Which oil pressure gauge???

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 04, 2006 11:26 am

What is the correct oil pressure guage for the M38? 0-60psi or 0-120psi?
There is a picture in the manual that shows a 120psi guage in the panel. Wes, I have read where you say always go by the book.
From what I read on other post, the oil pressure is very low on these engines when they are at operating temp. I believe I would lean more to the 0-60psi gauge for the 4 cyl engine if that is the case

Ken.

OKCM38CDN · Post by **OKCM38CDN** » Wed Jan 04, 2006 4:24 pm

Ken, I beleive the correct one is the 120 psi from the factory with Douglas connectors, however a 60 psi will work with the correct sender. Not sure if they made a sender with Douglas connectors at 60 psi.

Also Douglas connector sending units can be hard to come by...

Hope this helps...

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 04, 2006 5:22 pm

Hal did you put a 120psi gauge on your M38? What is the oil pressure when the engine is at operating temp. I realize that the gauge doesn't have effect on the pressure. I'm curious what your pressure is at operating temp.

OKCM38CDN · Post by **OKCM38CDN** » Wed Jan 04, 2006 6:15 pm

Yes, I was able to find a 120 douglas connector sender...

I think I run about 20-30 PSI... it just barely comes off the scale... It does read though...

Hope this helps...

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 04, 2006 7:40 pm

Doesn't make sense why they opted to put that high range guage on a engine that doesn't put up half the pressure of the gauge.

BobW · Post by **BobW** » Wed Jan 04, 2006 9:08 pm

I think it was because they were trying to standardize parts on M series vehicles. Some other M series vehicle needed 120psi so they all got it. Later they realized it wasn't a good idea for the Jeep and changed to 60 psi. I am using a 120psi guage with a 60psi sender on my M38. Everything looks correct and I just divide by 2 when reading the gauge. For example when my gauge read 60 it really means 30.

SteveJ · Post by **SteveJ** » Thu Jan 05, 2006 9:25 pm

My 52 M38 CDN came with a 60 psi gage and sender with douglas connectors It reads about 45psi on startup then runs just below 30 when warmed up. I also had a 53 M38A1CDN that also had a 60 PSI gage and sender. It sure makes it easier to read the oil press.

Cacti_Ken · Post by **Cacti_Ken** » Thu Jan 05, 2006 9:41 pm

My intention is to restore the jeep the best that I can with the correct parts. I am disappointed that a 0-120psi gage is a correct item.
The gage on my GMC 8 cylinder PickUp is 0-80. The oil pressure is 55psi at 2000RPM.

GregS · Post by **GregS** » Fri Jan 06, 2006 8:37 am

Ken,

When you say "correct" parts, is that with factory original parts or correct parts for the M38. I ask this because many parts would have been correct for the M38 but not correct for a factory class restoration. A good number of parts were swapped out when the jeep was in motor pool, those parts would be correct for the jeep, just not correct for a factory class.

Cacti_Ken · Post by **Cacti_Ken** » Fri Jan 06, 2006 10:34 am

I know it won't be a factory class restore. since I am going to use an electronic voltage regulator, and I'm not sure if that is qulified as a motor pool option either. So what the hey, I guess it won't make any differernce what I use. What ever I prefer. A good looking and running jeep for showing off and parading really was my first intention when I started the restore.

GregS · Post by **GregS** » Fri Jan 06, 2006 10:51 am

A 60 PSI guage will do just fine and look appropriate, just not for a factory class restoration.

Post by **wesk** » Sat Jan 07, 2006 9:17 pm

Ken,
The army was pretty agressive in the retrofit of the 60 psi sender /gage to the pre- 55 jeeps. The transistoruzed regulator was originally introduced in the field and on late Willys stuff around 1956. It didn't show up in the ORD 9's but it did show up in the 1960's and up supply parts lists. So your motor pool jeep under judging for a claimed period of say 1958 would be correct with 60 psi gage/sender and transistorized voltage regulator and voltmeter. You could even add M series turn signal kit.