Cracked Oil Pump Housing on John Deere 750 from 1982

[Paul Campanis]

I would be very grateful for any insight into how to find out why my engine blew.

When we went to rebuild the engine we noticed the oil pump had broken! Now we are faced with a major rebuild.

We use this tractor for a food ministry to the poor and sick (cancer patients whos doctors have them on a nutrient dense diet).
All the food is giving free of charge and we have been blessed with amazing production.

I would appreciate any resources on rebuilding the engine. We are sending the crankshaft out to have the services ground. I am not sure whether or not to rebuild the head. The valves look good.

Please see photos below.

THANK YOU IN ADVANCE !


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[pmsmechanic]

I'm guessing that either the oil pressure relief valve is stuck or you are using a very thick viscosity oil.

 

[Paul Campanis]

Thank you pmsmechanic!
I like that line of thinking...

Do you know where the oil pressure relief valve is. I cannot find it here:

https://partscatalog.deere.com/jdrc/sidebyside/equipment/78833/referrer/navigation/pgId/17468307

 

[pmsmechanic]

If you go to the next page in the parts book it shows a picture of the oil filter. The piece marked 1 with the plug and a spring is most likely the pressure relief valve.

 

[Paul Campanis]

Well Spotted !
Thank you !

Here it says what it does.

Oil Filter Valve Assembly CH15497 CH10249

Check out the deal on Oil Filter Valve Assembly CH15497 CH10249 at Yanmar Tractor Parts

www.hoyetractor.com

 

[Paul Campanis]

I could use good instructions on how to install and test the Oil Pressure valve system.
Never have I done that before but I think it is vital now.

 

[pmsmechanic]

I could use good instructions on how to install and test the Oil Pressure valve system.
Never have I done that before but I think it is vital now.

Install a "T" on the filter side of the pressure regulator. You might have to scrounge up something that fits the threads. On one side of the "T" install a pressure gauge. Fill the assembly with oil and install a grease zerk on the hole that's left over on the "T". Using a manual grease gun pressurize the whole assembly. It should leak oil when you reach the relief pressure it's supposed to be set at.

I would also make sure that all you oil passages flow oil freely. You don't want to rebuild the engine only to find that there is some junk stuck in a oil passage somewhere.

 

[Paul Campanis]

Thank you for that idea pmsmechanic. I like it.
Do you have a photo of what that might look like?
Or, do you have a link to the "T" fitting?
Here is what is coming off of my JD750.
It is just a small spin on filter.

 

[pmsmechanic]

McMaster-Carr

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www.mcmaster.com

Try this website. These are all pipe thread fittings. I don't know what thread your oil filter has. If I was you I would take the pressure regulator out of the engine block and take it with you to a automotive store like NAPA and see if they can't match you up with something that fits. It might take a combination of adaptors to get everything to fit. I know grease zerks and pressure gauges are pipe thread.