M1009 Brake Issue

[kallisti5]

So, ever increasing drama.

1) Got CUCV, had a (recently created) sludge mix of DOT 3 + DOT 5 in it (brakes semi functional)
2) Completely flushed out brakes with DOT 4 (availability + price thing)
3) Changed old rubber brake lines on front + suction bleed w/Teflon tape on bleeder screw. No issues.
4) Huge improvement in braking + consistent results, brake light stuck on and won't pass inspection.
5) Changed rear rubber brake line + suction bleed w/Teflon tape on bleeder screw.

NOW. Complete loss of brakes.

When engine running: Rapid depress, resistance. Slow depress... no resistance to floor.
Brake light goes off when you mash the pedal, but comes on when you gently press brake pedal.
When engine not running: brakes pump up to resistance as usual.

Proportioning valve not tripped. No leaks anywhere. Random small black flakes in brake fluid though. (seals?)

I went back to re-bleed the front right looking for air, and my bleeding sucks the front caliper piston in... but only will remove fluid
from master cylinder if I pump brakes.

My guess is the master cylinder seals gave up the ghost. Agree / disagree?

 

[cucvrus]

Did you thoroughly bleed the rear brakes? I had this issue a few times and used the mighty vac and drew all the air from the system. Other times a few pumps and boom its solid. I suspect air in the system. My last frame off M1008 I bled the brakes in 10 minutes. (with the height sensor) On a few M1009's I spent an hour. Just the luck of the draw. It is a hard to say situation from afar. But that is worth a look see. Happy Holidays and Good Luck.

 

[kallisti5]

Heh, I've run *almost* 48 oz of off-brand Dot 4 through them now over a few hours with a cheapo hand pump... running out of containers to store brake fluid in

 

[cucvrus]

Yea not sure. I used the Mighty Vac and had it bled in 10 minutes time. What is a cheapo hand pump? Not that it matters but I was using DOT 5 fluid. Running out of containers. Don't you cycle the clean fluid back thru? Or once thru you dispose of it? You mentioned you completely flushed the system.

 

[kallisti5]

Yea not sure. I used the Mighty Vac and had it bled in 10 minutes time. What is a cheapo hand pump? Not that it matters but I was using DOT 5 fluid. Running out of containers. Don't you cycle the clean fluid back thru? Or once thru you dispose of it? You mentioned you completely flushed the system.

Yeah, I haven't been reusing the fluid since I want to make sure all the DOT 5 is gone. (but, at this point i'll likely start using the removed fluid)

Cheapo hand pump one of these: https://www.amazon.com/Vacuum-Tester-Bleeder-Automotive-Adapters/dp/B073CNGMRG
The cheapo hand pump's lines are starting to breakdown and collapse after a few uses. The bleeder valves are letting a lot of air in which makes bleeding rough. (a few of the nipples are deformed, etc)

I invested in some new russell speed bleeder valves, going to try one last bleed via those and the ol' pedal method... tired of suckin' on these calipers

 

[kallisti5]

25 minutes from civilization and no garage out here, working conditions aren't exactly ideal beyond the view.

 

[dependable]

If you had a mix of DOT 3 or 4 with 5, and it was in there long enough to get mixed up, and everything else is good, might be good to follow you first guess and replace the master cylinder. The silicon and alcohol based brake fluids do bad things to systems when mixed. Bleed everything out extra, I would advise against re using any brake fluid you have run though this system.

 

[kallisti5]

If you had a mix of DOT 3 or 4 with 5, and it was in there long enough to get mixed up, and everything else is good, might be good to follow you first guess and replace the master cylinder. The silicon and alcohol based brake fluids do bad things to systems when mixed. Bleed everything out extra, I would advise against re using any brake fluid you have run though this system.

For some history, here is the unholy mess i received it in. I was making a guess about someone mixing DOT 3 + 5 since it looks such a mess with "globs" in the rear reservoir.

 

[Barrman]

Where exactly are you?

That master cylinder needs to be rebuilt or replaced. They are cheap, so pick up a new one.

 

[kallisti5]

Where exactly are you?

Around 20 minutes from Blanco, TX. We're building up a ~7.3 acre lot.

That master cylinder needs to be rebuilt or replaced. They are cheap, so pick up a new one.

Yeah, I guess if I'm going to bleed again anyway, might as well swap the master. Didn't realize they run only like 30 bucks.

 

[cucvrus]

This is my M1009 after sitting wrecked since 2007. Very clean. I kept it well maintained and it helped. Good Luck. The MC is warranted for life at Autozone.

 

[kallisti5]

A follow up... The master cylinder was *definitely* the cause. After bench bleeding and replacing I noticed an immediate huge improvement. All brake warning lights went off immediately.
I replaced the caliper bleeders with Russell speed bleeders... best thing i've ever done. Saved hours messing around with hand pumps.

After hacking in a horn replacement in an O'rilley parking lot, she inspected successfully.

So... definitely can confirm that a mix of DOT 3 + DOT 5 eats seals


My hydro boost looks damaged, I think it's just superficial? I noticed a bunch of hacks (during her military service?) to the steering lines... the rubber on those hacks is pretty brittle + bulged. I think steering lines + hydro boost is my next project. (*cough* and fixing the horn to be less... "dangling by wires behind the grill")

 

[cucvrus]

That spliced rubber hose is how they all are from the factory. Everything looks pretty normal under there. Easy to remove the grille to install the horn.