TR6 Dot 5 in a TR6 rebuild

[ceedub]

Any opinions on using Dot 5 in a new TR6 braking system? I have heard of mixed results. As I am completing a frame off resto on a '72 TR6, I thought that this was the time to consider using a less damaging brake fluid. I have had experience with my MG's using dot 3 and ruining the paint in the vicinity of the MC. I am also using the HVA transmission conversion with a Toyota 5-speed. The directions for the conversion insist on dot 4 for the clutch system. Anyone tried dot 5 in this conversion with success or do I have to use this paint remover in the clutch system as required? I am new to the Triumph forum but enjoyed a number of years with the BC Forum for MG's and learned so much from its participants.

Cheers from rainy Victoria, BC
CeeDub

 

[TR3driver]

I use DOT 5 in all my Triumphs, and I love it. It does have some downsides, but IMO the advantages outweigh the disadvantages. Check out this thread for more:
https://www.triumphexperience.com/phorum/read.php?6,857951,858831#msg-858831

Sorry, haven't tried the "hydraulic TOB" and probably never will. But my understanding is that it uses ordinary EPDM O-rings, which should be compatible with DOT 5. Personally I would probably try it, but the risk is that you will have to tear it all back apart to replace 50 cents worth of O-rings.

 

[dklawson]

When I purchased a reproduction master cylinder for the Spitfire it came with a disclaimer saying that the warranty was void if you used DOT-5. I called and asked the vendor who told me that TRW (who made the repro part) had determined that DOT-5 did not provide the same lubricity to keep the moving seals in good condition and that was their justification. Regardless, like Randall, I use DOT-5 in all my British cars including the Spitfire. I have yet to experience problems from DOT-5 but to each his own.

 

[TexasKnucklehead]

I also have a HVDA toyota conversion and spoke directly with Herman about using DOT5 with the hydrolic throw out bearing. Herman has used 2 different TOBs and one fails fairly quickly with DOT5, while the other seems to work fine. Apparently one has square cut o-rings, and the other doesn't. I would call Herman and discuss it with him before taking the chance of having to tear it all apart again.

 

[Jersey_Royal]

If silicon fluid gets into your servo, it will be sucked into your motor, and cause a mess, destroy your engine.

Silicon when burned turns to a white graining stuff not to different to Sand..... Silica

DOT 4 is what you want juts be careful with rags

Cheers
Guy

 

[glemon]

I have used Dot 5 in my last couple of LBCs, though this is hardly a scientific sample, I remember fixing hydraulic leaks and seaps in master and slave cylinders from time to time in prior LBC ownership. I have had zero, zilch, nada, master or slave cylinder leakage issues, worn out seals etc. in the ten or so years I have run Dot 5. I also like it that it doesn't eat my paint. You mileage may vary, I have heard other people say they have had more leaks with DOT 5. My Healey 100 was a DOT 5 conversion from DOT 3, the TR250 it was put in a totally rebuilt system. Only issues were with a couple of the homemade bubble flares in the homemade hydraulic lines, don't think that had anything to do with the fluid but more to do with the skill of the mechanic and the cheap harbor freight flare kit!

 

[titanic]

https://www.buckeyetriumphs.org/technical/Brakes/Fluid/Fluid.htm
This article from the Buckeye site on brake fluid gives a really good comparison of the different brake fluids and dispels the myths about Dot 5. I have used it in my cars for over 20 years without any problems.
Berry

 

[martx-5]

Since the TR6 and TR4 have separate reservoirs for the clutch and brake fluid, why not just use DOT5 in the brake system, and DOT4 in the clutch?? Yeah, I know you have to be careful about adding the correct fluid to each system, but it will lessen the chances of fluid spillage. Since I also have the Toyota conversion in my TR3, I've thought of doing just this, but the TR3 has essentially one reservoir for both. When I finally do my double master for the brakes, I will have separate reservoirs and will probably use the two different fluids.

 

[Jersey_Royal]

I had used silicon for at least ten years without issue, just the usual long spongy pedal on occasions. But
not any longer.

look here under vacum booster

https://adlersantiqueautos.com/articles/brake1.html

One wonders why it isnt used in by modern day manufactures.

