Forum Home Forum Home > CJ-2A Discussion Area > Tech Questions and Answers
  New Posts New Posts RSS Feed - Oil pressure question
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Oil pressure question

 Post Reply Post Reply
Author
Message
jhg View Drop Down
Member
Member


Joined: 07 Nov. 2016
Location: colorado
Status: Offline
Points: 917
Post Options Post Options   Thanks (0) Thanks(0)   Quote jhg Quote  Post ReplyReply Direct Link To This Post Topic: Oil pressure question
    Posted: 15 Sep. 2023 at 10:09pm
Obviously at idle, pressure is a bit higher than when it is warmed up (30 minutes drive time).

At moderate rpm's pressure stays right about 32-35. Then (30 minutes) same rpm's it will read right at 39-40.

Is that normal? I have no actual concern. Just wondering.

I run rotella T4 10-30 diesel oil in it.
1948 cj2a. Rebuilt L-head, steering, T90, WO 636, steering, brake lines. So far.
Back to Top
Oldpappy View Drop Down
Member
Member
Avatar

Joined: 09 Apr. 2018
Location: Tennessee
Status: Offline
Points: 4912
Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep. 2023 at 10:13pm
That's good enough oil pressure. I wouldn't worry about it.
If you can't get there in a Jeep you don't need to be there!
Back to Top
jhg View Drop Down
Member
Member


Joined: 07 Nov. 2016
Location: colorado
Status: Offline
Points: 917
Post Options Post Options   Thanks (0) Thanks(0)   Quote jhg Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep. 2023 at 11:39pm
I am happy with it. Why does it read higher later when it is warmed up? At idle reads lower, at rpm higher.

I would have thought it would read the same or lower as well.
1948 cj2a. Rebuilt L-head, steering, T90, WO 636, steering, brake lines. So far.
Back to Top
Lee MN View Drop Down
Member
Member
Avatar

Joined: 13 Aug. 2008
Location: Harris, MN
Status: Offline
Points: 4952
Post Options Post Options   Thanks (0) Thanks(0)   Quote Lee MN Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep. 2023 at 11:42pm
Originally posted by jhg jhg wrote:

I am happy with it. Why does it read higher later when it is warmed up? At idle reads lower, at rpm higher.

I would have thought it would read the same or lower as well.


Multi-Viscosity Oil doing its job ?

Lee
               LEE
44 GPW-The Perfected Willys
49 2A
“If you wait, you only get older”
67 M715
American Made Rolling History
Back to Top
cowboy64 View Drop Down
Member
Member


Joined: 01 Nov. 2017
Location: south arkansas
Status: Offline
Points: 123
Post Options Post Options   Thanks (0) Thanks(0)   Quote cowboy64 Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb. 2024 at 8:03pm
Best post I could find to ‘highjack’ or revamp,, GPW engine, all bearings were plastiguaged and right in middle of specs,, can’t remember bore size, installed engine in my M38,, ran GREAT, 30-35 lbs oil pressure,, till temp came up to operate ing range,, oil pressure fell steady as temp rose,, checked with several known good oil pressure gauges ,, all the same ,, Melling 53 A pump appears to be in spec,, engine is on stand now ,, oil pump is all that’s been removed,, any guidance or what to watch for as I slowly disassemble to diagnose will be greatly appreciated,,, serial number pad behind water pump simply has the letter A.. thanks in advance,, Michael
mam
Back to Top
Ron D View Drop Down
Member
Member
Avatar

Joined: 27 Oct. 2019
Location: South Carolina
Status: Offline
Points: 1446
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ron D Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb. 2024 at 8:36pm
Originally posted by cowboy64 cowboy64 wrote:

.....oil pressure fell steady as temp rose,


fell steady to what psi?    Zero?
1951 M38
1951 M100
Back to Top
Bruce W View Drop Down
Member
Member
Avatar

Joined: 29 July 2005
Location: Northeast Colorado
Status: Offline
Points: 9651
Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb. 2024 at 8:43pm
  So what was the oil pressure at operating temperature?
  GPW engine serial number is on an oval-shaped pad on the right side, behind the oil filter. 
BW
It is NOT a Jeep Willys! It is a Willys jeep.

Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You!

We Have Miles to Jeep, Before We Sleep.
Back to Top
cowboy64 View Drop Down
Member
Member


Joined: 01 Nov. 2017
Location: south arkansas
Status: Offline
Points: 123
Post Options Post Options   Thanks (0) Thanks(0)   Quote cowboy64 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Feb. 2024 at 3:50am
30-35 psi at start up .. would turn ignition off as pressure went below 5 psi… 
mam
Back to Top
harve View Drop Down
Member
Member


Joined: 02 Sep. 2011
Status: Offline
Points: 66
Post Options Post Options   Thanks (0) Thanks(0)   Quote harve Quote  Post ReplyReply Direct Link To This Post Posted: 29 Feb. 2024 at 12:27pm
I’d be interested to find out what cowboy64 finds , concerning the low oil pressure when hot
Back to Top
Slowtwitch View Drop Down
Member
Member


