Teflon Tape compatability with Silicone

[Paul B.]

While replacing original brake lines on my 59 with new ones, I reused the original brass junction blocks, but at a couple of joints got leaks. It appears that during original assembly, these locations were over torqued leaving a deep groove in the brass block sealing surface. I am wondering if I use Teflon tape on the brake line fittings threads will it react OK with the silicone brake fluid I am using.

[Tom L.]

Re: Teflon Tape compatability with Silicone

The threads have nothing to do with the seal, they only clamp the flare on the line to the seat in the block. Are you using Stainless lines?? They are difficult to seal.

[Paul B.]

Re: Teflon Tape compatability with Silicone

I am using regular steel brake lines, not stainless steel.

[Jim L.]

Re: Teflon Tape compatability with Silicone

While replacing original brake lines on my 59 with new ones, I reused the original brass junction blocks, but at a couple of joints got leaks.

This happens often.

The brass takes a "set" to the contour of the flare of the original line and won't re-form to the contour of the flare of the new line. The right solution is to replace the brass blocks with new ones.

In any event, teflon tape (or any other sealant for that matter) should not be used with flared fittings. The flare of the tube and the mating surface of the brass block are what seals, not the threads.

Jim

[Bruce B.]

Re: Teflon Tape compatability with Silicone

I agree with everyone, no tape or sealent on flare fittings.

I used stainless steel lines on my 57 along with silicone brake fluid. You have to be very patient, look for leaks and keep tightening the line fittings.
After numerous attempts I have no leaks and the brakes feel great after 3500 miles.

[Chuck G.]

Re: Teflon Tape compatability with Silicone

NOT Corvette specific, but recently I put a front disc brake kit on my 56 Chevy hot rod to replace the original front drum brakes.

Along with the kit came all new stainess steel brake lines.

I did use teflon tape on the fittings, but simply to "lubricate" the threads. Where the SS lines went into the original brass blocks, I carefully and slowly tightened things with a flare nut wrench while stabilizing the brass block with another wrench.

I had no leaks. I'm using "regular old brake fluid", not silcone.

Others have said it, but these seal "at the flare" not by the threads. The SS lines are much harder than the original Bundy pipe (TBW) lines. I think if you tighten things slowly, you just might "reform" the brass block face to "accept" the new SS line.

If it won't work, the only alternative is to get new brass blocks.

Chuck

[Anthony P.]

Re: Teflon Tape compatability with Silicone

I just installed all SS lines on my 62 and I was able to use my original brass blocks (they cleaned up very nice). I did have 2 minor leaks on the 2 front blocks and those sealed with a little tightening..

Tony

[Joe M.]

Re: Teflon Tape compatability with Silicone

Not sure if the SS is 'harder' but previous discussions mention the pitch of the threads being different.

As to hardness, I installed a SSBC emergency brake kit on a 69 vette and found I had to replace the SS star wheel with the original as the SS star was too maleable. SS varies in hardness.

I used SS lines and original blocks on my 63 and had a few leaks which went away after tightening the couple of fittings tighter than I felt comfortable doing.

I will use steel lines on the 61.

Had a leak on the 63 fuely inlet line between the filter and fuel bowl. An almost imperceptible nick in the flare was the cause of the leak.

[John H.]

Re: Teflon Tape compatability with Silicone

Not sure if the SS is 'harder' but previous discussions mention the pitch of the threads being different.

Joe -

I don't recall that discussion offhand, but there's no difference in the thread pitch on the fittings between TBW and SS lines; only the line material is different.

[John D.]

Re: Teflon Tape compatability with Silicone

While replacing original brake lines on my 59 with new ones, I reused the original brass junction blocks, but at a couple of joints got leaks. It appears that during original assembly, these locations were over torqued leaving a deep groove in the brass block sealing surface. I am wondering if I use Teflon tape on the brake line fittings threads will it react OK with the silicone brake fluid I am using.

Paul, If you want an easy cure to your leak here it is. Use Loctite 545 hydraulic sealant. Not available in auto stores. Try Travers Tool, etc.
Shake the bottle (on the directions but no one reads them). Use a fine Q-tip as the applicator. Put a tiny bit on the ferrel of the brake line. Don't put any on the threads of the fitting as that's a waste.
Tighten up the fitting and the leak is gone. I like to give the sealant some curing time though.
This 545 has got me out of more jams on the FI units. JD

[Paul B.]

Re: Teflon Tape compatability with Silicone

Paul, If you want an easy cure to your leak here it is. Use Loctite 545 hydraulic sealant. Not available in auto stores. Try Travers Tool, etc.
Shake the bottle (on the directions but no one reads them). Use a fine Q-tip as the applicator. Put a tiny bit on the ferrel of the brake line. Don't put any on the threads of the fitting as that's a waste.
Tighten up the fitting and the leak is gone. I like to give the sealant some curing time though.
This 545 has got me out of more jams on the FI units. JD

Great suggestion - wanting badly to save original brass blocks - new ones have been ordered just in case - with gradual tightening I was able to reduce leak to just a drop under pressure, so this might just do it - thanks to all for the input.

[Anthony P.]

Re: Teflon Tape compatability with Silicone

Joe,
I just replaced my lines with SS lines and used the original brass blocks. The thread pitch between the original steel lines and the new SS lines were the same.

tony

Not sure if the SS is 'harder' but previous discussions mention the pitch of the threads being different.

As to hardness, I installed a SSBC emergency brake kit on a 69 vette and found I had to replace the SS star wheel with the original as the SS star was too maleable. SS varies in hardness.

I used SS lines and original blocks on my 63 and had a few leaks which went away after tightening the couple of fittings tighter than I felt comfortable doing.

I will use steel lines on the 61.

Had a leak on the 63 fuely inlet line between the filter and fuel bowl. An almost imperceptible nick in the flare was the cause of the leak.

[Joe M.]

Re: Teflon Tape compatability with Silicone

Obviously there is no thread pitch difference but I did find where I asked that question way back when and Joe L gave a comprehensive answer in a thread relevant to this discussion.

Have to figure out where I read about thread pitch?? Wouldn't be surprised if it came from SSBC. Had a bad brake line experience with them. Phoned the other day about the master C they sleeved for me and was told they no longer sleeve master cylinders and were less than helpful, again.


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