Ok- i have a 94 LT1 with a 97 block w/ stock aluminum heads, mods are in my sig.

although it has an electric CSR waterpump, and the radiator and rad. hoses are about 8 months old. I just replaced the thermostat about 3 weeks ago.

Anyways- saturday the car all of a sudden started overheating really fast, like 15/20 mins of driving and it would get hot, i couldnt even get home saturday night, had to park it at a friends house.
A buddy that has a 97 LT1 that races told me to clean the metal pipe that connects to the back of the heads and then clean the bolts and what not.
So i did that, and the water flowing through that pipe and into the radiator seemed to really be flowing good now. Well i filled it up with coolant, let it warm up, and went driving around and got it to heat up to the 1st mark above 160, then i stopped and opened the bleeder and let all the air out and filled the radiator up the rest of the way with coolant.

Well, this was fine for about 20 mins and then it overheated again.

We arrived at my girlfriends dads house and the car was pukin coolant out of the overflow, and startin to get up twards the red mark, so i shut it off as soon as i pulled in the drive way but kept the key on so that the fans and the electric waterpump would run and circulate the water.

Well - we let it cool down a bit, then took off the radiator cap- when we looked in- it appeared that no coolant was lost..., but i start the car up again after it has cooled back down to like 170 or so ( we stuck a thermometer in the radiator to read the temp) and started it back up with the cap off, coolant started coming up out of the radiator cap hole, and started goin into the overflow, but not fast enough, then it started overflowing from the radiator cap hole and just running everywhere.

We let the car cool down again, and i pulled out the 180 themostat, and put the housing back on. Took it for a drive, and in about 10 minutes the gauge in the car showed that it was getting hot again- goin up twards the red mark, so i pulled it back in the driveway and shut it off and the key too so the waterpump was off also, we poped the cap off the overflow and the tank was full of coolant, we stuck the thermometer in there and it showed about 150*, then we opened the radiator cap and of course- it was pressureized in there and some sprayed out, but when we got the cap off and stuck the thermometer in it the thermometer read 180*..

There is no water in the oil either..

I took the CSR pump out of the housing today and then turned it on- it spins, but im going to have it rebuilt anyways because it is atleast 3 or 4 years old..

the housing is all nastified, and pitted and inside the center of the housing where the impeller would sit, down in the groove in the bottom there was some coolant , but inside that there was a white substance. looked like eggwhites floating around when you scramble them in water and whisk them with a fork...

the car is firing on all cylinders also w/o missing a beat..

Anyone have any sugguestions?? BTW:- the car will sit and idle right at the 2nd mark on the temp gauge on the dash. but when you go driving is when it heats up. It seems like it will sit and idle there at that mark for like 15/20 mins and not get warm, but when i take it on a drive in less than 15 it over heats..

after i get this all straightened out im going to put in a 160 thermo- thats what the computer is programmed for. and a new clutch, but i have to figure out this cooling thing first....

 

u might wanna think about replacing the radiator.... i had junk in my system before that was real minor but clogged the thing up causing my car to sit and idle cool, then heat up going down the road...

 

im not sayin that it cant have **** in it, but i didnt see anything circulating in it when we were messing with it yesterday. and my radiator is only 8 months old.

 

U Have a cracked Head or a blown head gasket..good luck......T

 

I had the same problem. I was on my way from NY to FL and I pulled over to let my girlfriend drive in south carolina and when I got out of the car, I smelled coolant. I popped the hood and coolant was spewing out of the overflow tank and the gauge almost hit the red. I was able to make it to FL without it overheating since there wasn't any traffic but If I stopped, it would overheat. It ended up being the water pump. I couldn't find any leaks for a while but a couple days later it started leaking from the pump. But since you have a csr, it may be a different problem. But I had the same problem with the coolant pouring out of the overflow tank and it ended up being the pump.

 

Well, im going to replace the pump,and hopeuflly the housing and hook up the air compressor and force some air through the system... then flush it out w/ the hose..