I just finished changing the radiator and took it for a spin. Everything was fine but then it was getting pretty hot so I took it back home. My neighbor took a look under my hood for any coolant leaks so he opened the radiator cap and hot radiator fluid sprayed up in the air.

He said that he is pretty sure the thermostat is not opening so fluid is not getting in the engine. He said to fill the radiator with water to the top and turn on the car. If water sprays again, then the thermostat is not opening and to get a new one.

Is he correct? If the thermostat is not opening and coolant is not getting to the engine, why would the coolant be super hot? Wouldn't it be cooler?

If this isn't the problem, what else could it be? There is no smoking and my car didn't lose any power.

 

Aren't you not supposed to open the radiator cap when its hot, because it will spray coolant?
There's that warning label on the cap

 

Do you mean your temperature gauge started to climb? Was the car moving at that time? Do your radiator fans kick in when you turn AC ON?

No, what you observed is actually normal - coolant normally is under some pressure which increases its boiling point and makes it 'overheated'. The moment you open the cap pressure falls and coolant literally boils up throughout the system as LvR recently pointed out here.

 

You probably had very little coolant in the block and heads and a lot of air. Engines that have the thermostat in the "cold side" like the Maxi can be a bit tricky to get the specified amount of coolant into the system when refilling the system. If there is no hot coolant contacting the thermostat, it can't open. There is a bleed screw in the engine coolant outlet pipe (the screw is at the top of the coolant control valve housing) that should be opened to release air when first running the engine after refilling the cooling system. A couple of radiator topups (let the engine cool before adding cold coolant) in between runs and bleeding the air out of the system (only coolant should eventually come out of the bleeder) may be required. The expansion tank should then be filled up to between the hot and cold marks to complete the job. Your neighbor, by the way, is very lucky that he didn't get scaulded.

 

Yes, the temperature gauge was going pretty high and on its way to overheating when I took it out on the freeway. When I accelerated, it got hotter so I had to drive at lower RPMs and get it home.

I went for a walk with my wife an hour later and there was no more coolant in the newly installed radiator and none in the reservoir which is strange because there wasn't any noticeable coolant spill. I filled the radiator with water to the top and turned on the car with the cap off. Every 10 seconds, a medium sized bubble would pop up. Is this hopefully the cooling system burping? Is there a bleed screw for all this somewhere?

Maybe I put the coolant in wrong. After getting the radiator in, I just filled it up and the reservoir up to the line, started the car, let it warm up, and then drive. Is it possible that the first set of coolant was in the engine?

It is strange because the car sounds normal, my oil isn't watered down and smell like coolant, no white smoke out the back, and there is no power loss at all. With no power loss, it can't be the head gasket, right?

Thanks for the help. I need to get this fixed immediately since my wife is pregnant and due in a few days. I can't afford to have my car blow up on the way to the hospital!

 

Oh crap. This morning I start the car and it sounds like water is running through so I get out and there is coolant resting on top of the upper intake manifold. Just want a confirmation that this is really bad, right?

 

You appear to now have a leaking hose such as a heater hose, TB coolant supply hose or block outlet hose. These are all basically connected to the engine coolant outlet pipe and/or routed close to it (on the driver's side of the engine, up high and somewhat buried). Fill up the rad right to the top, start the engine and start looking for the leak (don't forget to check for air/coolant at the bleeder). If the coolant is up on top of the upper intake I doubt that it's that bad. As I mentioned, refilling the coolant on these cars has to be done carefully to prevent overheating caused by not enough coolant in the system.

 

if the thermostat is stuck closed, the coolant in the radiator wouldn't get hot
if its stuck open, then your engine wouldn't overheat.

you need to get the air out
jack up the front of the car, open the radiator cap, then run the engine
let it warm up then keep the rpm at 2000 for a minute without overheating the engine
add coolant if the level goes down

 

You didn't put the coolant in wrong because there is no wrong way. The only thing you can do wrong is miss the opening and pour it on the ground.

What I believe in doing is filling the radiator then starting the car with the radiator cap off. As the engine warms and the thermostat opens you will see bubbles and the coolant level in the radiator go down. When that happens, add more water until the radiator is full again. Put the radiator cap on and fill the reservoir if needed. It works a little better if the front end of the car is higher than the rear. Check the reservoir for a few days, it would not be unusual to have to add more.

 

also have heater set to hot