M813 5 Ton Overheating

[Jared]

Hello,

Have a 5 ton M813 that overheated a little while back. Had been driving about 55 for 15-20 miles when it started steaming and pegged the gauge. Had for the previous several years always been rock solid at 180. Replace the thermostat and cleaned out the 2 vent lines but it's still running hot. Very short run got it to 220. Read some posts here and the advice seems to be if the water pump pulley turns and there are no leaks then that's probably not the problem.

Any suggestions?

Regards,
Jared

 

[74M35A2]

Guessing radiator scaled up. Is the cold side hose collapsed under suction, or what is the temp difference between the two large radiator hoses?

I'd drain and do a Cascade flush until fully warmed up, drain, and repeat. But, start with the difference of hose temps, and belt tightness.

 

[Archytas]

Could also be a blown head gasket.

 

[WillWagner]

Could also be a blown head gasket.

Nah, the gasket on an 855 will push compression out the sides before putting pressure in the cooling system. Is the top tank real hot and the bottom tank on the other side of the lower rad hose cold? The reason for checking the temp away from the outlet is that if the w/p is failed and no coolant circulating, the heated coolant will go down the coolant inlet into the lower rad pipe and into the bottom tank. Another thing, is the fan coming on? Did you look to see if the belts were still on the w/p?

 

[Archytas]

Nah, the gasket on an 855 will push compression out the sides before putting pressure in the cooling system.

Right. Because CI engines ALWAYS do what we want them to.

 

[WillWagner]

No, because of the design and installation of the liner and head gasket design. I should correct myself though. The old style gaskets, metal with neoprene grommets around one of the center head bolts and white water passage grommets will not put compression into the cooling system. The newer style, Cummins labeled them "Celastic", will put compression into the water passage if the liner bead fails, this usually happens from a low liner. The crappy material used on the "rubber" water passages combined with the seal bead around the gasket will force the compression that the low liner allows to escape right to the weak link, the water passage. This symptom didn't start until around 1996-1997 when the crappy new style gaskets were released. They also had a bad tendency to leak oil from the pt cavity, that is non pressurized, and the oil passage.

Yes, CI engines ARE predictable. The base engine is just a CI fired 4 stroke, very predictable and, for the most part unless someone has had their hands in it and f-ed it up by building an issue into it, do what we want them to do how we want them to do it. The base part is easy to diagnose. When electronics were added, That made it so they weren't predictable and did things that were never seen before and not work how we want them to work.

 

[73m819]

Could be the water pump, some of the 250s in the 809 series had PLASTIC impellers, they tend to break away from the drive hub from the shaft, I know a few SSers that have had this issue, when I had my truck apart after I taught it to fly, I replaced my water pump with a metal impeller, the on I took off was plastic.

 

[Jared]

Good info - Thanks. Have some things to check. May take me a while but I'll post results.

 

[Jared]

Took it to a truck repair shop. Wanted to have the coolant drained and flushed and I really can't do that at home. Took along a recently purchased NOS pump just in case. Turns out it was the impeller. Had seen a posting on the site saying if the pulley turns and no leaks around the pump it was probably OK. Then saw another saying that some of the pumps had plastic impellers and they do break. That's what this was. Interesting that the NOS pump would not fit the engine block. They just used the impeller from the new pump.