strange coolant loss..??

hi folks

Can anyone tell me what may cause a loss of coolant when there are no visible external leaks, and the cooling system holds pressure when tested??

It does show a P0302 code (misfire on cylinder 2). I pulled the plug and it looked fine, so this may be ignition related.

There seems to be no coolant contamination in the oil, and the LIM valleys look dry.

Maybe a faulty rad cap??

thanks for any help

Peter

Even if you pass a cooling system pressure and leak down test you could still have a LIM or head gasket issue. Also, no visible contamination in the engine oil or vice versa.

Sure you don't have any external leaks and any coolant coming out the overflow discharge hose at the plastic reservoir. Also, take note that the radiator cap is on the reservoir and not the radiator.

Also, be sure to post engine size and mileage.

my 3.4 00 alero did the exact same thing. i lost coolant, and couldnt find a leak anywhere. you should probably have the head gasket/ intake gasket checked. several aleros have blown that gasket, and thats what mine did. i lost coolant for weeks, and it didnt show in the oil or any visable leaks, then it just blew one day. there are recalls out saying that the gaskets that are put on them arent compatable with the dex-cool that is in them. let me know what you find out.

Thanks for the advice guys.

I have a feeling that it might be a LIM or head gasket, I just was surprised that the cooling system would hold pressure under those circumstances.

Is there a way to diagnose whether it is a head gasket or LIM? Are the symptoms different?

thanks

Peter

For headgaskets you could run a compression test. How is the engine temperature? In most cases the engine will overheat and coolant will run out the overflow.

On LIM gaskets you may not see it short of a teardown and visual inspection.

The temperature does seem to spike when the coolant level drops. Once the coolant is topped up, it seems fine. Good tip about the compression test, I can try that for the head gasket.

thanks!

Peter

lollll easy one .. all 3.4 does that, about each 120 000 kilometer(aprox) the intake gasket need to be changed oil and prestone mix up so that is why you loose a lil prestone and heat spike are cause ur air/fuel ratio is probably lean caused by the air intake gasket my alero did that as welll alero is all about Wheel bearing, Intake Gasket, Top plate ... that is the top 3 alero problem's lol anyway u should check it out Good Luck

Lucky for me..it turned out to just be a waterpump. It turns out there was a slight leak when it runs hot, and it was not visible unless using a mirror and flashlight. A sharp eyed (and honest) mechanic in a little town figured out my problem.

thanks to everyone for their advice

Peter