1998 k2500 454 getting hot

[newguyinnc]

It sure sounds like a water pump or clogged water passage problem. Are you sure the correct L29 head gaskets were used? They aren't the same as Gen V and previous head gaskets, but they will interchange freely. Putting a previous generation BBC head gasket on a Gen VI and vice versa can cause similar issues to this.

The motor did this same thing before the motor was rebuilt and had never been apart before this. My mechanic is an older gentleman and a good family friend. He called what he called his "big block guru" today and he wants to come down himself and actually see how the coolant is flowing. He asked who built my engine and when told, his exact words were "well then that takes human error out of it, he's the best around". He's almost wondering if the impeller on the new water pump isn't spinning on the shaft at higher rpms.

 

[1998_K1500_Sub]

Driving down the highway at 70mph gauge says 215. If I pull off at an exit it'll climb to 235. If I rev it to 2000 rpm it'll quickly come back down to 215. The whole time it's doing this, the ECU sensor in the intake is reading around 200°.

Well, at least that’s consistent with what it does when the engine is a road speed.

If there’s truly a problem here, it appears to be a restriction somewhere in the engine coolant circuit.

The radiator coolant circuit and thermostat seem to be unrelated.

 

[BeXtreme]

The motor did this same thing before the motor was rebuilt and had never been apart before this. My mechanic is an older gentleman and a good family friend. He called what he called his "big block guru" today and he wants to come down himself and actually see how the coolant is flowing. He asked who built my engine and when told, his exact words were "well then that takes human error out of it, he's the best around". He's almost wondering if the impeller on the new water pump isn't spinning on the shaft at higher rpms.

Could be a bad or wrong impeller on the brand new pump right out of the box. Could have been the right part number and wrong impeller. After everything else you have done, the water pump is almost the only thing left to try. Did the motor get a new one when it was rebuilt?

 

[newguyinnc]

Could be a bad or wrong impeller on the brand new pump right out of the box. Could have been the right part number and wrong impeller. After everything else you have done, the water pump is almost the only thing left to try. Did the motor get a new one when it was rebuilt?

Yep, brand new water pump when motor was rebuilt. I actually have an Edelbrock high flow water pump sitting here we tried to install and neither bolt pattern on the hub will match up with the pulley or fan clutch. I'm thinking the same thing about the pump other than there have been 3 pumps on this motor and they all did they exact same thing. Chances of getting 3 bad pumps?

 

[newguyinnc]

Well, at least that’s consistent with what it does when the engine is a road speed.

If there’s truly a problem here, it appears to be a restriction somewhere in the engine coolant circuit.

The radiator coolant circuit and thermostat seem to be unrelated.

I thought the same thing, but have had 3 different pumps on this motor and I have good flow coming back into the top of the radiator from the heater core.

 

[newguyinnc]

I've got half a notion to get a clear piece of hose to replace the upper radiator hose temporarily so I can physically see what kind of flow I'm getting with the thermostat open. I think if I've got good flow there, then there has to be a restriction in the block, heads or intake......which doesn't make any sense after having the most reputable engine builder in the area build it after hot tanking and rebuilding.

 

[1998_K1500_Sub]

I thought the same thing, but have had 3 different pumps on this motor and I have good flow coming back into the top of the radiator from the heater core.

Each half of the engine (with its associated head) may have different coolant flow properties that tend to cause higher flow on one half vs the other.

A pump imbalance could also exist at each outlet of the pump, but after three pumps, the flow in halves of the engine seem suspect and not the pump(s).

The flow in each engine half could be readily measured with pump removed, engine off and thermostat removed of course, and

- a water source (garden hose),

- an adapter (garden hose to coolant inlet hole in block),

- a blocking plate (to block off the opposite coolant inlet hole in block),

- a common water pressure gauge (to measure the pressure of the applied water, i.e., measured at the inlet to the block),

- a pail (to measure the outflow from the thermostat housing), and

- a stopwatch.

 

[1998_K1500_Sub]

… physically see what kind of flow I'm getting with the thermostat open. which doesn't make any sense after having the most reputable engine builder in the area build it after hot tanking and rebuilding.

The problem might be something unseen in the coolant passages.

Consider the flow test I proposed.

Or modify it to your liking.

Or dismiss it, as you see fit

 

[Frank Enstein]

Put the Autometer capillary bulb/sending unit in a "tee" fitting with the computer's temp sensor then compare the temps.

Putting an electric fan switch in the cylinder head is a great way to make the fan come on earlier.

Autometer gauges are +/- 3% over the entire range of the gauge so they are pretty accurate.

 

[newguyinnc]

The problem might be something unseen in the coolant passages.

Consider the flow test I proposed.

Or modify it to your liking.

Or dismiss it, as you see fit

That's actually a really good idea. I'll do some homework on a garden hose to block adapter. If one isn't available, I suppose I could always make one with a flat piece of steel and weld a bung to it to clamp a garden hose to. I have a plasma cutter and mig welder.