I need to replace the cap/seal on the break fluid reservoir; have some weeping into the top catch area and the rubber seal on the cap is bad (no fluid on the floor inside the car). There is still plenty of fluid in the master cylinder reservoir and the breaks feel great! So I think I caught it before air entered the system.

Before replacing the cap/seal, I want to top off the break fluid. Any recommendations for what type of fluid to add? And is it OK to mix & match with what's already in there?

Thanks!

-Chuck

Myself and alot of others use Ate Super Blue DOT 4, you should flush your brake fluid every 2 years one can will do it easily, with left some left over if you buy a whole can.. They make both a Blue and a Non-Blue so you can see when youve flushed it through..

Brake fluid Approx. 0.35 liter / 12 fI. oz. meeting SAE Spec. J 1703 a

Mix and Match is not OK with certain Brake Fluids, research (Google) before doing that because you did not state what your currently using.

but got this regarding the reccomended Ate SupeBlue and mixing from research (Google)

Super blue brake is a DOT 4 brake fluid. It has a boiling point of 536°F and a wet boiling point of 388°F. Resist brake fade much longer than traditional brake fluid. Can be mixed with brake fluids meeting the same specifications (DOT 3 and 4)and with DOT 5.1.

One no no is mixing Dot 5 w/ any of the others, Dot 5.1 is different (not-silicon based as Dot 5 is though confusingly named simular) again it is always wise to research (google) for your situation specifically.


Click to view attachment

Googling "break fluid" may yield coffee advertisements.

I prefer to use BRAKE fluid in my cars.

but can't type..

Thanks for the tips guys. Problem is, I don't know what spec is in there now. I guess I can email the PO for some info.

Who cares what's in there now. It is obviously time for a change of brake fluid, we are not talking big $$ here. Research brake fluid types and flushing procedures on this forum and learn. The information available here is an unbelievable wealth of knowledge....read and learn. You will feel much piece of mind when you know that your brakes are in good shape.

Just do it.

Vysoc

Unless the put DOT5 in there.

I used to use Castrol GTLMA, but just realize that I can get ATE for the same price, so I'll be using that from now on.

any DOT3 or DOT4 fluid will work for you, it is advisable to flush out the entire system every year or two. two full quarts seem to do the job fine, use a bunch more on the passenger rear side a little less on the driver side, then a bunch more on the passenger front,and a little less on the driver front. this usually uses two quarts for me. If the car has really dirty fluid, I soften repaet the process. besure to syphine out the old fluid from the resevoir first, thus preventing mix of old and new fluid as you top it off.

also do not top it off unless the pads are new, if you top it off with worn pads, then later replace the pads with new, the fluid level will go up, and could overflow

vavloline synthetic or castrol LMA are my two favorites for my modern cars like the 914

on my classic cars I tend to use silicone fluid (DOT5) but using that requires a complete rebuild and replacement of ALL rubber parts if they were used with DOT 3/4

Depending upon your driving style, use DOT4 or 5.1 NOT 5.0

Most street guys can get by with an off the shelf 4.0 If you want a better fluid the ATE Blue and 2000 is good. They are the same but one has a dye. Swap them at each fluid change so you can tell when the new fluid is in the system.

Before you consider topping off the fluid, take a look at the condition of the pads. If you fill the reservoir and then decide to change the pads, you'll have to remove some of the fluid to avoid spillage.

The Cap'n

Thanks all. Yes, the pads are new as well as the rotors. And the brake fluid was recently changed and nice and clean, just a bit low from the weeping cap (bad seal). New cap and seal on the way, that's why I would really prefer to add just a little fluid to top off. What happens if I simply add some DOT4?

Dot 4 should be fine unless the PO put in Dot 5 (doubtful but there is a chance maybe but probably not)..

If you're not sure, take a bit of the old fluid out and pour in some of the new fluid in a small glass. If the old fluid is DOT5, they won't mix and will separate. DOT5 is also often colored as well if that is any help.

I do use it in a vintage motorhome I own as it sits quite a lot and doesn't get raced! I still use the old Castrol LMA for my Porsches - they've known nothing else for the last 30 years or so.