Brake system flush

[angelfj1]

This week I plan to change over the TR-250 from Castrol GT LMA to Silicone brake fluid. I have a new master and rear wheel cylinders, but do not have new pistons/seals for the calipers. Since I will be disconnecting the lines and replacing most of the hydraulics, is it still necessary to flush the lines? if, so what is the preferred fluid?

Thanks in advance.

 

[lotuslover]

I would flush it all out with clean silicone fluid and lots of it. It doesn't make sense to leave any of the old fluid in there to contaminate the silicone fluid, kind of defeats the purpose of changing over.

 

[Guest]

Yes, you must flush it out... NO you will NOT get all the glycol fluid out... and NO, british rubber components do NOT have elastometer compatibility with Silicone fluid... AND if the rear seal of the M/Cyl. fails/leaks, and the booster sucks fluid through it into the vacuum of the intake, you can kiss the engine Bye-Bye! with silicone becoming an abrasive upon burning inside the combustion chamber.... KEEP the Castrol in it and flush every 1-2 years!

 

[DrEntropy]

mehheh... Sherman hits it outta th' park. :laugh:


Do NOT bother to go "silicone".

Flush it with LMA every year or so, eschew that "advanced" crap!

The alternative is to get all new calipers and cylinders, flush the system, dump the M/C for a new or rebuild, all too much!!!

Castrol LMA is CHEAP!! Th' time to flush it once every year or so is the same.


..just another opinion. :laugh:

 

[Steve]

I'll add a third to that one. Waaaaay too much agravation involved with silicone in systems that were not designed for it.

 

[Guest]

I purchase Castrol LMA in quarts by the case! (No, I do not drink it! LOL)

 

[Steve_S]

Two of my cars have run silicon for a long time. The MGC has had it since 2000 and the '67 BGT since the 90's. Neither has ever had any problem whatsoever. The rubber that originally came in these cars cannot handle silicon, but the modern replacement rubber parts have no issues with it whatsoever.

The MGA will get silicon next because their MCs are known to leak, and when they do they paint on the bulkhead gets destroyed. Silicon will not harm paint and that's more than enough reason for me. The other cars have LMA, which I have run in most of my cars over the years, and also have had no problems.

 

[Basil]

Two of my cars have run silicon for a long time. The MGC has had it since 2000 and the '67 BGT since the 90's. Neither has ever had any problem whatsoever. The rubber that originally came in these cars cannot handle silicon, but the modern replacement rubber parts have no issues with it whatsoever.

The MGA will get silicon next because their MCs are known to leak, and when they do they paint on the bulkhead gets destroyed. Silicon will not harm paint and that's more than enough reason for me. The other cars have LMA, which I have run in most of my cars over the years, and also have had no problems.

Steve, I ran Silicon in my EType (back when it was actually running) and had no problems either. However, I did notice the brake pedal felt a tad "spongy" no matter how much I bled the brakes (and with all new components). I'm just curious if you've found your breaks with silicon to be just a tad less firm than with regular brake fluid?

 

[tony barnhill]

I'm with Steve & Sherman on this one.

 

[Guest]

Back when I was under the tutilage of John Bamberg (Rolls-Royce Master), he was getting 55 gallon drums of Silicone Brake fluid from G.E. who were THE only source in those days. BTW, silicone and Rollses don't get along! The stuff had just been released from proprietary status by the military... just like WD-40 once was. Every car or truck we converted (including clutches) had a problem with off-gassing from atmospheric changes... just as air changes properties with temp and humidity(ever wonder why a 757 has nitrogen in its tires?). Folks would lose the clutch totally only to have it return suddenly. Brakes were reported spongy... several lost them totally when they drove into high elevations, to have the brakes begin working again when they came down to lower elevation. I have been told by an un confirmed source that Silicone fluid no longer has that problem... and that the fluid works if one starts off with a new, dry system.... like the 72 TR6 that I'd doing a frame-off resto for a customer... he wants silicone and we are replacing the entire brake system... I have no problem with that, per se... but another source stated that the elastometer in original british rubber doesn't mesh with the silicone.. no time element given... so who knows if it's 2 years or longer? As a business, I have liability concerns. After last year's restorative brake job on the TR250, and seeing all the problems therein... combined with the other problems from yesteryear, I'm holding my aces close.

I wound up converting ALL the vehicles back to glycol in the days of working under Mr. Bamberg!

 

[JPSmit]

I wound up converting ALL the vehicles back to glycol in the days of working under Mr. Bamberg!

which is the perfect leadup to my question. I'm getting nowhere fast with DOT5 in my clutch. If I convert it back, am I correct that I have to re-rebuild my master/clave cylinder and replace the hose? or can you clean silicone out of a sustem?

 

[Guest]

I used de-natured alcohol along with comprerssed air... and was successful 100% of the time upon going back to glycol.

 

[Steve_S]

Steve, I ran Silicon in my EType (back when it was actually running) and had no problems either. However, I did notice the brake pedal felt a tad "spongy" no matter how much I bled the brakes (and with all new components). I'm just curious if you've found your breaks with silicon to be just a tad less firm than with regular brake fluid?

Only if they aren't bled really well. Silicon fluild tends to hold air bubbles more than standard fluid.

I have been told by an un confirmed source that Silicone fluid no longer has that problem... and that the fluid works if one starts off with a new, dry system.... like the 72 TR6 that I'd doing a frame-off resto for a customer... he wants silicone and we are replacing the entire brake system... I have no problem with that, per se... but another source stated that the elastometer in original british rubber doesn't mesh with the silicone.. no time element given... so who knows if it's 2 years or longer?

