We just installed a new GM Opti, plug wires, and spark plugs in our 1996 Z28. While we had the car apart we installed a new GM water pump and upper and lower radiator hoses.
Upon fire up, the car runs well but builds engine temperature very rapidly. The engine temp climps north of 220 after just a few minutes of running (based on the dash gauge and the Interceptor scan gauge). Oddly, the heat from the dash vents at operating temp is only lukewarm. We have added about 2 gallons of coolant, and are not quite at capacity, it seems.
Do we have air trapped in the system? Or a blockage somewhere?

Any help would be greatly appreciated!

R & K

 

yes most likely air is trapped you need to bleed the system with the two bleeder screws.

 

here yea go try this http://shbox.com/1/4th_gen_tech2.html#radflush

 

did you take the radiator cap off to see if water was circulating?
when you removed the old pump did you remove the small splined shaft that mates the
waterpump to the drive gear coming from the timingchain cover?
is the system bled well as described in the post above?

 

like stated before you need to bleed the system using the directions on shoebox's site

 

If you don't get all the air out, that is exactly what it will do.

 

Hey Guys...

We finally found some time to tinker with the Z28 again. We ran the car up to temperature a few times with the top bleeder open, and as the car warms we get what seems like a steady stream of coolant from the bleeder, no air. We have not opened the bleeder on the thermostat housing for fear of soaking the opti with coolant.
The car warms up slowly, blows right past the 160* t-stat temp and slowly continues to climb. I drove the car around our neighborhood for exactly 10minutes and then shut the car off at 206*.
Upon opening the hood I can hear percolating in the radiator - lots of it. The air from the dash vents on the hot setting is still cool.
What concerns me is that the driver's side of the radiator was cool to the touch upon shut-off, while the passenger side was fairly hot.
The water pump is a new GM unit, and we did not disturb the splined shaft that drives the pump when we installed it.
Do we still have air in the system, or do we have another problem?

We sure would like to resolve this problem and drive the car again...

Thanks very much for the help,
Rick & Kristi

 

I am confused. You ran the car with the bleeder screws open? I would recommend following the proper procedure when bleeding. It doesn't take much air the the system to cause a problem. To me it seems like there is air in the system or the coolant is low.
Your thermostat starts to open at 160*, so the car will not run at that temp. Are your fans coming on?

 

I idled the car with the bleeder open, but closed it before I drove the car. I have added about two gallons of coolant so far.
The fans come on exactly as expected.

 

You have to crack the bleeder on the TS housing too. Just stuff some rags around the base of the housing to catch the overflow and crack the screw until all the bubbles go away and a steady stream of coolant comes out.

 

I also squese the hoses to try and force water into the water pump.
It takes me about 30 min to bleed the entire system, and i have done it tons of times.