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brake fluid revisited

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hondo402000

hondo402000

Darth Vader
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Ok I made a mistake on previous post as all that replied, I made a mistake, I should have been asking about dot 3 or 4 not silicone brake fluid, so it it ok to use any 3 or 4 in a girling system other than castrol? any problems with swelling up rubber parts using anything else but castrol? sorry
 
Well... yes and no. The last heated debate I got into on the subject can be summed up like this.

At some point in the 1970s the original rubber brake compounds used by Lockheed/Girling were changed from materials that were ONLY compatible with DOT-4 to materials compatible with both DOT-3 and DOT-4. No one I've exchanged emails or messages with knows exactly when the rubber was changed.

So, IF you've recently (since 1980?) rebuilt your brake system with new rubber bits (including hoses and servo internals (if fitted)) then you should be able to use DOT-3 or DOT-4.

As for mixing DOT-3 and DOT-4, you shouldn't have any problems mixing brand 'A' DOT-3 with brand 'B' DOT-3, but I'd avoid mixing DOT-3 with DOT-4.
 
I must have been asleep on that one. I thought it was Castrol all the way. Unless you went with silicone after a complete re-build of the system.
 
"Clutch and Brake Reservoir: Castrol Girling Brake and Clutch Fluid to S.A.E. 70 R3 spec. ...Where the proprietary brand is not available other fluids which meet the S.A.E. 70 R3 specification may be used." -- from a Moss Motors reprint of the TR4A Owners Handbook. Going back several years further, it is essentially the same statement in the Triumph Herald Owners Repair Manual, except that the standard was S.A.E. 70 R1 and the "preferred" brand was "Wakefield Castrol."

It's a moot point for yours truly; I've always used the then-current grade of Castrol, beginning with "Crimson" in the late 1960s, even some "Green" as well as "Amber" and the current GT/LMA (which hasn't had "Girling" in the name for many years). But I have known many, many people who gleefully, ignorantly...and successfully used Prestone or Kmart or dozens of other brands of glycol-based brake fluid without incident; I'm assuming that those fluids all met that S.A.E. standard.

As for silicone brake fluid, apparently some early versions didn't have the proper "swelling agents" or something like that, but no more, and not for a long time now. And I've heard occasional stories to this day of how the function of some hydraulic brake light switches is adversely affected by silicone fluid. Beyond that and the occasional difficulty in getting rid of air bubbles introduced, no worries!
 
Andy, I assume that those recommendations from the TR4 manual would correspond to what we simply have been calling DOT-4, is that correct?

Bill Spit, I have NEVER run DOT-3 in anything British and I don't think I could make my hands poor it into the reservoirs. However, I have been assured that the rubber did change and know of people (in the Mini community) who swear they have been running DOT-3 in their rebuilt brakes without issue. Like you, I've always operated on the understanding that Castrol LMA was the fluid to use... until I switched to DOT-5.

BTW, I'm one of the people who can personally confirm that the change to DOT-5 silicone fluid killed my otherwise OK brake light switch. No worries, my car now has a mechanical switch on the brake pedal like most modern cars.
 
[ QUOTE ]
Andy, I assume that those recommendations from the TR4 manual would correspond to what we simply have been calling DOT-4, is that correct?

[/ QUOTE ]Quite possibly, but I honestly don't know which is which. Sorry.

[ QUOTE ]
...I have been assured that the rubber did change and know of people (in the Mini community) who swear they have been running DOT-3 in their rebuilt brakes without issue.

[/ QUOTE ]Again, pure speculation, but this might have something to do with a difference between Girling and Lockheed systems, and when each company might have changed specification on seals and related bits?

[ QUOTE ]
BTW, I'm one of the people who can personally confirm that the change to DOT-5 silicone fluid killed my otherwise OK brake light switch....

[/ QUOTE ]Guess that must still be a problem, then! Only problem I've ever had with a hydraulic brake switch is a terminal corroding enough to break off. When that happened to me, I ended up "borrowing" another switch off a parts car that was older than the car needing the switch! /ubbthreads/images/graemlins/grin.gif
 
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