M38A loosing oil pressure

bobbymc · Post by **bobbymc** » Sat Jun 30, 2018 7:14 am

Hello everyone
Thanks for the add, i own a 1953 M38A, I have slowly been bringing back to
Life, yesterday i finally got it registered and took it on a 15 mile drive. Iv noticed my oil pressure dropping to almost 0, engine is not knocking or not loosing oil. It’s a new mechanical gauge and i have replaced all lines with
Original parts. My question is should i replace the oil pump? And if so how difficult is it. Thanks in advance.

Post by **wesk** » Sat Jun 30, 2018 8:42 am

There are several things you can do at this point.

You didn't tell us if this low oil pressure is new problem or has always been low since you bought the jeep. I'll assume it's a new problem.

1 - Connect an external pump to the main oil gallery and pressurize the system by using an applied pressure of 45 lbs. Now what does your direct reading gauge read? Close to zero again means internal bearing wear beyond limits. A more normal reading means the pump is bad or needs to have it's pressure adjusted.

2 - Remove, disassemble & inspect the pump. If internal condition warrants replacement then by all means replace it.

3 - Do not rule out an erroneous gauge reading until you have substituted a known good gauge.

dpcd67 · Post by **dpcd67** » Sat Jun 30, 2018 10:36 am

What oil are you using? You said your pressure dropped, so that implies it was at a higher reading before it dropped.
What was it when you started it, and what oil are you using.
Also, since you asked how to replace the oil pump, that tells me that you have not studied your Operators and Maintenance TMs.
Part of owning a military vehicle; get a complete set of TMs and study them every day. I still do.
Don't start replacing parts until you have found the root cause. Trouble shoot the cause first and do not chase symptoms with new parts.

bobbymc · Post by **bobbymc** » Sat Jun 30, 2018 12:51 pm

At start up it is at 45 psi- after about 3O minutes or at normal running temp it drops to around 3 psi at idol. I run 15-40 motor oil. It’s a new problem, it started when i changed oil lines from filter. Thanks again

4x4M38 · Post by **4x4M38** » Sat Jun 30, 2018 6:29 pm

Why did you change the oil lines?

Did you replace them with new lines or
used or new, old stock.

Did you put the replacements back in the exact
same positions?

Aging flexible pressure lines, even unused, in the
package new, old stock can deteriorate and cause
obvious and not so obvious problems.

bobbymc · Post by **bobbymc** » Sat Jun 30, 2018 6:56 pm

All parts where bought new old stock from a local military surplus. All put back in the same position, same exact hoses. Thanks i believe i have found the issue, will post back if it cures the problem. Thanks for all the feed back.

charlesfitton · Post by **charlesfitton** » Sun Jul 22, 2018 5:53 am

[quote=".....Thanks i believe i have found the issue, will post back if it cures the problem.[/quote]

Tell us more..

bobbymc · Post by **bobbymc** » Sun Jul 22, 2018 12:06 pm

Sorry if forgot to post back, the problem was the oil filter cap.
The nut on top was loose, i tighten it down and boom . Constant 28 psi oil pressure.

MarkR1951M38 · Post by **MarkR1951M38** » Fri Aug 24, 2018 3:25 pm

I just went thru the same routine...oil pressure dropping off after warmup. Solution was to run straight 30w oil. Any 10Wxx oils will loose pressure after warmup...guess they default to 10w after heating up.