Can you have too much oil pressure?

mbehne

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Searched and found lots of low questions but not high. Is there such a thing as too high? This truck and MV's in general are new to me. At cold start it will read 120psi. Warm idle is 90 and loaded hot still just about 120. This truck had just received spin on filters and fresh oil before I got it. Is there a way to mess up the filter install and be running the engine bypassing the filters or such as I got no instructions with it. Any other thoughts?
thanks,mike
 

scooter01922

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I would venture a guess that perhaps the sender and the gauge are not matched. If you have the 0-60 sender and a 0-120 gauge you would have readings similar to yours. I would first double check your readings with a good mechanical gauge and report back.

Looks like someone beat me the the answer while i was typing ....
 
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m16ty

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There will be either "60" or "120" stamped into the sender. Sometimes you have to scrape a little paint to be able to read it.
 

mbehne

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Thanks guys, I was thinking if it had the wrong sender it would show low but I'm backwards. I'll get a manual gauge on it and check the sender stamp #'s. Mike
 

mbehne

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Spot on! Pulled the sender, plainly stamped 60psi. Manual gauge reads 70 cold idle, 40psi warm idle and 60-65 @ 2200 warm.
 

scooter01922

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There ya go, much better. Some good readings you got there, must be a nice tight engine. Now just get the right sender and you will be all set.
 

Amram

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My truck barely reads 30 psi most of the time.....Does that mean it has a giant blackhole in it somewhere sucking all the oil pressure away. It doesn't really leak anywhere.
 

Dipstick

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Yup. Already did the mismatched sender and gauge thing. I always thought 90 PSI cold was a bit much. Now I get about 30 at idle with Shell Rotella 15W-40 and Jatonka spin-ons. Whistler turbo rebuild is up next. I think the exhaust turbine seal is leaking oil. My Whistler is "Brutus". 30 PSI at idle is pretty decent. Have driven/rebuilt good running diesels with less at idle.
 

Amram

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Ok.....good to know 30 psi is good pressure for a 60psi guage. I replaced my oil with Mobile1 15w40 and installed Jatonka spin-ons as well. Oscar seems very happy now with this.
 

TAKPAK

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I had both the gage and the sending unit go bad on mine. Replaced both with matched set. Currently, running up to 90 PSI when cold at 2000 RPM, then settles in at 60 PSI hot, at 2000 RPM's. Stays right at around 60 PSI most of the time. Engine has been replaced, in 1995 according to the data plate. Low miles and tight. Has the "thick deck" block/head and the upgraded "D" turbo. I'm using Delo 400 15-40.
 

Dipstick

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takpak.....that's the type of oil pressure reading I used to get before I switched to matched 0-60 gauge and sender. Now my oil pressure is in the 30-45 psi range. I was a Navy Engineman from '73-'77.
 

TAKPAK

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takpak.....that's the type of oil pressure reading I used to get before I switched to matched 0-60 gauge and sender. Now my oil pressure is in the 30-45 psi range. I was a Navy Engineman from '73-'77.
Thanks for the info. You were an engineman eh? So was I. What ship was it? I was on the Pyro, AE-24. 70-72! Made EN-2 just before I got out.
8)
 

MarcusOReallyus

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To answer the original question, yes, you CAN have too much oil pressure. That does bad things.

That's why we need accurate gauges!
 

Carlo

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My 1966 M35A2 has this same high presure. I dont have any oil being blow out the blow by tube and no oil leaks. Seeing my motor is not blowing it out I would rather have to much than not enough. Dou you have the continental or white motor? C or D turbo?
 

TAKPAK

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Same as you Carlo, I don't have any leaks and no oil spewing out anywhere. Originally, when I got the truck last year, it showed over 60 pounds. Then it scared me one day, went pegged the gage at 120 PSI and stayed there. Then, it suddenly dropped to 0 (zero) pounds. At that point, I figured the original set had give out. So, I ordered a matched gage and sending unit. After that, it showed around 80 or so at startup, then after it's warmed up good, hovers around 60 PSI. I have not absolutely determined what engine it is, but I'm pretty sure it's the Continental. It has been replaced, in 1995 according to the data plate, with an entirely new engine. Has the "D" turbo, and the "thick deck" block/head arrangement. Really good running engine.

