4000 pressure relief valve

Ultradog MN

Well-known Member
Location
Twin Cities
What would make a PRV valve not work properly?
I'm still only building about 1700 psi on this latest 3 cyl 4000.
I took the top cover off again today and hooked a hose so it would pump the oil back into the sump.
I have a good, full flow.
Everything else inside was intact. So I pulled the pump and checked it out. As I mentioned before, from the paint on the bolts it has never been out. Intact gasket confirms that, seals are good. Everything looks good on the pump though you can't do much more than spin the gear.
So Now I'm wondering if maybe it's the prv.
I didn't think to check the paint on the prv before I repainted everything.
I remember having problems on a 3000 once and called the dealer to see how much they were.
He told me his computer said they hadn't sold one it over 10 years. So I didn't buy it and found the problem elsewhere.
I wonder if it could be a problem here.
Also, I guess I could check on Messicks but would a prv from a 3000 work in this system?
I have one of those in a junker.
I'm sure this is something simple.
But if anyone has any ideas I would appreciate hearing them.
PS, that gauge is a new, cheap China Maid job so you never know.
But to be 1K PSI off would be odd.

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Does the pressure go up and down with RPM? If so, it's your pump, not the PRV. Just because you have "good, full flow" doesn't mean the pump will back it up once you start putting a restriction against it.
 
Good thinking Bern.
I never thought to check pressure at higher rpms. Just at idle.
Should it normally produce 2500+ at idle?
I don't know but assumed it would.
I will check that on Monday after I get a new gasket.
 
Yes, a good pump should give you 2500 PSI at idle. Also, look close at oil temp when you do this test. If you have 1700 PSI with cold oil, what do you have with hot oil? If the pressure goes down proportionately with an increase in oil temp, that's also a dead ringer for a pump issue, or possibly a blown o-ring on your pressure tube.
 

No.. pressure will be lower at idle... and then go up with rpm and then as it approaches 2100 lbs the relief valve will start to modulate and the gauge may flutter between 1700 and 2200 or it may stay steady around 2000 pending on the relief valve. I though the book said test at 1600 rpm for max pressure buts it been too long.

bad pumps may test good for a few minutes when cold and then test lower and lower after 3 or 4 minutes of running.. they will only show 1500 lbs or less at rpm...

really bad pumps will test low from the go down.
 

Okay,, I said it was 1600 rpm and I was a bit off.. the book says pressure test at 1650 rpm on the 10 series... Dont have the other books in front of me at the moment.
 
I disagree with your statement. A good pump should easily be able to make relief valve pressure when deadheaded at idle. It's the marginal pumps (many in Ford tractors) that do not.
 
Not quite sure what you meant by that reply. What I'm saying though is that any GOOD pump will make relief pressure at any speed if deadheaded. Ford may say to test a pump at "x" RPM, however my statement is still true.
 

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