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TR2/3/3A Is there a Silicon safe Master Cylinder for TR3?

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TuffTR250

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I installed new Brake and Clutch Master Cylinders on my TR3A along with all new wheel cylinders/rubbers and pipes. I used Silicon Brake fluid from Moss and Master Cylinders from TRF. Within a couple of weeks both Master Cylinders are leaking out the front. I know that the Master Cylinders from TRF are specifically labeled that the use of Silicon Brake fluid invalidates the warranty. However, I have seen the threads on this forum where people have used silicon fluid in their TR3 with good results. I called both TRF and BPNW and both stated that they did not know of any place selling TR3 Master Cylinders that were designed to use silicon fluid.

Does any one know of a source of either Master Cylinders or Master Cylinder rebuild kits that are safe to use with Dot 5 silicon brake fluid?

p.s. I do not want to use Dot 3 LMA brake fluid!!

Thanks and Regards,
Bob
 
The rebuild kits I got from TRF a couple of years ago seem to be holding up just fine with the DOT 5 I also got from them. No warnings not to use DOT 5 either.

Just out of curiousity, what brand was the fluid from Moss? I know that not all DOT 4 is the same; perhaps the same applies to DOT 5? I have no evidence for that, it's just a thought.
 
I have had no problems with my master cylinders which have been rebuilt with kits from Moss... been using Silicone for about 13 years now.
 
I've used the purple silicone DOT 5 fluid from Roadster Factory since I restored my 1958 TR3A in 1990 (109,000 miles) and not had any leakage from the front of the master cylinders. I replaced all the rubber seals and hoses when I started to use the silicone fluid and never had any issues since then.
 
You should not use DOT 3 period, LMA is DOT4.
 
The Moss silicon fluid brand name is Cartel. I'm guessing that the newer rubbers used in the India manufactured Master Cylinders from TRF are not working with silicon, but only a guess. I was hoping I could find a source for rebuild kit that will guarantee that their rubber seals will work with silicon.
Regards,
Bob
 
Been following this thread. I have no idea where the thought that silicone brake fluid causes leaks! Silicone doesn't damage anything. If the rubber cup leaks, it will leak no mater what you put in the system, but DOT-5: just might be a little quicker to show up. Poor honing job in the cylinder, scratch in the cylinder, poorly made cups will all contribute to a leak. I have DOT-5 in the TF and MGB. Been in the MGB since 2005, no leaks! Been in the TF since 2009, no leaks. Both cars had their brake systems completely redone, even with new lines. If your system is leaking, don't blame the fluid, fix the system! :hammer: PJ
 
PAUL161 said:
..If your system is leaking, don't blame the fluid, fix the system!
Click to expand...

Time to explain my 'Red Hat Theory'

I had a problem in one of my cars, as it happened I recall I was wearing a red hat that day. Some time later a friend had the same problem in his TR and I noticed that he, too, was wearing a red hat. Soon I began noticing others with related issues who often wore red hats. The conclusion was obvious.

Sub-par replacement parts, aging seals, faulty installation and inexplicable failures will always be with us -- because many of these will happen to people who are using silicone fluid and some will even happen right after a conversion to silicone it is natural to assume a causal relationship where none exists.

As a nephew once explained to me: Trees make the wind blow by waving their branches.
 
I just received new master cylinders from Moss and spent yesterday removing the old ones. Because I have a fair amount of paint damage in my engine bay, I was planning on switching the entire system over to DOT 5 because I didn't want to deal with the mess again in the future. Yesterday, I saw using silicon fluids voids the warranty and now I'm second guessing my original decision.
 
Bill. were there labels on the boxes that the master cylinders came in from Moss saying that the warranty is not valid if you use silicon brake fluid? The master cylinders I got from TRF specifically had a big label on the outside of the box stating that. Maybe Moss will warrant theirs with silicon. I have not asked Moss that question.
Regards,
Bob
 
Switch to the silicone fluid. I've used it for 23 years in my TR3A. One of my master cylinders is still the original one from when I bought it brand new in 1958. The other master cylinder, I had sleeved with a brass insert in Long island and with new seals, I never saw the "WARNING" until a few years ago. I just ignore them.
 
TuffTR250 said:
I was hoping I could find a source for rebuild kit that will guarantee that their rubber seals will work with silicon.
Click to expand...
I don't think you will ever find that. They don't even guarantee that they are compatible with DOT 4!

Part of the problem is that those standards are "performance" standards; they don't say anything about the actual content of the brake fluid (except that DOT 5 must be at least 70% of "a diorgano-polysiloxane").

In fact, "back when", Girling brake seals weren't even compatible with all DOT 4 brake fluids! You had to use Castrol brand fluid or the seals would fail in a matter of weeks. I don't think that is true any more, not sure whether the seals changed or the fluid changed; but I demonstrated it to my satisfaction back in 1978. All new seals, all new fluid, parked the car for a month or two ... when I got back to it the system was dry and every cylinder showed signs of leakage or damage. Repeated the process with Castrol brake fluid (before LMA as I recall, might have been Crimson) and the seals were still working fine over a year later.

Here is an interesting comment from Moss:

What About the Stories of Silicone Brake Fluid Causing Seals to swell?

These stories abound on the internet, but I have not actually spoken to the person it happened to, so I cannot comment on the actual incident that started the story. We do know that it is very, very unlikely that a brake fluid meeting FMVS 116 would do that. The testing is designed to make that sort of thing impossible. I can tell you that the literature is full of reference to the grotesquely swollen and gooey seals that you get if the brake system is contaminated with petroleum based oils or solvents. It does not take much of this kind of contamination to ruin all of the seals in a system. The contamination can usually be traced to the use of improper cleaners, rags contaminated with motor oil or grease, or handling the seal with hands that have petroleum based contaminants on them. We have tried to duplicate these reported problems by soaking brake cups in DOT 5 fluid, but we have never found a problem. However, these stories have a life of their own and it is doubtful that they will ever go away. It is perhaps a modern version of the traditional British natural rubber brake seal warning about using “the wrong fluid”.

https://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/brake_fluid_long.html
 
Moss said:
These stories abound on the internet, but I have not actually spoken to the person it happened to, so I cannot comment on the actual incident that started the story.... these stories have a life of their own and it is doubtful that they will ever go away...
Click to expand...

Yep, like alien abductions and Elvis sightings -- reports on the evils of DOT5 will always be with us.
 
If it were me Geo, I'd throw all those red hats away! :highly_amused: PJ
 
Here is the outside of the box of my new master cylinder from Moss.

8629855070_af56d14159_m.jpg
 
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I called Moss and the Sales person on duty today (Sunday) said he had a note saying that the manufacturer does not warrant their Master Cylinders if you use silicon fluid however Moss offers a 2 year warranty because they tested and found no problem with silicon. Might want to validate this with Moss Tech Support, but I would hope that the Sales team got their notes from Tech Support.
Regards,
Bob
 
Did you take the master cylinder apart to see what is going on? Some of these have been sitting a long, long time and the assembly lube can dry up and cause problems. I had this happen on wheel cylinders. Took them apart, cleaned them up, reassembled, worked fine. I would check with Moss first to see if disassembling voids the warrantee! Or if your warrantee is voided already, what do you have to lose?
 
At the end of the day, new master cylinders are only $40 and from what I gather there is an overwhelming recommendation to go to DOT5. Just got to make sure what I do not replace is fully DOT3-free.

Thanks for the help again guys!
 
Hopefully it never had DOT3 in it as DOT4 is for the British rubber seals and cups.
 
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