Ok, got my new block in and its running great. got home yesterday night and the car started overheating. I have figured out that it will only heat up bad if it has been driven a long distance, and then you slow down. For example driving 10 minutes and then when you stop at a red light it will try to heat up. Another funny thing is that i still have the stock water pump, which is cam driven, so when i rev the car up the temp will go back down cause the water moves through the motor faster/ anybody got any ideas? im gonna check o make sure both fans are coming on today.

 

bad temp sens. mine done the same thing .make sure water is full too

 

Sounds like air in the lines. Try bleeding it out.

Thomas.

 

I know its overheating, trust me its not the sensor. Ive bled the air lines several times and cant seem to get anything (air bubbles) out of them. Anyone think it could be a clogged ratiator or a bad t-stat?

 

im having the same problem actually right now and after the car runs for a really long time temps start to rise in traffic at still only and then the low coolant light will come on im gonna check on the stat this weekend let me know if you come up with a solution ps didnt try bleeding system yet.

 

Im going to drain and try and clean the radiator out with the pressure washer in case something might be clogging it. Ill probably get a new t-stat to because they arent but $15 and mine is the stock one with 130K miles on it.

 

im running mr gasket .026 head gaskets, anyone have coolant issues with them? like the size of the coolant passage holes being to small?

 

Is it a brand new block? I would drain from the petcock and the drain plugs on both side of the block. Take the intake elbow off and then the thermostat housing and run water down there (lots of rags so as not to kill the opti) and let it drain out the block. Then put the drain plugs back in the block and fill the block up from that thermostat housing, put a new thermo in it and put the housing back on. Then fill the rest of the system up, get it up to operating temperature and bleed the **** out of it.

 

Make sure you guys are getting the correct T-stat, the LT1 is different from the standard SBC which both checker and autozone lists as the right one. NAPA carries both of em, so check it out before you buy. My car was acting very similar, replaced clogged heater core(wasn't leaking), replaced the heater restrictor valve cuz it was leaking, and replace the wrong t-stat with the correct one, and everything is fine now.

OHH ya, and I don't care if you bled it before, do it again dammit! And again after that, why not.

 

I was thinking of just by-passing the heater core with a patch tube to see if it might be something clogged in the heater core. I work for the auto parts store, so I know people etting the sbc style stat is a common mistake.