Oil pressure and water temp mechanical gauges

chicklin · Post by **chicklin** » Wed Jan 04, 2012 7:55 pm

I've got a '53 M38A1 project that came to me in the middle of reassembly. I've got the engine running now, but before I go any further, I want to get an oil pressure and water temp gauge on it. Trouble is, I'm not sure where to hook them up.

For the oil pressure gauge, I understand that the sending unit was originally on the top/back of the engine where the little 1/4" tube runs up from the bottom. I don't have a tee or a sending unit or anything there. The 1/4" tube runs from the bottom of the block straight up into the top. So, which end should I put my mechanical gauge? And, can I just delete the tube altogether or does it serve some other purpose? Should I put a tee at the top so the tube can still flow but I can also hook in the mechanical gauge?

Same question on the water temp. Where would I put the mechanical sensor? I see several ports around the intake and upper part of the engine but I'm not sure which ones are water and which ones are vacuum.

Thanks in advance!

Post by **wesk** » Wed Jan 04, 2012 10:44 pm

Are you hooking up the correct military senders for the military gauges or are you switching to civvy gauges? If you are switching to civvy gauges are you using electric senders/gauges or mechanical gauges.

Have you downloaded the maintenance and parts manuals yet? They are free and will answer these questions.
http://www.willysmjeeps.com/v2/modules. ... oad&cid=39

This is an illustration right out of one of those manuals.

You mentioned the missing air cleaner on the G503 site.

These normally sell for around $40 used.

Bretto · Post by **Bretto** » Thu Jan 05, 2012 5:43 am

Where are you seeing those go for $40? I've only seen then for $100+

donthedickens · Post by **donthedickens** » Thu Jan 05, 2012 6:37 am

Brett,

Nice photo history of your rebuild.

What do you have the brake shoes burning in the fire pit?
And it looked like maybe a few other parts were in the fire also.

Bretto · Post by **Bretto** » Thu Jan 05, 2012 7:02 am

HA HA. Ya, I was having a hard time getting the old brake linings off that were the glue on type. I deciede to try that. Worked great, they baked right off. Then I was able to reline them with new linings and rivets. They were the only items in the fire.

Post by **wesk** » Thu Jan 05, 2012 9:31 am

Brett,

$100 to $150 is the price of the rare M38 air cleaner. I have seen these M38A1 air cleaners go for $35 to $75 dollars in the last two years. Managing this site and one other I do stay abreast of the selling prices on the jeeps and their parts.

Bretto · Post by **Bretto** » Thu Jan 05, 2012 9:37 am

Wes, I think that was where I was basing my price on was with the M38, different animal.
-Brett

chicklin · Post by **chicklin** » Thu Jan 05, 2012 3:30 pm

Wes, those pics help a lot, thanks.

chicklin · Post by **chicklin** » Thu Jan 05, 2012 8:18 pm

Got the oil pressure gauge installed and went to install the water temp gauge. There was a pipe plug where the sender is supposed to go, so I pulled that out and tried to put the sender in and the threads are all buggered up. I noticed the plug only turned about 1 turn before coming out, so it wasn't really in there to begin with.

So, my question is whether or not I can get the larger fitting that is screwed into the block? Is that a standard plumbing fitting or is it something special to allow the sender to seat properly?

Post by **wesk** » Fri Jan 06, 2012 12:49 am

Are you installing the military sender or a civvy sender?

chicklin · Post by **chicklin** » Fri Jan 06, 2012 7:46 am

wesk wrote:Are you installing the military sender or a civvy sender?

Civvy mechanical sender.

Post by **wesk** » Fri Jan 06, 2012 9:45 am

They will not always have the same thread as the military and most of their kits come with their own adapter bushings. You will have to use a pipe thread bushing that adapts the tapered pipe thread size in the head to whatever thread your civvy sender has or to one of the civvy sender adapter bushings.

chicklin · Post by **chicklin** » Fri Jan 06, 2012 9:48 am

wesk wrote:They will not always have the same thread as the military and most of their kits come with their own adapter bushings. You will have to use a pipe thread bushing that adapts the tapered pipe thread size in the head to whatever thread your civvy sender has or to one of the civvy sender adapter bushings.

The civvy sender looks like NPT to me. I thought that's what the fitting in the block was, too. Is it not?

Post by **wesk** » Fri Jan 06, 2012 10:07 am

You will have to use a pipe thread bushing that adapts the tapered pipe thread size in the head

From my previous post.

Be sure to chase those corroded threads in the head with a tapered pipe tap.

chicklin · Post by **chicklin** » Fri Jan 06, 2012 1:56 pm

Yeah, so the hole in the head is 1/2" NPT and the sender is 3/8" NPT, so I was just going to replace the bushing that is already there (which is 1/2" to something less than 3/8" but more than 1/4") with a regular NPT reducer bushing.

The problem is, the mechanical sender requires a bushing with a seat in it for the sender and nut to seat properly and not leak. The reducer bushings at the hardware store don't have this seat, it's just a straight-through hole. I think I'm just going to get an electrical gauge with a standard 3/8" NPT sender that doesn't require a seat.