Help - 1.5 L Coolant problem

97 Mirage 1.5 L w/150K mi. Had the valves gorund, new seals, head gasket, timing belt, etc. about 7 mo's ago. It wasn't loosing coolant/no water in oil, so I did not have it checked for cracks or resurfaced. Also, reused old head bolts. Ran great for about 6 mo's. Recently the coolant sytem started acting up - heater doesn't get very warm, tempertaure gage shoots up then back down. Check coolant level - it was pretty low. Added water/antifreeze, seemed OK for about a week - then same thing - coolant low again. Changed oil - no water in oil, no water/atifreeze in the drive way, none visible in the engine compartment. Removed radiator cap - notice air leak. Replaced cap - turned engine over a few times - removed radiator cap - air leaked out agian. Can a head gasket go bad and allow the engine to pump air into the coolant system, with out getting water in the oil or out the exhaust? I haven' noticed any white clouds coming from the tail pipe. Could it be the old head bolts?

I am going to make sure this post gets answered by one of our tech gurus here.

Check your radiator cap. How does it look? How old is it? Is the rubber seal still pliable? How about the spring?

I suggest that you check the heater core area. On most of the newer cars they dump coolant outside the vehicle not inside. Most have a tube that directs the flow below the vehicle so you may never see it if it is a slow leak.

You may also have another issue with the head gaskets since you utilized the old head bolts. Most of the newer cars have torque to yield bolts and once they have been used once they cannot be used again because they will not maintain proper torque and that may be why it ran well for 6 months and then started to go by the way side.

Mitsubishi headbolts are designed to be reusable. As long as they weren't stretched too far and were torqued to spec, that should not be your issue.

Radiator cap can defintely cause issues if the seal is worn. Fluid essentially "disappears" becasue the system is no longer sealed and it will evaporate. It also causes overheating because its not sealed properly.

I would try replacing the cap first. If it doesn't cure it, at least you are only out $7.

On that note though, it is possible to have a bad headgasket and not have leakage into the cylinders. Does the car run rough at all? Maybe try doing a compression test and post up the results.

You might also pull the spark plugs and see if one is cleaner than the others, or has a tint of the coolant color (not sure if it's orange, red, or green in your car). If you find one plug that appears really clean compared with the others, that cylinder is likely burning coolant. It may be in small enough quantities that you don't notice it out the exhaust. In this case you wouldn't necessarily see the coolant in the oil either. If you have access to a cooling system pressure tester, pressurize the system to the same pressure that the cap can support and see if the system holds pressure or gradually drops. If it gradually drops, there's a leak somewhere and you may be able to find it with the pressure still on the system. Carefully inspect all hoses and hose connections as well. If you can see the water pump, check the weep hole.

-Rod

Yes it is possible for coolant to leak into the combustion chamber without contaminating the oil. I'm with Shorod in getting a pressure tester and pressurizing the system. This would help you pinpoint the leak. I also agree with GTP Dad on reusing the head bolts being a mistake. Fel-Pro shows they are a washered torque-to-yeild bolt, and it isn't uncommon for TTY bolts to lose their tension and cause leaks when reused.

To those of you who replied, thanks - albeit too late. As this is my son’s primary mode of transportation to the local Jr. college, I needed to get it fixed quickly. After reading up on the head bolts and gaskets on AutoZone.com. (the Bolts are not reusable and the torque procedure is something out of the comic books), I convinced myself the best bet was to replace the head gasket and bolts. I did so over the weekend. Car runs good, heater works, no coolant issues and appears to have solved the problem – for now. I figured out why they named this car the “Mirage”, it just appears to be a car – it’s really a money pit.

I'm not finding any defininitive answer, but it appears that the headbolts are indeed TTY.

In my post I meant to add MOST to the beginning to say "Most Mitsubishi head bolts are reusable."

So before we can really help anymore you need to do some diagnosis with a pressure check, and/or a compression check.

EDIT: I started my post before your reply and got called away from the computer. Good luck on the car being fixed this time. :)