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Model specific boards => Golf mk2 => Topic started by: RossyB108 on 19 February 2011, 21:41
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Hi,
I fitted new rear brake lines and a master cylinder a couple of months ago because I was getting spongy brakes (and my pipes were very corroded). They've been really good since, until...
About a week ago my brakes started getting a little spongy at the first press again. It's quickly got worse until now my foot nearly reaches the floor.
If I press the brakes and straight away press them again, the brakes are hard and normal but after about 5 seconds or so of not braking they are spongy again!
I'm guessing I've got air in the system but can't understand why it would suddenly happen again after a good 6 weeks of them being fine (since the new parts) and also get worse so quickly too :angry:
I can't see any signs of a leak, but the only other thing to note (which is probably nothing), there's a wierd noise that comes from the rear near side corner when I take my foot off the brake quickly - a bit like a minature donkey being run over - which stops as soon as the brakes up, I'm wondering if it's air in the bias valve coz I know that's around that area.
Sorry to waffle, wanted to get the detail in - hope someone has experienced this before and knows what it is, I can't keep throwing £ at it to find it's not resolved!
Thanks!
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Could be air trapped in the rear calipers, try bleeding it through again.
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i had problem with a mk2 the once, kept bleeding it but had a crap brake pedal, found i had a slightly sticking calliper which must of been holding the air. might be worth pushing back the front and winding back the rear callipers so all the pistons are totally in.
and to do with your other post you can put a higher spec brake fluid in the system but its not going to help unless your doing trackdays and alike (youll overheat the brake pads and get fade before your brake fluid boils) but if you do make sure all the old stuff is pushed out. you shouldnt have 2 different types in the pipes i dont think it mixes well!.
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Check that the brake bias valve is all in good order, they are prone to seizing and leaking etc. Always worth changing as once they are fooked... they are fooked.
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Thanks for the replies. Got my brakes bled at the garage today, feel spot on now - I'll keep an eye and report back if I get the dreaded sponge back again...
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Ok, my brakes have gone again.
They slowly got worse over the last couple of weeks and this weekend really got quickly worse.
I'm not far off hitting the floor when I brake the first time, after pumping the pedal acouple o ftimes they are ok. can't understand it.
The donkey is still there too.
I did also notice that is I pump the brakes a couple of time so they are firm, if I hold my foot on the brake it very very slowly pushes to the floor, barely noticable at first.
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You have a leak somewhere getting worse by the sounds of it.
You need to look for sweating on any unions and bias valves could be just the brake pipe unions where the flared nut was loose or not flared enough to hold true on the nuts?
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I've had a good look and can't find any evidence of a leak, and the level of fluid never goes down
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Could be a master cylinder problem
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Try jacking up the rear end, supporting on stands, get the back up as high as you can.
Clamp the rear brake regulator valve, pump the pedal about 20 times.
Leave the car overnight, and bleed the rears.
Quite often the air seems to settle in the rear of the system.
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Do you think I could have damaged the new master cylinder when I fitted it? How fragile are they?! I bought the new one becuase I thought the problems were because of the cylinder but I have the same issue even after fitting the new one! Just seems unlikely to have developed the same fault, it'll be expensive and VERY annoying if I change the MC again to find it's doing the same thing.
I'll jack up the rear and bleed, but it wont solve the problem as it'll be the same again after a couple of weeks.
I was thinking of blanking off the rear brakes from the front union/brake pipe splitter near the engine bay somehow, to isolate the rear. That way it should narrow down the problem. If the front of the car is fine, at least I'll know to buy a new bias valve and or new/upgrade calipers.
Dam it.
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At this stage If the M/C is new send it back to supplier to check it out cost of postage if its faulty then they will exchange it for you hopefully?
Otherwise I don't see you having any pressure equipment to check for leaks?
The SERVO is very tough, the skin on the cylinder would need a drill to puncture the surface for it to loose pressure!
Is the servo NEW? Did you use brand new rubber seals to mate the M/C to servo?
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No, the servo looks original.
MC came from GSF and it was the better quality option (22mm). I used a new seal that came with the MC but the surface of the servo wasn't great. Although saying that, after a bleed the brakes work perfectly for at least a couple of weeks and I'm guessing the MC to servo seal is seperate from the fluid? So air is getting into the fluid somehow.
Thanks
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What about the resivior seals that sit on top of the M/C?
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A new pair did come with the new MC and it also came with some lubricant to put on them before fitting the res.
It's a bit tight rought there but I can't see any obvious leaks.
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I know this sounds simple you have taken the resi cap off to check the level and not just from the outside?
All I'm saying is it might not be clear visually if dirt is giving you impression of the level!
Before parting with any money I would make sure every caliper piston winds back ok and all rubber seals are in good order.
It could still be M/C or Servo issues here?
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Ok thanks clipperjay, I'll check the calipers etc. and the levels...
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Update.
Two weekends ago I replaced my rear calipers with mk4 ones and fitted new braided hoses all round, (except for the small hoses that fit over the rear beam coz I couldn't get in there and the fittings look well corrdoded so left those ones for now).
After fitting and bleeding, the peddle felt firm and sharper, But over the days since, I have noticed the very gradual spongyness creeping back again, I'm guessing within the next 2 or 3 weeks depending on the amount of driving I do, the brakes will have gone again.
This is seriously getting on my wick now.
I've replaced:
Master cylinder
Rear brake pipes
Hoses for braided ones (except rear beam hoses).
Rear calipers for mk4 ones
- There are no leaks anywhere that I can see
- Air is getting into the system and takes about 4/5 weeks before the peddle is near the floor
- A double pump on the brake peddle makes the brakes work and feel firm and normal (but I shouldn't have to double pump every time I need to brake!)
- The brake fluid level doesn't change (that I can see)
- The rear brake compensator valve works and isn't seized or leaking
My next plan is to have the rear braided hoses fitted and the corroded union and pipes replaced at the back near the rear calipers in case that's where air is getting in.
After that if the problem is still there, I guess the only parts left to replace are:
- Rear compensator valve
- Front calipers
- Servo
What a joke, am I really the only person this has happened to???
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Just giong back through some old posts to update.
I found the problem in the end - I was just being a dumbass.
I opened up the rear bias/brake compensation valve with some mole grips and pressed the brake pedal hard for a few seconds. Found brake fluid coming out of one of the rear calipers hose connections. I did it up nice and tight, re-bled and bingo no problems since (5 months).
The bios valve only lets though a little fluid (depending on how it's set up) so I wasn't getting any leaks but air was slowly getting in the system from the rear caliper over the course of a couple of weeks.
At least I have a mint brake system now!
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:grin: everyone gets caught out over small things funny I'm having brake issues aswell!
I'll sort it out but very slowly indeedie!
Good job though for your patience on it :laugh: