I am going to change my temp switch for my aux fan located in the left cyc head and I have heard horror stories of stripping threads when removing the old sender. Any tips other than make sure you do it when the engine has sat overnight, and how much fluid loss should I count on ?? Thanks guys.

 

You are correct to do it when the engine is cold. Have not seen any problem with the sender threads. Use a "Pipe Thread Sealer with Teflon" for reassembly (don't use Teflon tape - shreads of it can get into the cooling system and cause blockages).

Recommend siphoning out the antifreeze down below the sender level (out the rad. cap), if you are planning on reusing it (and don't want to make a mess). Raise the Vette on the side with the sender, so it is "higher" than the fluid level.

Should be an hour job at most.

Plasticman

 

Thanks, and seeing it should be made of brass there should be no problem now that I thik of it. Did you put anti seize on it or just the teflon ???

 

My best advice is when you crack the sensor free,dont just keep turning it until it comes out...Turn it loose a bit,then tighten it back a bit then turn it loose some more and tighten a bit.Go back and forth.Especially do this if the sensor feels tight and doesnt spin out easy.

That helps to release the sensor without seriously damaging the threads.I did that with spark plugs too that began to feel tight when turning them out.I also use some spray lube as I go back and forth to ease it turning out.

Some of these sensors have been in there for so many years its easy for them to strip and roll the threads on removal.
If you get the sensor out,and the threads look wavyinside the hole,you may want to run a tap cleaner or tap tool to make them true again.

I had to retap my entire plenum once because of this.It wasnt a problem though.Helped the new bolts to go in with ease.

 

When I changed mine, I did so without any draining and made
the switch with VERY little leakage.

The switch is relatively high. With the rad cap on and the
thermostat closed (ie: COLD engine), the likelihood of siphoning
fluid from the higher areas such as the thermo housing, upper rad
hose or rad header tank is reduced.

As a precaution, I spread floor-dry and set out a large low-profile
drain can. Then I wrapped the new switch with teflon tape in
the appropriate direction so that threading it into place didn't
peal back the tape. I set the new switch close at hand, loosened
the old switch with a socket, then backed it out with one hand
while I held the new switch at the ready with the other hand.
Even though I took a moment to get the new switch properly
started in the threads, there was very little coolant loss. Frankly,
I was surprised at how little.

BTW - I was unaware that people have had trouble stripping threads
on removal - the advice given about being careful during removal
seems sound.

I'm uncomfortable with the thought about chasing the threads
with a tap. If you know what you are doing and it looks necessary,
fine. Otherwise, I suggest leaving it alone - too many people seem
to have trouble with taps and problems might be created where
there were none. If you think you will be chasing the threads,
pick up a pipe thread tap beforehand and be sure to use a handle
so it goes in straight. 3/8" x 18 NPTF.

If I needed teflon sealant, I would buy the brush-on kind. But
I have lots of the tape and can apply it so there is little chance of
any winding up inside. If some did, it would only be a thread-like
piece and I wouldn't be concerned about this in the cooling system.

Use care in tightening the new switch. If you have had trouble
stripping threads in the past, then you want to be very cautious
here to avoid creating a lot of work. Perhaps use a torque wrench?

.

 

You didn't mention what temperature your new switch
will activate the aux fan or where you purchased it.

In case anyone is interested, Echlin "Coolant (Thermo)
Fan Switches" with various activation temps are available
from NAPA as follows:

ON ............... OFF .... P/N#
204-220º ....... N/L -- FS113
213-229º ....... N/L -- FS112
224-236º ....... 212º - FS110
229-245º ....... N/L -- FS111

Either the FS110 or FS111 is the replacement for OEM, don't
have my notes here.

I belong to the group that believes coolant temps should
be 195º+. I installed a 213-229º switch to engage the
aux fan a bit sooner to reduce peak temps in slow traffic and
while waiting between Auto-X runs.

.