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Post by Ryan_M on Apr 4, 2016 12:40:33 GMT -5
My MB motor oil pressure is at 20psi at idle and maybe 30 at higher RPMS. Should I be concerned?
I reviewed the videos of when it was in the generator and that gauge also read 20psi but I figured it was just due to always running at low RPM's.
Should I change the oil pump?
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Post by Deleted on Apr 4, 2016 12:55:40 GMT -5
As a genny motor was it fitted with an oil filter (w/flow restriction) or a restrictor orifice at the timing cover?
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Post by Ryan_M on Apr 4, 2016 13:59:21 GMT -5
Flow Restriction? Restrictor orifice? Didn't even realize there were such things.
I removed the Military oil filter that was on it originally and installed a random orange (Fram?) civvy Jeep style one that I found in a junkyard. New lines and a new fitting on the side of the block beneath the fuel pump. Trying to google these restrictors now. Is there something I can look for on my set-up that will allow me to determine what I have?
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Post by Deleted on Apr 4, 2016 14:04:47 GMT -5
Oil pump pressure is governed by a calibrated spring at the pumps own pressure relief valve. 20 at idle and higher at higher RPM is ok but nevertheless something to keep your eye on, especially this summer. You just don’t want to see it down around 5. Is this the original oil pump? Last known rebuild or replacement?
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Post by Ryan_M on Apr 4, 2016 14:13:07 GMT -5
I believe this is the original oil pump but I don't know for sure. Given how incredibly unmolested the rest of the motor was I'm guessing it's been untouched since it was installed at the factory.
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Post by Deleted on Apr 4, 2016 14:31:46 GMT -5
I think the early L134 had a .070 jet at the timing cover gear oiler but they went to .040 in the '50s. The oil filter has a small restriction in the vert tube inside. I might be talking out my axx.
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Post by athawk11 on Apr 4, 2016 17:25:13 GMT -5
Oh Rick...my hairy ape like friend... The MB is a chain drive block. No oiler. Wink, wink.  |
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Post by athawk11 on Apr 4, 2016 17:29:51 GMT -5
I will add...
The Willys service manual states the acceptable minimums to be 6psi for warm idle and 20psi at 2,500 RPMs. I'm thinking you're good to go.
Tim
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Post by Deleted on Apr 4, 2016 17:31:31 GMT -5
From a poor memory, I believe Willys said 10psi idle, 30 down the road.
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Post by Magilla Gorilla on Apr 4, 2016 18:27:06 GMT -5
Oh Rick...my hairy ape like friend... |
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Post by Deleted on Apr 4, 2016 18:28:19 GMT -5
You slay me Hawkridge. 
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Post by Haines Garage on Apr 4, 2016 18:42:26 GMT -5
Oh Rick...my hairy ape like friend... The MB is a chain drive block. No oiler. Wink, wink. That's a GPW Engine... In your pic. And you are 100% correct. |
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Post by Ryan_M on Apr 4, 2016 18:51:59 GMT -5
I just went for a lengthy drive. At low idle the pressure hangs at about 15psi. At normal driving speed all the way up to 60mph (with overdrive) I don't think it ever reached 25psi. A hard blip of the throttle when in neutral maybe bounced the needle to 28psi.
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Post by athawk11 on Apr 4, 2016 18:52:00 GMT -5
Rick, just having some fun with ya. I assure you, it's a term of endearment.
On further review, Lee is right, but so am I. Kind of. Chain drive acceptable minimum...10 psi. Gear drive acceptable minimum...6 psi.
HG, yes sir...GPW.
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Post by Deleted on Apr 4, 2016 18:56:51 GMT -5
Rick, just having some fun with ya. I assure you, it's a term of endearment. I know pal, I love ya too. Right turn Clyde! Attachments:
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Post by Deleted on Apr 4, 2016 19:40:49 GMT -5
My thoughts and a guess, since the idle oil pressure is good the internals in the engine are probably good....low oil pressure at speed, I'm betting the pressure relief valve in the oil pump is bleeding off too early....
