Thread Sealant on Temp Sender Threads

[Joe C.]

If there is no thread sealant used, will there be any leaks from the threads?

Assuming that no sealant is used for better continuity, then wouldn't it also be necessary for the intake manifold to head bolts and head bolts to engine block not to have sealant on threads as well. This would certainly make the ground strap on the throttle linkage vital.

Please advise.

My temp gauge works intermittently. Not long after the engine reaches op temp, the gauge drops to zero. It will occasionally come back to its normal reading.

Temp sender wiring, gauge have both been checked, so the problem lies with the sender.

[Clem Z.]

Re: Thread Sealant on Temp Sender Threads

If there is no thread sealant used, will there be any leaks from the threads?

Assuming that no sealant is used for better continuity, then wouldn't it also be necessary for the intake manifold to head bolts and head bolts to engine block not to have sealant on threads as well. This would certainly make the ground strap on the throttle linkage vital.

Please advise.

My temp gauge works intermittently. Not long after the engine reaches op temp, the gauge drops to zero. It will occasionally come back to its normal reading.

Temp sender wiring, gauge have both been checked, so the problem lies with the sender.

teflon tape is a no no but non hardening permatex should not cause a problem. use a ohm meter between the head the the installed sender and see what you read. a coating from the coolant on the sensor would also cause a problem

[Mike M.]

Re: Thread Sealant on Temp Sender Threads

although i've never tried this concoction, i wonder if mixing powdered aluminum(radiator stop leak) in a dab of teflon paste would allow for continuity between sender and intake.ohm meter readings may prove or disprove this theory. mike

[Ronald L.]

Re: Thread Sealant on Temp Sender Threads

Joe, I'm at the same juncture, on re install, sealant or no?

I had a slight weep last year with these senders on an aluminum manifold. I was thinking the pipe thread teflon stuff, and as Clem suggests, check continuity.

A year ago I went to great lengths to find the problem why new gage and sender calibrated together did not function once installed completely. I started with a sender in a beaker of water on the hot plate, then the gauge and sender hooked together and a power lead from the battery, gradually one step at a time the gauge was hooked to the real connector via a lead, then the real radio area ground, and eventually the sender went back into the intake. That was the point where sometimes things would work, and times they would not and it did seem grounding was problematic given the coolant level was as full as possible and the system has been burped.

[Dan D.]

Re: Thread Sealant on Temp Sender Threads

I know sealer of any kind is a big no-no, but this is a tapered pipe thread. That should 'punch through' most any sealer. I have never had one leak, and we are only talking about 10psi or there about. Its not like city water at 100psi.
My guess is a bad sender. You say it works for a while and then quits - probably temperature and/or vibration induced. More reason to suspect the sender. -Dan-

[Wayne W.]

Re: Thread Sealant on Temp Sender Threads

I have a hard time believing sealer has any effect on the electrical connection of a sender. If that pipe thread is tightened well, no sealer has a chance breaking that connection.

It certainly is not causing the existing problem.

[Joe C.]

PS

I normally use pipe sealant with teflon..............the white paste that looks like Elmer's glue and smells like shlt. Never had a problem until recently.

Will spend some time checking sender today.

If I have to replace, which one has proven to be the most accurate over the widest temp range? I don't care what it looks like. Wells, Standard, Niehoff, GM replacement, Lectric Limited?

[Joe C.]

Re: Thread Sealant on Temp Sender Threads

I have a hard time believing sealer has any effect on the electrical connection of a sender. If that pipe thread is tightened well, no sealer has a chance breaking that connection.

It certainly is not causing the existing problem.

I agree, but who the hell knows? Before I condemn the sender I thought I'd check to see that some metaphysical Corvette-only aberration (I don't know about you, but I'm sick and tired of the overuse of the word "anomaly". Every time I see or hear that word, I'm reminded of 2001, A Space Odyssey) might be at work here. To my knowledge, when threads are jammed together and torqued, there SHOULD normally be metal-to-metal contact along the pitch diameter, I reckon, of the threads, and only along one surface where the clamping force is occurring. How does that sound? Any sealant should only fill the remaining void at the opposite sides of the pitch diameter, and down to the root diameter, up to the crests.

[Ken A.]

Re: Thread Sealant on Temp Sender Threads

Joe, I'm at the same juncture, on re install, sealant or no?

I had a slight weep last year with these senders on an aluminum manifold. I was thinking the pipe thread teflon stuff, and as Clem suggests, check continuity.