Joined: 23 Jan. 2023
Location: Montana
Status: Offline
Points: 89
Post Options Post Options   Thanks (0) Thanks(0)   Quote Slowtwitch Quote  Post ReplyReply Direct Link To This Post Posted: 29 Feb. 2024 at 1:54pm
I would try heavier oil.
Back to Top
otto View Drop Down
Member
Member
Avatar

Joined: 26 Feb. 2012
Location: Orygun
Status: Offline
Points: 2266
Post Options Post Options   Thanks (0) Thanks(0)   Quote otto Quote  Post ReplyReply Direct Link To This Post Posted: 29 Feb. 2024 at 1:56pm
Originally posted by Slowtwitch Slowtwitch wrote:

I would try heavier oil.
Sounds like a task for Motor Medic!
47 CJ2A w/fuel injected boat engine
48 CJ2A
64 Ford Econoline Travelwagon
If you can't get there in a Jeep, get a motorcycle!
Back to Top
cowboy64 View Drop Down
Member
Member


Joined: 01 Nov. 2017
Location: south arkansas
Status: Offline
Points: 123
Post Options Post Options   Thanks (0) Thanks(0)   Quote cowboy64 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Feb. 2024 at 6:27pm
Just plain old Mobil 30 w,, will slowly remove parts to try and diagnose,, will definitely keep informed as I dig into it,, to nice of an OLD engine to not be enjoying!
mam
Back to Top
muley View Drop Down
Member
Member
Avatar

Joined: 25 Jan. 2021
Location: idaho
Status: Offline
Points: 821
Post Options Post Options   Thanks (0) Thanks(0)   Quote muley Quote  Post ReplyReply Direct Link To This Post Posted: 29 Feb. 2024 at 8:41pm
You mentioned the engine installed into M38 and that you had swapped in good known gages during prelim troubleshooting.  Are you still 24V and using the stock electric gage and if so did you check the sending unit?
Joined Jan-8 2015
I never met a mule I didn't like!
OD Mule 01-52 M38
Big Red 19fiddy CJ3A salad
Back to Top
cowboy64 View Drop Down
Member
Member


Joined: 01 Nov. 2017
Location: south arkansas
Status: Offline
Points: 123
Post Options Post Options   Thanks (0) Thanks(0)   Quote cowboy64 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Mar. 2024 at 6:41am
It was converted to 12volts many years ago,, at one time I had three gauges on engine.. 
Michael 
mam
Back to Top
WeeWilly View Drop Down
Member
Member
Avatar
Sponsor Member x 2

Joined: 07 May 2009
Location: Clayton IN
Status: Offline
Points: 3423
Post Options Post Options   Thanks (0) Thanks(0)   Quote WeeWilly Quote  Post ReplyReply Direct Link To This Post Posted: 01 Mar. 2024 at 1:55pm
 I had an engine like that which really puzzled me.  Oil pressure was 35-40 on start up and would keep that pressure even when the engine came up to 180 degree temperature. When I took  it out on the road with in 2 miles the oil pressure would drop to about 12 lbs. at 30 mph and about 3 lbs at idle. After driving it like that for a few years the crankshaft broke at #2 journal.  I can't prove it but i believe the crank was cracked where it broke and opened up with heat to allow the loss of oil pressure. I hope yours is not this severe and am also watching to see what is causing your problem. Good luck with your search.

    Jim
47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
Back to Top
cpt logger View Drop Down
Member
Member


Joined: 23 Sep. 2012
Location: Western Colorad
Status: Offline
Points: 3043
Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 01 Mar. 2024 at 7:25pm
OK, I have a weird one out of an Alaskan bush plane. There is zero chance that this is the same cause. However, the symptoms are very similar. 

The pilot said the oil pressure was normal as it had been for the five years after we had overhauled this engine. Then one day way out over the tundra, the oil pressure jumped from 40 PSI to 80 PSI. He eased off on the throttle & got the airplane home. That night he swapped in his "spare" engine & sent us his old, now spare, engine.

He requested us to hold off on the overhaul until he could attend the tear down. Of course we agreed. We even sent him a mid-time engine to use as a spare engine for the rest of the summer flying season, as also requested. He did have four more of the same airplane in his fleet, so a spare engine was nice to have.

When the time came, with him helping/watching, we pulled it apart. All was normal until we split the crankcase. The case came apart, but the front main bearing saddle stayed with the crankshaft. I am glad that the owner was there as he said "If I wasn't there to see it, I would not have believed it.". 

None of us had ever seen anything like it. If he had not seen it happen & eased the airplane home, It would likely have failed before he got home. That would have been bad. Perhaps deadly bad.

The broken saddle had rotated enough to seal off the oil passage feeding the front main & rod bearings as well as the propeller controller. The only thing feeding the front bearing & #1 rod bearing was splash lubrication. The propeller went to high pitch, or "low gear" as it is designed to if it loses oil pressure. With the oil pump having fewer bearings & no propeller to feed, the oil pressure went up.  

Amazingly, the crankshaft was just fine. IIRC, We had to turn it down one size. Other then that, it passed both Magnaflux & ultrasound tasting.

We overhauled the engine again, that crank case was replaced. It now sits behind glass for folks to marvel at. All four pieces of it. The crank cases are usually two halves.

The engine went to full TBO, (Time Between Overhaul), twice more. I know as I overhauled it two more times after that.

Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2022 Web Wiz Ltd.