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Learned Gentlemen

 

I am about to start a brake overhaul on my TR4 to include reconditioning the calipers, and fitting new seals in the rear wheel cylinders and master cylinder. Hoping not to restart the debate of Silicon vs DOT4 I have decided to change from Silicon back to DOT4 I have heard mention that I need to flush the system out with Methylated Spirits to remove all traces of the old fluid. I would  welcome any advice on how to carry this procedure.

Cheers Chris.

 

 

 

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As a former industrial chemist, I would expect it's actually more difficult to rid the system of silicone fluid than DOT4, which is miscible with methylated spirit and of course, with water.

I understand you don't wish to reopen the age old debate on which hydraulic fluid is best... but why not stick with silicone? It's worked very well in my TR6 and GT6 for years, after a complete braking system overhaul on each car, but I won't bang on about the theoretical chemical benefits of silicone. If you really do wish to change, be prepared to open up every cylinder in the system, clean it thoroughly with meths first then DOT4 and replace every rubber seal. Then blow through all the pipes repeatedly with compressed air. Because of the tenacity of silicone, it will be very difficult to rid the entire system of every trace. Sorry not to sound more encouraging.

Nigel

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Chris,

If you decide you don’t want to refurbish your calipers, I have a number of sets of refurbished calipers for sale. They were refurbished by Bigg Red and have been totally stripped, castings have been replated and then rebuilt with all new pistons and seals. They have a 12 month hydraulic guarantee from Bigg Red.

if you, or anyone else wants a pair as a discounted price for TR Register members, do let me know.

David

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Hi Chris, I'm with Nigel on this. You need to know the silicone oil has all gone, as any residual wont dissolve in Dot4 and may gradually float up to the master cylinder, with uncertian results. Maybe it has been doen before but its not the same as swapping from glycol to silicone. Meths wont work:

http://prntscr.com/p9zh15

Peter

Edited by Peter Cobbold
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Silicone oils are miscible in hydrocarbon solvents... So I suggest wash the metal brake lines with Xylene/Toluene or if you can't find those, Kerosene... Then afterwards wash through with methylated spirits and blow dry.  The rubber seals and hoses will quickly degrade in said hydrocarbons but since you say you plan to replace them should be OK.

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When my car (4VC) was rebuilt in the early 1990s, all the brake rubbers were replaced, braided flexibles fitted and the system filled with silicone brake fluid. 

It's been like that since 1993 - 26 years is a pretty good test!

Ian Cornish

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So much for your not opening the silicon fluid debate then! I would just replace all the rubber including the flexis and wash the lines with Meths and start again from there.

Stuart.

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4 hours ago, Chris Hubball said:

A question I forgot to ask,  I have Aeroquip braided hoses fitted, all round if I make the change to DOT4 will these need to be changed along with the seals ?.

Cheers Chris

I think those hoses are teflon-lined, so that's another material to ponder. My guess is its inert, but I dont know for certain Best email Aeroquip. Peter

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16 hours ago, Nigel Triumph said:

Chris,

The servo on my TR6 has lived happily with silicone fluid for more than a decade. Sounds like staying with silicone could well be your easiest option.

Nigel

My servo has seen silicone for 25 years, including  a period when oil was leaking past the m/c seals. Some oil may have been sucked into the servo, but it works fine. I'd far rather have silicone oil lubircated servo than glycol -water and resulting rust. Peter

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1 hour ago, Peter Cobbold said:

I think those hoses are teflon-lined, so that's another material to ponder. My guess is its inert, but I dont know for certain Best email Aeroquip. Peter

Teflon (PTFE) is resistant to almost every known chemical compound. In fact it's the most chemically resistant polymer known and is more resistant to chemical attack than stainless steel. I've used braided Teflon hoses with silicone fluid on my GT6 for 20 years and my TR6 for over 10 years. These brake hoses are all fine and will no doubt outlast their owner!

Nigel

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18 hours ago, Chris Hubball said:

Thankyou gentlemen for your comments, the main reason for changing to DOT4 , is as that as old age sets further in I may fit a servo the seals of which I have read somewhere do not take kindly to Silicon Fluid.

Cheers Chris.

Where did you read that Chris?

Pete

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On 9/24/2019 at 1:45 PM, Peter Cobbold said:

My servo has seen silicone for 25 years, including  a period when oil was leaking past the m/c seals. Some oil may have been sucked into the servo, but it works fine. I'd far rather have silicone oil lubircated servo than glycol -water and resulting rust. Peter

Peter,

be very careful with silicone leak in a servo...cost me an engine rebuild already...

 

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Gentlemen

Still weighing up the various options on my brake overhaul only to have another issue raise its head. What is the difference between DOT5 and DOT5.1 brake fluid I currently have Automec  DOT5 in the system, if I was to change to DOT5.1 will it mix with DOT5 or will need to flush the system out and change all the seals.

 

Cheers Chris

 

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My tr6 has had silicone fluid in the brake and clutch systems for 20 years approx.

when i replaced the calipers i considered going to dot4, as it is less compressible, but decided to stay with Automec dot5

all has been well for 10K spirited miles

 

steve

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1 hour ago, Steves_TR6 said:

My tr6 has had silicone fluid in the brake and clutch systems for 20 years approx.

when i replaced the calipers i considered going to dot4, as it is less compressible, but decided to stay with Automec dot5

all has been well for 10K spirited miles

 

steve

Completely agree about DOT5 silicone working well, from my experience over nearly 20 years.

Not sure about your comment on compressibilty though. Theoretically, by definition liquids cannot be compressed, a given volume of liquid occupies a defined space regardless of pressure.

To be more practical and less theoretical, I've never found a car with silicone fluid to have a 'soft' brake pedal, if the brakes were fully bled and adjusted.

Nigel

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20 minutes ago, Nigel Triumph said:

Completely agree about DOT5 silicone working well, from my experience over nearly 20 years.

Not sure about your comment on compressibilty though. Theoretically, by definition liquids cannot be compressed, a given volume of liquid occupies a defined space regardless of pressure.

To be more practical and less theoretical, I've never found a car with silicone fluid to have a 'soft' brake pedal, if the brakes were fully bled and adjusted.

Nigel

Hi Nigel

i see your point, i’ll try to dig out the ‘research’ that i based this upon, was a few years ago now

steve

here’s some interesting perspective, not sure it’s the same as i found previously but similar.

https://static1.squarespace.com/static/5c6dec53b10f25d4edf0b3f7/t/5c6ee9b815fcc037d1732d42/1550772664859/Selecting+Brake+Fluid.pdf

Edited by Steves_TR6
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