98 Buick Century cooling system

runaround

My car ran hot (just short of the "RED" marks) on interstate. Pulled over, called relative...went home...got water and returned to car. I started car and the engine was sound. Filled radiator, discoverd water pump had gone out (had been making slight roaring noise which I thought to be the AC clutch bearing...I was wrong). Was able to drive home without incident. Shut off engine and could hear the 'boiling' in the radiator. Figured I would fix it the next day.

Bought new water pump..installed (much easier than I thought it to be).
filled with water/anitifreeze (I know about the 'bleeder" screws above the water pump and thermostat housing, and utilized them).

Now for my problem. It appears that the system is not venting. After the car has run and thr water has heated up, it still wants to cross over to 'where we don't want it to be,' (in the red). I shut the engine BEFORE the 'red' was reached. I checked the hoses and they were REALLY pressurized, telling me the system was NOT venting.

I bought a new 15psi cap...and did the same thing. At that point I thought it may have been a sticking thermostat..I removed it...system still pressurizes without venting. Next, I removed the thermostat and replaced housing. Still pressurizing without venting.

Can anyone here help me with an answer as to what is going on? Is it possible that I have a blown head/intake manifold gasket that is blowing into the cooling system causing these high pressures? please note that after the engine has cooled a bit that the hoses are soft and squeezable (normal).

Also, from what I can see, there is no water in the oil, but there is evidence that oil is in the cooling system (not a lot, but it is there).


thank you

dtor 53
[email protected]

Exactly what process were you using to purge the air from the system using the bleeder screw? The best method for this is to park the car with the front end of the car on a uphill incline. This will cause the air in the system to rise towards the front of the car (And bleeder screw). Start the car, Turn the heater on full hot position, let it run for a min. Open the bleeder screw until you see coolant come out, then close it. Wait about a min, then repeat the process several times until all that comes out of the bleeder screw is coolant (No more air). Also, keep your overflow bottle filled so that if the system needs to take in more coolant, it can. You should also be feeling full heat coming out of the floor vents in the car at this time. If not, the thermostat is not opening or the heater core has a blockage in it. If the heater core is blocked, you can remove the heater core hoses and flush the core "Both directions" until nothing but clean water comes out. You did run the heater on full heat when you refilled the system with coolant....didn't you? If there are signs of oil in the coolant, you would think that the car would run low on oil on the dipstick also eventually. If this is the case, and you are seeing signs of "Motor Oil" in the coolant, It's time to replace the intake gasket on this car before it gets worse and coolant starts mixing with the oil (Not good). If this car has a 3.1 V6 in it, they are notorious for intake gaskets needing replacement. Do some research and buy a upgraded intake gasket setup that addresses this issue, then have a helper assist you when you set the intake in place and postion it. If you replace the intake gasket, I would also flush the cooling system good before you refill the system.