carbongmc

iTrader: (10)

OK, heres the total story. I bought a 89 Isuzu pick up 2.3L carb motor. When I brought it home, it had a dead miss to it. So, I changed the cap and rotor, plugs, and wires with no change in it. I pulled the front cover to find the timing was off. I changed the belt with a new one and new tensioner, retimed it, and took it for a spin. On that first drive, it over heats on me very quickly. I get it home and pull the head. I get the head resurfaced and install a new head gasket. It cranks and purrs like a kitten. I did not install the Tstat back in it because the heater core isnt hooked up. I really didnt see the point. So, the issue I have is that on the interstate, above 60mph and 2k rpm, the truck wants to run hot. It starts off about 190 degrees, and within 6 or 7 miles on the interstate, its creeped to about 225-230 and climbing slowly. If I keep it at or under 55mph, it stays in check and doesnt get over 210 or so. With all this, I thought the coolant might be flowing too fast for the heat to be pulled out by the radiator being it doesnt have a Tstat to slow down the flow, so today I reinstalled the Tstat. It "seems" to climb up slower, but it still gets hot. I let it get to almost 230 today doing 70mph, and I slowed down and it steadly dropped the temps. Im lost now. What am I missing here? Why is it getting hot when the radiator has the most air passing over it, and cooling off when it sits still? Its the complete opposite of what you would think it would do...HELP!!!

Atomic

iTrader: (42)

Does it have a clutch or electric fan on it? If electric, are you sure it is spinning the correct way? (Common mistake with a homemade harness)

carbongmc

iTrader: (10)

Im using the stock clutch fan, and its good. I had an elec fan on it and took it off bacause the stock fan pulls alot more air. I dove it to work today, and I did 60mph on the interstate and the temps stayed at 200. But, if I went ANY faster, they would start climbing up again.

carbongmc

iTrader: (10)

After reading on some older truck forums (this thing is an 89) I think the carb might be leaning it out on top and producing more heat then can be delt with in the stock cooling system. My plan is to rejet the truck a little bit richer on top end, re-time it, and go from there. If anyone has any other ideas, please let me know. Im kinda grabbing at straws here....

Atomic

iTrader: (42)

Radiator doesnt have a ton of leaves covering it does it? Trying spraying it out from both sides with a water hose...

mhotrodscooter

iTrader: (13)

Are you having to add in fliud to the radiator? Being the heater core is disconnected it's possible the radiator is full of stop leak or something just a thought. Also I would check the temperate with a manuel gauge just to see.

Sc00by

I had a good friend of mine that used to have a 95 GMC 2500 with the 5.7l engine in it. He started running into that same problem several years back. In town, idleing, 45mph city cruzing he had no issues. But when he got on the hwy temps would start creeping up. After tons of trouble shooting he finally took it to a mechanic. What he found out is one of his main bearings on his crank had gone bad. It didn't cause any noise or flutuation on his factory oil pressure guage but when the engine was turning higher RPM the bearing would start generating more heat and the temps would start creaping up. My buddy used to keep his truck CLEAN!!!! Even the mecanic made a comment on how clean the inside of his engine was (around 180k on the clock). new bearings were installed and he had ZERO issues with the temps climbing.

Sorry for the somewhat long post but I felt I needed to explain a little.