I just filled my MC with Dot3

[wilcom]

I rebuilt my MC and was using a bottle of brake fluid for cleaning and lubing the MC as I put the new plunger in. I filled the system and and put the cover on and only then did I see the DOT4 on the cap and went to look at what I had used......Dot 3...

Is 4 just more heat resistant or is there something in Dot 3 that will render my new seals useless?

arrgh, glad I don't make my living doing this stuff, I would be one hungry puppy!

[Bob_Roller]

The DOT 3 fluid won't do any harm, it's just a bit lower grade than DOT 4 fluid, a little lower heat resistance .

If it makes you feel better, you can remove the fluid in the reservoir, refill with DOT 4 then bleed the brakes, a couple of reservoir fills during bleeding, will get the unwanted fluid out  of the brake system .

[wilcom]

Thanks Bob...........

I will flush with dot 4 ..............

I'm on my way up to Las Vegas for a lil job this afternoon and wont be back till tomorrow....didn't want it to set in the dot 3 for 24 hours if it was a witches brew for DOT 4 seals.

Thanks Again

Joe

[Bob_Roller]

Not to start a dreaded thread on what fluid brand to use, I personally use  the same brand in all of the vehicles .

My latest purchase of Castrol LMA GT4, has on the bottle, that it is now a synthetic fluid, instead of a glycol based fluid .

[Barry]

My latest purchase of Castrol LMA GT4, has on the bottle, that it is now a synthetic fluid, instead of a glycol based fluid  

Yes the last bottle of brake fluid I bought - not Castrol - was synthetic based DOT 4. I think I rationalised it as "synthetic glycol". What I can't remember which would be a big plus is if it no longer acts as paint stripper.

It's very confusing though now that there is :-

Dot 4 synthetic based but compatible with glycol,

Dot 5 silicone based and NOT compatible with glycol

Dot 5.1 which is synthetic based but compatible  glycol.


BTW I agree DOT 3 will do no harm at all provided it came from a new sealed container. It just has a lower boiling point and if it was me I wouldn't rush to change it unless I was planning to go racing and use the brakes heavily.

[Justin B.]

I've used the Castrol LMA in everything since my "MG days" when it was the only thing around here recommended as a replacement for "girling"  fluid.