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Converting to DOT5/silicone brake fluid? Best choices for rubber suppliers?


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I'm considering converting from DOT3/glycol to DOT5/silicone brake fluid this winter. As part of that, I'd plan to replace all the rubber bits in master, slave, and wheel cylinders.

 

Are any of the suppliers preferred over others? This is one of those areas where quality is quite possibly not equal among all the options... TIA.

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No, I'm not sure at all, Iain and Neil.. I went with DOT3 originally and I like the idea of the fluid the system was designed for. There are two very different camps re: DOT5/silicone.

 

My fluid is now about 8 years old, so probably worth considering to change. After some work at a very well respected TR shop a few years ago, my reservoir started spilling, and while I haven't damaged body paint yet, the reservoir itself looks kinda ratty.

 

As I said, thinkin' 'bout it.

 

But let's say I decide to stay with DOT3/glycol ether. The basic question of varying quality between rubber bits from all the suppliers is still valid. Are hydraulic rebuild kits any different in the TR ecosystem?

 

i-LvWVw3K-X2.jpg

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Well I have had it in both my cars (over 10 years in one) with no downsides & no corroded paintwork!

Cheers.

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The reservoir seems to be corroding or building up some sort of deposit at the bottom where the hydraulic lines come it, too. I have a sheet of pressure-sensitive plastic film on the bodywork there to protect the paint, but this needs some attention before driving season begins. So the reservoir (my original) needs to come off over the winter for rehab.

 

One of the things I'll install, irrespective of fluid type, is the Moss upgraded reservoir seal.

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Well I have had it in both my cars (over 10 years in one) with no downsides & no corroded paintwork!

Cheers.

 

Excellent! Not everyone is so fortunate, monty. There are a ton of cars with brake fluid-damaged paintwork.

i-zBBmrLG-X3.jpg

 

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Don, I've used silicone for 20 years in the 6. No problems and no corroded or seized cylinders. It needed a new master cylinder last year, but I had re-fitted the m/cyl in 1995 after using it with glycol. So all new rubbers are best.

Peter

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Hi Don,

 

I have had DOT 5 in my 4A for 17 years. I drained and stripped the system for inspection around 8 years ago. It was still like new.

 

All my rubber came from Moss Europe and as long as new rubber is installed, I would recommend DOT5.

 

Cheers

Graeme

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My 6 came to me with Automec Silicone in the brakes and clutch.

 

Looking through the receipt book the car seems to have ‘gone silicone’ a long time ago, more than 10 years.

 

I’ve not had a problem with either system, however doing some research the silicone fluid is significantly more compressible than regular dot4, and i do have a longish brake pedal action which i dont like.

 

Steve

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Excellent! Not everyone is so fortunate, monty. There are a ton of cars with brake fluid-damaged paintwork.

i-zBBmrLG-X3.jpg

 

i-WJ4QpfK-X3.jpg

 

Sorry Don for my ambiguity. It is silicone fluid I have had in my cars hence the no corrosion comment.

Cheers.

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Sorry Don for my ambiguity. It is silicone fluid I have had in my cars hence the no corrosion comment.

Cheers.

Yeah, on rereading your post yesterday I saw that's what you meant, monty. Thanks for the clarification.

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My TR4 changed to Silicone for brakes and clutch when it was re-built in the early 1990s. It went back on the road in 1993, so I've been on Silicone even longer than Peter Cobbold. A rear brake cylinder started weeping in 2006, so I replaced it - but, as far as I am concerned, that is just one of those things.

Ian Cornish

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I can beat you by a couple of years Ian - I used Namrick silicone when I rebuilt my 4A, which was back on the road in 1989, so the fluid probably went in in '88. No problems since, although the fluid in the clutch m/c went black fairly quickly.

 

 

I chose silicone after finding that a rag soaked in the old brake fluid lifted the primer-filler on my boot lid, that had previously resisted every paint stripper I'd tried.

 

Pete

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Does anyone know:

Can you mix silicone brake fluids from different brands with each other?

Thanks,

Waldi

My guess would be yes (it's supposed to be inert after all), but I'm not sure guessing is a good approach when it comes to brakes.

 

Pete

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Hi Pete,

yes it does but not in the same way as DOT3 or 4.

 

DOT 3 or 4 is hydroscopic. It will absorb/Adsorb water and mix with it.

 

DOT 5, like all fluids will allow water to exist within its environment. So your pipework and calipers could well be going rusty without you knowing.

The master cylinder has a vent. The atmosphere changes pressure continuously so water moisture is drawn into the cavity above the fluid in the MC.

It condenses and falls into the DOT5.

 

DOT 3 or 4 with thoroughly mixed water can cause corrosion but may be not as extensively as one may think.

DOT 5 with separated water within it will cause corrosion where the water sits.

 

You still need to inspect the pipework periodically

 

Roger

Edited by RogerH
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