Hey all I have a 89 4Runner 3vze. For quite some time the radiator had a pin hole leak near the top. It was the original all metal radiator. The leak was so small I just topped it off every few weeks and it never took much and I was on my way. That started about 2 years ago. Well today I decided I'm gonna finally replace that radiator. Long story short. Radiator is in all nice and hooked up. Fire it up let it run to get air out of the system and it starts bubbling out after a minute or two. So I cap it, watch, waiting waiting, temp is climbing, climbing, kill it before it overheats. I can hear the air in the system and I can bleed it out with the nifty cap release. But every time I start it the air pressure builds back up. And the air does look kind of exhaust like. So is it possible that for the years I've been driving with a leaky hg pushing air into the cooling system it has just been bleeding out the hole as a "relief" type system letting me go merrily on my way? I have no other head gasket type symptoms. White exhaust, oil/coolant mix or vice versa. Thoughts?

 

Do a compression check. Curious to see what come from it

 

Also, at operating temp. The heater blows cold when idling. But blows hot at 1500+ rpm. Rear heater does not blow hot at all. Could is possibly be just the crappy aluminum core plastic tank radiator?

 

Air in the system. I've heard about that happening for years but never happened to me till now. Mod please delete thread. Happy Valentine's all

 

You should let them run longer than a couple of minutes. They do not completely purge until after the thermostat opens and you should have the climate control set to hot and fan off.

Also if you have a head gasket leak sometimes you can give it light revs while the cap is off. If it's leaking combustion gasses into the system sometimes it will blow coolant all over the place.