I recently replaced the brass elbow on the oil pressure sending unit. Appears to be leaking pretty heavy near the threads? What sealant is recommended? I keep seeing don't use any kind of teflon tape?

Also...Should the base of the dip stick be tapped into the block? I received the car after the 400 BB block was recently rebuilt...base is very loose.

Thanks!
Chad

 

I use Rectorseal pipe dope on brass fittings. Yes the dipstick tube should be driven down into the block.

 

The problem with using Teflon tape is the possibility of electrically insulating the sending unit. The gauge works by varying resistance to ground depending on pressure. The tape could change the resistance, affecting accuracy.

Teflon paste is a good substitute for the tape.

 

Everyone says this, but in half a century of working on these cars, I've never had a sensor grounding problem when using teflon tape. The threads always cut through the tape and make metal-to-metal contact.

 

X2 for Teflon tape. Never had a problem.


-peter

 

The problem happens when too much is used, I have seen it.

 

I think the same way, but since it’s mentioned in the service manual it must be a common enough issue to be a concern. I would think for enough tape t be on the threads to prevent electrical contact, you would have a hard time threading it in.

 

This conversation is really down to earth.



...thank you, thank you, try the sole.

 

I’ve never had a problem the Teflon tape either. I dont use a lot and I don’t apply it to the first couple of threads. This makes it easier to start the fitting without cross threading it and ensures proper metal to metal contact. NPT are usually tapered so when you have it all the way tight the threads provide the seal. The purpose of the Teflon tape is not to provide a seal, its to reduce friction so you can thread the fitting in further.

 

x 2

 

X3 ,lead pipe dope was used back in the day before Teflon was invented, lead was the lube of choice as we all know, reduces friction, allows the metal threads to crush into them selves and seal.