I just dropped in a 350 Vortec with a 454 tbi and custom chip, and it ran ok(needs a little turning). I drove it to work today which is about 20 minutes each way and it cooled fine. But tonight when I left work I stopped to pick up some injector cleaner/octane booster and some gas. I got on it a few times (6k) and the temp started to go up quick, all the way up to 250. So I turned around a parked it real quick and popped the hood and it didn't seem like it was running extremely hot and I could even put my hand on the radiator for about 5 seconds so that wasn't really hot at all and the overflow was filling to the top. So I kept the fan on for a few mintues and let it get down to about 225, and decided to go home cause it was only 1/2 mile away. I got on it once more time and it started to heat up fast again. Then I made a U turn to get to my street and stayed off the gas and it started to cool (to about 225). Then what I got in my driveway, I let it idle for a minute and it started to heat up again. I popped the hood again and the overflow was still full and the radiator was still cool. I started to crack open the rad. cap and heard all this gurgling that sounded like it was coming from the overflow but the level wasn't moving. Then I took the cap off all the way and it was about a 3rd low (in the overflow I guess). I've considered bad thermostat, bad water pump(just installed remaned about 6 months ago. And my dad even suggested a hose colapsing, but couldn't see how that could happen if it still got hotter while idleing. Any ideas would be great.

 

bad rad cap?

 

How could I tell if that cap is bad or not?

 

Could it be the water pump?

 

I know this might sound stupid but here's my thoughts on this. Is the fan on the right way? My cousin works at a shop and he told me someone installed a cooling fan backwards (the van came in like that) and the people couldnt understand why the can kept over heating. I work on computers and people sometimes install fans backwards (making the system overheat and hang). I've seen it enough times. Is the thermostat opening? I have to agree with everyone on the radiator cap though. That little cap can be the culprit behind expensive repairs that fail to fix the problem. Is your radiator clogged? A local shop here will rod out the radiator and weld on new tanks for 40 bucks. These are just simple questions. I just try to adhere to the K.I.S.S. rule. Keep It Simple Stupid.

 

Well I think I have it figured out but haven't tried to fix it to confirm yet cause it just happened tonight, but Njspeeder asked if I topped off the cooling system with the motor running after I dropped it in and I don't remember doing that. All I remember was filling the radiator up so I could get it started and after that all my attention was on getting it tuned right so he suggested that it probably has and air pocket somewhere. I'll find out tomorrow.

 

ALot of air in the system... ie insufficieant coolant.

Start the car, turn the heater on "hi". remove the radiator cap top off the radiator with coolant and let the car idle. When the coolant in the block gets to the right temperature, the thermostat will open. When this happens the coolant level will drop in the radiator as the system starts to circulate. Top off the radiator again.

The thermostat might close due to the initial flow of cool radiator coolant. Repeat the topping off process until the engine gets up to temp and the coolant is flowing consistantly. You will see a steady stream from the tubes.

This will give you a properly filled system...