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Soft pedal

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dcurbet
Posts: 3807

Soft pedal

Post#1 » Thu Jan 02, 2020 4:30 pm

I need some help getting my pedal hard again. :roll:

I ve been putting some miles on the 230ge just getting to know it better. The right side caliper was sticking a little bit and I was getting a slight pull to the left. Brakes were fine however. Replaced the caliper with a good used unit and then I could not get the wheels to lock up anymore. Tried everything I knew and sought advice from mechanic friends and from board members here and I am still stuck.

This is the time line.
Truck pulls to the left when braking. Obvious failure with the Front right brake caliper seized.
Replaced with used unit.
Soft pedal symptoms. Bleed everything correctly still can’t get rid of soft pedal.
With all the fluid that I pushed through it I’m thinking master cylinder has given up. New master cylinder installed and bled multiple times (at master and front and rear and front again).
Same effect.
Ok need to adjust the rears. To be 100% - new cylinders installed. Adjusted, bled great.

New caliper now installed on the right front. Bled nice but I still can’t stop the truck. Full pedal travel power no wheel lock.

Axle has no play, recently overhauled.
Rear valve wide open, manually set in open position.
Hand brake catches on click 1.
New brake hoses up front. Partial new co ni lines (which I have been getting scolded for by one of my friends, apparently a no no). Pads are not jammed. Master disengages so no issues there, rod is fine.

Ideas? Not sure what to do next. Thought I would involve the board. Maybe someone has been there done that. At this point I would have to check the flow in each circuit individually. I did notice that much more fluid came out of the rears when I was bleeding them compared to the fronts. Should be the other way around or same.
Thx in advance.

User avatar
EHKO
Posts: 1162

Re: Soft pedal

Post#2 » Thu Jan 02, 2020 4:38 pm

Bad booster vacuum check valve? Just guessing here. Maybe allowing air to get in??

dcurbet
Posts: 3807

Re: Soft pedal

Post#3 » Thu Jan 02, 2020 4:54 pm

Yes, Inexpensive enough to replace - I’ll eliminate next. I’ve tried braking with the engine under load without much difference...

User avatar
Otiswesty
Posts: 4872

Re: Soft pedal

Post#4 » Thu Jan 02, 2020 4:58 pm

Why are the CuNi lines bad? I used them along the the frame and for the locker hard lines as well. Original were steel and rusting. I plan to replace the short hard lines, after the soft lines, to the calipers with steel due to the exposure.

dcurbet
Posts: 3807

Re: Soft pedal

Post#5 » Thu Jan 02, 2020 5:04 pm

The idea is that steel is hard and you can tighten and untighten multiple times whereas copper ones are soft and after a few times of bolting un bolting the orifice narrows thus reducing the flow. Makes sense ...

Mdan1
Posts: 91

Re: Soft pedal

Post#6 » Fri Jan 03, 2020 5:43 am

So after you replaced one caliper, bled, etc, the fronts will not lock up? Does your g have the front abs module?

dcurbet
Posts: 3807

Re: Soft pedal

Post#7 » Fri Jan 03, 2020 5:45 am

Yes pretty much.
W460 has no abs.

dcurbet
Posts: 3807

Re: Soft pedal

Post#8 » Sat Jan 04, 2020 6:04 am

Sat for a couple of days after installed new right caliper.... I feel like the brakes got a bit better after sitting... not sure i can explain it other than maybe the master purged some air. It’s not perfect brakes yet but I can kind of stop it and it’s almost drivable.

autonovice
Posts: 2043

Re: Soft pedal

Post#9 » Sat Jan 04, 2020 9:19 pm

Got to be your caliper half seals u went cheap and didn’t replace when u tore your caliper apart. If you take out your RF tire and look at the crack on the caliper halves, there might be very small amt of fluid filling the crack.

dcurbet
Posts: 3807

Re: Soft pedal

Post#10 » Sun Jan 05, 2020 3:05 am

I hear you I thought of it too so sure, maybe, but after 50 presses of the pedal there would be much more fluid somewhere... I test drive it up and down my street. Plus when I got the used caliper I didn’t break it open, it looked fine, pistons moved well so I just installed it. Regardless it’s not the same caliper anymore. There s a new one in its place.
I think it’s in the control of the system (master and booster) somewhere in there lies the problem. It’s a ‘dumb’ system really, in the sense that there isn’t much to it. Booster, master, lines and caliper pistons. It’s got to be air since no obvious fluid is leaking, just has to be. I installed the new master correctly, bench filled it and bled it before installation but maybe not all air got out. I ll try bleeding it some more. Anything else I can try?

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