oil pressure sending unit

[honeaj]

Hello all. I have just acquired a '51 M-42 on which the oil pressure, coolant temp, and fuel guages do not work. Vehicle had new wiring harness put on a few years ago, so it should not be bad wiring. My question is regarding the oil pressure sending unit. Does the oil pressure sending unit merely measure oil pressure or does it also have a function of distributing oil along various paths based on oil pressure? Also, to boil it down, can it be replaced with a mechanical set up? Thanks in advance for any and all answers/ advice. Jerry

[Charles Talbert]

Hello all. I have just acquired a '51 M-42 on which the oil pressure, coolant temp, and fuel guages do not work. Vehicle had new wiring harness put on a few years ago, so it should not be bad wiring. My question is regarding the oil pressure sending unit. Does the oil pressure sending unit merely measure oil pressure or does it also have a function of distributing oil along various paths based on oil pressure? Also, to boil it down, can it be replaced with a mechanical set up? Thanks in advance for any and all answers/ advice. Jerry

The gauge is for pressure monitoring only, replacing it with a mechanical gauge with a pressure tube is just fine. I would suggest using copper tubing, some gauge kits come with plastic tubing, OK for that amount of pressure, but if it gets near heat it melts, it cuts or damages easily also. Copper tubing routed in a safe area has worked well for us.

[honeaj]

oil pressure sending unit

Thanks Charles for the response. I thought that might be the case but wasn't sure. Thanks again. Jerry

[Warren Watt]

Sending unit

The M37 schematic shows a ground connection from the oil pressure sender. Can anyone verify this? The one I bought has a spot on the top of it that has a small dab of solder on it. Almost like it is ready to accept a wire for grounding purposes. I have tried using an aligator clip / wire to simulate a ground connection. No change to the gauge readout "zero" oil pressure. I'm going to test my gauges and the sending unit tomorrow but still wonder about the ground wire.

[carmen]

What I always wanted to know what is the correct pressure gauge for the M37, the 120 PSI or the 60PSI?

Carmen

[Charles Talbert]

2 birds, 1 stone

There is no ground wire needed on the oil pressure sender, it grounds through the body of the unit.

The 60 PSI is correct for the M37 & all vehicles with gas engines. The 120 PSI gauges are used with diesels & multifuel engines on the larger trucks. You can use it on a M37, however you have to have the 120 sending unit also or you will get an inaccurate reading.

[Warren Watt]

No ground wire makes sense

since it is attached to the block anyway. Sid Beck confirmed this information. I had asked him about it while placing a parts order.
Thanks Charles.

[11B40]

Late, But, my sender wasn't working and I added a mechanical gauge right down where the sender would be. This was to just check I did indeed had pressure when I bought the truck. I chucked the sender in my vise upside down and added a pipe coupling and nipple, sprayed in some PB-Blaster and let it soak a few days. Reinstalled and my sender works again. This truck did quite a bit of sitting around before I got it. Just a thought.

[Warren Watt]

11b40

[QUOTE=11B40;69668] I chucked the sender in my vise upside down and added a pipe coupling and nipple, sprayed in some PB-Blaster and let it soak a few days. Reinstalled and my sender works again.



Thanks for the input. I believe I'll try that as well. Nothing to lose at this point.

[Warren Watt]

Sender

I chucked the sender in my vise upside down and added a pipe coupling and nipple, sprayed in some PB-Blaster and let it soak a few days. Reinstalled and my sender works again.

I went to remove the sender today to try the suggestion quoted above. Much to my surprise, a lot off coolant started coming out. Looks like I have attached it to a port in the water jacket. Soon as I get a petcock for that port I'll move it down to a lower port that should be in the oil galley side of things. Maybe then I'll get a proper pressure reading.
Still learning.....

[Gsmith]

I went to remove the sender today to try the suggestion quoted above. Much to my surprise, a lot off coolant started coming out. Looks like I have attached it to a port in the water jacket. Soon as I get a petcock for that port I'll move it down to a lower port that should be in the oil galley side of things. Maybe then I'll get a proper pressure reading.
Still learning.....

Ummmm, you sure you didn't remove the temp. sending unit? It's up in the back of the engine. The oil pressure sending unit clamps to the oil fill tube and comes off the oil galley directly below the sending unit.

[Gsmith]

To be precise the temp. sender is in the head up behind the oil filter canister. I should have stated that earlier.

[Warren Watt]

Sender and me

Ummmm, you sure you didn't remove the temp. sending unit? It's up in the back of the engine. The oil pressure sending unit clamps to the oil fill tube and comes off the oil galley directly below the sending unit.

GSmith - I am sure about the locations of the two senders. Thanks for the input. The non military block is from a plymouth.
I had installed the oil pressure sender in the only 1/4" port that is next to the oil fill tube. This is where the block drain petcock belongs. I bought a petcock to install.
There is a 1/8" threaded port slightly lower and in front of the 1/4" port. I am going to pipe from there and bush up to 1/4" to attach the oil psi sender. This 1/8" port is on the same horitzontal line with the other ports that serve other oil hard lines.

[Warren Watt]

Progress

I replumbed the oil pressure sender and installed the block petcock. Started the engine and had 50 psi oil. Great! Good to see. Consequently, the gas gauge started giving an actual readout too. Progress is good.
I ordered a new water temp sending unit and 2" round gauge to get that aspect squared away (Bob's Speedometer).

[Gsmith]

Progress is good indeed! Glad you got it worked out.