OK,

I tackled swaping out my old temp-gauge for a "new" working used one but ran into a rather bad roadblock to completion near the end. I found that the new sensor body thing didn't have a threaded nut that goes over the top to hold it into the block like the last one did. I checked all along the length of the capillary-tube into the dash also. I didn't find one, nor did I remember seing one when I was testing and looking at the whole thing before I even started.

So... my $20-dollar solution may have not been such a solution after all...? I see no way to put the old nut with a hole in it onto the "new" unit to get it to thread into the block and hold it down in there.

I can't figure out how that nut (if it had one?) could have come off this "new" unit, unless the cap-tube was broken before and then fixed, but whoever had it fixed did not include the nut that goes there?

Anybody have any insight into this mystery, or an idea for a solution!?

So close... but no proverbial cigar after contorting upside down for more than a half hour!

I'm sure you've had plenty of advice on this problem, and I may even have offered my two-cents-worth before.

Here's what I would do: If the sensor fits into the hole in the block and all you want is a locking nut, just screw the thing down with a little Loc-Tite and forget it.

If it doesn't fit, try going through a selection of brass fittings. You should find something with a set of threads that will fit the sensor and be able to adapt that to mate with the hole in the engine. Don't sweat the fact that the sensor isn't right down inside the block; the difference in temperatures across an inch more water isn't going to affect your readings enough to notice.

If you want to have the stock gauge working for appearance, do what you can to make it work. I have set up several vehicles with an electric accessory temp gauge on the A pillar (using one of those pod things to mount it.) I mounted the additional sensor to the engine using a 'T' fitting so I had both sensors reading the same water sample.

I'm finding that the stock Volvo temp gauges in the PV and 120 series cars aren't very accurate when they do work!

Steve

Volvolio;

...unless this is some sort of joke...(I cant imagine someone rebuilding the assembly, and then not putting the nut back on...) I suggest getting (the correct) nut and slotting it on a bandsaw, then using gasket goop to seal things, I expect it will be just fine...the bulb seats on a V seat and the nut just holds it in place....

If it works, but you don't feel like dinking around with it, I'll buy it for thirty!

Is it April?

Thanks for your comments guys. I was already thinking last night about options for rigging up some way of passing the nut around the tub by slitting a channel though the nut or something to that effect. I don't give up that easily at all, so I'm sure I should be able to come up with a solution with a slit-nut and a washer or something. I also had another thought about having a machine shop bore out the old nut to the diameter of the sensor body so it could pass through that way, then backing it up with a slit-washer that I could bend around the tube.

We'll see. It should still be worth the $20 if I can figure out a McGiver-fix. Must have been a "Doh!" moment when the realized they had got it fixed without the proper nut hold-down on there. It's not cheap to have the cap-tube fixed in my understanding.

The threads in the head are standard, flare tubing, I think.
I suspect with sufficient animal cunning you could work out a deal
with a split nut and maybe an O-ring. Not something you could do in 5
minutes, but something you could play around with and get to work.
Or maybe a nut with a big enough hole to go over it and then a split sleeve
inside the nut.
Don't give up too easy!
--
George Downs Bartlesville, Heart of the USA!

Yeah, the nut itself doesn't have to seal, it just has to press the sender down in the hole firmly enough to seal that against the bottom of the hole. I could see a nut slit enough to pass the sender tube through working well enough. Darn shame you got sold a gimpy temp gauge, though. Someone somewhere along the line had to have fixed the gauge by repairing the tube, then discovered they left the nut off.
--
I'm JohnMc, and I approved this message.

Might even be able to make a very fine slit in the nut, open it up enough to
pass the tyube through and then squeeze it back shut. Perhaps a split washer
underneath would also help.
--
George Downs Bartlesville, Heart of the USA!

Bummer dude... Sounds like it's back to square one. And I bet the guy who sold it to you knew all along it was garbage. Not cool.