700H Overheating

[AKLarry]

I'm trying to help a buddy with his 700H that is now overheating. Ironically he bought it used and until 3 weeks ago he couldn't get any heat. For real no heat, in the cab that is, (I forgot to say he's running this machine in Alaska pulling a drag building winter trails) anyhow... I replaced the valve at the block as it was mangled with pliers and we couldn't move it either way. I fixed broken wires on the temp control valve, replaced the temp control valve, he plugged the radiator off with cardboard, nothing! We figured a thermostat and a water pump would be a good start. Around the end of January I pulled it in to check this out, replaced the water pump with no event, couple scores in the wear plate at the back but nothing major. I went to replace the thermostat and discovered there wasn't one in there.

So here we are now everything back the way it should be and now it's overheating. I'm wondering if there's something I'm missing, maybe a vapor lock? Maybe there's something I'm missing, that caused the previous owner to pull the thermostat?

Thanks for the Help!

 

[Vetech63]

It seems every time an engine overheats, the first thing done is the thermostat is pulled out. Take a flashlight and check your radiator core for blockage. They are very hard to clean because the access is horrible. Air flow through that radiator core is what cools the engine.

 

[Mcrafty1]

Stupid question maybe but have you determined that the engine is actually overheating and not just a bad sensor(s)? Like checking with an infrared heat gun an the like?

 

[Mcrafty1]

Like Vetech63 said, check the rad and check the top/bottom radiator hoses for temp difference with a heat gun to determine if the radiator is cooling the water or not.

 

[Delmer]

Something fishy here... Did it overheat the first time it was used with the new thermostat? Taking the thermostat out is a bad idea, every modern engine that I've seen has a bypass thermostat, there are three openings to the thermostat, 1. the coolant coming from the engine, 2. the coolant going to the radiator, 3. the coolant recirculation passage back to the engine. If you remove the thermostat, there's nothing to force the coolant through the radiator. Even without that happening, if the radiator was plugged so air couldn't get through, it wouldn't help not having the thermostat. Put the flashlight on the other side of the radiator, so you can see through it, better yet one of those milwaukee scene lights, cause you won't see through it in most cases.

Need some temps, and what it's doing, losing coolant? boiling after half an hour? five minutes?

 

[AKLarry]

I'm not sure why the previous owner had done that. The machine ran fine the first day he ran it after i put the thermostat back in, but I think the ambient temp was lower that day. Also he tows a 10' wide drag and the amount snow varies from time to time. That will greatly effect the load and heating of the engine.
When I found the Thermostat gone I immediately went to the water pump. I had a Deere ag tractor once that wouldn't make heat and I found it had no thermostat. I put a thermostat in it and come spring the machine cool. I tried a bunch of stuff and in the end the machine had a plastic impeller on the water pump and all but the hub of the impeller was gone.
Long story short that was not the case here. This motor has a metal impeller. I will get more specifics on time to overheating and symptom of overheating etc.
I had thought to tell him to take a infrared gun. I'll make sure he does that.

 

[Diesel Dave]

It seems every time an engine overheats, the first thing done is the thermostat is pulled out. Take a flashlight and check your radiator core for blockage. They are very hard to clean because the access is horrible. Air flow through that radiator core is what cools the engine.

Further to what Vetech63 suggested, if the rad external core looks decent I would check that the fan is not installed backwards which would decrease air volume.

 

[AKLarry]

So the fan is in the dozer the way the parts book shows attached below.

I'm thinking it would move more air if it were flipped around as illustrated in my sketch...

 

[Diesel Dave]

Assuming it’s clockwise rotation (looking from the front).
It’s a blower fan so I would think the parts book orientation is accurate.

 

[Acoals]

It seems every time an engine overheats, the first thing done is the thermostat is pulled out. Take a flashlight and check your radiator core for blockage. They are very hard to clean because the access is horrible. Air flow through that radiator core is what cools the engine.

Yeah, don't clean anything, just pull the stat, easy!

 

[Junkyard]

What are the odds we get a bad radiator cap twice….?