That time element is considerably more than 2 years. I would say more like 20 years. Older rubber compounds were not able to hold up very well to silicon fluid but when silicon fluid became common in personal vehicles, the compounds changed. The rubber in the brake system of my BGT was pretty old when I changed it, and had silicon fluid in it the entire time. It all looked brand new, with the exception of hoses which showed normal wear.

I'm getting nowhere fast with DOT5 in my clutch. If I convert it back, am I correct that I have to re-rebuild my master/clave cylinder and replace the hose? or can you clean silicone out of a sustem?

All rubber must be replaced. Metal pieces can be cleaned. You have to get rid of all traces of the silicon fluid because the two types do not mix well. "Goo" will develope and clog the system.

 

[Guest]

20 years? Any engineering or research data to substantiate that? :shocked:

I am always open to correction/update/enlightenment! Today's correct information soon becomes yesterday's incorrect history! My involvement with silicone and Mr. Bamberg spanned several years. But that WAS long ago... :crazy:

I have eschewed this hotly debated topic with more than a few folks in the past 2-3 years and still have to rely on Lockheed's CURRENT website that substantiates that the rubber in the british cars still is not compatible with synthetic fluid and silicone traps air pockets, resulting in 2-3 times the compressibility of glycol, thus a spongy pedal.

No dis-respect meant to you or any others,... but given the resources the Locheed/Martin corporation possess, combined with the otherwise doubtful and legally risky nature of condoning and/or recommending other than originally specified components or fluids for a potentially life saving system such as brakes, I rather stay on the safe side.

 

[PAUL161]

No dis-respect meant to you or any others, Basil... but given the resources the Locheed/Martin corporation possess, combined with the otherwise doubtful and legally risky nature of condoning and/or recommending other than originally specified components or fluids for a potentially life saving system such as brakes, I rather err on the safe side.

Even though I have silicone in the 72 "B" and have had no abnormal results in it's all new system, I would certainly would not put it or any other non approved fluid in an aircraft brake system. I agree that much high dollar research has gone in to aircraft components and some has bled over into the automotive industry, a good thing. But, I do disagree with the FAA one one thing, I disprove of ultra lite pilots not needing a proper pilots license. They still use air space. Sorry, I got carried away.

 

[Steve_S]

20 years? Any engineering or research data to substantiate that? :shocked:

None at all. My statement is purely based on what I have seen with my own cars and those I have seen go through the local British repair shops.

I fail to see how the problem can be targeted solely at British car part rubber. Many rubber components are shared between many makes and models from all over the world including hoses, wheel cylinder bits, o-rings, etc.

After tens of thousands of miles of hard driving on silicon in my cars, plus all the others using it on the road, I see no need for concern. But that's my personal opinion and everyone should do what they are comfortable with. There is certainly NOTHING wrong with traditional Dot3/4 other than the paint issue.

 

[Guest]

Trouble is, it isn't considered a proper test model by the powers that be. (What you have seen or what I have seen...) These conclusions aren't accurate. As far as british cars being singled out.... I understand it, because the brits had their own standards of engineeirng, including an exclusive fastener standard that gave birth to british-only tools.

I do not condemn you for your preference. It is your own perrogative to use silicone fluid..... in your own cars. Due to our legal system of today, I do not use it in any of my customers' cars where the manufacturer dictates something else...such as DOT 3.....People are sue-happy, so I'm going to cover my butt!

I choose not to use silicone in my own stuff because I own the tools and have the wherewithall to flush my systems and keep them clean. I did it with my 1990 Suburban for over 10 years with no problems from Houston's very humid climate!

 

[Basil]

I choose not to use silicone in my own stuff because I own the tools and have the wherewithall to flush my systems and keep them clean. I did it with my 1990 Suburban for over 10 years with no problems from Houston's very humid climate!

I used it in My Jag EType mainly due to the idea that "if" it does leak onto my firewall it won't ruin the paint (and I had spent a fair penny on that). However, I'm probably going to revert back to the recommended non-silicon fluid when I re-do my brakes this time, but I'll need to be very careful I don't get the stuff on the paint! That would not make me happy.

 

[Steve_S]

Trouble is, it isn't considered a proper test model by the powers that be. (What you have seen or what I have seen...) These conclusions aren't accurate.

...which is precisely why I stated that my observations were not backed by any scientific data, and that everyone should do whatever they are personally comfortable with.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]As far as british cars being singled out.... I understand it, because the brits had their own standards of engineeirng, including an exclusive fastener standard that gave birth to british-only tools.[/QUOTE]That doesn't account for rubber compounds, which usually aren't even made in England, nor are they made to British (or anyone's) specific formula. They are made from generic rubber formulations used on thousands of other car parts.

 

[Guest]

The rubber compounds made in countries other than Britain are not taken into consideration in my rebuttal, true. But, there is a reason. In my extensive research about this very hotly debated topic, the rubber compound issue was addressed by Lockheed ia an article I read on the internet 3 years ago where they specified the elastometer in British rubber components as non-compliant to silicone fluid. Moreover, when the issue of spongy pedal and off-gassing causing unpredictable no-brake conditions is factored in, and the fact that if the master cylinder rear seal leaks into the booster cavity (which is fairly common) and silicone fluid is burned in the combustion chamber, it is bye-bye engine because silicone reverts to silica, which, when burned abrades everything in sight, I absolutely will not use the silicone.

Given the cost of the fresh engine as opposed to the cost or inconvenience of flushing glycol every 2 years, I'll take the glycol fluid. LBC's aren't Toyotas, after all!

They must be looked after constantly!

And, Basil, saving the paint becomes a moot point if you wrap that gorgeous E-type around a tree because of a sudden loss of braking, anyway! :shocked: