hi, how often do you need to do a brake fluid flush done, have never done with on my x300, and I have 110 on the clock. thanks.

 

I flush mine every 2 years/24000 miles

Cheers
DD

 

hi doug, just wanted to ask you real quickly my mechanic told me that if I did do the brake flush, If I happen to have a master cylinder going bad, it would break it all the way or something like that. This true at all?

 

I guess all sorts of weird things are *possible* but in this case I wouldn't worry. Fresh fluid is important. Besides, even if it IS true, if the m/c is going bad wouldn't you want to know ? :-)

Cheers
DD

 

I would like to chime in too.
If the brake fluid is replaced by pumping the brake pedal, then yes the master cylinder piston will be in an area it hasn't been since new. This can cause the piston seal to leak and replacement would be needed.

I agree with Doug, it would be good to know the master cylinder is on its way out anyway. I prefer this to happen in my driveway rather than on the interstate.

 

2/24k

 

Leaving engine oil OUT of the formula.

I change EVERY fluid on my Jags every 2 years, trans, p/steer, coolant, diff, brake fluid, regardless of usage. Have done so since 1968, never had any scary moments.

 

I purchased the Prestone DOT 3 Synthentic Brake Fluid, is that a good one??

 

I use "standard" DOT4 whichever brand is on special when I want supply. It only has to last 2 years so what the heck.

 

The manual recommends DOT 4 only. It is my understanding that DOT3 will dissolve a DOT 4 system in quick order.

I concur with others for two year intervals for brakes, power steering, differentials, transmission and coolant. Although 25'000 kms is the max I would go before changing the transmission fluid.

 

I forgot to mention that a vacuum brake bleeding tool can be purchased for a reasonable amount, and is handy for changing the fluid without assistance. Will not harm your MC either. Just be careful to follow instructions, and avoid pushing air back into the lines. Works great if done by the book with a decent bleeder.

 

Where did you hear that? I'm asking, not arguing. It merits verification. I did some quick Googling and couldn't find anything right off the bat. Lots of conflicting info about brake fluids in general, though :-)

I know DOT4 has a higher boiling point, presumably due to the borates that are added, but I hadn't heard that using DOT3 would actually damage a DOT4 system. It could well be true, though.

Cheers
DD

 

A senior tech told me way back when I was a wee motorcycle mechanic that type 3 is a lot more corrosive and wrecks the seals in a type 4 system. I also remember reading it in a service bulletin somewhere, but that was years ago. I have not actually tried to verify this, ergo why I earlier led with "I am told". I know it has a higher boil point and that is why it is used in motorcycles. I have had many mechanics that I respect warn of the consequences. My Jetta's use type 4, and I have always been careful not to use DOT 3. I would hate to think I have been so fussy about it for so long for no good reason! But I am open to being wrong about it... And no worries about asking Doug! I learned a long time ago not to get bent out of shape over these things. I will be the first to admit that I am not quite perfect. Yet.

 

My curioisty being piqued I've been doing a little research. A few tidbits:

It *appears* that the synthetic DOT 3 and 4 are frontwards and backwards compatible in terms of reaction with rubber components. Non-synthetic fluids...perhaps not. There is SO much info out there, much of it anecdotal, that's it's hard to know for sure....thus I use the word "appears"......

Commonly marketed synthetic fluids have the polyethylene glycol base as their older, non-synthetic counterparts. It's just that they've been "synthesized" differently. Different additives, I guess.

The Prestone DOT 3 synthetic mentioned earlier has boiling points that exceed the DOT 3 standard and meet the minimum DOT 4 standard.

Early (perhaps non-syn?) DOT 4 fluids, although they had a higher boiling point than DOT 3, were known to break down more dramatically IF they got hot. Perhaps this is one reason for the recommendation to flush the fluid regularly? I dunno. Apparently it was UK/Euro cars that first started using DOT 4 although the recommendation for regular flushing predates DOT 4 fluid.

Given that DOT 4 is nearly as common as DOT 3 the easiest thing would be to simply use DOT 4. However, my gut feeling is that no harm will come from using the synthetic DOT 3 mentioned above.

If I come across anything concrete I'll give a shout

Cheers
DD

 

I surfed around for quite a while and like you Doug, encountered a whole host of anecdotal opinions that seem to confirm both sides of the issue. Your points are clearly reasonable though, and I would tend to agree that the two would appear to be compatible. OTOH, It isn't too much trouble to only use the recommended fluids in their particular application, and to follow manufacturers recommendations relating to change intervals. However, I'll wait for the day when the manufacturer states it is safe to use either before I recommend it.

Just my opinion. I'll also keep looking into it and report what I find. Hats off Doug! I certainly mean no disrespect, and have no qualms in deferring to you.

 

Deference appreciated but not required as I certainly didn't come up with anything conclusive....and in the end we both say that the easiest solution is just use what the manufacturer suggests.

Cheers
DD