Silicone brake fluid conversion - existing system

[steveg]

Update - just disassembled one of my calipers. I bought some denatured alky, but also noted that aerosol Brake Parts Cleaner does a great job if one has one's system in pieces, as I do. Plus it doesn't eat the paint as the alcohol does.

I think a few cans of brake parts cleaner will work just fine.

Have ordered all new rubber parts. Belt and suspenders!

 

[steveg]

Hi all,

Just did a Jag XKE dot 5 complete flush last Thursday. Its been 5 years since the last flush the owner told me . Fluid was blackish, has S/S lines throughout and Low Pressure lines renewed last flush. Another disadvantage to DOT 5 is it does not have the lubricating capabilities as a Glycol base DOT 3/4 and seals will wear out faster in your M/C and slave units. In my earlier post what I mean in the sentence about silicone just carrying water is true, it is not hygroscopic meaning water absorbing so any moisture that enters the system ( however it can get in ) will just travel and go to the lowest point or get stuck seals and over time if the car is not used will cause rusting to the ferrous cylinders. What I am trying to promote here is flush your systems regularly DOT 3/4 and DOT 5 ! Yes storage has a lot to do with how moisture can get into a system, climates the car is living in ect. , all systems are vented to the atmosphere , thus allowing a certain amount of moisture in . The Jag I replaced all the components in was professionally restored and fluid bottles well marked DOT 5 only. I cannot answer why the entire system was pretty much trashed.
As for the servos it is still a big no to use DOT 5, see pic posted on instructions, Harley Davidson is now not recommending use of DOT 5 as well as Wagner Lockheed.View attachment 49039

Again this is from my experience ( my day job) yes it can be used and has been for many years but these are problems that keep popping up and now manufacturing companies are backing down from its use. Im not here to start a pros and cons thread, just google the info yourself.

Carroll
Top Down Restorations Inc.

Carroll - some bikers online are using this to lube their pistons when using with silicone fluid - I plan on doing so:

 

[Grantura_MKI]

My rule is to build all brake systems from new....meaning I sleeve every cylinder with SS, as the originals are getting harder to come by. I have many customers on dot 5 with NO issues. Many collecters tend to let there cars stand for long periods.
if you do jot flush competely, the residue will form I the resivour. You will notice the fluids not mixing...time to start again.

 

[glemon]

I converted my TR250 to Silicone during the restoration in 2008 or so because I kept having issues with a leaky union in the engine compartment and didnt want to paint it again (and again).

I blew out the lines with air and flushed thouroughly with DOT 5. The only issue I have had since was with the clutch master, which was the only part I didnt replace in the restoration (tried to get by with a rebuild). So nine years virtually problem free with DOT 5.

Also ran it in my Healey 100 for ten years before that, no problems.

Back when I ran DOT 3 (Castrol LMA) (70s 80s and 90s, various British cars) it seemed like once a year or maybe two a rear wheel cylinder or master cylinder or something would start leaking.

I went from being fairly skeptical/neutral on the subject to a pretty firm believer in the stuff. Didn't have any problems switching, but probably better to start fresh or clean the system better than I did, maybe made a difference that my parts were new and hadnt been exposed to DOT 3 for long.

 

[John Turney]

For those of us, like Steve, who live in California, moisture getting into a brake system with DOT 5 fluid is a non-issue.

 

[RAC68]

Since Silicone Brake Fluid is not Hydroscopic and absorbing water from a highly humid atmosphere will not happen as would when using Dot 3/4. As a result, I see it unlikely water would penetrate a well maintained and functioning brake system when Silicone fluid is being used.

Although some may use their Healey every day, occasional use is the predominant schedule of use and long periods of inactivity are common (especially during the cold month). Therefore, as I see it, Silicone's lack of equivalent lubricity to Dot 3/4, if true, would cause less of an issue toward increasing seal ware then would the use of a Hydroscopic Dot 3/4 during extended times of inactivity.

