I was just drivin my z28 and it got really hot. I came home and took the radiator cap off there was no coolant. I let it cool down and filled it back up. when you start it with the cap off it pushes all the coolant out of the top. Does anyone know what could cause it.

 

you might make sure your fans are turning on

 

Could be alot of things.

 

Might look in the front of the radiator for plastic bags.
Turn your air on and see if the fans come on ok.(Bad relay).?
Stuck thermostat.
Clogged radiator.
Don't drive with an overheated car as your bank book will go south.(blown engine).Hope this helps.

 

Almost forgot the waterpump.Is it leaking on to your driveway?My02.

 

Well I changed the thermostat and it was still heating up. i took the rubber hose off the heater core it took it about 15 secs to push coolant out of it. so i hooked it back up and unplug the other one and just a lil coolant would come out of the heater core and it will not push hot air out. but it will run cool with that metal and rubber hose unhooked form the heater core. The passager side fan will come on a couple of secs. so i dont know what is going on

 

Sounds like you might have a clogged system.

1. First, I would check to see if your fans are coming on. If they are,
2. I would buy a flush kit for $10 and flush out the radiator and heater core. If it won't flush, it's probably the water pump.

I'm still thinking about this one. Good luck on it! Let us know what you find.

 

Obvious first thing to do is check the entire system for leaks. Have the system pressure tested if necessary.

The LT1 reverse flow cooling system has a real problem with any air in the system. When you refill the system, you have to purge the air out using the two bleeder screws, one on the t'stat housing, and one on the hoses. IF you don't do it right, its going to overheat.

Did you get the correct t'stat for the "LT1"? You can't use the same one you use in every other small block Chevy. Most parts shops don't know that. What temp t'stat did you get? 180*F is stock.

Check the overflow hose that runs from the radiator fill neck to the reservoir. If that's cracked, the radiator pushes coolant into the reservoir when it heats up, but can't suck the coolant back into the radiator when the system cools down and pulls a vacuum.

Check for hydrocarbons in the coolant = bad head gasket.

To flush the heater core, pull the two hoses off at the pump end, and force water through them both ways with a garden hose.

When working on the coolant system, DO NOT get coolant on the OptiSpark distributor, or your next post will be "why is my engine running so poorly?"