The Stovebolt Site Forums The Shop Area Engine Shop temp gauge problems

here for my hubby again

so he bought a temp gauge for his truck. put it in his 235, no problems, worked fine.
than he had his engine rebuilt. but the hole in the head is bigger. so we get a reducer bushing. 1/2inch to 3/4. fits in the head perfectly. even fits over the temp gauge. but then he notices that the bolt won't tighten over the temp gauge. after pulling it off he sees that the sides of the bolt on the temp gauge has 4 flat sides. almost as if the bolt is a square shape. why? so they add some plumbers tape to hopefully help seal up the extra left by the funky shaped bolt.
fill radiator with water and bam it starts leaking. but not because of the square bolt. which we still need to find out what to do about that.
they noticed that if you push on the copper wire attached to the gauge that it would go straight thru the nut until the gauge hits the bottom. so all the water is coming up from the hole created thru the center of the bolt.

I know this isn't coming out correctly but I hope someone knows what I'm talking about.
or tell me how to post pics from my phone :/

hope someone has the answer. thanks in advance guys!

The bulb type sender needs a special fitting to seat into. The reducer he bought doesn't have the seat. Others have overcome this. Surely someone will post a fix shortly.

It sounds like you have the right temperature sender adapter/reducer?

the threads on the bolt don't do the sealing, it is the flanged area aroung the bulb that gets compressed between the square bolt and the seat in the bushing, you can't just use pipe fittings. As they arent pipe thread, I tried that and found out the one I was using was actually 5/8" NF bolt thread, There are at least 2 different size holes that were used in the heads, you just need to figure out which one you have. I have different heads that have it either way, I just can't recall off the top of my head which way it goes, but no matter they make adapters for either way. OH and by the way the reason the compression nut is square is so that it wiil fit through the square hole in the dash, that will eventually locate the gauge once you get all the tubing threaded through it. Jim Carter has any of the proper bushings you will need, there are most likely other vendors as well, he is just who I used.

CAUTION!!! what ever you do in the process is not to break the tubing or the bulb that sits in the head (gas filled) or you will be replacing that all the way back to and including the gage on the instrument panel.

If the threads on your head are 1/2 npt

And your using the stock mechanical gauge 5/8 -18

Then you need the adapter linked above
Here is the napa part number
...pic...


Put your pics on a hosting site like photobucket or any of the others
And link them in the thread

you guys are my hero. when we talked to napa the first time they didn't tell us any of this. but because of you guys we finally knew what to ask for and they have it.

thanks everybody!