1998 k2500 454 getting hot

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newguyinnc

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That's a lot just to chase after a cooling issue. Do you have the stock fan shroud installed?

Is the water pump, the proper pump for use with a serpentine belt? The serpentine belt require a reverse rotation pump. If you somehow got a pump for a v-belt application it's being turned backwards and won't pump well. The differance is in the impellers.
Everything is installed and correct for the engine. Seems like the cooling system isn't able to push through the block and heads fast enough or with enough volume. Three different water pumps, 3 different thermostats and always the same problem. Even tried just running a restrictor instead of the thermostat before I had the engine rebuilt and had the same problem. 215° running and 235° when you stop. And that's with an empty truck. Pulled a trailer , about 5,000 lbs , for about 8 miles with it to the local landfill and with a load on it it was periodically creeping up to around 225° driving without stopping.
 

newguyinnc

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What haven't you changed?
Everything in the cooling system is new. Engine is freshly rebuilt with less than 150 Miles on it. Torque converter was checked at a reputable tranny shop before putting the new motor in it. The only things that aren't new are the catalytic converters, which were checked by a local exhaust shop and the O2 sensors. When the motor was installed, we did all new sensors , new starter, cap, rotor, plugs, plug wires, etc. Since the rebuild didn't fix the problem, have since done a new 4 core aluminum radiator, new a/c condenser, fuel injectors and fuel pressure regulator.
 

454cid

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What is this "4 core aluminum" radiator? A 4 core was typical of the higher capacity brass/copper radiators, but aluminum radiators usually have fewer rows of much wider tubes, and are more efficient. Where did you get it?
 

newguyinnc

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What is this "4 core aluminum" radiator? A 4 core was typical of the higher capacity brass/copper radiators, but aluminum radiators usually have fewer rows of much wider tubes, and are more efficient. Where did you get it?
What is this "4 core aluminum" radiator? A 4 core was typical of the higher capacity brass/copper radiators, but aluminum radiators usually have fewer rows of much wider tubes, and are more efficient. Where did you get it?
It's an alloyworks true 4 core all aluminum radiator specifically made for that truck. Comes with aluminum tanks and all the correct quick connects for the existing tranny lines. It replaced the brand new factory 3 core radiator. Seems like no matter what I change, the same problem persists. It's like there's an obstruction in the cooling system of the block that just isn't allowing the full flow of coolant through it. Heat gun says 120° at the radiator on both sides, about 160° going into the water pump, 200° at the thermostat housing, yet the middle of the driver's side head where the sensor is located is 235° with the thermostat open.
 

GoToGuy

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Do you have the correct coolant mix? And correct functioning radiator cap.
It is a big block, and will generate a lot more heat to transfer.
My 1 ton dually new had 200 or 210 thermostat. After 3000 miles I swapped it out for 185.
Going over I-80, Donner Summit, to Reno, in the bed luggage,tack, six bale's alfalfa. Pulling a two horse trailer with change storage area, never got over 200, yeah August vacation.
It sounds like you loaded a parts Cannon and blasted everything at it.
But you haven't actually found the cause.
It runs at higher temp. Does it boil over? Does it pressurize the cooling system beyond normal? Do you experience any pre-ignition.
During a loaded, working condition did the temp go unusually high, or slight equal to increased load ?
What does the service manual reference with this model and build?
What are other similar built trucks experiencing?
Have you checked for Service Bulletins on your model build or any big block trucks? That's what I would do. Good luck
 

Schurkey

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You're gonna hate my answer.

The temp sensor in the side of the head, that drives the dash gauge, is often 10--20 degrees hotter than "true" because it picks up heat from the exhaust.

That may be why your infrared thermometer "heat gun" shows 200 at the thermostat housing, but 235 at the middle of the head where the dash-gauge sensor is.

Verify temp using a scan tool, and the OTHER temp sensor in the intake manifold water crossover. While the scan tool is connected, pay attention to short- and long-term fuel trims, spark advance, knock sensor activity. I bet you have no other indications of overheating.

First Guess: You have nothing to be concerned with. It's not "really" running hot. It's not boiling over; it has no indications of overheating except the dash gauge. Mentally subtract ~20 degrees from whatever the dash-gauge shows when fully warmed up.




The comments made about "4-row aluminum radiators" are correct. And looking for service bulletins isn't a bad idea.

I have a 7.4 K2500 very similar to yours, but one year older ('97). But I don't work mine hard enough to really know what temp it'll run at. However, tomorrow I'm towing a couple of cars (separately, not together) so I'll keep an eye on the temp gauge.
 
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454cid

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Heat gun says 120° at the radiator on both sides, about 160° going into the water pump, 200° at the thermostat housing, yet the middle of the driver's side head where the sensor is located is 235° with the thermostat open.

When you stated both sides of the radiator measure 120 degrees, where did you measure? At the top? 160 degrees, is measured at the pump intake?

My radiator is obviously hotter on the driver's side, since that's where the hot coolant comes into it, and it cools as it flows across to the passenger side.
 

newguyinnc

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When you stated both sides of the radiator measure 120 degrees, where did you measure? At the top? 160 degrees, is measured at the pump intake?

My radiator is obviously hotter on the driver's side, since that's where the hot coolant comes into it, and it cools as it flows across to the passenger side.
120° at the middle of drivers side and about the middle of passenger side. 160° was measured just above the hose on the intake side of the water pump. I have 2 of these trucks, both with big blocks. One runs a consistent 195° no matter what weather or conditions you throw at it, the other one is the one I'm having problems with.
 
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