Oil pressure relief valve

[Christianfishn]

Hey all, trying to find the tm for locating the oil pressure relife valve. Either I keep overlookin it or am stupid. Could someone point me in the right direction for a diagram that shows where it is and how to ensure it is functioning? I thought it is found under the oil pump but am not sure. Any help here would be great. Im changing my oil pump soon and want to check it for sticking etc. Thanks all.

 

[richingalveston]

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I was not aware of there being an oil pressure relief valve on a cucv. If there is it has to be on the pump itself.

 

[cpf240]

Are you maybe thinking of the one at the oil filter base?

 

[Kaiser67M715]

The filter has a relief valve, that bypasses a dirty filter. I'm not positive in the 6.2 but the civi 6.5 had it in block, same with the anti-drainback valve

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[Christianfishn]

I have checked the vacle under the oil filter housing. Thought that was the drainback valve...
I just want to make sure when I change my pump I take care of everything I can. Usually these relif valves have little springs that after sitting for a few years then being used could break.
Earlier this year I had a sudden low oil pressure issue (confirmed with mechanical guage) from the rear top of the block. Went from 30 at idle to 7-10. It went away for a week then came back and has been that way ever since. Once the oil is very hot it reads almost no pressure. Driving gets up to 20. I know it sounds terrible but have put on 6k miles including a 950mi trip in one day with this issue and every now and then it haunts me and i start looking for an engine but mine continues to run minuse a periodic lifter tick. I know it needs more oil.
Ive had a very hard time trying to get the pan seperated from the block... Tried little chisels, rubber mallet, wedges, cant get the thing to seperate so ive put it off :/ ive checked the oil for metal fragments best I can without dropping the pan. I guess thats a different thread though and I went off on a tangent haha

Thanks for the help, I guess I wont be able to find a relief valve if there isnt one!

 

[cucvrus]

Oil pumps do NOT create oil pressure.In a high mileage engine, low oil pressure is often due to a combination of worn main and rod bearings and crankshaft journals. The oil pump itself does not create pressure. It produces flow and the resistance to that flow produces pressure. Resistance is created by the orifices in the engine block through which the oil flows, and the amount of clearance between the bearings and crankshaft journals. As the bearings wear, clearances increase allowing increased flow which reduces pressure.

 

[Kaiser67M715]

Oil pumps do NOT create oil pressure.

Yes and no, oil pumps create volume and flow, the clearance in the engine helps to create pressure, BUT low volume and flow can also mean low pressure. It's essentially fluid dynamics 101, change one part of the equation, another must change, in this case if clearances are fine, flow or volume can change the pressure.

I would pull the pan and inspect, having a new pump on hand if everything seems fine won't hurt, but should you find excessive bearing clearances, and you want to rebuild, it would probably be better to have a new pump then a used one that probably has eaten some metal.


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[cpf240]

The filter has a relief valve, that bypasses a dirty filter. I'm not positive in the 6.2 but the civi 6.5 had it in block, same with the anti-drainback valve

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Per the GM Product Training Manual for the 6.2 liter diesel engine:

"The filter used in this engine is called a full flow filter, because all engine oil normally flows through
it. If this full flow filter becomes clogged, the engine is equipped with a by-pass valve which is spring loaded. This
valve protects the engine from oil starvation by opening when increased pump pressure tries to pump oil through a
clogged filter. When the pressure causes the by-pass valve to open, the oil by-passes the filter and the engine
continues to receive lubrication."

I did find the part mentioned in the -20p TM