Took her out for a spin yesterday and the computer put the car into limp mode (if there is such a thing) Was driving, sudden loss of power, all gauges looked good, except check engine light was on. Pulled over, turned off engine, looked for obvious things and noticed coolant boiling and filling up reservoir past the full line. turned keys to check temp gauge and it showed very hot. well over 220. weird, wasn't doing this while driving.

anyway, got rebuilt water pump, new thermostat, both fans work great, belt looks tight (so in theory, it should not be any of those things). Only think I can think of that I have done is I recently did a coolant drain and refill and may have overfilled it with a (50/50 mix). But if I did, it wasn't by a huge amount. nothing boiled over in to the engine compartment.

Anyway, had car flat bedded home, by that time it was cool, so I restarted it, drove it into garage (it acted like nothing ever happened) grabbed a few beers and said I'll worry about it later, it was hot and I was tired. so here I am worrying about it now. I need to get back to the car and make certain my fans are still working, but other than that.....

Is it possible to over fill your coolant and have this occur? or some sort of vapor lock going on inside water jackets?

 

If you drained all the coolant you need to bleed the system of air when you refill it. Trapped air pockets in the engine can definitely cause overheating.

You need to idle the engine with the cap off the radiator. Let it get up to temperature and ensure the thermostat opened by feeling the upper radiator hose. Let it run like that for 5-10 min or so after the last air bubble is seen burping up from the radiator cap opening. That should ensure all air is bled out.

Replace the cap and should be good after that. Should also ensure your overall mix is as close to 50/50 as possible.

 

Similar thing happened to me a couple weeks ago. Over-pressured the cap and coolant filled up and overflowed the bottle.

Blown HG's in my case. 5 cylinders blown and between both pairs of middle cylinders.

GD

 

Thanks for your responses Guys. Never purposely bled the coolant system before, maybe just been getting lucky, as I do let it run to make sure it is full, before putting radiator cap back on. which I more or less did this time as well. but never really wait for it to get up to temp before putting cap on. it always seems to settle and I check it the next few days and keep adding coolant until its full.

GD - sorry to hear about the blown gaskets, that aint no fun.

 

Another method for filling with no air pockets that works well is to fill from the upper radiator hose and essentially fill the system backwards. With a thermostat in this is much harder but you could remove it and fill from there until coolant comes out the upper radiator hose. Works extremely well use this method in dirt track cars all the time.

 

It's OK. It's a learning experience. And an upgrade opportunity. AFR heads are on order and I'll be using their recommended head gasket which is a bit thicker this time around.

Definitely make sure you have all the air out before you jump to the head gasket conclusion though.

GD