Installing temperature sensor in 560

[Mike SE IL]

This is so simple I feel dumb asking it. Fist a little background. I was using Old Molly (Gramp's old 560 Farmall) to dig a post hole. When I put it in the shed there was steam coming out of the radiator cap but the temperature gauge hadn't moved. OK, after 11,000 hours maybe it was time for a thermostat and a gauge. We determined the thermostat wasn't the problem because there wasn't one. I put a new one in anyway. Got the old gauge out, put new one in the dash, installed sensor bulb. That's where my problem developed I can't explain.

There's a nut that pushes against a flange on the sensor bulb to hold it in place in a brass adapter that screws in the head. Holding it in my hand I screw it all together and it fits tight. BUT when I put the adapter in the head, insert the bulb and tighten it down the nut gets tight but the bulb is still loose. Removed it, in my hand it gets tight, reinstalled it won't get tight.

After sleeping on it I suspect what is happening is when I tighten the adapter in the head it is compressing the brass fitting just enough the nut gets too tight to turn before it bottoms out on the flange on the bulb.

Sound reasonable? So what is the solution?

 

[Fritz Maurer]

Well if it screws together again normally after removing the adapter from the head, I’d just put some pipe dope on the threads and thread it back in the the head just enough so it doesn’t leak.

The retainer nut is so far away from the compression area it seems strange that it would do that.

 

[Mike SE IL]

Well if it screws together again normally after removing the adapter from the head, I’d just put some pipe dope on the threads and thread it back in the the head just enough so it doesn’t leak.

The retainer nut is so far away from the compression area it seems strange that it would do that.

It makes no sense but it is all I can come up with. I guess I'll try not screwing it in as far and hoping it doesn't leak. I tried putting and o-ring on the bulb and that didn't help either

 

[Fritz Maurer]

I didn’t think of that, that should have worked. Definitely never encountered this before.

 

[used red MN]

Hello Mike, welcome to YT! I agree that this seems odd, however stuff you buy today particularly for these old tractors is often made in the land of “almost right.” The alloy of the brass adapter may be such that it is just to soft. If the original gague “adapter well” will accept the threads of the nut on the thermal tube I myself would probably just reuse that one.

 

[used red MN]

… I tried putting and o-ring on the bulb and that didn't help either.. How big of a wrench are you using to screw that adapter in? As Fritz suggested put some thread sealer on it a tighten it not allowing yourself any more then 8” of leverage on the tool that is tightening it. There is only 8 - 15 psi in the radiator it does not take a lot to seal that.

 

[Mike SE IL]

Hello Mike, welcome to YT! I agree that this seems odd, however stuff you buy today particularly for these old tractors is often made in the land of “almost right.” The alloy of the brass adapter may be such that it is just to soft. If the original gague “adapter well” will accept the threads of the nut on the thermal tube I myself would probably just reuse that one.

Two problems. The nut is behind the sensor bulb No way to get it off. Second, the original nut was fine threaded while the new one looks more like pipe thread.

BTW thanks for the welcome. I've lurked literally for years but never posted. Also on NewAgTalk with the same user ID Been there so long my user ID number is 26

 

[TedinNE]

The new gauge used to come with a new bushing. Most new gauges are not compatible with the old bushing.

 

[used red MN]

Trust me I am aware of how it is constructed “captures” the nut so it can’t be removed and that the threads may be different, that is why the sentence started with “if” Just was a suggestion.

 

[bc]

The sensor has to shoulder up against the inside of the bushing in the head. Then the bushing around the sensor screws in and tightens down on the sensor shoulder.

When reinstalling my engine I noticed the head just had a regular pipe bushing in it and the sensor would slide on down into the head. Got a new bushing with a shoulder inside of it to fix it.