Weird fan switch leak issue

[Baker7888]

Hey guys I've got a weird one for ya.

Recently replaced the fan switch in my LT1 Malibu with a Be Cool unit that turns on around 190ish or so. On LT1 it is in the water pump. I can't get this damn thing to stop leaking. It is tapered thread and I have tightened it as much as I dare to, which IMO is plenty tight enough to not leak. I have cracked an intake manifold in the past (didnt know any better) The switch is installed with no sealer, although the fan switch I pulled to replace was fairly new and I had some teflon brush-on sealer on that one, so some residual sealer remains. Being tapered thread and also a ground switch I did not think teflon was needed or recommended. I was trying to avoid draining my coolant down. Any thoughts?

 

[Ribbedroof]

LT1 should be a 3/8-18 machine screw thread, not tapered, so it will need sealant

 

[Built6spdMCSS]

Copper crush washer.

 

[Baker7888]

LT1 should be a 3/8-18 machine screw thread, not tapered, so it will need sealant

Thanks for the response. I am using Be Cool P/N 75099

3/8 - 18 NPT , 210 off 190 on

I did not realize it was supposed to be machine thread. Glad i didnt go any tighter. Do you know where I can find a switch that turns on in the 190-210 range, having a hell of a time. Everything seems to be NPT

 

[Baker7888]

LT1 should be a 3/8-18 machine screw thread, not tapered, so it will need sealant

Are you saying to seal the switch that I have? I may have my terminology wrong, looks tapered to me … all switches i can find are 3/8-18 … all regular bolts and what not are 3/8-16

 

[Ribbedroof]

There are many thread types...

NPT National Pipe Tapered (which sounds like what you have)
UNC Unified National Coarse (coarse bolt thread)
UNC Unified National Fine (Fine bolt thread)
UNS Unified Special thread (typically machine screw threads)

I swear one reference showed it as UNS, but can't find it now.

If it screws into the hole, put sealer on it and go. Surprised it didn't have sealer on it as-delivered.

Does the car not run an ECM? The way I understand it is that most people program fan settings through the ECM

Sorry for the sidetrack.

 

[Baker7888]

There are many thread types...

NPT National Pipe Thread (which sounds like what you have)
UNC Unified Nationa Coarse (coarse bolt thread)
UNC Unified National Fine (Fine bolt thread)
UNS Unified Special thread

I swear one reference showed it as UNS, but can't find it now.

If it screws into the hole, put sealer on it and go. Surprised it didn't have sealer on it as-delivered.

Does the car not run an ECM? The way I understand it is that most people program fan settings through the ECM

Thanks, yeah it looks like pipe thread to me. I have a bunch of them and they are all the same. One of them is the original one. It’s a carb swap motor so no ECM. I put teflon tape on it and it doesnt seem to be leaking now, fingers crossed, will check again tomorrow. Had me flustered for two reasons, A, I did not think pipe thread required sealer, and, B, the switch is normally open and grounds to the water pump housing so adding sealer theoretically could inhibit that, although i know the treads will cut thru it (not to start a debate) a lot of ppl will say not to seal the threads. I used a few wraps of teflon tape per suggestion of a furnace tech friend. I have the brush on stuff as well but he said the tape is better. I did not seal the first few threads to ensure metal contact.

 

[Clone TIE Pilot]

NP threads deform each time you screw and unscrew them. So they lose sealing ability over each reassembly and they often require a sealer of some sort. Pipe dope is really just a thread lube so you can tighten NPT fittings tighter in an attempt to form a new sealing surface within the threads. Teflon tape is what actually seals NPT fittings. You often leave the top couple of threads uncovered by tape for a electrical ground contact.

 

[Baker7888]

Thanks for the info!

 

[Baker7888]

Hey guys. The teflon tape worked like a charm.