[Dean_S]

A post addressing issues specific to the rear brakes would be a great addition.

The small [6mm] caliper bolt indexes the rotor to the hub so the bolt holes line up. Once the wheel is mounted and torqued, this bolt does not do anything. These bolts do not need to be tight and can be lightly torqued to facilitate later removal. Thanks for the write up. Dealers might be guilty of tightening these excessively. With a new vehicle, I remove these bolts and bed down in never seize.

Thanks!

 

[Dean_S]

Good write up.

Maybe I missed this if already mentioned but it's a good idea to keep an eye on the brake fluid level in the reservoir when pushing the caliper piston in. It can potentially overflow when pushing fluid back from the caliper.

Les

Unfortunately, you have to take panels off to expose the reservoir. Not sure how tricky that is.

 

[Dean_S]

"Sealed container" That is a bogus concept. The reservoirs are vented to atmosphere. Every temperature change, barometric/altitude change and every application of the brakes moves air in/out of the reservoir causing moisture contamination. A part full container of fluid with the lid on tight on your shelf is basically immortal. The issue was garage attendants decades ago leaving containers open. The sealed part became misunderstood when sealed against air infiltration was the intent. Assembly lines get fluid from bulk tanks... sealed for your car's fill?

I have kept reservoirs full to the tops as less air means less air to expand and contract [contamination]. Yes, you need to evac fluid before caliper work, but no problem with that as you should be watchful anyways. When replacing pads, the reverse flow of fluid in the lines moves moisture contaminated fluid to the reservoir and you can evac that and replace with new, and that should be done before a brake bleed to keep from flushing the contaminated fluid in the reservoir through the system. Moisture cannot enter the system anywhere except the vented reservoir.

I have not seen a bladder barrier brake reservoir for decades that prevents this obvious design flaw.

< end of rant > ;}

 

[Dean_S]

As brake pads wear, the reservoir level goes down and fitting new pads would simply restore the level to where it was when the prior pads were new. However, the increased air space increases the moisture pickup from thermal cycle and barometric breathing while there is less fluid to carry that moisture. So contamination increases with lower reservoir levels. Some will say to never add brake fluid when levels decrease from pad wear. But you can decrease breathing by adding fluid and also increase the amount of fluid that will absorb the moisture. There is the obvious reservoir overflow problem when fitting new pads/rotors etc. The problem with moisture pickup is rust in the master cylinder bore that accumulates at the end of the area swept by the MC cup seals. This does not appear to cause an immediate problem, however, during brake work if you press the brake petal down as far as it will go, the soft cup seals will be damaged by the rust deposits. One should avoid long strokes of the brake petal during maintenance. Moisture gets into the fluid at the MC only and decreased boiling point fluid in the MC reservoir not cause brake fade in very hot calipers. For that to happen the moisture would must diffuse through the brake lines to the calipers and lead to significant moisture there. Moisture in a stored half full container with tight lid is trivial. The color of brake fluid is a good indicator its contamination. Part of the problem is cast iron master cylinders. A stainless steel MC bore liner might be a great advance. Combining a hygroscopic fluid, cast iron and exposure to atmosphere is really a stupid situation.

GMDD/Terex tried to tackle this problem on heavy duty mining trucks by switching to hydraulic oil brake gear. Great idea, but the mining maintenance crews added brake fluid and destroyed the brake systems. Cannot ignore the human element...

 

[Dean_S]

Mostly obscured by plastic cowling and right where you would expect it to be. You can just see in there a bit.
Are brake pads all very worn? A leak is a serious issue.
If you can see that fluid level is good, then its a level sensor error or wiring issue.