M-12 motor questions

[joe-fran]

I have a 1987 E-28 with the original M-12 universal diesel motor.

I would like to replace the current low oil pressure idiot light with a proper oil pressure gauge. I assume I need to replace the idiot light sending unit with something different.
1. Where would I buy the new sending unit?
2. Would a new sending unit be compatible with a used oil pressure gauge or do I need to buy a compatible gauge? (I have a used gauge already.)

also my water temp gauge reads low. I will be replacing the thermostat this spring and may want to install a second water temp gauge in the engine compartment. Would the second gague just wire up to the same sending unit as the cockpit guage or do I need to do something special for a second gauge?

Thanks in advance

Joe

 

[Tom Metzger]

Joe - Yes, you would have to replace the oil pressure switch with a resistive sender. They are available at auto parts stores.

The new sender should work with your old gauge, and it is easy to hook up to make sure before you start drilling holes.

When you hook up two gauges to one sender you will need a sender designed for two stations. They are simple series electric circuit normally, but when you parallel two gauges you need twice the current, therefore a sender with 1/2 the resistance.

I went in a different direction and installed a buzzer for the oil pressure and temperature so that I didn't have to depend on looking at the gauge or idiot light. On the E-34 they are located where it is hard to see them.

 

[exoduse35]

Joe, most senders are screwed in to tho oil system using a 1/4" pipe thread. You can use brass fittings to tee off the system and use both the idiot light and gauge senders. Also it is a very good idea to keep both and make the idiot light audible. The other thing to watch for if using both is that they so not get to hanging too far off the block as the vibration can crack the fittings if not supported and allowed to get too much weight too far out in space. Edd

 

[Tom Metzger]

On my M-25XP the senders are 1/8". I used common galvanized steel fittings for strength and compatibility. On my engine the the nipple from the block has to be quite long to clear the exhaust manifold.

 

[exoduse35]

That is it! perfect! And yes 1/8 not 1/4 ... sorry...

 

[Dan Morehouse]

Joe-I installed an additional temperature guage @ the helm because the stock one (mounted at the aft end of the stbd. cockpit seat) was too hard to see. I connected a jumper wire from the sensor input terminal on the old guage to the sensor input on the new one. When the new instruments are powered up, the new one reads, and the old one goes dead. When the new one is powered down, Shazaam! the old one reads again. It doesn't seem to be harming anything, so I'm inclined to leave it alone.

Tom, I'd also like to install an oil pressure guage. Would there be any point in equipping it and/or the temp guage with a buzzer as well?

Dan Morehouse
1981 E-38 "Next Exit

 

[Tom Metzger]

Dan - I think anything that gets your attention when there is a problem is a good thing, so a buzzer is important to me. Mounting the gauges at the helm doesn't help me as I usually steer from one side or the other. Not true; Chuck the auto pilot usually steers under power.

A buzzer cannot share a sender with a gauge; it needs a switch.

Not having read a Capt. Marvel comic in a long time I don't understand how your temperature gauges are working. Do they read correctly?

 

[Dan Morehouse]

Tom - if I recall, the new guage is powered with the plotter & other instruments on a dedicated breaker, while the old guage is powered thru the ignition switch. So their power is different, but they are on the same sensor wire. The old guage is first on that wire, that is, upstream from the new guage. How the sensing current turns up its nose at the terminal on the first guage it arrives at and continues on to the second guage instead didn't make any sense to me either.

Each guage reads differently by a few degrees, so obviously at least one, if not both, are reading incorrectly. Maybe that explains why the engine temp. never gets above 160 degrees unless something is plugged up or the tranny has seized.

When you say a buzzer needs a switch, does that mean a temperature switch (for coolant) or a pressure switch (for oil) seperate from and additional to sensors for those guages?

Dan Morehouse
1981 E-38 "Next Exit"

 

[Maine Sail]

Guys please be aware that if doing any re-plumbing of the Universal oil sender system that the Kubota engine block is tapped 1/8" BSPT thread and then converted to 1/8" NPT thread with an adapter.

Don't remove this adapter and try to stick an NPT nipple in there, as I have come across before. These are not a thread match. As Tom mentioned you can easily add an oil pressure gauge using the right sender, Teleflex has them, just don't try and stick anything that is NPT into the block directly without the BSPT to NPT adapter..

 

[Emerald]

Guys please be aware that if doing any re-plumbing of the Universal oil sender system that the Kubota engine block is tapped 1/8" BSPT thread and then converted to 1/8" NPT thread with an adapter.

Don't remove this adapter and try to stick an NPT nipple in there, as I have come across before. These are not a thread match. As Tom mentioned you can easily add an oil pressure gauge using the right sender, Teleflex has them, just don't try and stick anything that is NPT into the block directly without the BSPT to NPT adapter..

And for Yanmar owners out there thinking similar thoughts, my 3GM30F uses BSPT, and I would assume most other Yanmars do as well. McMaster Carr sells thread adapters, which ended up being my route.