The Age Old Temp Sender Dilemma - HELP PLEASE?

[Don L.]

Good morning all. Apologies if this thread is redundant, however, before posting, I searched TDB - current and archived - without finding clear info on my specific issue.

I am in need of a new water temp sender for my 1972 350 base engine. I had to destroy my original sender when I had my cylinder heads re-worked a few years ago. I installed a replacement and the gauge has not read accurately since. I've had enough and want it right. My AIM confirms that the OE sender was delivered to St. Louis as a part of the engine assy, therefore, I can't find the right GM part number. Might someone here happen to know the original part number or a replacement that is known to have the exact same resistance characteristics as the OE unit? Better yet, might someone here have, or be able to direct me to a good replacement sender?

Thanks for reading.

[Mark E.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

A few years ago, I naively installed a new sender from NAPA for my '70 LS5. It works fine.

[Gary B.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Don,

The temperature sender for 72-78 Corvette was GM 6490453, which I believe is GM-discontinued. Wilcox Corvette, Doc Rebuild and others sell reproduction versions. I can’t speak to their accuracy.

Wilcox has an informative tech page on temp gauges and senders:

http://repairs.willcoxcorvette.com/category/temperature-gauge-info/

They used to sell, and maybe still do, a component that connects inline with the gauge to custom adjust the resistance to get an accurate reading at operating temperature, i.e, to correct for an inaccurate sender.

Gary

[Mark E.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Also, do not use any type of sealant or tape on the threads. I've seen this cause bad readings a couple of times.

[Larry M.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Consider buying a used/tested one from David S (Calif) or others.

Larry

[Joe L.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Also, do not use any type of sealant or tape on the threads. I've seen this cause bad readings a couple of times.

Mark------


Yup. And no sealer is necessary. The threads are "dry seal".

[Don L.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Thanks guys.

Might anyone have experience with this option? I am assured by the vendor that it is matched to the gauge and will read as original.

Advice appreciated.


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[Larry M.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Don:

Buy it ant test it. Then report back to us. LL and K&B and others all make the same claim. But we need for folks to buy and test and report findings to make any kind of judgement on the reproductions (and the later GM replacements).

Larry

[Gary B.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Don,

Many vendors sell a reproduction of that temp sender. I suspect they are all made by one manufacturer, so I doubt it matters who you buy it from. For me, it would simply be a question of total cost, including S&H, plus in stock availability.

Gary

[Don L.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Don,

Many vendors sell a reproduction of that temp sender. I suspect they are all made by one manufacturer, so I doubt it matters who you buy it from. For me, it would simply be a question of total cost, including S&H, plus in stock availability.

Gary

Thanks, Gary. I want this one to be right first time and am researching for a better outcome than my past experience. I bought one from Paragon (?) in 2018 and it's approx 40 degrees low vs what I measure with a pyrometer. R&Ring a sender is too much of a PITA to do trial and error, which is why I am soliciting the advice of this group.

Thanks again.

[Leif A.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Don,
Autozone and others have AC Delco units, as well as, Wells TU5. I've found the Wells TU5 to be quite accurate. I usually buy three at a time and use whichever one gives me the best results and return the other two. No need to go to the Corvette vendors for this.

https://www.autozone.com/engine-mana...852/521031_0_0

[Don L.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Will do....

[Gary B.]

[Gary B.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Thanks, Gary. I want this one to be right first time and am researching for a better outcome than my past experience. I bought one from Paragon (?) in 2018 and it's approx 40 degrees low vs what I measure with a pyrometer. R&Ring a sender is too much of a PITA to do trial and error, which is why I am soliciting the advice of this group.

Thanks again.

Don,

You might find an NOS GM 6490453 on eBay. If I had to choose one without knowing the accuracy, I think I’d take a chance on an NOS sender before a repro.

Gary

[David B.]

Re: The Age Old Temp Sender Dilemma - HELP PLEASE?

Mark------


Yup. And no sealer is necessary. The threads are "dry seal".

I believe that's correct, the threads are NPTF and not standard NPT. As the OP will be installing the sender in an iron cylinder head, he may have good luck and not need sealant. OTOH, mine took several tries to seal in an old aluminum intake; finally three wraps of teflon tape and a dab of Rectorseal 5 did the trick. I did chase the manifold threads with a 1/4 NPTF tap.

After installation, I checked resistance between the manifold and the sender outer housing, and it was essentially zero. That said, the resistance of the sender itself when installed (center terminal to ground, no coolant) was about 100 ohms higher than on the bench (750 vs 650). Both measurements were taken at ambient temp, about 80F here in FL. I can't really account for that difference, but I was satisfied the sealant was not insulating the sender from ground. In fact a new sender will probably arrive with teflon tape already on it, and I don't believe that should cause a problem.

I also checked two new Delco senders on the bench, and those measured at 550 and 560 ohms respectively. I doubt my old one is OE, but it's at least 25 years old. The old one was definitely more in the ballpark based on prior guidance of the TDB, and the gauge seems to function fine with that old one installed.

My experience is with a '62 application, but hopefully somewhat relevant.