Brake fluid resistant sealer?

[midget]

Any recommendations for a sealant to line the master cylinder area in the chassis please.
After carefully cleaning, etch priming and top coating with 2k paint my NEW van chassis has already bubbled up from small "spillage".
I fitted the old master temporarily to get on with new brake pipe fitting, and a small amount must have still been in there
Noticed this when attempting to fit new cylinder. I am not aware of any paint that fulfills this criteria successfully long term.

Although a van, this problem will be common to all models--apart from most with Marina brake modifications.

[oliver90owner]

No eye deer, but silly cone flooid might be an alternative to alchol break flooid?

[midget]

Been warned off that stuff, due to it not being compatible with older seals?
Following recommendation of trusted source that dot 4 is adequate.

[oliver90owner]

Really?

From the net: DOT 5 Silicone Brake Fluid is compatible with a wide range of brake materials including SBR, EP, Neoprene and Natural Ruber.

[amgrave]

I’ve used Silicon fluid for 4 years now and have not had a problem with it. If anything I find it better as I often leave the car standing for six weeks or more and in all this time have not had a sticky cylinder once, it would be unusual for that not to happen with dot4 fluid. I also know of someone who has had it in his system for over 12 years with no problems. Kinda makes the seal argument a bit off

[pde2000]

I put silicone in 20 years ago when i put in a new master cylinder, and replaced all the seals at the same time. I wish i had replaced all the lines too, as one later sprung a leak. I was advised that rubber that had been used with dot4 would need replacing as well as completely removing all the old glycol based fluid first.

Any glycol fluid left will absorb moisture and then corrode and corrupt materials it contacts. Silicone is a good choice if renewing the entire brake system, and then needs less servicing.

[midget]

That's what I was sort of alluding to. So as I am fitting new master/callipers and line's anyway, I will now renew rear cylinders as well and use dot 5.
Previous info was not to just refill old system with silicone.

Thanks for inputs

[amgrave]

That's what I did, replaced the whole system including all lines. I found the bleed nipples on the rears are placed before the cylinders themselves so came to the conclusion it would be best to fill the rear cylinders with fluid before fitting them as the bleed process would end at the nipple and before the cylinder. Not so important at the front. I also found the silicon fluid is slightly thicker than DOT4 but otherwise acted the same. Personally I think the negative put about against the silicon fluid is to do with the sales of the standard fluid and brake parts would fall dramatically and comes from the trade, that's why you won't find much about it on the web and what you do find tends to be against it. So far I have found it acts exactly the same as DOT3/4 fluid in operation with the benefit of not attracting water and seizing the cylinders if not used for a while, you don't have to change it every two years and it does not affect paintwork if spilled. Good luck with your new brake system.

[midget]

Having made the decision to make the change I am now slightly confused as to which brand to choose from the many options.
Also it seems the type dot 5 can be either glycol or synthetic based? Any recommendation please?

[amgrave]

Don't get confused with DOT5.1. If I remember rightly there was not many makes about when I changed to silicon and I can't remember what make it was. Google silicon brake fluid and see what comes up, I remember it was expensive and I bought a litre of it but found it was too much, half that or even 200ml if you can get that size.

[amgrave]

Automec dot5 brake fluid is what I used, just remembered the name. Google the name and you will find it.

[pde2000]

that's what i used too; http://www.morrisminorspares.com/miscel ... re-p831111

[Mark Wilson]

Hmmm. I am replacing the entire system, so I'm tempted to use Dot 5 for the advantages listed above, but the instructions for the new Lockheed style servo I've got explicitly warn against using silicone fluids. Has anyone used one of these with Dot 5?

Mark

[amgrave]

I have not used one but I repeat the industry does not like you using silicon fluid because it means everything lasts longer so they don't make so many sales.

[midget]

Thanks for that. I saw Automac on ebay, but deliberately didn't mention it to see the recommendations. I'll go for that.

[Mark Wilson]

Quick bit of research suggests the only downside to silicon apart from cost is that it is more compressible than glycol and the pedal is therefore spongier. Have any of you found this to be relevant to classic daily driver use?

[amgrave]

I have not noticed any difference in the braking performance using silicon fluid. You are right about it being very slightly more compressible and it adds about 1/8 of an inch to the pedal travel but I have found this makes the brakes feel more like a modern but without the snatchiness.