John Deere 750 CUT Radiator

[xp190]

Hello Folks

My 1985 JD750 has started getting hot in these summer days.
I did a coolant flush about a year ago, cleaned the exterior of the radiator, new belt and thermostat after an overheating incident.

Last time I was using it just to ride around on, the temp climbed to 100*C and stayed there. It did not boil over, but this seems too hot.

I started looking things over, and the rad has seen better days. I am suspecting that it is clogged and no longer dissipates heat as fast as it should.
I started looking for a replacement, but I have had no luck.
The OEM parts are no longer found anywhere, and I could not find a replacement on any grey part sites.

Would anyone have any idea if a replacement radiator could be had for my JD750?
The part number is CH15524 from the Deere parts catalog, engine is 2T80U-J.

If not, I will take it to a rad shop and have it cleaned/repaired as best as possible, but I'd prefer to go with a replacement.

I'd prefer not to have to scrap this old gal just because she gets a bit hot, and she has been a real help in the winter months.

Thank you kindly
xp

 

[5030]

Did you try flushing it from the fan side outward? Spray on a dilluted mixture of Dawn dis soap and water and clean from the fan side.

 

[xp190]

When I was flushing it last year, I took it out and soaked it in detergent, rinsed it and blew it out with compressed air.
It was quite badly packed with all sorts of dirt, but since then, it has not seen any real use, so the exterior of the rad is still clean, yet it is overheating, which is why I'm suspecting the interior is the issue.

I thought about some sort of flush which would remove the scale build up, and I do see a bit of it when I open up the cap, it probably gets worse closer to the bottom.
I might remove it again, and try to soak it with CLR to see if it will help. I know CLR is not the best for seals, so the rad has to come out.

 

[nyone]

Take a flashlight and hold it to the back of the rad while you look in the front. Typicaly the corners clog up first. Things can look clean but not allow air though.

If it is a blockage in the liquid side you may try soaking it in something like vinegar.

 

[Harry in Ky]

You're convinced the coolant is actually as hot as the gauge says it is?

 

[xp190]

The gauge is also new, so I'm sure that it is as hot as the gauge says, but I will verify with another thermometer.

 

[5030]

When was the last time you renewed the coolant? I change mine every other year without fail.

CLR would work but the rad certainly has to be removed. Used to be able to buy DuPont rad flush crystals at the auto parts store but I have not seen it for years.

 

[bohaslup123]

The gauge is also new, so I'm sure that it is as hot as the gauge says, but I will verify with another thermometer.

had the rad on a jd755 cleaned and rebuilt several years ago-cost was about 150.00-sloved all the heating problems-Iam sure you can find a shop in your area that still does rad repair-good luck

 

[xp190]

Thanks for all the input

I spent a bit of time troubleshooting this weekend.

I took out the rad and gave it a bath in CLR, some sediment came out, but not much. The exterior was very clean, a few fins bent which I straightened out.
Flushing everything out, I did not see any resistance to flow, probably not plugged up, but there is quite a bit of sediment I can see through the rad cap.
After flushing I put everything back together, filled it with water and rad flush which will stay there for a few days, then I ran it.
When I say I ran it what I mean is I let it idle for a few minutes, then took it for a short ride around the block in high gear and high rpms, not flooring it, but 2000rpm at least.
The temp still creeps up to 100*C, just under it during the ride so no change, stopping and letting it idle will very slowly bring it down.
I checked the temps before and after flushing.
I verified the temp gauge with an IR temp gun, the upper radiator hose showed 70-80*C, the thermostat housing showed the same temp as the gauge, and that is where the sending unit is found, so 90-98*C right on the body.
The lower radiator hose was always 20*C lower then the upper, so that seems to me the rad is doing it's job, I am not sure how efficiently, but that is a significant drop in temp, and I think it should be keeping the engine cool, yet it still gets hot.

I am not able to find an operating temp for this engine, the manual says the thermostat opens at 71*C, and I replaced it about 2 years ago, but does that mean it should stay at 71*C? It normally ran at 80*C, I assumed, possibly incorrectly this is it's operating temp.

After all this, I am now suspecting something else is at work here, possibly a bad head gasket, but I do not see oil in the coolant, nor do I see coolant in the oil.
I have not adjusted valves on this engine since I bought it quite a while back. I think a compression test might be helpful here followed by a leakdown test.
I do not have a diesel compression tester, any suggestions for one?

And of course, any tips on what else I could check?

Appreciate all the help, looks like this is going to be another adventure, hopefully just as exciting as replacing the clutch was.

Thank you
xp

 

[xp190]

Some more details

I got my hands on a cooling system test kit. I loaded it up to 15psi, the tool didn't hold that great, but I managed to seal it and it held 13psi overnight, so no leaks there, or at least nothing serious. Rad cap seems okay too.

I'm no diesel expert, but what else could be causing it to overheat like this?

I'm going to take the valve cover off at some point and see if anything is broken, and do a pressure test also.

cheers
xp