Temperature Gauge Sending Unit

[Jesse Delanoy]

I'm in the process of replacing all of my engine gauges, and have gotten all of them done except for the temperature gauge. I ordered a nice new ISSPRO temperature gauge and 1/2" sending unit, to replace my old gauge and sender.

However, I'm totally unable to remove the old sending unit from the front of my engine. In trying to do so, I've turned the brass hex-head into a pretty perfect circle, by using every wrench and tool available to me.

My question is, is there anywhere else on the engine that I can mount a new sending unit (either my existing new 1/2" unit, or the 1/8" unit that Don advertises for the same temperature gauge), so that I can simply disconnect the old sending unit and leave it in place?

As always, thanks for the help.

Jesse Delanoy
s/v Agape
Baltimore

[High Hopes]

Oy. Everything takes longer than you think.

I have a few suggestions. If you haven't removed the old sending unit, use a SIX sided box wrench to remove it from the bushing now.

Try filing two new flat surfaces on the old sending unit, one of each site. I think mine was steel. You may want to use a Dremel tool or other grinder, but a coarse file works well. Make the surfaces substantial and then use a pipe wrench to loosen it.

If it is still stuck, drill the 1/8" FPT hole bigger (a non-trivial task). Then use a hacksaw blade to cut towards the 1/2" thread. Then chisel carefully from the outside of the fitting near the cut and hammer towards the gap. This will reduce the diameter of the fitting just a bit making it easier to turn. This is a desperate maneuver, but it does work well if you proceed very carefully.

Good luck.

[HerbertFriedman]

Temperature Gauge sending unit

Reply to Steve. I am about ready to replace the temperature sending unit and install that three way valve to convert to the flushing system that you desciribed some time ago. I had asked at that time if anyone had any difficulty removing the 1/2 inch sending unit. I did not expect to see any problems with rounding off of the flats as did the author of this thread, I expected more of a problem with the fitting breaking off due to lots of corrosion and having to fight to get all the old threads out. Did you have any problems getting the sending unit out of the block? BTW, I agree with your suggestions of grinding new flats but I would have thought a heavy vice grip with a "breaker" extension to get more leveage would have removed the sending unit even with rounded off edges.

[High Hopes]

Herb,

I have a 1975 A4. There were no issues encountered removing the bushing. I used a 12 point box wrench. The technique of cutting through a fitting was used in a different location - I don't remember where or even if it was on the A4.

Good luck with the flush valve. Be sure to get an Apollo valve. I ordered some off brand valve and the actual diameter of the flow opening was very small, even though the ball itself was big.

[tenders]

Did you try a small pipe wrench? Flats on fasteners are optional with those.

[Don Moyer]

Jesse,

Some folks drill and tap an 1/8" pipe-threaded hole in the water jacket side
plate to install the 1/8" sending unit. You must be very careful, however,
since the cylinder walls are not very far from the inside of the plate, and
the indications you get are as accurate as in the area directly below the
thermostat where all the water leaving the block and head tends to meet and
mix.

Alternatively, I've drilled many 1/2" pipe plugs out from the front of heads
and a few sending units as well. It's really not too difficult if you have
a 1/2" electric drill at your disposal. The sensing element usually drills
right out with a 3/8" drill bit, and then you will need to up-size your
drill bit to approximately 1/2" and ultimately to 11/16" (necked down to fit
in a 1/2" electric drill). The 11/16" bit is just slightly smaller than the
official pilot hole spec but they're easier to find than a 45/64" bit, and if you wobble
the bit around a little the hole will open up enough to clean out the
remaining threads of the old sending unit so you can clean out the rest of
the threads with a 1/2" pipe tap.

If you opt to drill into the side plate, you can center the hole 1-1/2"
back from the flywheel end of the plate and you should then have
approximately 1-1/4" depth clearance from the outside of the plate to the
cylinder bores. An 1/8" pipe tap will require an 11/32" pilot hole.

Don

[rigspelt]

Just to document another experience on a 1974 engine with a stuck sender: I had a heck of a time getting the old temp sender to turn. I applied a drop of Kroil every day for 4 days, and gently applied pressure with a good-fitting long handled wrench. I gently tap-tapped the wrench too, every day. Imagine my relief when it finally turned out, intact!

But that sender had only been turned half into the threads. The inside threads were filled with hard scale. I bought a 1/2" tap and carefully used it to clean out the threads. Worked like a charm.