96 overheats when I come to a stop

[Iggyblazer619]

Hello,

So I haven't been driving this truck in awhile but I did a lot of repairs on it about half a year ago and everything seemed fine. I had to replace the radiator because of a crack in it. Because of running low on radiator fluid I burned up the water pump and also replaced that. a few months before all of this I had a bad t-stat that wasn't making hot water in the winter so I had replaced that. So it appears to me that most of the parts of the coolant system are opperating. Recently I noticed that when i am driving in town and come to a stop light the temp gauge redlines which i cant imagine is good. The only thing i could think of was that my fan wasnt running. I opened up the hood and it is spinning while the engine is running. Any suggestions on what my problem could be?

[Schrade]

If any engine ever starts to overheat, turn the heat on max immediately. Middle of summer, 99 degrees, stop n go traffic? Too bad. You sweat or the motor melts down goodbye motor. Turn the heat on max.

Have you checked for leaks? Are you sure the system is full of coolant?

[Iggyblazer619]

Yeah the system has plenty of coolant. I just can't figure out what would cause it to run fine at all times except for when I come to a stop. Could it be a flow issue internally?

[blazes9395]

These 4.3's are very durable, strong engines. One thing- as with any engine- if they run hot, you will damage it, usually a blown head gasket is a result. Verify the cooling system is in fact overheating, and its not just the guage on the dash. If it is overheating, its usually a result of either a blocked system/leaky system, low coolant, or faulty part. You already mentioned you replaced the rad, and thermostat, water pump. Was the rad a new rad?

A cooling system pressure test would be a good idea to make sure there are no leaks in the system too.

[Iggyblazer619]

The radiator was a new one so there shouldn't be any problems there. I have always just checked the fluid level in the overflow tank. Is it important to check the level in the actual radiator too. I was assuming if the radiator is low it draws from the overflow tank. And since there was plenty in the overflow that the radiator was fine also.

[ericn1300]

Basically, an engine that over heats at speed has a coolant flow problem, an engine that overheats when at stop has an air flow problem. Check that your fan is on when the over heat condition occurs, and that there are no airflow obstructions.

[Rick Norwood]

Originally Posted by Iggyblazer619

The radiator was a new one so there shouldn't be any problems there. I have always just checked the fluid level in the overflow tank. Is it important to check the level in the actual radiator too. I was assuming if the radiator is low it draws from the overflow tank. And since there was plenty in the overflow that the radiator was fine also.

My 2000 Jimmy did the exact same identical thing. That's what I thought too. Don't go there. I drove my truck in to a Rad shop after pulling my hair out too. Within 30 seconds the mechanic said the Rad is plugged.

Here's a what he did, and it is free.

Bring the engine to operating temp and SHUT THE ENGINE OFF. With the ENGINE OFF, reach your hand into the fan shrould and compare the temperature of the lower part of the Radiator with the upper part of the radiator. If the bottom of the Rad is cold or cooler than the top, the Radiator is PLUGGED and you are not getting the cooling capacity you need.

The Radiator was 16 months old when the overheating started. I also swore it couldn't be the new Rad, but it was. I had to pay them for a complete Rod-Out and flush and I am good now.

[Iggyblazer619]

I don't drive the truck much because I am at school right now but I will definitely check that soon. Thanks for the advice. I'll be sure to post my findings

[Schrade]

Originally Posted by Iggyblazer619

The radiator was a new one so there shouldn't be any problems there. .

Yes, there sure SHOULDN'T. So to be sure, check the temps of the input hose, and output hose.

If they are the same temp, there's a flow problem.