mk2001c

Just replaced the intake manifold gasket, and I'm getting ready to flush and fill the coolant system. I can't quite tell from the service manual where the bleed valves are. Second question - is there a flush product (Prestone or Zerex) that you'd recommend? The manual says not to flush with a chemical product. I can't tell by looking at the label if they have chemicals. I assume they do.

65Z01

I would just flush with water and fill with the proper coolant mix.

imavettegirl

Look in your owners manual. It says in my 87 manual that you fill coolant run car when it cools it pulls water from overflow. It may take several times to get air out.
That was a summary.

:hurray:

Irishpilot03

I bled my coolant system from the bleed valve on the thermostat neck. This was on my '94, so I hope that helps.

ZELLSLIFE

To bleed it from the screw on the thermostat neck do you just run the car and turn the screw or is there something else you do? :seeya

silver & red CE

I don't know exactly when GM switched over, but a some point they just have a single bleed valve on the t-stat housing. I know my 96 has just one, 92 has two bleed valves, somewhere in between they switched.

Eric

mk2001c

Found it on the thermostat housing - thanks.

c4cruiser

My 92 service manual says not to use chemical flushes. For a 92 (and probably later LT-1's) flush 3 times with water and pull the knock sensors to drain the water from the bottom of the block. Use distilled water on the last flush. These flush steps include drain, refill, run the engine to a temp of least 150deg each time.

When you have drained everything, pour in 2 gallons of antifreeze (green coolant for pre-95) and then add distilled water. With engine running, bleed the system at both bleedvalves. Make sure coolant is at the top of the filler neck in the expansion tank and replace the cap. Again, for a 92, the engine should run a minimum of 3 cycles where coolant temps go from cold to operating temp and cooldown again before any high-speed operation. Clean out and re-fill overflow tank with a 50-50 mix of distilled water and coolant.

ittlfly

You might check for a 2nd bleed valve on the drivers side tucked up under the throttle body. Like mentioned before I don't know when they switched from 1 to 2 bleed screws either and mine is a 92 also.

Irishpilot03

If you're going to bleed the system from the thermostat housing, start up the car and let the system get under pressure. Then open the bleed valve while the cr is running and wait. If there is air in the system, coolant will spit and sputter for a bit, then a steady stream of fluid should come out. When that happens, you're finished.

Mez

I had to loosen the upper radiator hose to purge air trapped in the system while filling the system. Once coolant started coming out of the radiator, I put it back on and used the bleed screw on the thermostat housing then started the engine. I could not get coolant into the radiator until I pulled the upper hose off to let air escape.

I also recommend distilled water instead of tap water. Tap water has a lot of chemicals and clorine that cause problems over time. Its only a $1 a gallon at the grocery store, so not a major expense.

John Row

Too get a significant volume of coolant into the radiator, you have to get the engine hot enough to open the thermostat.

If you are going to bleed at the t-stat, be sure to put some rags around to sop up the coolant. Guess what's under the bleed valve!