The Ford Barn

Philgoodtoo · 03-07-2017, 11:51 AM

I had to replace the original 1938 V/8 in my Standard Tudor with a 1940 V/8. My problem is that the temp probe won't fully seat in the cylinder head, and leaks. Is there an adapter that can be applied? Or any other ideas?

tubman · 03-07-2017, 01:34 PM

I don't know if this helps, but I had a similar problem with my '51 Mercury engine. Try as I might, I could not get the temperature sending unit to quit leaking when I installed it in one of my "Edmunds" heads. The heads were used, and I think there may have been a slight corrosion problem in the threads in the head. I finally solved it by wrapping the threads on the sending unit with some thin copper tape I got from my neighbor (who is an EE). It worked like a charm. You can't use Teflon tape because the sending unit has to ground electrically to the head.

One difference here is that my sending unit seated all the way into the head while yours doesn't, which may be a different problem. Later, when I looked on the internet, I found the same tape for sale; I think it was on Amazon.

Terry,OH · 03-07-2017, 03:45 PM

The thread on the temperature probe is 5/8-18 straight thread and the threads in the head are 3/8 NPT. Ford had an adaptor for the different threadsI believe the part number is 01A-10889. I believe weatherhead also has an adaptor. Check at NAPA

dakotafarmboy · 06-10-2018, 01:09 PM

I am getting ready to install my original temp sending units back into a 1953 flathead and searched whether I could use teflon thread tape.

This old thread indicates I will lose my ground if I use the tape so I will nix that. Anybody disagree?

I have never seen "thin copper tape", but then I have never looked for it before. Wondering if I can use some other pipe dope or even some Permatex Aviation sealant (same as I used on head bolts)?

Next, I would naturally have assumed the temp sender threads to be 3/8 NPT, but Terry's last post here says they are 5/8 -18 straight threads.

I am wondering how others address this. As far as I know, these just came out of my old ford heads and I am switching Merc heads but am assuming my holes are all 3/8 NPT. What now?

JSeery · 06-10-2018, 02:43 PM

The sender works by grounding through the head so the threads on the sensor have to conduct through to the threads on the head. You can not use anything on the threads that interferes with conductivity.

tubman · 06-10-2018, 03:19 PM

Sponsored Links (Register now to hide all advertisements)

Quote:

Originally Posted by dakotafarmboy

I am getting ready to install my original temp sending units back into a 1953 flathead and searched whether I could use teflon thread tape.

This old thread indicates I will lose my ground if I use the tape so I will nix that. Anybody disagree?

I have never seen "thin copper tape", but then I have never looked for it before. Wondering if I can use some other pipe dope or even some Permatex Aviation sealant (same as I used on head bolts)?

Next, I would naturally have assumed the temp sender threads to be 3/8 NPT, but Terry's last post here says they are 5/8 -18 straight threads.

I am wondering how others address this. As far as I know, these just came out of my old ford heads and I am switching Merc heads but am assuming my holes are all 3/8 NPT. What now?

Try this : https://www.amazon.com/XFasten-Condu...per+tape&psc=1.

dakotafarmboy · 06-10-2018, 04:08 PM

OK. Thanks guys. I will order some copper tape.

What about the threads? Do you think the sending unit is 3/8 NPT?

03-07-2017, 11:51 AM	#1
Philgoodtoo Junior Member Join Date: Mar 2013 Location: Monrovia, CA Posts: 27	Engine temp sending unit I had to replace the original 1938 V/8 in my Standard Tudor with a 1940 V/8. My problem is that the temp probe won't fully seat in the cylinder head, and leaks. Is there an adapter that can be applied? Or any other ideas?

03-07-2017, 01:34 PM	#2
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,303	Re: Engine temp sending unit I don't know if this helps, but I had a similar problem with my '51 Mercury engine. Try as I might, I could not get the temperature sending unit to quit leaking when I installed it in one of my "Edmunds" heads. The heads were used, and I think there may have been a slight corrosion problem in the threads in the head. I finally solved it by wrapping the threads on the sending unit with some thin copper tape I got from my neighbor (who is an EE). It worked like a charm. You can't use Teflon tape because the sending unit has to ground electrically to the head. One difference here is that my sending unit seated all the way into the head while yours doesn't, which may be a different problem. Later, when I looked on the internet, I found the same tape for sale; I think it was on Amazon.

03-07-2017, 03:45 PM	#3
Terry,OH Senior Member Join Date: May 2010 Posts: 4,743	Re: Engine temp sending unit The thread on the temperature probe is 5/8-18 straight thread and the threads in the head are 3/8 NPT. Ford had an adaptor for the different threadsI believe the part number is 01A-10889. I believe weatherhead also has an adaptor. Check at NAPA

06-10-2018, 01:09 PM	#4
dakotafarmboy Member Join Date: Apr 2018 Location: South Dakota Posts: 40	Re: Engine temp sending unit I am getting ready to install my original temp sending units back into a 1953 flathead and searched whether I could use teflon thread tape. This old thread indicates I will lose my ground if I use the tape so I will nix that. Anybody disagree? I have never seen "thin copper tape", but then I have never looked for it before. Wondering if I can use some other pipe dope or even some Permatex Aviation sealant (same as I used on head bolts)? Next, I would naturally have assumed the temp sender threads to be 3/8 NPT, but Terry's last post here says they are 5/8 -18 straight threads. I am wondering how others address this. As far as I know, these just came out of my old ford heads and I am switching Merc heads but am assuming my holes are all 3/8 NPT. What now?

06-10-2018, 02:43 PM	#5
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: Engine temp sending unit The sender works by grounding through the head so the threads on the sensor have to conduct through to the threads on the head. You can not use anything on the threads that interferes with conductivity.

06-10-2018, 04:08 PM	#7
dakotafarmboy Member Join Date: Apr 2018 Location: South Dakota Posts: 40	Re: Engine temp sending unit OK. Thanks guys. I will order some copper tape. What about the threads? Do you think the sending unit is 3/8 NPT?