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TR4/4A TR4A Brake Fluid Issue


Jedi Hopeful
Newbie here with a long question. Im working on a rust free TR4A with the exception of the brake/clutch mounting areas. This area has suffered from spillage or leakage of conventional brake fluid which has damaged the paint,pitting the brake/clutch mounting bracket,dissolving the rivets on the serial number tag,etc. It also ran down the brake/clutch pedals rusting them until they had no movement. After rebuilding the pedals with a new shaft,grease,paint,cleaning up the the M/C mounting area and bracket I was ready to install my new M/C only to read "Using Silicone Brake Fluid Will Void Warranty". The clutch M/C and slave cylinder did not have this label and I was wondering if anyone else has gone ahead and used silicone in a new M/C with this warranty label. The way TR4As are made any future leak will surely run down the pedals again which is what Im trying to avoid. I thought about seeing just what the silicone would do to the new M/C and if I had a problem I thought I would rebuild it with a kit from NAPA who also stocks wheel cylinders that are approved for silicone fluids. Sorry about having such a long first post and Im not trying to debate the silicone vs conventional fluid issue, its just that Ive had silicone in another restored US made vehicle for twenty years without any issues and was looking forward to using silicone in the TR4A.


Jedi Warrior
If it has a label that states the DOT5 (silicon) brake fluid use will void the warranty... then it probably just has not been tested with this fluid yet.

I don't see any reason why it would not be compatible with your new M/C, as long as all brake parts have been properly cleaned or have been replaced.

Mickey Richaud

Staff member
Country flag
And welcome to the Forum!



Great Pumpkin - R.I.P
I think the word Banjo meant is 'hygroscopic'. And all DOT 5 made in the last 20 years or so has had a "seal sweller" additive, to compensate for exactly the problem mentioned.

"Observant owner" - yeah, right. I was at Triumphest a few years back, when someone unloaded an absolutely pristine TR4 from their trailer in the parking lot. He had cleaned under the hood thoroughly before loading the car; I think he would have noticed a leak at that point. But it was all over the firewall when it came off the trailer. No way to repair the damage without pretty much stripping the firewall for repainting; certainly nothing he could do about it at the show.

(However, if memory serves, he won both Uff-Da and a gold in the concours. The judges took pity and ignored the ruined paint; the rest of the car deserved a gold.)

If it were my car, I'd put in the DOT 5 and deal with any problems that develop. Seals are cheap, and the standard seals work just fine with DOT 5. (It's also compatible with natural rubber seals, but AFAIK they have not been available for several decades.) But it's your car, you have to decide which modifications to make (and installing DOT 5 counts as a safety-related modification). All my Triumphs have it, and I love it.

Geo Hahn

Country flag
I just rebuilt the clutch MC and got a leak at the supply line out of the reservoir (TR3A) -- real glad I had DOT 5 in there -- an easy fix but repainting the firewall would have made it a long day.


Jedi Trainee
I am using DOT 5 in the brakes and clutch system, all new systems (IE pipes, hoses, MC, calipers, drums everything) and no leaks, issues to date.
do feel that the brakes seem a bit softer

oh ya if you are into the brake systems you might take a closer look at a PWDA rebuild as that guy is a notorious leaker https://www.buckeyetriumphs.org/technical/Brakes/MCPDWA/MC.htm

welcome and good luck, your journey is just beginning
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