C2 temperature sensing unit install

[Roger M.]

When installing a temperature sensing unit on a '66 327/350 should I tighten it until all threads are in the manifold or stop when it becomes hard to tighten? I have about 4 threads still showing. The unit I removed was the same way. No water leakng but no temperature increase as engine heats up either. Didn't know if the unit not being all of the way in was the issue or not. I have done the "ground the unit's wire to the engine block" test and it indicates the sensing unit as the issue (gauge pegged while wire was grounded).

[Mike T.]

Re: C2 temperature sensing unit install

Roger - trying to run the sending unit all the way down could either damage the sending unit or cause the intake to crack, expecting you're still using the aluminum 66 intake. Run it down till you're satisfied it's snug and call it good.

[Roger M.]

Re: C2 temperature sensing unit install

Thanks Mike. That is what I figured but wanted to make sure.

[Larry M.]

Re: C2 temperature sensing unit install

Once you do that, use a good multimeter to measure OHMS between the top connection of the sending unit and the block. It should be around 600 ohms at room temperature and will decrease to around 100 ohms as the engine is running and up to temperature.

For detailed calibration, shoot engine temperature with a good IR gun at the sending unit and also record the ohms at this time. Then compare from the various charts we have available. If you don't have the charts and info, let me know your reading and I will provide the conversions.



Larry

[Joe L.]

Re: C2 temperature sensing unit install

Thanks Mike. That is what I figured but wanted to make sure.

Roger-----


You can take any guess-work out of it if you use a torque wrench. The torque spec is 20 ft/lbs.

[Larry M.]

Re: C2 temperature sensing unit install

Roger-----


You can take any guess-work out of it if you use a torque wrench. The torque spec is 20 ft/lbs.

I would use a bit of Never-seize or pipe sealant with teflon on the threads. MAYBE reduce the final torque by 20% from using these sealants/lubricants.

Larry

[Joe L.]

Re: C2 temperature sensing unit install

I would use a bit of Never-seize or pipe sealant with teflon on the threads. MAYBE reduce the final torque by 20% from using these sealants/lubricants.

Larry

Larry------


Many, many years ago I did exactly as you suggest. Afterwards, I ended up with a situation of erratic temperature readings. I just could not figure out what the problem was. I figured maybe I got a bad sending unit so I tried another. Same problem. Finally, I thought that maybe I should not have used the sealer so I removed the sender, cleaned the threads in the cylinder head and sender and re-installed. Now things worked perfectly. I never used any sort of sealer on these threads again.

I know that some folks say that it should not make any difference on sender function if sealer is used. Well, my "empirical data" showed me it does.

Also, the threads on the temp sender are what GM calls "dry seal" and require no sealer. The factory did not use any and I know of no SERVICE senders that are supplied with pre-applied sealer.

[Michael H.]

Re: C2 temperature sensing unit install

Larry------


Many, many years ago I did exactly as you suggest. Afterwards, I ended up with a situation of erratic temperature readings. I just could not figure out what the problem was. I figured maybe I got a bad sending unit so I tried another. Same problem. Finally, I thought that maybe I should not have used the sealer so I removed the sender, cleaned the threads in the cylinder head and sender and re-installed. Now things worked perfectly. I never used any sort of sealer on these threads again.

I know that some folks say that it should not make any difference on sender function if sealer is used. Well, my "empirical data" showed me it does.

Also, the threads on the temp sender are what GM calls "dry seal" and require no sealer. The factory did not use any and I know of no SERVICE senders that are supplied with pre-applied sealer.

I agree with Joe no sealer or tape, dry install only. I tried 4 different senders before I found one that read correctly.

Mike

[Jim L.]

Re: C2 temperature sensing unit install

Once you do that, use a good multimeter to measure OHMS between the top connection of the sending unit and the block. It should be around 600 ohms at room temperature and will decrease to around 100 ohms as the engine is running and up to temperature.

For detailed calibration, shoot engine temperature with a good IR gun at the sending unit and also record the ohms at this time. Then compare from the various charts we have available. If you don't have the charts and info, let me know your reading and I will provide the conversions.



Larry

Larry, I hope you don't mind if I clarify your statement slightly.

If you are going to measure the resistance of the sending unit, DISCONNECT the wire to the gauge first. Never try to make that resistance measurement with the gauge connected to the sender. Best outcome, with ignition off, you'll get a possibly incorrect reading. Worst outcome, if the ignition is on, you could hurt your DVM or VOM.

Jim

[John D.]

Re: C2 temperature sensing unit install

Joe, Very good info. The only sealant I have used in rare occasions is a touch of Loctite 290. The green watery sealant. Just gets in the inside of the threads a tad. But that's not a good idea
. I threw my Teflon tape away long ago. More damage done to fuel injection expensive fuel meter covers with that tape. Judges don't like it either.