GenVibe - Community for Pontiac Vibe Enthusiasts

Hello All,

New member with an ongoing problem. My 2006 Vibe 5sp overheats within two city blocks of driving. However, it can idle, and even have a sustained rpm of 2000-2500 while parked, and never go beyond normal operating temp. I have replaced the thermostat and radiator cap. When it overheats, it appears that all the coolant blows back into the reservoir, and out the overflow tube. I have ZERO engine codes. I have heat while in the driveway, although it takes quite a while to warm up, and of course no heat at all when it overheats. Radiator does not appear to be blocked. I haven't been driving it to avoid further damage, but I, and everyone else who has looked at it am stumped! Wouldn't a bad head gasket cause overheating at idle? Wouldn't the water pump leak if it was bad? No hosed are being sucked flat, and I have done what I hope was a completely thorough job of bleeding air from the system. The car has 109k miles on it, and was purchased with a prior salvage title due to a collision with a deer. Front end was repaired, and I have the service records from when they rebuilt the valves and head at 108k. Please, any help would be so very much appreciated!

Does the fan work? It should come on when you turn the A/C on. It should also come on when the temp goes above a certain point.

Yes, cooling fan operates as it should. I forgot to mention that

First use this to test: https://www.amazon.com/UView-560000-Com ... B000NPDL76

If that passes then use one of these and do a pressure test on the system to see if it hold pressure over night: https://www.amazon.com/Mityvac-MV4560-R ... B003V9L05G or https://www.amazon.com/8milelake-Univer ... BT6VX3QTNQ


The above items should be available at most any good auto parts store, if not take your car to a good service garage that can do these tests on your car.

Other things to check: thermostat installed in the proper direction; radiator core rotted out - check that all fins in the radiator are tight and are all there. Fins need to be tight in the core tubes to conduct heat from the tubes, and if loose, the fins can close up as air starts to flow though the radiator blocking the air and keep the air from flowing though the radiator. Blockage to the hoses or water pump. If someone tried to fix the problem with some types of head gasket or block leak added to the radiator. Some of these leak block chemicals are not compatible with antifreeze and will form into balls in the cooling system, blocking coolant flow. I have seen golf ball sized hard gobs of this blocking the radiator hose to the water pump because some people are incapable of following or reading directions.

It is always bad trying to trouble shoot a problem after other hands have been in the mix so you have to leave the door wide open and any and all possibilities because you never know what people will do.

That sudden spike while driving is possibly from the head gasket. High rpm in neutral is not the same as under load. I agree with the tests noted above. A compression or cylinder leak-down test should be easy enough to do on this car, too.

And a handy tool for this kind of work is an infrared thermometer. I got one for under $20 and I use it for everything, even cooking. You can check individual tube temps in the radiator, and find flow problem in the system by reading delta T.

Consider that the exhaust might be restricted by a melted catalytic convertor or muffler crumbling internally. I lost an engine that way, got rear ended and damaged the muffler internal baffles, blocked off the flow and a few overheats later the head gasket gave up. You can test it by removing the upstream o2 sensor and attaching a pressure gauge to the hole.

I'm sure you did, but did you hook up a code reader to see if there is any pending codes that have not yet tripped the light?

I haven't hooked it up to a code reader, as I didn't have any codes to read. I will see about getting that done. I will get the pressure tests done within the next week, and will let you know what I discover. Thank you all for your help!