how does a pushrod to a brake's master cylinder change position?

'92 Honda Accord LX whereby the front brakes aren't releasing properly. I've changed the MC as
it was leaking onto the braker booster outer shell. The brake booster shows no sign of fluid
internally with the MC removed. I have minimal freeplay between the brake pedal & the back of
the pushrod - I move the pedal ~ 3mm before contact with the pushrod. It appears from reading
tegger's info I may need to adjust the pushrod - how could it suddenly change when it is locked
in place and been functioning properly for years?

TIA, Ross

 

Sticky calipers???

G-Man

 

All master cylinders are NOT created equal...

JT

 

I agree - seems to be a reasonable possibility, although I'm surprised both sides would stick at
the same time. Would like to have some best guess opinions before I start swapping out more
parts. Neither is leaking and the left front is grabbing more than the right.

Thanks G-Man

 

This fact would apply to a MC/pushrod working fine before a change and then malfunctioning
after. In my case the problem started suddenly before any work was done. I then started looking
carefully as to why - which is when I saw leakage from the MC and replaced it - problem still
exists so now I'm trying to guess at what the next cause may be. I am about to adjust the
pushrod to see if a change in functionality occurs. Any other guesses appreciated.

Thanks, Grumpy auContraire

 

I move the brake pedal slightly to make contact with the pushrod and then move the pushrod ~5mm
easily - with no resistance - before it contacts the MC. This I am confident of. No adjustment
needed as I see it.

Haynes manual - Honda Accord 1990 thru 1993 All models indicates:
Dragging brakes
1. Incorrect adjustment of brake light switch
2. Master cylinder pistons not returning correctly
3. Restricted brake lines or hoses
4. Incorrect parking brake adjustment

1. I don't believe it is this as it visually appears to function ok and has not been touched to
become misadjusted.
2. Replaced MC - bench bled prior to install.
3. Bled all wheel cylinders to replace all old brake fluid in the system with no noticeable
problem of fluid movement through the lines.
4. Parking brake applies to rear brakes - my problem is definitely on the front.

 

I'm going with sticky calipers - removed both - right side has rubber damage and may have leaked
at one point, although there was no fresh fluid - just a dirt caked dark area. Will post the
results in 2 days when I receive the calipers and can install. I'd still like to hear opinions
too. Thanks in advance.

 

Are you sure? If so, then the pushrod adjustment is fine.

Not if you actually do have freeplay.


How to check the calipers:
Remove caliper from mount bracket and hang it from the upper A-arm with
some wire
Watch caliper piston while helper presses pedal to the floor
Piston should move out immediately when pedal is pressed, but move back in
slightly when the pedal is back up again.

If piston does NOT move in when pedal is released, the piston may be stuck.
Eject piston about 3/4", spray brake cleaner to remove dirt from dust boot,
then lift dust boot back from piston. Is the piston black and brown?

Each full pedal press moves the front piston out about 1/16". Each full
pedal press moves a REAR piston out about 1/4".

 

it's not the pushrod, it's the calipers. take the calipers off, pump
the pistons all the way out and recondition them.

 

My '92 doesn't have a removeable knee bolster so I removed the seat so I could get a reasonable
perspective on what is going on. Having eye glasses (old age) I was finding it hard to focus and
get a clear sense of the action. As I mentioned in another thread all seems good from my
understanding of things. Thanks for confirming here though - sure do appreciate it.

Dam, wish I hadn't removed the calipers yet so I could test them as you describe below. NAPA had
a listing for 2 types so I needed to bring one in to get a match. I removed both as I was
gambling on being able to give mine to them for core value and walk out the door with rebuit
ones. They had one type in stock .... turned out I need the other, so they've been ordered and
will be in day after tomorrow. I will save this info for future reference as I don't want to
reinstall, bleed, remove and test. The car has over 290K and I pull a small utility trailer on
occasion so good brakes is imperative. Out of interest, at 284K I was at the top of Roger's
Pass, BC with the following load:
all weight in kg
loaded empty
total weight 2650 1530
rear wh & trailer 1900 790
trailer only 1000 240

trailer pulled great (std. transmission) but slowing/stopping was very poor, so I had to always
anticipate, downshift as much as possible and descend the mountains like a big rig - slow from
the top to the bottom. I drove from Kelowna, BC to Kenora, ON - Lake of the Woods - 200km east
of Wpg. MB

 

Thanks jim. I've jumped to that conclusion now. Appreciate your opinion too. NAPA doesn't carry
rebuild kits - just rebuilt units. So to save me time & effort I'm going to replace both front.

 

sticky calipers it was! problem resolved.

Thanks to everyone ... appreciate the input very much

 

Sounds like we are in the same boat..see my thread about 92 accord
brake calipers...which version do you have, are the caliper pins bolts
that thread directly into the caliper ears (US model) or are the
caliper ears regualr holes and a small bolt threads into the caliper
pin? (Japan version). I seem to have the Japan version on my USA
built Accord???

Mark