Ray(64BJ8P1)

 

[Patrick67BJ8]

I first converted to Silicone in the mid '80's and flushed the lines with denatured alcohol. I did not rebuild any of the master, wheel, slave or Booster when this was done. I did eventually rebuild the wheel cylinders about 5 or 6 years afterwards. I attribute the rebuilds to wear that was already there. Fast forward: I did a frame up restoration starting in 2009 and finished a couple of years ago. I had the Booster rebuilt because I thought it was a good time to do it since everything was off the car down to the last rivet. I felt the Booster never worked quite right after the rebuild and it eventually failed and I feel now that if I hadn't had it rebuilt it would still be working okay. It seems like a crap shoot on everyone's success with the silicone brake fluid. I received my Booster yesterday and installed it this morning and after I bleed the brake system I'll see if it's going to work okay.

 

[steveg]

Interesting white paper from e-type owner on DOT 5:
https://etype.chrisvine.com/wp-content/uploads/documents/DOT5 Silicone Brake Fluid.pdf

 

[steveg]

Another thing is the people who really put DOT 5 down don't seem to be using it.

I've done both my Toyota calipers and one of my Jag rears - blowing out with compressed air then cleaning with brake parts cleaner works great.

I've installed new rubber parts throughout and am installing new masters and a new clutch slave. Belt-and-suspenders.

 

[RAC68]

Hi Steve,

Wow, that was a very definitive clearly written article defrocking a multitude of misconceptions extended about the use of Silicone brake fluid. I hope, but am not confident, that all will read this article so that we can address the procedural issues that really matter in transitioning from Glycol-based fluids to Silicone on a Healey by those that have decided to do so.

It seems that Silicone fluid lubricity is a benefit and not a negative issue as asserted prior.

Thank you for finding and sharing this article.
Ray(64BJ8P1)

 

[DerekJ]

Interesting article - (reminds me of the oil threads )but at the end of the day I'm still left with the question - why bother switching? It seems to bring a lot of extra work with the potential for screw ups, and for what real benefits? I bleed my brakes every year and have never had any problems with glycol. Does anyone know the reasons why the US military have stopped using silicone? And if silicone really is a better product why would it not be used in racing applications?

 

[steveg]

Interesting article - (reminds me of the oil threads )but at the end of the day I'm still left with the question - why bother switching? It seems to bring a lot of extra work with the potential for screw ups, and for what real benefits? I bleed my brakes every year and have never had any problems with glycol. Does anyone know the reasons why the US military have stopped using silicone? And if silicone really is a better product why would it not be used in racing applications?

The main reason for using is to keep your paint nice. In my case, since my car's in pieces and I'd just finished painting my engine campartment, it wasn't that much additional work.

 

[Randy Forbes]

Interesting white paper from e-type owner on DOT 5:
https://etype.chrisvine.com/wp-content/uploads/documents/DOT5 Silicone Brake Fluid.pdf

The man is a good writer; no way would I have been able to read the entire thing without nodding off__though there was a couple close calls!

For me, the real meat started near the bottom of page five (5) and then I was engaged enough to continue to the end.

The paper does indeed clear up a lot of myths, and I learned more from reading it than in the decades prior. It's not as though I'm not convinced, it's just that as an old dog, I'm not that interested in learning new tricks. I'll stick to using glycol based fluids (several quarts of ATE 200 is always on my shelves for the BMWs) and drain/bleed them every couple of years. It's not an inconvenience, and it's a good opportunity to give the entire brake & clutch hydraulic circuits a good inspection (something they wouldn't otherwise get if I subscribed to a 15-year interval).

If it works, don't fix it.

 

[Brinkerhoff]

I love this topic because I confess , I have wasted a lot of time thinking about both of these subjects.

 

[dklawson]

Steve, thanks for the article link. It was very well written and informative.

The article addresses the lubrication issue well. The article mentioned warranty issues with regard to small shop rebuilders. My previous posts were from repeating information from TRW regarding their new, replacement parts. I am not saying that TRW's lubrication comments or reasoning are correct. I am however saying that one must be aware that even if DOT-5 fluid is not responsible for failure of a new or rebuilt brake component, the vendor may decline warranty coverage if DOT-5 has been used.

