I have an 88 gmc with a tbi 350 in it. it had a new engine put in in 97 but they kept all the old tbi stuff and electronics, etc. I have never had a problem with it running hot until recently, about 3 months ago i put in a 180 degree thermostat and it would run right at the first 1/4 on the temp guage inbetween 100 and 210. Just in the past two weeks the temp has been consantly staying at 210-245. I had a water pump put on and the radiator cleaned inside and out and still the same problem. I replaced the sending units to the guage and ecm but that didn't help either. There is one code that is a run rich code but it has only turned on the check engine light once. Other than that one code there is nothing else. Any idea's on what might be wrong?
Any help would be greatly appreciated,
Dave

A new fan clutch fixed all my problems. What thermostat did it have in it before? I have heard of a lot of problems with putting in thermostats other than stock. Did you get the run rich code after changing thermostats? Do you have the fan shrouds on still?

charlo

I put a new fan clutch on already and my fn shroud is still on but it is moved up a little due to the body lift , but it has been ike that for a long time. the new thermostat was put in a long time before this problem started. But thanks for the help, any more i appreciated.
-Dave

I forgot to mention that when i went to time it the little notch was jumping around.
-Dave

I would try installing a good mechanical gauge to verify that it is actually running hot, could be a problem with the gauge cluster or dash. have you had to add anti-freeze to keep it full or does it seem like it's boiling/pushing any out. Also how's your exhaust, a plugged muffler or catalytic convertor can hold the heat in the engine and make it overheat

I just had a new cat put in and brfore that ran it without the cat for a day with the same problem. I think i might put in a good mechanical guage to see the exact temp, i know there is a problem with fuel delivery but i am not sure what it is, i am guessing it is not electronic because of the lack of computer codes.
Thanks, Dave

Originally posted by 88GMCPRIDE
I just had a new cat put in and brfore that ran it without the cat for a day with the same problem. I think i might put in a good mechanical guage to see the exact temp, i know there is a problem with fuel delivery but i am not sure what it is, i am guessing it is not electronic because of the lack of computer codes.
Thanks, Dave HAVE YOU CHANGED YOUR FUEL FILTER TO LITTLE FUEL WILL LEAN OUT MOTOR MAKING IT RUN WORM HAS IT BEEN CUTTING OUT ?WHEN THE MOTOR GETS WARN THE ECM TRYS TO RICHIN UP THE MOTOR TO COOL IT DOWN THIS IS WHAT SET CODE HOP THIS HELPS ;)

I replaced it a few month ago but i might try doing it again, thanks
Dave

Originally posted by 88GMCPRIDE
I replaced it a few month ago but i might try doing it again, thanks
Dave find somone with a scanner a good one this can tell the correct person every thing going on. o2 sensor go bad and dont always set codes this cood be leaning motor out

Thanks for the help, But anyone have any more suggestions?
Thanks,
Dave

Rather than going through the trouble of installing a mech guage, stop into a local garage and see if any of them have a good temp gun, like a Mac or Snap-on, point that baby at various parts of your motor and see what the temp is, your thermostat neck should be close to the temp the guage reads. For kicks point it at the exhaust manifolds, them sucka's git hot!

Yeh at the radiator shop they had a temp gun and the inlet ro the radiator was 193 while the outlet was 173. When pointed at the sending unit, (by the exhaust manifold it was ~400. Is this normal with a 180 degree thermostat,
Thanks for the help, Dave

So i figure it is something with the fuel delivery. The truck has 150000 miles on it any common things go at this mileage?
Thanks for the help,
Dave