Overheating 6.5L M998?

[karlsmith]

I replaced the water pump and thermostat and it's still running hot. Took the thermostat out, and can see the fluid cycle in the reservoir, but has made no difference. Any ideas? I think the 6.5 doesn't have the auxiliary clutch fan like the 6.2?

 

[Bulldogger]

Is it displaying signs of overheating or just the temp gauge showing that? Gauges lie.
I don't have a 6.2L so can't offer more on the sensors that engine uses, since I'm not sure they're the same. If you haven't replaced the thermostat and flushed and filled the coolant, that's a great thing to do, whether or not she's giving high temp signs.
I plan to replace my sensors and gauges, as they are old and I don't trust them (not that we ever should!).

Bulldogger

 

[Action]

Clean between radiatot andcoolers and straighten bent fins.

 

[ryanruck]

Clean between radiatot andcoolers and straighten bent fins.

Yep, go get a radiator fin comb and straighten the fins out:



When cleaning the radiator don't use a super high pressure pressure washer to clean it out or you'll start flattening fins and making more work for yourself.

I'd maybe even suggest getting one of those coolant flush kits and plumbing it into the system and running some CLR through everything since it sounds like you could also have blocked passages in the radiator. Just make sure to flush the system extremely thoroughly before filling it back up.

 

[NDT]

Radiator could be plugged. Hydraulic fan clutch the same between 6.5 and 6.2. Are you sure you installed the appropriate pump for v-belt or serpentine application?

 

[jeffy777]

I replaced the water pump and thermostat and it's still running hot. Took the thermostat out, and can see the fluid cycle in the reservoir, but has made no difference. Any ideas? I think the 6.5 doesn't have the auxiliary clutch fan like the 6.2?

In my mind(The mind of the criminally insane):
1. I would use an infrared thermometer your gauge may be reading wrong.
2. All M998's have the aux clutch fan, I thought. Later versions, have differing belt configurations. All should have the clutch fan, I think. (I don't know of a HMMWV config that does not, but...)
3. You can have any number of obstructions. I would after that flush the coolant and run hoses to see how the flow is with the thermostat out. I think it will still flow somewhat around the water pump. (Do not run truck dry or with garden hose. I think that would be bad even for a small period of time.)

Be careful new engines are the cure for running too hot too long.

 

[Action]

nm

 

[karlsmith]

You guys are awesome, thanks! Going to start out with the flush, then move to the infrared to measure the heat off of the cold cylinders to determine if a jet is obstructed. Will post the resolution. Radiator must not be something that is replaced when they do an MWO refit. Mine was done in 2007 and only has 4K on the odometer (purchased this year). An interesting tidbit, is that it had an "06" hoodmarking (commanders call sign). Had a boatload of commo stripped off of it, but the engine is the peppiest I've ever driven.