Topic: DOT 4 Castrol Synthetic Brake Fluid

[chrisfranklin]

Have been using this Synthetic DOT-4 fluid for the last few years.  However, I have also blown through two brake master cylinders in the past two years.  Apparently leaks occur in the master cylinder.

Was reading the other day that Synthetic brake fluid might cause leakage in master cylinders.  Can't really prove, one way or the other, that the synthetc fluid is responsible (I could just be harder than most people on brakes).  But, it might explain a few things.  

Otherwise, though, the EBC front rotors (slotted, dimpled) and EBC pads and Russel stainless steel lines I use are awesome.  Revo tires don't hurt my braking either.  Have had few Mercedes that can't seem to stop with me  

[McJeep]

Do the 94's specifically call for dot 4 fluid?

[chrisfranklin]

Do the 94's specifically call for dot 4 fluid?

Nah, don't think any Jeeps ever made do.

But, in my YJ's case, I read the Castrol Syntec DOT-4 container and it suggested it was ok to mix DOT-3 and DOT-4 (also, it didn't suggest that any issues would occur using DOT-4 Synthetic in system that typically uses DOT-3)

I probably shouldn't draw any conclusions about Synthetic brake fluid, DOT-4, but it might should be approached cautiously (kind of like people with higher mileage cars are warned to do when changing from regular to synthetic oil [maybe due leaks of synthetic oil that occur on cars/trucks with worn/older gaskets]).  

My YJ has 13 years on the clock, so old stuff is going to break no matter what I do.  It's just that the brake master cylinder I had to replace over the summer was only about a year old!  :(  

[Guardian7]

Very weird, I had the exact opposite experience with a Toyota Landcruiser I owned a few years back. I used the DOT 5 Synthetic brake fluid, it did amazing stuff for my clutch master which had been blowing every 6 months after I dropped a V8 in my Landcruiser with a larger clutch assembly off a Chevy truck but using the factory Toyota master cyl. It also repels water unlike normal brake fluids which absorb water and are made from water soluble compounds. So it never blew again after changing to Synthetic. Did you flush the system out really good when you switched over to Synthetic, I have read warnings about mixing the 2 very different types of fluid?

[chrisfranklin]

Did you flush the system out really good when you switched over to Synthetic, I have read warnings about mixing the 2 very different types of fluid?

It all started with me just adding some Castrol DOT-4 to the resevoir if the DOT-3 fluid was low (user instructions mentioned this was "ok").  Ultimately, bled the system and then went solely to Castrol DOT-4 a few years ago.  

I was just throwing this out there in case other people have had used the DOT-4 Castrol Syntec Brake fluid and had gone through a Master Cylinder rather quickly, too.  Course, I might have just had a bum replacement master cylinder, though. So, see how long this one lasts.

The Castrol DOT-4 did seem to provide more positive brake performance, though.  

(course, making brake-related upgrades has shown some interesting results for me in the past as far as wear is concerned.  Example: Will swear than a set of the (too) excellent performing Hawk pads literally "ate" through my stock rotors - their minimum thickness exceeded in way less than a year.  And, these were rotors that had never been turned!  

[Guardian7]

I don't remember the brand I used but it wasn't Castrol I just remember it was a purple color DOT5 rated and warned about mixing with regular brake fluid.

[rcopes]

Guardian, You are exactly correct, Dot 5 should not be mixed with dot 3. When I swap a vechicle over I change every thing I can. Another great advantage of Dot 5 is it will not eat your paint. We have used dot 5 on the rides that we have Built for years just for that reason alone, nothing like screwing up brand new killer paint job because you spilt a liite brake fluid. Customers don't understand that !!! It also has a higher boiling point.

[Tall Boy]

Chris,
  I used to buy starter motors all the time from kragen auto, which is also checker and schucks auto. My starter would go out once a year from their company. I broke down and saved the money for the dealer starter and it lasted till I sold the car , probably three or more years. I was just thinking maybe you are not using a dealer part for the master cylinder.
 Whenever I buy aftermarket, I go Napa, or dealer.

[Guardian7]

I too have had that issue with starters and alternators from PEP Boys, what good is a lifetime warranty if you have replace it every 6 months and some starters are a lot of work to change like on a S10 Chevy Blazer 4x4, you either pull an engine mount and lift the right side of the engine or you drop the exhaust system and tranny oil pan.