90 DOHC Coolant loss, no leaks, even with thermostat out.

[bwildered]

90 LX, 140K. Been loosing coolant for a few months now. Zero leaks. Adding water, so I'm now 100% water. Currently loosing a quart every 40 miles, one way to work. Took out the thermostat to do a flush before using a head gasket chemical (really not worth tearing into) and its still loosing coolant, and runs just as hot as with a thermostat. Still not 100% sure it's a head gasket. No white vapor exiting the exhaust, or drippage at the tailpipe. Compression test readings were 154, 147, 140, 147. Is that enough of a variance to assume the head gasket?

Thanks in advance for any beneficial input.

[1st Gen]

My 91 Protege LX has been loosing coolant for the last 100 thousand miles. Two different motors, three different radiators, and one rebuild, and it still happens. I keep an unopened jug of distilled water in the trunk just in case I have an over heating issue. That cause of the last rebuild was because it ran out of coolant and I was too in a hurry to stop. Warped the head
In my case, it's always been the radiator leaking. (I think) That's likely your problem too. If you have a stock radiator with the plastic top caps, look under the overflow hose that runs from the fill cap to the overflow bottle. I've had two OEM units crack under that hose. I have a duel core radiator now that has metal caps that has been doing much better. There is a pin hole in it though. I can see it when it warms up, and I can smell it.


Good luck, and post back what you come up with.

[bwildered]

Zero leaks. i.e., 40psi pumped into the cap, no drippages.

[SgtRauksauff]

maybe try a leakdown test? push air through a sparkplug hole, and see/listen for bubbles coming out the radiator. it might only happen when it's hot enough to leak, then it evaporates right away, leaving no trace. maybe some UV dye in the coolant and a blacklight, sort of what they do for AirCon leak testing?

good luck!