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MG MGB Technical - brake fluid

hi
i recently drove the 79mg from d.c. to illinois, absolutely no problems.

i need some brake fluid and castrol dot 4 is not to be found.
i got some prestone synthetic dot4.

a) will it mix o.k. with the wxisting castrol ?

b)more important, will it do any damage to the british rubber brake parts ???????

thanks

john
john sutter

John,

I am using Valvoline synthetic in my '74 GT with no problems. I am getting ready to do some brake work on my '71 roadster and will probably use it there also. As you said, Castrol is hard to find. The Valvoline label says it is compatable with all other brands.

Now a question for the Guru's. Are we still getting natural rubber in our repalcement parts and rebuild kits? Somehow, I doubt it.

Mack

M Sneed

John - DOT 4 is DOT 4, whether it is Castro or Preston or the brand (I can't remember the name) That is in my garage. DOT 4 is, by definition LMA regardless of brand.
Cheers - Dave
David DuBois

Unless it is an NOS part, none of the current rubber is natural or SBR which was popular when the cars were new. Most is EPDM rubber.
J Heisenfeldt

"Unless it is an NOS part, none of the current rubber is natural or SBR which was popular when the cars were new."

If it is NOS rubber, I wouldn't use it, it will have deteriorated from age. Even if pure rubber were used, to be rated DOT X, a brake fluid must be compatible with all seal material, including natural rubber. Cheers - Dave
David DuBois

SBR rubber which used to be quite common in brake parts is not compatable with DOT 5 fluid.
John H

John-
I'd suggest returning it and exchanging it for some Valvolene SynPower brake fluid. It has a wet boiling point of F343 (dry boiling point of F513). Most DOT 4 brake fluids have a wet boiling point of F311 (dry boiling point F446). It is also has the advantage of being markedly less hygroscopic than either DOT 3 or DOT 4 petroleum-based brake fluids. Yes, it is compatable with whatever brake fluid you have in your brake system, with the exception of silicone-based DOT 5 brake fluid.
Steve S.

This thread was discussed between 22/07/2008 and 23/07/2008

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