M925a2 running warm

[Steelreaper80]

My M925A2 is running about 20-30 degrees too warm. Engine temperature is running between 220-230 degrees and Trans temp holds steady at 225. I confirmed the gauge with an IR Temp gun. Upper Radiator hose is down to 195. The fan is working and comes on at 185 degrees and operates normally. Truck runs fine and has full power. At idle it comes back down to 180 degrees. Only going down the highway does it get to 220-230. Any suggestions? Radiator was flushed and filled last year with the red HD diesel O.A.T coolant. It ran at normal temp all of last year but only in the last month or so has it been getting too warm for my liking. Thanks guys!

 

[Elk1111]

I’d start out by changing the water pump and flushing everything again.

 

[simp5782]

My M925A2 is running about 20-30 degrees too warm. Engine temperature is running between 220-230 degrees and Trans temp holds steady at 225. I confirmed the gauge with an IR Temp gun. Upper Radiator hose is down to 195. The fan is working and comes on at 185 degrees and operates normally. Truck runs fine and has full power. At idle it comes back down to 180 degrees. Only going down the highway does it get to 220-230. Any suggestions? Radiator was flushed and filled last year with the red HD diesel O.A.T coolant. It ran at normal temp all of last year but only in the last month or so has it been getting too warm for my liking. Thanks guys!

Your fan shouldn't come on till 195/200

Is your fan staying one the whole time your gauge is saying 220/230? If so then you have a belt slipping or a water pump issue.

If no then i would run a new ground strap for the engine.

 

[WillWagner]

IR temp gauges SOMETIMES are correct. Install a known good gauge and see what it says. Also, check the outside of the radiator core. Bugs, mud, fins de bonded from the tubes will cause slow steady heating issues. Is there a stat in it? No thermostat will cause overheating. Diesel systems have 2 cooling loops, radiator and bypass or block. When the stat is closed, the coolant is shunted back to the inlet of the WP, this is the bypass or block loop. It helps the engine come up to temp quicker. When the stat opens, the body of the thermostat moves down and closes off the bypass loop and forces the coolant into the radiator loop. If no stat is installed or it is stuck open, 1/2 open, partially open, the coolant flow will take the path of least resistance, which is back into the block. The seal around the lower part of the stat is important too, it will also cause the above issue, but usually only on hot, hard, long uphill pulls.

Another thing, the new red, orange, ELC coolants don't mix well with the rubber pieces parts in older systems. It attacks rubber parts and can cause issues with the parts disintegrating over a short time.

There are other things you can do to troubleshoot like watching the thermostat drop, watching fan on/off temp, checking block pressure, checking water pump inlet pressure.

 

[Steelreaper80]

Your fan shouldn't come on till 195/200

Is your fan staying one the whole time your gauge is saying 220/230? If so then you have a belt slipping or a water pump issue.

If no then i would run a new ground strap for the engine.

It is definitely the water pump. It is puking coolant out. The good news is that I have a brand new one sitting on the shelf! I will put the new one on Monday. I tried to keep the temp down to 220 but occasionally it would creep up to 230ish. Did I fry anything? The new coolant looks brown instead of red so I know I will have to flush the system. I also have a block heater that I have been waiting to install. I guess now is the time.

 

[cbrTodd]

It is definitely the water pump. It is puking coolant out. The good news is that I have a brand new one sitting on the shelf! I will put the new one on Monday. I tried to keep the temp down to 220 but occasionally it would creep up to 230ish. Did I fry anything? The new coolant looks brown instead of red so I know I will have to flush the system. I also have a block heater that I have been waiting to install. I guess now is the time.

Hopefully you can replace the water pump and flush the coolant and get by without anything more difficult!

If you still have the original style of head gasket, I concur with WillWagner and do not recommend putting the extended life / organic acid type coolant back in. Despite the fact that the jug says it is fully formulated, my experience has been that it still eats silicone seals like the ones around the coolant passages in the printo-seal style head gaskets. I put Zerex G05 in my 923a2 and it started leaking at the head gasket less than a year later.

 

[WillWagner]

One more thing to check. If it is puking coolant from the cap, check the cap. If the cap will not hold the pressure stamped on the cap, it will overheat. A 10 PSI cap will raise the air to boil point to about 225. If the cap is failed, the coolant will boil around 212 + or - depending on concentration. Check the cap AND the radiator...if the seal bead on the neck is FUBAR, it will not seal allowing the air to boil to be sea level, 212 ish. Do this BEFORE the pump. Water pumps work or they don't. Normally the engine will overheat in minuets if it is failed, no circulation, top and bottom of the radiator are cool, engine is hot.

 

[Steelreaper80]

I drained the coolant and noticed it was extremely low. I ran Thermocure through the engine for 4 hours. It really worked. The water came out BLACK!

I could only get about 6 gallons into the system when filling from the overflow tank. After 5 flushes and fills, I drained the water, changed the pump, and installed the block heater. Both have been sitting on the shelf for over a year. Once I pulled the pump and the freeze plug I could see the inside of the block. It looks really good! I did a final flush with distilled water only and then it dawned on me. There is a 9/16th plug at the top of the driver's side of the radiator. I did my final fill from there and then topped off the overflow. 10 gallons! I am an idiot! It was probably running hot due to a combination of low coolant, bad water pump, and stupidity! I read the TM but it is occasionally not the easiest to follow. I put in just the normal green Peak low silicate concentrate and distilled water and added the SCA's from Fleetguard. All air has been bled and I made sure the thermostat opened and everything ran at 185 for 20 mins then shut it down. No leaks! I learned something today. It was a very long day but I think it was worth it. I will put it under load on an 800-mile round trip trek Thursday and Friday. We will see how it does. I still have a bad rear main seal leak but I will have it changed in about 2 weeks. Thanks for all the advice guys. I truly appreciate it.

 

[Russ Knight]

Good job!