Brake Fluid and Testing It

Hi Folks -

I was considering doing my brake fluid via the turkey baster method. Then of course I started to get thinking...does this method even help? The fluid in the lines never comes back to the cylinder, so that will stay there.

Does water intrusion to the system via the hydroscopic fluid spread all the way up to the master cylinder via osmosis? Would I actually be helping clear the system of some water by doing a turkey baster change? Or is the only true way to service the brake fluid to flush it out one caliper at a time?

At that rate, assuming a brake fluid test strip or tester is accurate...does it paint a good picture of overall condition of the fluid in the whole system?

Thanks in advance!

Edit: follow up question...do the brakes and the clutch share the same reservoir in this truck?

 

If you want to do it right, then flush your lines. If you kinda want to do it, then use your turkey baster. Having said all that, my 07 FJ has never has either method done and it stops just fine. Do what makes you feel safe I guess.

 

I'm assuming that you want to bleed the system? If so, it's best to start with fresh fluid in the reservoir. Note that the fluid in the reservoir is exposed to some ambient as air needs to be sucked in and purged as the brakes are used. This is most easily seen in motorcycle master cylinders, but the compensation port will cycle some fluid back to the reservoir at the very beginning of the stroke before closing and providing pressure. It can be seen disturbing the fluid.

The fluid in the calipers / cylinders is the most used because of heat.

I don't think the reservoir on my Sport can be emptied. So, I just do a thorough bleed every 2yrs or 3yrs. Try to get at least a full flush of the reservoir.

 

If you turkey baste the fluid out of the reservoir and just fill it up, it won't make much difference to your overall system. I use the turkey baster to remove as much fluid as possible from the res so I don't have to excessively pump the brakes during a flush.

 

No I don't necessarily want to bleed the system. Just want figure out if it's even useful at all to change all the fluid in the reservoir...or should I wait until I have time to do a proper flush.

 

Exactly. Don't mess with it if your are not bleeding.

 

Fair enough. The fluid at the cylinder tested at 0% water intrusion so I'm tempted to leave it for another year or two. I never did the brake fluid in my Jeep until of course I replaced the calipers. Ideally I'd wait until I replace the brakes in order to do a fluid flush but I have a feeling these drum brakes are going to last a while.

 

That makes sense. The fluid near the linings always comes out looking used but doesn't seem to get mixed upstream, just from observation. Given how long the linings last, I think it would be a good idea to bleed them from time to time. Get the fluid that absorbed moisture out of the res and get the used up fluid near the linings swapped out.

I have had issues on the motorcycle side, as did a friend, so that bleeds over to the automotive side for me.

 

Makes sense. Sounds like I really don't have to worry about getting ALL of the fluid out. Maybe just an honest try at getting most near the linings/calipers along with the cylinder since that's easy.

Is this the same reservoir as the clutch fluid? Any implications there when bleeding the brakes?

 

No, empty reservoir and bleed.

 

Is this in regards to your 2019 in your profile? I think the recommended interval is 10 years.

Haven't touched my 2012 Tacoma yet, and I probably wont for another few years at least. I did a complete flush on an old car I had. Fluid was probably original at 15 years old and looked terrible. The brakes on that car were not great to begin with, so I did notice a bit better feel and stopping power there

Edit: I know I didnt answer your question. Mostly wondering why you'd do this on a three year old truck?

 

Again, when you go to bleed, it is best to get as much out as you can. On the ORs, it is stupid easy. Double pump of the PTS button or Ignition On and just push on the brake pedal a bit. It will pump fluid out the nipple. Takes two folks, but so nice. Note that unless you cycle the ABS, there will always be some old fluid.

The ORs have a separate res for the clutch. It sees much less pressure and heat, but I'd still bleed it.

 

Recommended interval for brake fluid is 36 months.

 

Turkey baste the fluid out of the res and refill it with fresh fluid first, if you’re going to bleed the brakes. Then you’ll be sending mostly fresh fluid to the calipers instead of mostly old when you bleed them. If you’re not going to bleed the lines at all, then there’s not much point in replacing just the container fluid.

 

Ahh yup, 3-5 years good call. I must have been thinking coolant

That being said I bet theres maybe a handful of folks on the entire site here who actually follow that

 

Coolant is 60 months, lol.

 

I would test the fluid first its probably fine. Using a little hand pump to suck it out of the reservoir and adding new stuff certainly helps but it isn't quite the same as bleeding the entire system. Also I am paranoid about draining too much out of it so what I do is drain the reservoir, add new stuff, bleed it a bit, check the reservoir, add more until I'm reasonably sure "new" stuff is coming out and not "old" stuff.

 

Not to derail the thread - but Im pretty sure Toyota recommends 10yr / 100k miles for their original SLLC

 

Looks like their old red is 30k, pink is 100k/10y then every 50k after that. I still change around the 5 year interval in AZ due to the temps we see. Noticeable decrease in engine temps and more consistent running temps after the change each time. I do my trans fluid every 30k as well. Some don't agree with me but I haven't had components fail in 5+ high mileage vehicles doing this, so I'll stick with it. When I let things run longer I had much more failures.

 

this is false. All brake systems have a diaphragm style gasket that seals the system from air flowing in and out. The cap/cover has a hole in it to allow air into the back side of the diaphragm as the fluid level in the reservoir goes down from pad wear. No air touches the fluid unless there is a leak in the system or the cap/cover is off in a properly working brake or hydraulic clutch system.