Brake Fluid Flush Rambling

[awright2009]

So, supposedly my motorcycle needs to flush the brake fluid every two years, and it's been 4, so I figure I'd better do that, and also do so without spilling a drop of brake fluid.

 

Eventually I get to thinking I should probably flush the fluid on my truck as it's going on 8 years. -- Normally I'm the type of guy that never flushes brake fluid, but I figure it would be good practice for the motorcycle. I've used those harbor freight hand pumps before, and I do have a mityvac hand pump that I never used, but they kind of suck. For the motorcycle there is an air compressor connected vacuum pump that seems to work pretty good, that I'll likely use for the bike.

 

I also have a C7 Corvette, and those guys use a "Motive Products Power Bleeder"

 

So I figure I would give that a try on the truck, there is one with a plastic cap, and another with a metal cap. Supposedly the metal cap can hold more PSI, so I got the power bleeder with metal cap, and they also make a bleeder bottle for collecting the fluid, I accidentally bought a copy from a company called GENESIS , but it works very well.

 

Anyway, I figure if I'm flushing the brakes, might as well use good fluid as it tends to last a long time. So it seems Castrol "React" SRF is the best, which is better than some fluids even at "wet boiling" which means after it has absorbed some water already. Kind of expensive though, $50 for one liter

 

I took all four wheels off, one at a time, and noticed Discount Tire has air tooled my Gorilla acorn nuts to death, so I put back on the stock lugs that I saved.

 

You can put the bleeder bottle on, get a 2.5mm zip tie and secure it down some past the nipple, then a 10mm to loosen / tighten. I did not use the box end so I can be sure the hose stayed on good throughout the process.

 

I had some trouble with the pump not building pressure at first, I looked inside it and used some of the grease already on it to better seal near the cap, and after a while it would build up to about 4/5 PSI, but I could hear it coming out at the brake reservoir. I was using the small gasket as at first I couldn't get the big gasket to fit on there. On my second try it went on easily, maybe the sun softened the rubber up as it was quite toasty outside. With the larger gasket it would hold pressure and pump more easily, I tended to put it at around 14 PSI.

 

Before attaching the pump I used a turkey baster from walmart to get the old brake fluid out of the reservoir. I ordered a mityvac syringe meant for this, but it was still in the mail and I had everything else. I do not recommend using a turkey baster as it drips fluid like crazy and the brake fluid will 100% ruin the plastic on it, but it got the job done. Remember brake fluid will ruin paint in seconds, so you don't want to be careless with it.

 

So the old fluid looked a little dark gold, but not too bad, except for the driver side front, which had some red rust color to it, I think my bleeder screw was not very tight on this side for some reason, so I expect that it got a lot more moisture in the fluid because of it and started rusting stuff. Interesting to note that the color of the brake fluid in the reservoir can be very different from the color at the calipers

 

 

So, if you need to bleed the brakes the power bleeder works pretty darn good, (use the big gasket with the metal cap) but the old pump the brake pedal method works great too, albeit you might round out your bleeders quicker using that method.

 

I still dont recommend flushing your brakes unless you have too though, and dont do it yourself unless you've bled brakes before I would say

 

 

Another note, for the crazy enthusiasts, Harley has stated that you need to actuate the ABS and then bleed again, now I'm sure their recommendation to flush every two years and do an ABS flush every two years is excessive and probably more to drive up for service business. But it had me wondering, how do you even flush ABS? I have never ever done this on a car/truck with ABS or even heard of anyone doing this.

 

Short story is it's probably BS and you dont need or want to do this on Harley's or anything. But essentially with an ODB2 connector you can get a scan tool that has "bidirectional" communication that talks to the ABS module. I got a cheap one off amazon that does this for about $100, I'll probably return it. But it will allow you to actuate pumps on the ABS module and also do an auto bleed. I'm convinced Harley is doing the auto bleed between these two manual brake bleeds.

 

There is a distinction between a "Bleed" and a "Flush" Bleed means get air bubbles out, Flush means push fluid through the lines including the ABS module. The GM service manuals actually describe a ABS flush procedure where they open the bleeders on each wheel and activate ABS while they are open flushing fluid. From what I see on Harley's they dont, they just bleed normally, have the ABS do the auto bleed, the bleed normally again. So that doesn't really flush anything as opening and closing the ABS valves may or may not move any fluid. So my conclusion is that it's probably BS and should be ignored outside of maybe flushing the fluid every now and again... But maybe that explanation is best saved for the Harley forums

 

 

I figure if you flush your brakes at least once every 10 years you are doing better than 99% of drivers out there... and I'm sure there are a lot of shady mechanics who just refill the reservoir and say they did it

[mikeyk101]

I think a big difference between motorcycles and cars/trucks is the volume of brake fluid involved. The contamination of the fluid is much more noticeable on motorcycle systems and can have a greater impact. On my Honda Goldwing  I do try to flush the brake fluid at least every 2 years and the color difference between new and old fluid is very noticeable. There have been a couple recalls with the rear brake systems on these. There has been talk that the problems have occurred because a failure to regularly flush the brake fluid and after seeing 2 year old fluid, it makes sense.

Edited May 29, 2022 by mikeyk101

[awright2009]

Yeah, I'm use to DOT5 in motorcycles that lasts a whole lot longer, I'll do the bike next and I think I'm a believer in terms of flushing brake fluid now, not as frequently as recommended, but definitely not never either.

 

Here's a good video using the same stuff I bought: (Different vehicle though, and I didn't put any brake fluid into the pump as you can keep it clean and just use the reservoir)

 

 

Here's one on a vette that is similar except for the larger gasket being used:

 

 

Edited May 30, 2022 by awright2009
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