1989 C3500 4x4 454 always runs hot

On a 20 year old unit, other than the obvious things you've likely checked like the fan clutch, thermostat function, ECM timing set etc, you have to consider the possibility that the rad is corroded and deposits are causing the issues. I would remove and repair/replace the rad if everything else checks out OK.

2 years ago i put a new core in the radiator that included and extra layer making the radiator a custom 5 core version. It may have helped a little. The fan clutch is extra heavy duty making the engine howl. Though noisier it is somewhat reassuring as the engine does not heat up on mild days unless towing. I've been told cooling was an issue on this model year and this is the main reason no 4 or five speed version was offered in 1989. I'd really like to talk with someone who has modified something ie, engine oil cooler, electric fans or some combination of changes to the engine that will make this engine run strong and cool.

When was the last time the fuel filter was changed and the fuel system cleaned? Lack of power and running hot could be caused by an engine running leaner than it should.

What rear gearing does it have? Higher gearing will make the engine work harder and hotter.

What exhaust system does it have? A partially blocked converter or muffler could also cause it to be low an power and run hot.

You already have a larger radiator. Is the fan shroud in place?

Running that hot I would install a heavy duty trans cooler and run synthetic fluids as well. You could install a rear facing hood scoop to release the heat from the engine bay. Something like the Z28 style from the 60's.

Good luck and report back what you find.

What type of air intake filter do you have? Paper, or foam?

Can we assume all the mechanical parts are there and in full working order... to include the fan shroud and thermostat. I would not run it past 220F.

Do you have the right fan and fan clutch combination. No-one's swapped some aftermarket parts in there?

I don't anyone makes a better fan clutch than GM, for a GM vehicle. On a heavy tow rig....I would not use electric fans as the primary cooling.

Does the truck have 4.10 gears and are you pulling loads within your rated range.

Don't know if you get off in the mud but make sure your radiator and condensor are not full of mud, or crap between the condensor and radiator blocking the air flow.

No check engine light is on I assume, no reason to expect a head gasket issue?

What temp does the truck run at unloaded in the summer now?

Have you checked the temp that the computer see's by using a scan tool to verify that the gauge temp is correct? and that you don't have a faulty sending unit.

On a tow truck like that...I would want the biggest 4 core radiator that fits, OEM fan and OEM HD fan clutch, correct thermostat, and proper gearing at the differentials.

I do think some of those older trucks were known to run fairly hot.

My 01 2500 suburban with 496 runs about 195F unloaded...its rather new to me, and so far I've not pulled any heavy stuff with it. With A/C on , idling or running, it never gets over 195 or maybe close to

200. What's your truck doing in present weather conditions..unloaded?

When the truck is warmed up and ambient temp is 80+F outside I assume you can hear the fan clutch cycle on and off under load? Also when engine warm and you open the hood you have a nice air flow across the radiator?

----------- Elbert snipped-for-privacy@me.com

If Someone has a line on a functional rear facing soop or a tidy way to vent the hood I'd like to try that. I'm not oppose to modifying the hood or replacing it with one that is alredy modified.

First i think I'll put a test tube in place of the cat converter to see if ther is any good to come from that.

What I had done is make a small plate with a hose barb thru it and mount that in place of the EGR valve. (gasket too) Block off the EGR vacuum, and connect the barb to a pressure guage. ( I have a old Vacuum/Fuel pressure gauge) Run at different RPMs and check the pressure. A blocked Cat will show pressure readings, where a clear cat will show next to nothing. If you have dual Cats then this approach may not work.

Cheers

Ever check the water pump? I've seen the wrong water pump installed on small blocks that caused overheating. Some pumps rotate in the opposite direction depending on how the belt wraps the pulley. Big blocks may have different pumps as well.

Hi!

I'm reasonably sure that can't have harmed anything. You don't want to cool the engine too much, but the thermostat should regulate things pretty well if it's working properly.

I know that somewhat later models (mid 90s) of these trucks often got an "extra" grille underneath the main grille because it wasn't enough to keep them cool. You've probably seen some with it--there is the main grille and then underneath it is a piece of plastic running the length of the grille with smaller slits in it. This was done to solve an overheating problem. I don't know how succesful it was, but I'm surprised nobody has mentioned it.

You really don't want electric fans--they cannot and will not move the air that an engine driven fan will. Things will suffer--anything that's being cooled won't be cooled as well, and your alternator will run hotter and closer to its limits from the added load.

A transmission cooler is always a good idea. Mount it as close to the front of the truck as is possible, in front of the other radiators. This will give it the ability to do the most good.

William

Hey I've had this twelve years now and I've been through at least four different thermostats with the same results. Now I finally removed the thermostat and this engine runs cool. Is it possible that none of the thermostats can pass the water well enoguh to not cause restriction? Can I buy one that is not a restriction?

Hey I've had this twelve years now and I've been through at least four different thermostats with the same results. Now I finally removed the thermostat and this engine runs cool. Is it possible that none of the thermostats can pass the water well enoguh to not cause restriction? Can I buy one that is not a restriction?

Have you tried a 160 degree thermostat? The engine will probably run a lot cooler, but it might be too low of an operating temp to pass a smog test. If that's the case, swap out the thermostat before you get a smog check.

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We don't have smog tests here in Walla Walla. I will check into getting a high flow thermostat. I have a 160 I just took out. It may have opened sooner but I'm quite sure it does not open enough. I'm trying to get some old equipment to make hay today but once that's in the barn I'll get into the thermostat thing again. Mike