A year ago I went to great lengths to find the problem why new gage and sender calibrated together did not function once installed completely. I started with a sender in a beaker of water on the hot plate, then the gauge and sender hooked together and a power lead from the battery, gradually one step at a time the gauge was hooked to the real connector via a lead, then the real radio area ground, and eventually the sender went back into the intake. That was the point where sometimes things would work, and times they would not and it did seem grounding was problematic given the coolant level was as full as possible and the system has been burped.

Boiling a sender in water is a difficult way to test a sender, you'll never get an instant reading vs. the gauge. Also the boiling water tends to ruin the seal at the terminal.

[Timothy B.]

Re: Thread Sealant on Temp Sender Threads

Joe,

Is there any chance the sender ground goes through the firewall connector and it's got some resistance there and the sender is fine.

I always use permatex #2 and wipe off any excess, sealer is not your problem IMO..

[Joe C.]

Re: Thread Sealant on Temp Sender Threads

Boiling a sender in water is a difficult way to test a sender, you'll never get an instant reading vs. the gauge. Also the boiling water tends to ruin the seal at the terminal.

Why not? I do it all the time. I don't know about your stove, but mine has a small burner with an actual control knob that turns. Now, if you rotate that knob to it's lowest setting, you can actually cause it to supply only enough heat to cause your food to "simmer". I like to test my knot making skills when I do this. Here's how I set up my very sophisticated injunyeereing test stand: I actually tie knots in the special dielectric testing string that I use in order to keep the electrical connector and upper part of the sender ABOVE the berling (or simmering) flooid.

Don't you realize that I am an NCRS master judge! This photo of my "Mister Tea" machine proves that I've got what it takes.

[Joe C.]

Re: Thread Sealant on Temp Sender Threads

Joe,

Is there any chance the sender ground goes through the firewall connector and it's got some resistance there and the sender is fine.

I always use permatex #2 and wipe off any excess, sealer is not your problem IMO..

Great idea, but in this case, I don't think so.

When the circuit acted up (went to zero after reading 165*, which is my engine's regulated operating temperature), I disconnected the sender and grounded the sender wire. The gauge then read full scale. That's the test that leads me to believe that the sender or it's continuity upstream of the engine block is faulty. Capice?

[Ronald L.]

Re: Thread Sealant on Temp Sender Threads

Ken,

You cannot power this if its underwater, you have to suspend it and ground it as if it was in the block - I used a metal beaker.

This is done with gauge and sender, outside on the bench. You wire it to a 12v power source ( the car battery if you like) and if it is hooked up as if in the car, this will give you confirmation over the heat range. The wiring diagram is on the web.

If you have a thermometer in that same beaker you can see how the gauge moves versus actual temperature.

So something like a monkey wrench will hold the sensor and provide a ground path with your aligator clipped on the beaker going to the battery ground. Your out lead of the gauge (green wire) goes to the top of the sender.

Your loop is now closed and you can test away, ice cubes (or snow) will drop the temperature and you can repeat.


It worked very well to show which sender was the closest at operating temperature.

Then, step by step, the leads were switched into the in-car circuitry until all but the gauge was actually in the dash.

This sounds complicated but if you understand current flow its simple: from the in connector in the dash, the ground circuit from cluster metal over to the radio, and the out lead that goes through the same cluster wire harnesses out onto the top of the engine and that subsequent ground path from intake past the motor mounts, starter ground etc. are all verified OK.

Joe - you take readings frm the base sender to the battery, if you have more than a ohm or two of resistance at operating temperature when the gage is going out, then you have a ground break from that intake area over to the neg on the battery.

[Edward J.]

Re: Thread Sealant on Temp Sender Threads

Joe, I would be reluctant to use sealer since the sender may need a ground path to operate correctly, Take a wire brush and clean threads of the sender and intake or head where ever its mounted. when installed if there is a leak its sometimes takes just another turn of the sender to stop leak.

It does sound as if the sender maybe the problem, but the after market ones may not be calibrated as the factory one were, so like you say make sure that is what it is.

[Gene M.]

Re: Thread Sealant on Temp Sender Threads

Aluminum (HP intake) and brass (sending unit) are two metals that do not get along well. The leakers are most likely from the threads in the aluminum getting a bit of corrosion from the brass previous installed. Clean threads in aluminum intake and coat with devcon (an aluminum base epoxy filler) and retap the pipe threads.