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Thread sealing for oil pressure sender?

W

wolf2600

NAXJA Forum User
Location
Austin, TX
Need to replace my 99's oil pressure sending unit.

Years ago, I'd heard that you're not supposed to use teflon tape on oil fittings, is this correct? What should be used to seal the threads on the sender?
 
Yes, the sender is self-grounding, so it needs a good metal-to-metal connection to the engine block. The Permatex stuff will work.
 
IIRC it depends on if you have a dummy light or a real gauge. A gauge should be a two wire job and isn't self grounding : use what you like to seal the threads. A dummy light grounds to the block : don't use teflon. Like others have said, permatex copper should do ya.
 
Like said the you will notice when you buy a new one there is a coating on the threads of the new sensor. No need to add anything else.
 
Ive allways heard not to use teflon tape on hydraulic systems with fine valves...
This is the first time ive heard about not using it on any oil systems.
 
I once used teflon tape on a diff plug, and the oil attacked
the tape, softening it and causing a leak.

Since then, I use Permatex Aviation Gasket Sealant
as a thread sealant. Stays pliant and works excellent.
 
yossarian19 said:
IIRC it depends on if you have a dummy light or a real gauge. A gauge should be a two wire job and isn't self grounding : use what you like to seal the threads. A dummy light grounds to the block : don't use teflon. Like others have said, permatex copper should do ya.
Click to expand...
I think you'll find that on XJ's at least the gauge sender is also one wire and grounds to the block. You can change from one setup to the other simply by replacing the gauge cluster and two sensors without any wiring issues. The only difference in oil pressure senders is whether it's a switch or a variable resistor.
 
wolf2600 said:
Need to replace my 99's oil pressure sending unit.

Years ago, I'd heard that you're not supposed to use teflon tape on oil fittings, is this correct? What should be used to seal the threads on the sender?
Click to expand...

You may use whatever sealant you like on "fittings" - I prefer LocTite #545.

However, the oil pressure sensor is "self-grounding," meaning that it grounds through the threads. Ergo, using PTFE (tape or dope) can - and usually does - interfere with the ground and keep you from getting any signal at all.

I have had good luck either using copper-bearing RTV or never-seez. In either case, tighten to 1-2 flats past finger tight (meaning spin it down using your fingertips - don't wrap your paw around the thing! - and then put a wrench on it for 60-120*. Preferably 60*, you can always nip it up a flat extra after cleaning and inspecting, but I don't usually need to.)

The same thumb rules may be used for the coolant temperature sensor on the cylinder head up through early 1996 (cylinder heads 2686 and 7120) - never-seez or copper-bearing RTV, and then 1-2 flats past finger tight. (This sensor is absent on late 1996 and up.) Same thread size (1/8" NPT) and same reason (grounds through threads.)
 
If your oil pressure sender has one wire then the sendor is self grounding throuh the threads.
If your sendor has two wires then 1 wire is signal ground and the other wire is sendor signal.
If you have a 3 wire sendor then 1 wire is signal ground, 1 wire is sendor signal,and 1 wire is 5 volt ref.
 
cruiser54 said:
You sure about that? They make a special blue version specifically for LP.
Click to expand...

Yes, Just installed a new gas range,instructions were very clear..no Teflon tape or paste containing Teflon.
The tube has "Blue" on the label,but its gray inside,I guess the gas reacts with the Teflon ?
 
cruiser54 said:
You sure about that? They make a special blue version specifically for LP.
Click to expand...
Reading up on this, it seems that there's little consensus on just why there is a difference in tape, but there is, and double density tape made for gas fittings is apparently yellow. It may resist chemical breakdown, or may resist shredding, depending on who you read, or maybe both, but threaded gas fittings are supposed to use yellow.

I am assuming everyone knows here that you should never use any tape on fittings with O-rings, flares (especially brakes), or unions.
 
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