1998 k2500 454 getting hot

[TagAllen]

I had heat issues for a while with my gen 6 454. I purchased my pump from Summit for the correct application. Summit had it listed wrong. It flowed the wrong direction.

 

[1998crewcab]

Have you tried pulling out thermostat
Yes it will take a bit longer to warm up
But you will see if it keeps gauge from moving around during stops and when driving

 

[newguyinnc]

Have you tried pulling out thermostat
Yes it will take a bit longer to warm up
But you will see if it keeps gauge from moving around during stops and when driving

I did. I cut the center section out of one and just used the base as a restrictor and it did the same thing. Next one I put in was a high flow and I drilled two 1/8" holes in it. Same deal.

 

[454cid]

I did. I cut the center section out of one and just used the base as a restrictor and it did the same thing. Next one I put in was a high flow and I drilled two 1/8" holes in it. Same deal.

That's still a much smaller hole than no thermostat. When I ran no thermostat the truck wouldn't heat up past about 150....I did that during a flush.

 

[newguyinnc]

That's still a much smaller hole than no thermostat. When I ran no thermostat the truck wouldn't heat up past about 150....I did that during a flush.

Yea, that's my problem though. I don't wanna rig a brand new motor with a bandaid fix. Need to find the underlying problem that's causing it. I'm gonna use this truck to tow a trailer out of state frequently.

 

[newguyinnc]

Well, mechanic installed another new water pump today and replaced the bypass hose. Told me they drove it in circles around the building and it never got over 210°. Took it out myself on the highway and did my normal test route with it and still doing the exact same thing. Talked to the engine builder today and he said no way he put the wrong head gaskets in it and unless you're an idiot, no way to put them on backwards if you're paying attention to the coolant holes in the block and heads. He suggested the lack of power combined with the heating issue is most likely too much back pressure in the exhaust, and improper fuel trim/advance settings ( in other words bad ECU). Gonna have the current mechanic gut the cats and if that doesn't work, the engine builder gave me the number of a mechanic with the capabilities to figure it out.

 

[454cid]

Yea, that's my problem though. I don't wanna rig a brand new motor with a bandaid fix. Need to find the underlying problem that's causing it. I'm gonna use this truck to tow a trailer out of state frequently.

No one is suggesting it as a fix, but as a diagnostic....showing that the engine can be cooled.

 

[Schurkey]

I might verify those things that might lead to an extra-hot exhaust--ignition timing advance, fuel trims, and restricted exhaust flow, though.

He suggested the lack of power combined with the heating issue is most likely too much back pressure in the exhaust, and improper fuel trim/advance settings ( in other words bad ECU). Gonna have the current mechanic gut the cats and if that doesn't work, the engine builder gave me the number of a mechanic with the capabilities to figure it out.

We've already cut the exhaust free , it's not back pressure.

So why is the guy suggesting it's too much back pressure?

Changed injectors because of bad long term fuel trim numbers. The only thing we can find is it doesn't seem to stay in advance the way it should, but I can't see where that would cause a 20-25° jump from highway speed to coming to a stop at the offramp. 215° on the highway, pull off and come to the stop sign, 225°. Cross over the overpass to head back the other way and stop on the side of the on ramp and in 5-10 seconds it'll be reading 235°. Rev it or take back off again it'll drop back to 215° in a few seconds.

Incorrect advance can absolutely lead to too-high engine temps, but the exhaust temps go sky-high when the timing is retarded. The fuel/air may still be burning when the exhaust valve opens.

Again, the engine doesn't seem to be running hot. You'd verify that with a scan tool--does the computer sensor show the same temp as the dash gauge, when the dash gauge is climbing? How are the fuel trims? If the O2 sensor system (front sensors, wire harness, ECM, and exhaust manifold/exhaust pipes) is OK, that'd be a reliable way to know if the engine is running lean. If the rear sensors are happy, the converters are likely not plugged, so you wouldn't have to "gut them" as an experiment.

Retarded timing makes the exhaust extra-hot, which bakes the dash-gauge sensor, which leads you to think the whole engine is too hot?

That truck is crying out for a scan tool.

