LT-1 Overheating after restore/rebuild. HELP!!!

OK.. I am new here so spare me the on slot if I oops.

Here is the deal. I have a 96 Z-28 with an LT-1 5.7 motor (or what ever motor it is that came in the same year Corvette) that I have been tasked with resolving an overheating problem on, a family members car. The car was totaled (Front End) and been restored to original order other than the overheating problem.

Extensive testing on the systems have shown that the cooling fans (all 3) operate, fan relays work and the temperature read by the computer is correct as far as what it reads on the dash panel and the temp of the fan triggering sequence. The temp sensor on the front end of the motor (the one that according to the dealer is the one that triggers the cooling fans) has been replaced to verify that it is in order since the damage was to the front end of the car, The wire lead to the temp sensor was replaced to insure no lack of proper signal to the computer. There there are no leaks and the radiator was flushed and the thermostat has been replaced.

When it runs all goes good till the temp rises. The first fan triggers and the temp drops then it rises back up and begins to build up steam in the cooling system. If it is shut down at the time of the first fan triggering or at a close temperature it immediately releases a large amount of overheated coolant and steam in to the coolant reservoir. It sounds as if the area that the steam buildup is coming from the driver side head? This happens every time it is run and causes a loss of coolant. It will eventually do this regardless if not shut down.

I personally did not do any of the restore work and the information that I have given as to pats replacement can not be personally verified other than the wire lead to the temp sensor.

My thoughts are that the coolant flow may be inadequate or blocked, thermostat may be wrong or bad or I have been unknowingly unable to remove all the air from the system after many attempts.

I am far from being an certified tec and am a self admitted backyard mechanic, yet defiantly not an idiot.

I understand the the operating dynamics ot the LT-1 motor are a bit different than what I may be accustomed to yet I am simply stumped....

Please help, Ziggy

I am also not an expert on the LT1, but I do know that the water pump is driven off the front of the cam. It would seem possible that this has been damaged by the collision.

Also, just FYI, the engine is reverse flow. Coolant enters at the top to keep the heads cool and the hot water comes out the bottom.

Good luck

And being reverse flow, make sure the thermostat was installed correctly, i've seen seasoned mechanics do it so definitely check it :) The spring should go towards the engine.

Make sure air flow to the radiator hasn't been damaged by the collision. Look at fins on condenser haven't been damaged.

Thanks for the help to all.

It looks like the problem I am having is simply removing all the air from the cooling system. Never have I had so much difficulty doing so. It must be the reverse flow deal. Air simply wants to stay on top and not flush down with the coolant.

Best I have been able to do is by (as I have been told) jacking up the front end, open the bleeder valve, remove the cap, fill and run with the bleeder valve cracked open till the symptoms go away. Repeating the process as necessary. I have done this 4 times and have had better results but no cure.

Anyone got any better ideas? Water pump, radiator and thermostat are ok.