My Duramax diesel runs at 60 PSI cold, then when hot, it drops to about 15 at idle, and 30 at 1500 RPM, and 50 at 2500 RPM. Go figure.....but the dealer says that is correct.
 

brianp454

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Searched and found lots of low questions but not high. Is there such a thing as too high? This truck and MV's in general are new to me. At cold start it will read 120psi. Warm idle is 90 and loaded hot still just about 120. This truck had just received spin on filters and fresh oil before I got it. Is there a way to mess up the filter install and be running the engine bypassing the filters or such as I got no instructions with it. Any other thoughts?
thanks,mike
Hey TAKPAK!. Nice to see you on here. I’m in Portland so best we will cross paths one of these days.

I think there are different issues here that are getting confounded, so I’ll try to address them one at a time.

Can Oil Pressure be Too High? Yes! Abnormally high oil pressure can suggest that oil is not flowing properly, can blow lines and filters, wastes power by adding necessarily high load on the pump drive, etc. If your engine is truly developing abnormally high pressures, you should check out why it is happening.

What’s happing here is that you have a system composed of a pump and fluid flow path (the engine). The pump (and regulator) generates a pressure to move the fluid and thus the flow rate varies as a function of pressure. If you make a plot of this you usually get a curve for centrifugal pumps and a line of sorts for constant displacement pumps such as ours. The engine also has a curve that also shows the relationship between pressure and flow. Refer to the pic I found on the internet to illustrate the point. The intersection of these two curves will give the pressure and flow for the overall system. Of course, the pump and engine curves can change as a function of the fluid (type, viscosity, dilution, etc.), temperature, clearances, etc. As the engine wears I would expect the impedance curve to drift so that operating pressure reduces. Note that with pump systems pressure is often measured as “pressure head” as a distance so that it easily correlates to the height of the plumbing system in industrial applications. Hope this helps, wanted to lend an explanation without writing a thesis.
pump_total%20SRC.jpg

Another issue is the accuracy, precision, etc. of the sending unit and gage in the truck. If you have concerns about these sort of issues you should check your gage and sending unit as the other guys suggest (and you already have checked it with another gage, hopefully it is reading properly). As an example, if you take a known good (preferably calibrated) gage and put it on a T with your sending unit and a pressure source such as regulated LP air, you should be able to step through the range in say 5 psi increments and get the same reading on both gages. Otherwise you have an error. It looks like the mismatched gage and sending unit caused the issue that kicked this discussion off.

What I consider the best value of the gage in the cab is not the pressure itself in relation to a standard, but more having the ability to see if anything causes a change in pressure. Specifically something that may be wrong with the engine or knowing when to shut it down to investigate.

I run DELO 15-40W in my truck with jatonka spin-ons and it rarely moves much from 30psi. I haven’t taken time out to check it vs. another gage.
 
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Dipstick

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I spent four years aboard the USS Coronado LPD-ll. Gator freighter. I was assistant supe of the boat shop. I too made second just before I got out. Never sewed it on though. Left a week early. Been regretting it ever since. I was the guy who's clean work uniforms still smelled like diesel fuel and hydraulic fluid. My shipmates presented me with a plaque with a GM fuel injector mounted on it just before I shoved off. It hangs in my living room to this very day. Always cool to hear from another EN/snipe/squid! My phone is 908-319-3029. Would love to hear from you. If we're former swabbies....why do we drive Army trucks?
 

Dipstick

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I just observed my oil pressure yesterday. 60 psi cold start up at 75 degrees OAT with Shell Rotella 15W-40. 30 psi at idle after a half hour drive with 170 showing on the temp gauge. Too busy while driving to notice what it was doing at speed. I'm going to have to check that out. In my diesel mind 30 psi at idle is magnificent.
 
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