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Post by athawk11 on Apr 4, 2016 20:12:28 GMT -5
My thoughts and a guess, since the idle oil pressure is good the internals in the engine are probably good....low oil pressure at speed, I'm betting the pressure relief valve in the oil pump is bleeding off too early.... Gary, Good call. I was thinking the same. Perhaps a spring upgrade...or maybe pull it and stretch it a bit. |
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Post by Deleted on Apr 4, 2016 20:24:56 GMT -5
My engine has never had tremendous oil pressure. It has always been close to what the manual reads. I had always used 10w 30 oil. A few years ago I switched to 10w 40 and got a huge improvement.
However, I do always keep a mindful eye on it, especially in the southern Summer's temps...it will thin out quickly.
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Post by Ryan_M on Apr 4, 2016 20:41:25 GMT -5
I think Gary may be onto something. Seems strange that it's strong at idle but really doesn't improve all that much at higher RPMs. My other jeeps are lower at idle and higher at speed.
I've never done anything with any oil pump. Is there a good tutorial on how to adjust the relief valve? I'm being lazy right now and not even cracking open the manual...
I'm also only running the 10w-30 because it was all I had on the shelf last week and knew I'd be doing an oil change very soon again anyways. I have since restocked my supply of 15w-40.
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Post by Deleted on Apr 5, 2016 1:02:57 GMT -5
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Post by Deleted on Apr 5, 2016 5:52:03 GMT -5
Clean the relief valve in the oil pump. It might be stuck. You can also shim up the spring with a washer behind it. Possibly try another gauge, but you said both read the same I think. Oilly
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Post by Ryan_M on Apr 5, 2016 6:44:18 GMT -5
Right on guys! I pulled the relief valve spring, stretched it a bit then shimmed with a few washers. I fired up the Jeep and the gauge instantly pinned itself at 80++psi. I shut it down immediately. Obviously too high but I (well, you guys...)appear have found the culprit. I removed the washers and just went with the stretched spring. Pressure on the next restart was right about 25 at idle at 40+ when revved. I don't have enough time this morning to dial it in but I feel a lot better now. I'll mess with it later when I have more time and my fingers don't freeze as soon as I walk outside.
Interesting to note the difference in the MB oil pump and the civvy one. I "practiced" finding the valve spring on the old 3A motor which still sits on the floor in my garage. That spring is much larger and there is a ball bearing for a valve. The MB spring is a lot smaller and has a thimble-like valve as opposed to a ball bearing. Basic knowledge for many but I had never touched an oil pump until this morning.
When I do get back to this - Is there such thing as too much pressure at idle? Should it drop down to 5-10psi or is 20 okay? And I'm thinking the upper limit should not exceed, what, 50-60psi?
I appreciate the help.
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Post by Deleted on Apr 5, 2016 8:04:26 GMT -5
The pressure relief valve only governs the maximum allowed oil pressure, so it really shouldn't have much, if any, effect on oil pressure at idle. Unless it's on a cold morning...
I would set the spring so the oil pressure doesn't rise above the maximum allowed at speed (I don't remember what the spec is, but 45 sticks in my mind and considering the old hot rodders adage: 10 psi per every 1000 rpm.... 4000 rpm "redline"= at least 40 psi.)and just let the idle fall wherever it wants to... Just my lowly opinion...
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Post by Ryan_M on Apr 5, 2016 8:23:18 GMT -5
I did not have time to let it warm up this morning and it's only about 20 degrees here. May explain the initial higher PSI at idle.
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Post by athawk11 on Apr 5, 2016 11:06:44 GMT -5
Well, that's good news. For comparison, my GPW chain drive with original military pump...
Cold Idle...25 PSI
Warm Idle...15 PSI
Cold 2,000ish RPMs...45-50 PSI
Warm 2,000ish RPMs...35-40 PSI
Rotella-T 15w-40
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