97 3.1 overheats after sitting overnight

[Major Funbags]

Hey Y'all,
I have a 97 3.1 monte. 60k miles on it. I've replaced the following items. Head gaskets, Intake gaskets, t-stat (acdelco), radiator, water pump(acdelco). Backflushed cooling system, Bled air out of system. Here's my problem. I've done all this work in a heated garage. When I start the car in warm conditions. It heats up normally and stays that way. However, If I start it the next morning. (30/40 degrees out) It doesn't blow warm air out of heater and eventually the temp gauge will slowly climb to the red zone and overheat. At that time I'll bleed the air out at t-stat and re start it. It usually is ok after that. Sometimes the heater will start to blow cold and if I rev it up the guage will drop to normal and blow warm again. Does anybody have an idea why colder conditions the day after would cause this? How is air getting introduced into cooling system and stopping the flow of coolant?
Please, Please, Please help me. It only has 60k. Good car.

[maxwedge]

Sure sounds like trapped air, isn't there a second bleeder on that car?

[Major Funbags]

I believe it's trapped air as well. However, I bleed both valves and get a steady stream on both. The next day, it over heats and I'm purging air on the side of the road. I pressure tested the system to 16lbs. It takes 5 minutes to drop to 13lbs. It's making me cuckoo.

[aleekat]

Originally Posted by Major Funbags

I believe it's trapped air as well. However, I bleed both valves and get a steady stream on both. The next day, it over heats and I'm purging air on the side of the road. I pressure tested the system to 16lbs. It takes 5 minutes to drop to 13lbs. It's making me cuckoo.

I thought it should hold pressure longer?
Have you replaced your cap when you did all that work?

[Major Funbags]

Just bought a Stant cap. Must let it cool down. Then I'll try again.

[j cAT]

does this vehicle still have the coolant recovery bottle ? is the bottle full with no leaks ? is the hose going to the radiator from bottle connected and not leaking ?

you need a pressure cap of 15 psi. if your cap is defective when the vehicle heats up the coolant will flow to the bottle if you have one. it the hose is leaking to the bottle the coolant will not go back into the radiator when the engine cools OFF !

[Major Funbags]

Recovery bottle and hose is intact and not blocked. New cap is a Stant 15psi. For some reason, when it's cold outside the system builds pressure and the coolant won't flow unless I rev it up numerous times. The 'low coolant' light pops on and off as I'm driving too. I filled the radiator as it was running and kept topping it off as it was getting low. Eventually I can't keep filling it due to the fact that as it warms up the level starts to rise and come out the radiator filler neck. I was able to get some air out of both bleeders afterwards. I'm ready to jack the front up and fill it that way. Perhaps after doing the head gaskets there's still air in there. I'll keep ya posted if it works.

[j cAT]

Originally Posted by Major Funbags

Recovery bottle and hose is intact and not blocked. New cap is a Stant 15psi. For some reason, when it's cold outside the system builds pressure and the coolant won't flow unless I rev it up numerous times. The 'low coolant' light pops on and off as I'm driving too. I filled the radiator as it was running and kept topping it off as it was getting low. Eventually I can't keep filling it due to the fact that as it warms up the level starts to rise and come out the radiator filler neck. I was able to get some air out of both bleeders afterwards. I'm ready to jack the front up and fill it that way. Perhaps after doing the head gaskets there's still air in there. I'll keep ya posted if it works.

this is why I said what I said.......................

the recovery bottle keeps the radiator full to the top . this is if the recovery bottle is full and you have no leaks at the recovery bottle/hose to from the radiator.


NORMALLY YOU DO NOT FILL THE RADIATOR EVEN IF YOU HAVE A LEAK.


THE RECOVER BOTTLE WILL DO THIS .

when the coolant gets hot the expanding coolant enters the bottle. when the coolant cools it goes from the bottle to the radiator.

if you find the coolant is always in the bottle but not in the radiator then you have a leak. the floor in the garage should show this as a puddle.

if no puddle then you are burning coolant because the heads are distorted/cracked/gaskets etc.

[Major Funbags]

Perhaps that's what is then. I will inspect each plug while I do a compression test. When head gaskets were done the heads were milled. Not sure if they were checked for cracks. I'll buy complete rebuilt heads for this car without batting an eye. It only has 60k. My Aunt never drove it.

[j cAT]

Originally Posted by Major Funbags

Perhaps that's what is then. I will inspect each plug while I do a compression test. When head gaskets were done the heads were milled. Not sure if they were checked for cracks. I'll buy complete rebuilt heads for this car without batting an eye. It only has 60k. My Aunt never drove it.

If you have a cracked head as an example. the coolant will get injested and consumed. when the engine is shutdown now the crack allows air to enter the engine instead of coolant being sucked into the engine from the coolant bottle as the coolant cools contracts.

with this you will not see any puddles/leaks.

the spark plug will show as a white color and very clean[leak]. normal plug should be a light brown / all plugs should look exactly the same in color, light brown.

[Major Funbags]

It is in fact. A cracked head. I guess when I had them milled. I should've asked them to check for cracks. Live and learn. Reman heads on the way.

[j cAT]

Originally Posted by Major Funbags

It is in fact. A cracked head. I guess when I had them milled. I should've asked them to check for cracks. Live and learn. Reman heads on the way.

the company that worked your heads is a crook. they knew that head was cracked. they then would not get the job if they informed you of the crack .

now you need 2 good heads.

I do not recommended head cutting. this causes the combustion chamber to be reduced. also when the heat has distorted the head ,this is a stress on the metal.

good to report back . this will help those with this type problem.