fasted58
fasted58 HalfDork
6/20/11 11:38 p.m.

teflon tape or pipe dope is not intended to seal, never depend on it for that !!

your soft line or slave cylinder is at fault

Travis_K
Travis_K SuperDork
6/21/11 1:39 a.m.

Try again. If it's leaking there is something wrong.

iceracer
iceracer Dork
6/21/11 9:34 a.m.

The flare is probably cracked.

dollraves
dollraves Reader
6/21/11 10:14 a.m.

FYI: Brake fluid will dissolve the Teflon tape.

curtis73
curtis73 Dork
6/21/11 10:48 a.m.

Not to mention that the threads have nothing to do with sealing a flared fitting. They simply mechanically press the flares together.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
6/21/11 11:34 a.m.

What they said. Brake fluid dissolves teflon tape. Sealing the thread won't help because that is not where the seal is. It is the flare. Either the line is deformed or the nipple inside the cylinder is (or its the wrong flare).

curtis73
curtis73 Dork
6/21/11 11:58 a.m.
Wonkothesane wrote: Curtis - Good point, I think the hole in the slave was just tapped too deep from the factory.

That's what SHE said.

amg_rx7
amg_rx7 HalfDork
6/21/11 12:16 p.m.

Hmmm... Lotsa people use teflon tape on the Miata rear brake junction box. Seems like they all leak if you don't and teflon tape is the fix.

Teh E36 M3
Teh E36 M3 HalfDork
6/21/11 12:24 p.m.

I've used teflon tape between an aluminum an-pipe thread adapter and a wilwood brake caliper without issue.

That said, for your issue, I would echo the above comments about the flare being the issue.

44Dwarf
44Dwarf Dork
6/21/11 12:26 p.m.

Aftermarket calipers and masters have pipe threads often. Everyone I've ever seen says not to use tape. CNC brand masters tell you before filling the master to use red or green loc-tite thread sealer on the fitting and do not over tighten.

Now if your talking a flare fitting its more likely that some one used a standard 3/16 line where there should be a metric line! The thread is so close and often will work just fine but the metric tube nut has some extra length to it before the treads.

44

erohslc
erohslc Reader
6/21/11 12:31 p.m.

Hmm, nothing dissolves real teflon (except maybe hydroflouric acid). If you have 'teflon tape' that dissolves, then it's suspect.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
6/21/11 1:14 p.m.
erohslc wrote: Hmm, *nothing* dissolves *real teflon* (except maybe hydroflouric acid). If you have 'teflon tape' that dissolves, then it's suspect.

Not to be combative but... white teflon tape as used and sold for plumbing is Dupont branded polytetrafluoroethylene. It dissolves in seconds in petroleum based solvents. Gasoline works like a charm. DOT3 Brake fluid is polyethylene glycol-based and so... it might not actually dissolve it but as the root cause of the leak is not the thread interface... it isn't the right answer either.

Graefin10
Graefin10 Reader
6/21/11 2:02 p.m.

In reply to Wonkothesane:

You referred to the leak occuring @ the "soft line". The diagram you posted doesen't show it as a soft line and calls it a "pipe". Most slave cylinders I've serviced had a flexible hose (soft line) that connected to the cylinder and instead of a flare fitting had another type that used a brass sealing washer between the fitting and the flange of the cylinder. If it's that kind of fitting is the sealing washer missing?

dollraves
dollraves Reader
6/21/11 2:39 p.m.
Teh E36 M3 wrote: I've used teflon tape between an aluminum an-pipe thread adapter and a wilwood brake caliper without issue.

Interesting. I tried using it on the threads for the metal brakeline into the master cylinder on the $2010 GTX...stopped the leak for about a day or two, then leaked again. When we unscrewed the line, there was no teflon tape to be found. Mechanic friend of mine said it was because brake fluid dissolves teflon tape.

Now I have to go home and stick some teflon tape in a small bowl of brake fluid to find out. You know...FOR SCIENCE.

pete240z
pete240z SuperDork
6/21/11 2:45 p.m.
curtis73 wrote: Not to mention that the threads have nothing to do with sealing a flared fitting. They simply mechanically press the flares together.

Curtis has the answer and is the man. And has an awesome 'fro.

Pipe thread is tapered and the threads need a sealing compound or tape.

erohslc
erohslc Reader
6/21/11 7:01 p.m.

In reply to dollraves: Breathlessly waiting for the results (I currently have no 'teflon tape' to test it myself.)
I worked for a while as a machinist where we fabricated electronic parts out of solid Teflon chunks, and also fabricated parts out of Teflon sheet. Nothing would touch it, not cutting oil, not mineral sprit, not lacquer thinner, not even the heated tetrachoroethane solvent that we used to degrease.

I suspect that 'teflon tape' used in plumbing is really powdered Teflon in a carrier matrix of some other plastic; such plastic dissolvable in petroleum products.

(and I was wrong, even hydroflouric acid does not dissolve Teflon)

pete240z
pete240z SuperDork
6/21/11 8:32 p.m.

I sell s/s hoses for most applications. For all the nastiest applications we go to teflon lined hose. The worst for us is sulphuric acid.....but the teflon hoses are the magic answer to most nasty chemicals.

AngryCorvair
AngryCorvair SuperDork
6/22/11 8:44 a.m.
erohslc wrote: not even the heated tetrachoroethane solvent that we used to degrease.

ah, the good old days.

spitfirebill
spitfirebill SuperDork
6/22/11 8:52 a.m.

I love the smell of TCE in the morning.

Scott_H
Scott_H New Reader
6/22/11 10:47 p.m.

Teflon tape has no place on a car. In the rare cases where there is a thread that does provide the seal , ie pipe thread, Teflon paste is the choice. Tape and paste will both seal fine, but when you take it apart in the future the tape will be all cut up and little threads of the stuff can get everywhere. It can migrate into a master cylinder and block one of the passages of if used on fuel, into an injector.

It does not dissolve very well as stated and can land at the wrong place a long time after the dis-assembly.

fasted58
fasted58 HalfDork
6/22/11 11:05 p.m.

Teflon tape aka known as thread seal tape and pipe dope are NOT sealers, they are lubricants designed to aid in the deformation of the tapered male/ female threads which form the actual seal.

Sure, folks have wound a cpl extra wraps of tape on a loose fitting on the air compressor or water pipes and got away w/ it but that ain't the right way... and no way on a vehicle.

fasted58
fasted58 HalfDork
6/22/11 11:14 p.m.

In reply to fasted58:

Edit: thread seal and dope on tapered pipe threads on manifold fittings and the like are OK

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