description since you seem to see where all the coolant is going (on your floor!). (I also question the suspect head gasket diagnosis by your mech, but I'm certainly no mechanic). if it were my car, I would try and pinpoint the leak by getting the car up on ramps the next time it happens to see exactly where the coolant is coming from.

[aps1231]

Thank you for your replies.

1- The oil is clear like new (Just got the 60,000 miles service)
2- The coolant is definitely not overfilled. In fact, last night, I removed the cap, started the engine with a low coolant level (Bottom of the expansion tank), and then suddenly, the coolant went up and spilled profusely all over.

What's puzzling me is that it's intermittent. I drove the car 20 miles after replacing the thermostat, with no problems (Just lost two cups of collant). Then I got this problem again yesterday after driving two miles, and the temperature was a normal 185F. It looks like suddenly some gases escape into the coolant and push up the coolant out of the expansion tank.

[stephen wilson]

I hate to mention it, but, head gasket? You could try a compression or leak-down check. My Integra wouldn't "take water", and it ended up being the head gasket from being overheated.

[machone]

Any resolution to this? My '99 has the exact same symptoms, looking for any clues on what to try.

Thanks,
-Michael