I broke the Temp Sender off in the block, so I was just going to drill it out and re-thread it. I was shooting to put a JEGS water gauge in. The kit Includes 1/2" NPT adapter fitting and I was wondering if that is big enough. You know so when I drill out the the broke one, will I be able to thread the hole for the 1/2"?

OR is there an easier way to do it? Just keep the old one in there (its not leaking), and put it in another spot?

Thanks for the help guys.
Zane

 

I think it is 27BPT...If I remember correctly the 1/8th NPT is 28 threads per inch.
Some guys have used the NPT where the BPT is by screwing it in regardless of the difference,with no ill effects.

 

Here's further backup to his statement:

https://www.rx7club.com/showthread.php?p=9555250

 

a 1/8 npt sensor will screw right in there.
Works for me.

 

NPT does not "screw right in" to an unmolested stock iron. However it can be forced to fit.

 

So what you are saying is if you force it, it is no longer unmolested?

 

Early S4 Temperature Sender is M8x0.75 with bullet connector (seals on crush washer). This is what my 87 GXL came with (build date is 11/11/1986)
Late S4 is 1/8" NPT with bullet connector (teflon tape)
S5, Cosmo & FD are 1/8" NPT with Quick Disconnect tab connector (teflon tape)

The discussion about BSPT is for the OIL PRESSURE SENDER and it is 1/8" BSPT with 28 threads per inch. Regular NPT is 27 threads per inch. Adapters to switch between the two are available from McMaster-Carr for about $5 each. Be careful when attacking the sender. Give it a liberal soaking in PB Blaster once a day for a whole week and it should be much easier to remove. Threads might be salvageable too, but it really depends on how you approach it.

Torque spec for both oil pressure & coolant temperature senders is 8-12 ft.lbs.

If it were my engine, I'd pull the rear iron off before attempting removal using an Easy-Out, clean up the threads with the correct NPT tap and replace the sender (remember the teflon tape). As for putting a gauge sender in, your water pump housing has a flat spot in it that is perfect for drilling & tapping for threads. Aaron Cake demonstrates this in his 1976 Cosmo restoration videos on youtube. For your application, the sweet spot is on the front. Look for a spot that looks like it should have something, but doesn't.

If in doubt, PM Aaron Cake about the best way to proceed.

 

right you are senator

Good info!
However ....I just built an S5 TII engine and I was looking to block off the coolant temp sensor port (using an aftermarket temp gauge). My first thought was to use the temp sensor from my old engine (early 87 TII) that just dropped right through w/ no thread engagement. My second idea was to use a 1/8 npt plug that I had originally picked up for my n/a-t oil feed......no dice, the threads refused to engage. Finally out of frustration/curiosity I pulled my 1/8npt --> 1/8bsp adapter for my oil pressure sender and voila'! it threaded right in. I used a 1/8 bsp pipe plug and it works perfect, no leaks and I didn't even have any teflon tape.

 

Someone must have manhandled the rear iron before you built the engine. My 20B uses a FD's temperature sender in the rear iron.

 

Thanks that's what I was looking for. I ended up redrilling it and taping it for 1/8th. Well first we drilled it to a M8, but that did not turn out to well... So out to m9 (simple just go next size up) just so we could cap it off for the weekend. Then I discovered although there are alot of taps for M9's there are NO bolts in the whole world for them yeah not thinking. So it went up to 1/8, and cap'ed for the weekend. It will probably go up to 1/2 when the new one comes in.

Are you positive the coolant temp sender is 8 FT lbs and not inch pound? Because 8 to 12 Ftlbs is a lot on that.

 

I believe so, but check the S4 FSM's technical data to be certain. Just to be safe, give it 8ft.lbs (96in.lbs) and leave it with 1/8" NPT threads. Would really suck to breach the oil passage by drilling it out too large. If you need to put in a second gauge sender, do it on the water pump housing. Even 3/8" NPT is HUGE compared to 1/8" NPT. Aaron Cake shows this in the 1976 Cosmo videos on youtube, so check it out.

 

Good point had not even thought of the oil passage! Yeah how to make a bad day get really bad. I'll go check out Aaron's videos.