Each to there own and all that stuff

Cheers
GUY

 

[titanic]

A little late for another comment on this topic, but I just noticed a drop of fluid on the boot of the clutch master cyl. and decided to investigate. My records show that clutch&brake hydraulics were last replaced in 1996. At that time, I sleeved the clutch master cyl. with stainless steel, replaced the seals, and replaced the fluid (Dot 5). Today, I decided to rebuild the master cyl and decided that I might as well do the slave too. Both the sleeved master and cast iron slave showed no wear in the cyl bores. What did surprise me is that the seals were quite soft, almost jello like consistency. I don't know if Dot 4 fluid would have had the same effect on the seals and it would have been changed many times in 16 years.
I am skeptical about the claim that Dot 5 booster thing and would like to hear of any first hand accounts of the problem actually occurring.
Berry

 

[Cheapsnake]

Timely question since I'm in the process of rebuilding the clutch and brake cylinder, master and slave on my TR8. My last rebuild failed after about 4 years and I blame it on the fluid I used since it looks like mud with all the disolved rubber in it. I used garden variety brake fluid, whatever came off the shelf at the Autozone so can't say for sure if it was DOT 4 or 5. I do know it ate paint very well. So now, I'm looking for a fluid that won't eat the seals quite so quickly. Of course, the recommended fluid is Girling Castrol, but with aftermarket seals, is that even applicable anymore? I asked the vendor of the seals for his recommendations and he gave me a big, "Huh?"

Not knowing the make-up of the seals, I'm thinking synthetic (silicon?) is the way to go.

BTW, don't mean to hijack this thread, but if I am, say the word and I'll start a new one.

Tom

 

[poolboy]

I think you'd have known if you had bought DOT5 both because of it's purple color and it's high price.
I would bet that most seals were made with the intentions of using DOT 3 or 4 so I wouldn't blame the fluid exclusively for the deterioration of the seals

 

[Tr6easyrider]

Synthetic Dot 5.1 and silicone Dot 5 are two different fluids, they should not be mixed . You can mix Dot 5.1 with Dot 3 and Dot 4 , but not with Dot 5.
If you use Silicone Dot 5 (won't eat your paint) you will need to flush your whole system with denatured alcohol.
https://en.wikipedia.org/wiki/DOT_5.1

 

[Cheapsnake]

OK, at least I know I definitely didn't use DOT 5 and probably not 5.1. So I likely used 3 or 4. After reading up on it, I agree with poolboy that the selection of fluids is probablynot to blame for my seal failure. What I may be looking at, is not a chemical deteriation of the seals, but a mechanical one if my bore is corroded or otherwise compromised. The appearance of the fluid (black and thick) would point to that conclusion. Thanks for the info guys and for the Harbor Freight tip. I'm off to HF for the hones.

BTW, way more than you ever wanted to know about brake fluid here, https://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/brake_fluid_long.html

 

[TR3driver]

My last rebuild failed after about 4 years and I blame it on the fluid I used since it looks like mud with all the disolved rubber in it. I used garden variety brake fluid, whatever came off the shelf at the Autozone

That's actually quite interesting, Tom. I saw the same kind of problem, many years ago now, with a TR3A. At the time, the word was that you had to use Castrol brand brake fluid in Triumphs, American brake fluid would eat the seals. Supposedly the British seals were natural rubber and common brake fluid was not compatible (in spite of the DOT specification). I didn't believe that at the time, but managed to convince myself it was a real problem at the time.

But lots of folks said they used non-Castrol DOT 3/4 later on with no problems, so I'm guessing that either the brake fluid or the seals changed. Not sure which one, though; your description makes it sound like maybe it was the fluid that got "fixed" and you found some that wasn't fixed.

PS, an important point is that the DOT standard does not specify the fluid composition (except that DOT 5 fluid must be mostly silicone). It is actually a performance specification. And the DOT does not test products, the product manufacturers are supposed to police themselves. We all know how well that works.

One thing I didn't see in the Moss article : Conventional brake fluid can also absorb salt, apparently right through the soft brake lines (!) See
https://docs.google.com/file/d/0B2H2NJt34OffNWE5ZDE3NmQtYTViYy00NzI2LTkxODYtZjdhNzQ5YjYxZGY2/edit
(which is one of the documents referenced in the article on the Buckeye Triumphs site)

I am also convinced that water is much less of a corrosion concern with DOT 5 than some of the articles have stated. With DOT 5 present, any water will bead up (just like a freshly waxed car) and not 'wet' the surface. Hence it cannot cause corrosion. It might boil, if it ever got into the calipers, but that doesn't seem likely to me.

