VinR1

iTrader: (17)

My father has a '94 Z71 w/ almost 300k mi. He uses it to check the wells and feed cows...thats about it. I seriously dont think the truck has ever gone over 55mph. Besides a slight miss, motor ran fine except for running a little hot - around 230deg.

For fathers day, I had a local shop install a new Jasper replacement engine, complete cooling system, complete fuel system, and flush the tranny and replace the filter. Everything from the air filter to the oil pan and condensor to flywheel is brand spankin' new. The tank is original but the pickup to injectors is new as well.

We took it easy for the first 500mi, changed the oil per Jasper's warranty, and took it out on the highway - set the cruise at 55mph and in a matter of seconds, temp jumps to 230deg
I flipped a u-turn and went straight back to the installer and had a separate temp gauge installed under the dash - back on the highway and same thing...230deg
I have new 160, 180, and 190deg thermostats ive swapped and they dont make a difference

What could be the issue? Ive put more than twice the truck's value back in it and the #1 problem I was trying to fix is still there...

the only thing I can think of is maybe tossing the water pump-driven clutch fan for a pair of electric pullers...?

TIA

Fazz73jr

iTrader: (3)

I had the exact same problem with my moms '94 suburban. As odd as it sounds it ended up being a bad engine temp sensor and harness for the PCM. I don't know how it could make it get so hot. We even put a clutchless fan on and it would still overheat and get terrible fuel mileage. That damn little wire & sensor solved everything though.

VinR1

iTrader: (17)

the temp sensor in the side of the block on the driver's side? I personally swapped that one twice and the engine installer put a new one in as well... I'm certain, however, the wire and harness connecting to it is original - I remember it being very brittle.

I'll look into that next - THANKS!

1994Z28Lt1

iTrader: (1)

so you're saying you installed a separate mechanical temp gauge and its still running the same temp?? Does it stay cool until you get on the highway? have you pulled the radiator cap and let it warm up and checked to see if coolant is flowing through the radiator, it should be squirt through the tubes pretty good if the water pump is flowing enough, thermostat is open, and you give it a little gas

VinR1

iTrader: (17)

update

apparently the radiator that was installed about 2 weeks before the motor was not the correct one for the vehicle - externally identical but somehow too small. I haven't been told if it was mislabeled or just an oversight on the part of the shop that installed it but they're sucking it up and have ordered a large 4in aftermarket aluminum radiator and having it overnighted on their dime so we should know in the morning if it worked or not