The author is clearly much more comfortable about using old seals with new DOT-5 fluid than I am. This is where anecdotal stories surface. I have seen failure of rubber bits that were once used with DOT-3/4 and then used with DOT-5. Perhaps those seals were reaching the end of their service life at the time the fluid type was changed. Regardless, for my own peace of mind, any future DOT-5 conversions I make will continue to involve new rubber parts at the same time.

Again, a very well written article. It is long but I encourage those interested in DOT-5 fluid to read it. Most of the author's observations echo my own experiences and I will continue to use DOT-5 in my old cars.

 

[RAC68]

Hi All,

As I see it, the choice of what brake fluid to use is not one of which is better but which has the set of benefits that serve my functional requirements best. In Derek's situation, the Hydroscopic nature of a glycol based fluid is not a major issue when fully replacing (bleeding) fluid on a yearly basis. Randy also makes the point that changes his practiced and well understood operational procedures, related to the use of Silicone, has a potential risks that is not overcome by the benefits he would realize. Also, Doug brings up that some manufacturers will not warrant their parts when Silicone brake fluid is used, whatever the basis of the manufacturer's reasoning.

Although I can appreciate and respect the decisions of those not making the transition to Silicone brake fluid, I long ago did make that decision, not only for the protection of my paint, but for the fact the its benefits are a best match for the profile of use, operation, and maintenance of my Healey and Triumph. For me, the article had centralized and supported many of the perspectives I had developed from sources long ago misplaced as well as providing a base of understanding to address such potential issues as expelling air from the system. Looking back, I don't remember dealing with or even submitting a hydraulic part or component for warranty and don't remember seeing a warning relating to the use of Silicone brake fluid.exchange so never needed to review the manufacturer's position. I would be keen on understanding the basis or reasoning behind a component manufacturer like TRW, who sells large quantities of components to the military, restricting their sales to the Federal Government.

Have I been lucky? Are my experiences unique? I don't think so. However, switching is a choice and not an obligation.

Happy Father's Day,
Ray(64BJ8P1)

 

[steveg]

Following up:
Just finished cleaning all my calipers and replacing the rubber parts, lubed with the Dow Corning High Vacuum Silicone grease. Can report that a couple of cans of brake parts cleaner is all that was necessary for cleaning everything out, including my two reservoirs for my dual-circuit system. I'm returning the unopened quart of denatured alcohol with which I'd originally expected to do the flushing.

Will report back when I've reinstalled the system and filled/bled with the silicone fluid.

PS - Tom's Toys has extremely good sale prices right now on the Moss Classic Gold clutch master and slave cyls. The master even comes with a pushrod. NFI

 

[Lin]

Well, unless someone can talk me out of it, I am afraid that I have resigned myself to sticking with DOT 4 brake fluid rather than DOT 5 silicone. I checked with John Stuart Powerbrake in Canada. They rebuilt my master and my brake servo. They indicated that both were rebuilt and tested using DOT 4 and they advised against using silicone. Of course, their recommendation is no surprise.

This project isn't my Healey, but instead the Jag MK2 I am currently restoring. My primary concern is the brake servo. If the servo seals fail, it is a royal pain in the A_ _ to remove the servo for rebuilding again.

I was was ready to switch to silicone after experiencing master cylinder seal failure in my Big Healey with resulting paint damage. Oh well. I hate the stuff, but I guess DOT 4 it is.

Lin

 

[dklawson]

There is nothing wrong with using the DOT-4. It won't cause you any problems and according to what your supplier told you it was the fluid used during reassembly.

As with all brake fluid, keep up with periodic flushes to replace the fluid (every two or three years) and wash the area around the master cylinders frequently. If you take those steps you'll have years of service and hopefully no paint damage.

 

[John Turney]

Well, unless someone can talk me out of it, I am afraid that I have resigned myself to sticking with DOT 4 brake fluid rather than DOT 5 silicone. I checked with John Stuart Powerbrake in Canada. They rebuilt my master and my brake servo. They indicated that both were rebuilt and tested using DOT 4 and they advised against using silicone. Of course, their recommendation is no surprise. ...

Lin

If you were to switch to DOT 5 and had a problem, John Stuart would blame the DOT 5, so I would stay with their recommendation.