 

[newguyinnc]

So why is the guy suggesting it's too much back pressure?


Incorrect advance can absolutely lead to too-high engine temps, but the exhaust temps go sky-high when the timing is retarded. The fuel/air may still be burning when the exhaust valve opens.

Again, the engine doesn't seem to be running hot. You'd verify that with a scan tool--does the computer sensor show the same temp as the dash gauge, when the dash gauge is climbing? How are the fuel trims? If the O2 sensor system (front sensors, wire harness, ECM, and exhaust manifold/exhaust pipes) is OK, that'd be a reliable way to know if the engine is running lean. If the rear sensors are happy, the converters are likely not plugged, so you wouldn't have to "gut them" as an experiment.

Retarded timing makes the exhaust extra-hot, which bakes the dash-gauge sensor, which leads you to think the whole engine is too hot?

That truck is crying out for a scan tool.

Truck has had a scan tool on it several times. Initially when I bought the truck and realized it was getting hotter than it should, I put my scanner on and realized the distributor was a tooth off( -22.5°). Had the mechanic pull the distributor and correct it to get the timing set to zero. Heating issue never changed. The mechanic that's been working on it said it didn't seem like it was staying advanced the way it should be. I've tried finding an rpm to degrees of advance chart and haven't had much luck for this motor. I have a good scanner I can read live data on. I'm a good backyard mechanic, but can admit I have no idea what the long and short term fuel trims should look like and haven't found much good information on that either. Only thing I was able to see on my scanner was that on the long term fuel trim bank 1 was in the negative and bank 2 was like +9, so we changed the injectors and fuel pressure regulator. Ran a little better with a little more power, but the heating problem was still there. The kicker I told the mechanic to gut the cats a week ago and cut the exhaust pipe in front of the muffler to see if that helped, and instead he cut the exhaust in front of the cats and run it. Did the same thing it had been doing, but 5° hotter and what bothers me is that not having the rear O2 sensors hooked up never threw a code. Got me thinking possibly ECU.

 

[L31MaxExpress]

Truck has had a scan tool on it several times. Initially when I bought the truck and realized it was getting hotter than it should, I put my scanner on and realized the distributor was a tooth off( -22.5°). Had the mechanic pull the distributor and correct it to get the timing set to zero. Heating issue never changed. The mechanic that's been working on it said it didn't seem like it was staying advanced the way it should be. I've tried finding an rpm to degrees of advance chart and haven't had much luck for this motor. I have a good scanner I can read live data on. I'm a good backyard mechanic, but can admit I have no idea what the long and short term fuel trims should look like and haven't found much good information on that either. Only thing I was able to see on my scanner was that on the long term fuel trim bank 1 was in the negative and bank 2 was like +9, so we changed the injectors and fuel pressure regulator. Ran a little better with a little more power, but the heating problem was still there. The kicker I told the mechanic to gut the cats a week ago and cut the exhaust pipe in front of the muffler to see if that helped, and instead he cut the exhaust in front of the cats and run it. Did the same thing it had been doing, but 5° hotter and what bothers me is that not having the rear O2 sensors hooked up never threw a code. Got me thinking possibly ECU.

Most of the heavy duty trucks do not have a catalyst efficiency monitor in that time period. Even some of the 8.1 trucks are not monitored. From memory all the trucks have cats and rear 02s installed, but the 02s will not set codes. My buddy has a 99 K3500 4x4 Dually and even with the rear 02s unplugged, zero codes. Then PCM file and truck were stock, the rear 02 and catalyst codes were factory deleted. I believe only California trucks have them enabled.

The tune in my 2002 8.1 had the cat and rear 02s disabled as well even though they were present. Dual rear wheel cutaway van. Some of the later federal trucks did not even have the rear sensors installed. I have seen an 04 or 05 3500 without them as well as an 08 or 09 Workhorse RV without them.

Best guess, over 8,600 lbs
Federal truck = No monitoring
California truck = Monitoring

Some heavier GVW trucks were OBD1 until 97 or 98 as well. I pulled a 427 TBI out of a 97 or 98 C60.