This is admittedly an extreme case (car stored for 40 years without removing or changing brake fluid), but I have seen this kind of corrosion with DOT 3/4 in other cases:


By contrast, silicone acts as a metal preservative.

 

[Cheapsnake]

That's actually quite interesting, Tom. I saw the same kind of problem, many years ago now, with a TR3A. At the time, the word was that you had to use Castrol brand brake fluid in Triumphs, American brake fluid would eat the seals. Supposedly the British seals were natural rubber and common brake fluid was not compatible (in spite of the DOT specification). I didn't believe that at the time, but managed to convince myself it was a real problem at the time.

But lots of folks said they used non-Castrol DOT 3/4 later on with no problems, so I'm guessing that either the brake fluid or the seals changed. Not sure which one, though; your description makes it sound like maybe it was the fluid that got "fixed" and you found some that wasn't fixed.

PS, an important point is that the DOT standard does not specify the fluid composition (except that DOT 5 fluid must be mostly silicone). It is actually a performance specification. And the DOT does not test products, the product manufacturers are supposed to police themselves. We all know how well that works.

One thing I didn't see in the Moss article : Conventional brake fluid can also absorb salt, apparently right through the soft brake lines (!) See
https://docs.google.com/file/d/0B2H2NJt34OffNWE5ZDE3NmQtYTViYy00NzI2LTkxODYtZjdhNzQ5YjYxZGY2/edit
(which is one of the documents referenced in the article on the Buckeye Triumphs site)

I am also convinced that water is much less of a corrosion concern with DOT 5 than some of the articles have stated. With DOT 5 present, any water will bead up (just like a freshly waxed car) and not 'wet' the surface. Hence it cannot cause corrosion. It might boil, if it ever got into the calipers, but that doesn't seem likely to me.

This is admittedly an extreme case (car stored for 40 years without removing or changing brake fluid), but I have seen this kind of corrosion with DOT 3/4 in other cases:


By contrast, silicone acts as a metal preservative.

Apparently, the Girling fluid was spe'c to protect natural rubber seals prevalent at the time and the stubborn Brits just took a bit longer to "discover" synthetic rubber and non-Lucas electrical components. Since the seals that failed on my TR8 were replacement and most likely synthetic, I really don't think the fluid ate them up but absorbed enough water to corrode the cylinders, which in turn abraded the seals. Evidence of this corrosion is at the exterior of the cylinder entrance, which is VERY corroded after a relatively short period of time. Not nearly as nearly as corroded as yours, but enough to require serious work.

I always questioned the reasoning behind the recommended fluid changes, but I'm starting to see the light. I'm flushing my clutch and brake systems and will seriously consider silicone fluid.

BTW, the HF hones are 1 1/8" diameter and don't fit either the brake or clutch cylinders. So I resorted to the old standby, a wooden dowel with a strip of wet/dry sandpaper wrapped around it. Start with 320, then 1000, finish with 2000. Works like a champ and it's CHEAP!

Tom

 

[sail]

Similar experience with a new clutch master and slave however with Castrol that turned to black mud after about 6 years. I wrote it off to inferior seals, replaced from another source and switched to Dot 5.

 

[dklawson]

But lots of folks said they used non-Castrol DOT 3/4 later on with no problems, so I'm guessing that either the brake fluid or the seals changed. Not sure which one, though; your description makes it sound like maybe it was the fluid that got "fixed" and you found some that wasn't fixed.

Back in the day I did see original wheel cylinder seals turn to goo when exposed to DOT-3. But that was a long time ago.

The story I was told (and no one seems to be able to provide confirmation) is that sometime in the mid-1970s the brake rubber formulation was changed to something compatible with both DOT-3 and -4. Regardless, the latest parts do appear to be more compatible. A TRW (Girling) master cylinder I bought three years ago even said on the reservoir lid "DOT-3 Only". I thought that was quite odd. If the balance of your car's braking system has NOT been rebuilt (flex lines, caliper and wheel cylinder seals, proportioning valve, PDWA...) what mayhem might happen when putting DOT-3 into that new master cylinder?