Thermosensor Replacement - Sealing Concern
 

I'm in the middle of replacing my thermoswitch and am also changing out my thermosensor at the same time whilst I've got it stripped down, (mainly because I am suspicious that it does not always measure correctly). This question is about replacing the thermosensor, (NOTE: That's the one with the green body at the top of, and behind, the pump housing).

The old thermosensor, (which has never leaked), seems to rely on a washer to seal it against the housing. As the thermosensor screws in, the washer is pressed tight against the pump housing. The washer seems very "sloppy," as it has a substantially bigger hole in it than the diameter of the thermosensor thread that it goes onto. I know this shouldn't matter if it tightens snugly against the face of the pump housing. However, conceptually it seems very crude versus, for example, the thermoswitch directly below it, which seals with an O-Ring against a taper in its mating hole in the pump hosing. Also, the washer is not copper, (which I would expect for a crush washer), but is either steel or aluminium. Regardless of all this, as I stated, it has never leaked. A new washer was not supplied with the new thermosensor, nor can I find any mention of it on the parts list. I assembled the new thermosensor using the old washer and it seems to sit nice and snug, but I'm concerned that it may leak - something I won't find out until I get everything back together.

So, questions for anyone who has done this job. Did you find the same setup? Did you use the old washer again successfully? Any idea where to find the washer in the parts cat. (trust me, I've looked hard!). Did you use any thread sealant, (telflon tape)? Note - thread is very coarse and does not seem to bb the actual seal, rather it is the pressure on the washer that likely creates the seal).

Any "done that" experience would be much appreciated.

Thanks

Dave

I re-used the aluminum washer without problems. Not a drop.

As a suggestion, do not sand it unless you're going to use a very fine finish because if the sanding leaves score lines, it will leak slowly.

You might try buying a new washer, or using one that is a true crush waster from an oil drain plug.

Dave

I typically also use a little thread sealant on things like that.

Dave -

Thanks for the input, it's reassuring.

I'll have a hunt around the local stores this AM for another washer and if I don't find one I'll go ahead with what I have.

Regards

Dave

Mahjik-

Thanks, I'll put some teflon tape on the thread.

Note I just, finally, found it in the shop manual, and in the parts cat. Mazda refers to it as a "gasket," and, of course, recommends a new one on reassembly.
Anyone -

Any point in putting a little sealer also on the "washer? Can't see how this could do any harm.

Wouldn't a copper washer be better, or do you think aluminium is used because it matches the thermal properties of the water pump housing?

Thanks

Dave

It wouldn't hurt to put some sealer on the housing side of the washer. I do that from time to time when something could leak from the other side.

I would probably go with aluminum if that's what Mazda used. I suppose it could be a problem with the metal properties expanding and contracting from heat, but I'm no material engineer so I would say follow Mazda. ;)

You might also get into an electrolytic corrosion problem using copper against aluminum.

teflon tape

All -

Thanks again for the input. Just got a new aluminum washer that seems about the right sort of size. Will use teflon tape on the thread and a little gasket sealer on the washer. I'll post if there is a leak problem - hope not!

Regards

Dave