M35A2 low oil pressure.....

[ZRacer]

sounds like we need to swap gauges

You may just be right, Kohburn.

I've got a mechanical gauge that I will hook up first to see what is "truth".

 

[Kohburn]

So....out of curiosity, if my engine had too much clearance in the rod bearings...wouldnt I hear her knocking around a bit?

part of why accurate oil pressure readings are so important - you will see drops in oil pressure long before you get enough clearance for a knock. in which case you can usually just replace bearings and it's just like new. once you get a knock often the crank will be damaged.

 

[bart6453]

Good news!!!!

I got the mechanical gauge installed and at idle its at 75psi! YES!

But...I still have a non functioning gauge on my dash.

I bench tested the old oil pressure sender and it failed, of course the new one is just fine. But I still don't have any oil pressure readings.

At the gauge end of the wiring I have 12.7 ohm resistance while running, which I assume translates into about 75psi on a 120psi sender???

Also the other wire appears to be dead, no voltage and resistance to infinity.

Any ideas? Is it my gauge? Anyone know how to bench test a oil pressure gauge?

 

[Ord22]

your engine will knock and run rough if the main/ rod bearings were bad. oil press will go down as well. it will happen simultaneously.

 

[ellisk1989]

Can you or someone take a picture or tell me where to find the oil pressure sending unit is on the m35a2 thanks

 

[Valence]

Can you or someone take a picture or tell me where to find the oil pressure sending unit is on the m35a2 thanks

I was wondering the same thing. After some digging I found it in the Multifuel trouble shooting TM

http://www.steelsoldiers.com/showthread.php?116454-LDS465-1-Multifuel-Engine-Troubleshooting-Manual

 

[austinrussell]

I have the opposite problem. Once my Deuce gets started, oil pressure jumps to about 60 lbs. When it is running, it practically pegs the gauge at almost 120 psi. Even when warm and at idle, it reads 45 psi. Is this too high?

Mine does the same

 

[rustystud]

Mine does the same

More than likely, your pressure relief valve is stuck.

 

[jatonka]

It is possible that your sending unit is a 60 PSI unit, multifuel trucks had both 60 and 120 PSI sending unit available and someone might have installed the wrong one, I have seen it more than a few times in 20 years of this fun. JT

 

[WillWagner]

Verify it with a known good gauge and procede from there.

 

[rustystud]

It is possible that your sending unit is a 60 PSI unit, multifuel trucks had both 60 and 120 PSI sending unit available and someone might have installed the wrong one, I have seen it more than a few times in 20 years of this fun. JT

If the gauge was the wrong one and he was reading the main line pressure, then wouldn't that mean the wiring is wrong ? The cabin pressure gauge reads the "adjusted" pressure so if the wrong gauge is used then he would be getting a lower-than-normal pressure reading in the cabin, correct ?
Either way he needs to check it with a good pressure gauge and go from there.

 

[V8srfun]

I agree that the best coarse of action is to put a mechanical on it and see what is actually happening.

things to consider

all engines will have lower oil pressure when warm as the oil thins and the bearing tolerance grow from the heat.

the old military gauges are known to be miserably inaccurate at best.

fuel contamination could cause low oil pressure but simply checking your oil can confirm or deny that as a possibility.