I have a 95 geo metro. Car runs good and has normal power. When car is idling it runs fine with no overheating or coolant being pushed out of the overflow. I was told to replace the water pump, thermostat, and radiator cap. I have replaced them and the problem still occurs. I do have a 50/50 mix coolant and no leaks at all. recently I have performed a compression test and found my middle cyl in 25 PSI low witch could be a blown head gasket allowing exhaust to be pushed into the radiator. I ordered a product called steel seal and followed their directions with no success. I called them back and they have sent me a second bottle to run with the spark plug out of the engine. i have ran the second bottle in my coolant and have not rechecked my compression to see if its still low. I did find my belt slipping and replaced it with no luck. the temp gauge on the dash does not show overheating but I can tell the engine does get hot only if I am driving it. if its idling it runs great with no issues. Just wondering what else could be my issue. coolant is flowing but I think I may have to replace my head gasket witch on this car does not seem to be a huge issue. A couple more things that I will be trying is making sure my radiator fins aren't bent over and restricting anything and make sure my cooling fan is spinning the right way. other then that HELP!!!!! HAHA.
This is almost surely a blown head gasket. A compression test might not even show it, especially if the leak only happens under the pressure of combustion (which is much higher than just the compression from the cylinder moving). You could get a block check kit (which works by pulling fumes from the radiator opening through pH test fluid to determine if there are combustion gasses in the coolant), but I would pretty much just assume this is a head gasket failure.
Fortunately, HG replacement is usually pretty easy on small 4-cylinder inline engines. The hardest part of doing it on my Civic was getting off the exhaust manifold. I've never worked with a Metro but I'd expect it's similar.
Thanks for the responce. I did run the steel seal with the 1 spark plugged removed for 1 hour. not only did it bring the compression back to that cyl but im not getting exhaust gasses in my coolant anymore. I recommend steel seal for any blow headgasket issues. not only do they stand behind their product IT WORKS!!!. also found the person i bought the car from put the cooling fan on a toggle switch and hooked it up backwards so it was pushing air forward witch was causing it to boil and push out the overflow. i wired it back so it pulled the air through the radiator tword the engine and it does not boil anymore. WOOOOHOOOOO. I hope this thread helps others out. GOOD LUCK!!!
I recommend always to overhaul the engine when something like this takes place and not just add sealant.
Doing so will give you another 200k miles.
The process of overhauling is not as difficult and you may think. you will need a table grinder with a wire brush if you wan to just clean of any valves and not replace them.
Pull the engine if possible and take to car wash and spray clean. If you have good cylinders just replace the rings and pistons. Replace the crank shaft bushings and all bearings.
You can get a overhaul kit at car parts dot com.