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Mk2 front disc brakes dragging / sticking
by
Baron VonZeppelin
on 12 Jul, 2011 09:41
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Anyone here had to deal with this symptom before ?
89 Jetta Diesel NA with power disc front brakes - solid rotors.
Belongs to a good friend of mine.
He bought this car a while back, it had been parked for i'd guess 3-6 years.
Real nice car that was driven til about half the normal wear items needed attention - and it was parked. He bought it.
I did the front brakes on this car about 4-5 months ago (and all other needed maintenance).
Both rotors, both soft lines, passenger caliper, new pads.
The existing passenger caliper "seemed" like it was seizing - so i replaced it.(after 2 attempts to salvage it)
(melted/distorted plastic hubcap after 20 mile run after initial pad replacement)
All seemed mostly well afterwards. But both sides still got fairly warmer than usual in my opinion. The passenger side - a little more so.
Told him to put some miles on it and lets see how it does (better / worse).
He finally got around to driving it daily (its a back up car - he daily's an 85 TDGL)
After about 600-800 miles it has gotten much WORSE.
To the point that the passenger side wheel now gets hot as fire.
Driver side is much hotter than normal too - but not as bad.
At one point on a highway run to his workplace - he was actually loosing speed/power it got so bad.
So he called me and told me.
I went and checked things out this past Sunday.
Everything is in order ... i suspected the caliper bushing sleeve shims.
But they are fine and in place.
When they get "sticky / stuck" - you can jab the brake pedal a few times and they seem to release a bit. The rear brakes are doing just fine.
What could this be ? Maybe the master cylinder not allowing fluid to return properly sometimes ? Proportioning valve or something else ? Anyone dealt with this before ? HELP please .
Don't want to just blindly throw parts at it - if it can be avoided.
MANY MANY Thanks in Advance !
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#1
by
bajacalal
on 12 Jul, 2011 12:49
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1. The caliper piston itself might be fine but how is the caliper moving on it's mounting hardware. The whole caliper has to move freely for it to work effectively. You said the sleeve things are fine and lubricated, are you sure?
2. I have seen brake lines clog up which can result in pressure that remains in the caliper after you release the brake, because the fluid can't return to the master cylinder.
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#2
by
burn_your_money
on 12 Jul, 2011 13:16
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Do you have the anti-rattle springs installed properly?
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#3
by
mtrans
on 12 Jul, 2011 13:41
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How about rubber lines?
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#4
by
CRSMP5
on 12 Jul, 2011 14:27
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simple test...
loosen the master to booster nuts a few turns and see if it gets better.... ive seen rust form between the 2 and cause issues..
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#5
by
Baron VonZeppelin
on 12 Jul, 2011 15:25
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1. The caliper piston itself might be fine but how is the caliper moving on it's mounting hardware. The whole caliper has to move freely for it to work effectively. You said the sleeve things are fine and lubricated, are you sure?
=Yes, took both calipers off - and inspected / verified smooth travels.
Re-lubed all.
2. I have seen brake lines clog up which can result in pressure that remains in the caliper after you release the brake, because the fluid can't return to the master cylinder.
=Not ruling that out - but get good pressure/flow when bleeding.
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#6
by
Baron VonZeppelin
on 12 Jul, 2011 15:30
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Do you have the anti-rattle springs installed properly?
=Yes. Checked pads for smooth travel across the bridges with clip/springs in place ... while calipers were removed.
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#7
by
Baron VonZeppelin
on 12 Jul, 2011 15:35
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How about rubber lines?
Yes, put new ones on both sides from the start.
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#8
by
Baron VonZeppelin
on 12 Jul, 2011 15:40
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simple test...
loosen the master to booster nuts a few turns and see if it gets better.... ive seen rust form between the 2 and cause issues..
Thats a pretty damm good idea !
The brake pedal is really about all the way to the top - at rest.
Almost uncomfortable to step up on it.
Brakes work real good - but they don't know when to quit.
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#9
by
Baron VonZeppelin
on 12 Jul, 2011 16:11
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Keep the ideas coming - or tales of your own similar experience.
It will probably be next weekend before i mess with it again.
*Whats happening is evidently a continuance of a pre-existing condition it already had before replacing the items i replaced.
Initially - the Driver side pads were a little over half gone, Passenger side pads were REALLY thin.
Driver side is having heat/dragging problem too - just not as bad as passenger.
Lines were flushed very thoroughly when brakes were done initially.
Brake fluid is still crystal clean when bleeding.
Super flush and new passenger caliper didn't take care of everything.
Car was brought to me initially non-running.
Got it running - then went through everything inspecting replacing what else was needed to be reliable/roadworthy.
Then test drove it some afterwards.
Still a couple bugs in it ...
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#10
by
theman53
on 12 Jul, 2011 20:28
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Rubber line acting as a check valve?
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#11
by
Baron VonZeppelin
on 12 Jul, 2011 20:38
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Rubber line acting as a check valve?
It better not be - both are brand new from AutohausAZ.
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#12
by
theman53
on 12 Jul, 2011 20:40
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Rod from pedal to master cyl need adjusted?
All just guesses, but there can't be too much to go wrong here.
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#13
by
Baron VonZeppelin
on 12 Jul, 2011 20:48
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Rod from pedal to master cyl need adjusted?
Another damm good suggestion !
Keepem' coming guys
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#14
by
CRSMP5
on 13 Jul, 2011 06:51
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loosening master nuts will also deal with the brake linkage.. it will give you a complete its in this area to look at...
can be master.. can be pedal..
my worry is you say brake pedal is odd... so that alone says something there is wrong/bent/unadjusted properly... loosening master to releive tension will be a tell all..
id call your friend up and have him loosen them say 3 turns.. and see if it gets better.. you may loose power brakes though.. so its pretty much a test.. but ideal would be when car slowing down from brakes dragging you loosen them.. and if it all of a sudden rolls free you found the issue spot..