As my 1977 280z is all back together now and almost ready of inspection I decided to replace the temperature sensor for the gauge in the dashboard as it wasn’t reading anything. The old one came out pretty easily and was very corroded so no wonder the gauge didn’t work.

While installing the new sensor I apparently torqued it a little too much and broke the housing. I didn’t even use much force so I was pretty surprised. I first thought that I might have stripped the threads but no, I took a chunk out of the entire housing!

Have any of you seen anything like this?

P.S. I already sourced a new housing through my local Z club which will be coming in this week.

Um...NO! Never! Of course, not!

Expect the bolts holding the thermostat housing onto the head to be corroded. They may break off long, though. An induction heater can be your friend to get them out.

I think I would "pre" install that sensor into the new housing.

Scares me, I'm about to buy the same newer sensor but seeing what you have side by side looks a little off???

Well, duh. That's the wrong sensor.

The original is two-part. The sensor part has a bevel that seals against a bevel on the aluminum t-stat housing (look just past the female threads in the housing in the last picture). It's that "nut" (that may be now fused to the original sensor) that screws in, makes the sensor tight against the housing. The sensor itself is just supposed to slip into the hole.

The "new" one you tried to install - A: is too long and B: has an o-ring seal that the t-stat housing (in that spot) is not designed for...

The lates have a plethora of sensors and switches for the t-stat housing and most parts stores don't clearly differentiate. That hole is for the COOLANT GAUGE SENSOR and needs the two-part "coolant sensor (also sometimes listed as a "switch" for some unknown reason) FOR GAUGE". I also see that many of those are sold as the sensor only - as you can use nut over and over - if you're careful. The nut never sees coolant if the sensor is sealed properly. If not (and/or over the years) the nut can be corrosion sealed to the sensor body making you think it's just one part. It's not. In the first picture, the original parts do look fused - but if you take some time you can free the "nut" from the sensor body and see the part you actually need to be buying:

This pic is from the O'Reilly First Call website and it's the sensor only - use your old nut... Of course it's not available, but the picture is nice.

(In the early EFI, there also exists (coolant) sensor and ("thermotime") switch for the EFI. The sensor you're dealing with has nothing to do with EFI. It's a thermistor that runs the coolant gauge in the cockpit)

Edited May 27May 27 by cgsheen1

Still available through Beck Arnley if you can find it. Try Rock Auto.

Still available from Nissan as well. 25251-37700

My '77 has a one part sensor in it. I know this for sure as I had it out testing it, or trying to with the help of @SteveJ about 2 weeks ago. Not saying it won't work but that's what is in it know. I'll try and find the pictures I sent Steve through direct messaging. Just woke up, need more coffee right now.

If I remember right my '72 has the nut that holds it in.

Apparently it's been more than 30 days we were texting those photos of my sensor and my ohm meter, they're gone out of my gallery trash bin. Sorry, I'll have it back out soon to replace and maybe make a fool out of myself for being completely wrong.

Edited May 28May 28 by siteunseen

14 minutes ago, siteunseen said:

My '77 has a one part sensor in it. I know this for sure as I had it out testing it, or trying to with the help of @SteveJ about 2 weeks ago. Not saying it won't work but that's what is in it know. I'll try and find the pictures I sent Steve through direct messaging. Just woke up, need more coffee right now.

If I remember right my '72 has the nut that holds it in.

I looked through the messages you sent me. I didn't see any photos of the sensor.

ZCarDepot offers the sensor with the retaining nut: https://zcardepot.com/collections/electrical/products/coolant-temperature-sensor-for-gauge-240z-260z-280z-510

Well crap! Now I've gotta pull it to see for my self. I won't be able to sleep tonight.

12 minutes ago, SteveJ said:

ZCarDepot offers the sensor with the retaining nut: https://zcardepot.com/collections/electrical/products/coolant-temperature-sensor-for-gauge-240z-260z-280z-510

They also have a one piece.

Z Car Depot Inc

Coolant Temperature Sensor One Piece 240Z 260Z 280Z 280ZX...

Coolant Temperature Sensor One Piece 240Z 260Z 280Z - 800-693 (). Engine coolant temperature sensor in a one piece design.

16 hours ago, cgsheen1 said:

Well, duh. That's the wrong sensor.

No, it's not the wrong sensor... It's the aftermarket replacement that is (almost) "form, fit, and function" compatible with the original.

The aftermarket one piece design still seals on the same beveled edge and functions the same as the two-piece original. The O-ring on the new version is not intended as a liquid seal, and is actually not even necessary at all. I think they put it there as an attempt to keep junk out of the threads (from the outside getting in).

So, that said, what is it about the original two-piece design that is not replicated by the aftermarket one-piece? Answer is "the ability to clock the connector to a convenient position" before you tighten it down. With the original sensor, you could turn the body to whatever position you wanted before you did the final tightening of the flare nut. With the aftermarket design, when it gets tight, the connector position ends up where it ends up.

But other than that, they should both work just fine.