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sinking brake pedal by 92EcoDiesel Jetta on 13 Jun, 2009 08:05
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At a stop light, I can feel the pedal slowly sink but I still have brakes and it stops the car fine. So I put a vacuum gauge on the vacuum system and see what's goijg on. At idle, vac builds to 25" hg. Every time I push or release the brake pedal, the gauge shows a drop in vacuum, If I pulse the pedal in sucession 10 times, I get get the vac gauge down to almost zero bt builds up again. If I shut the engine off, the gauge holds vacuum so it's not leaking. So what does this tell you? Is there a vacuum reservoir for the brake booster with a check valve?
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#1 by Vincent Waldon on 13 Jun, 2009 08:24
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Booster sounds perfectly fine, as does your vacuum pump.
Brake pedal that's "spongy" usually indicates air in the system.
Brake pedal that slowly sinks to the floor is usually one of two things:
- if the brake fluid level is dropping, a leak
- if the brake fluid level is not dropping, a bad master cylinder -
#2 by Ziptar on 13 Jun, 2009 08:28
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I just went thought the same thing. Bleed the system first, bet it resolves it.
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#3 by 92EcoDiesel Jetta on 13 Jun, 2009 13:13
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I bled the front brakes when I did the pads but the rear drums were untouched since I bought. So I went to bleed them and there were no nipples either side! Broken off? Damm now I need new wheel cylinders and a master cyl also. The number of things I'm finding wrong with this car is just too many.
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#4 by Rabbit TD on 13 Jun, 2009 19:54
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I bled the front brakes when I did the pads but the rear drums were untouched since I bought. So I went to bleed them and there were no nipples either side! Broken off? Damm now I need new wheel cylinders and a master cyl also. The number of things I'm finding wrong with this car is just too many.
Well the bad news is the problems never end with these things, the good news is they are usualy pretty cheap and easy to fix compared to newer stuff. -
#5 by Ziptar on 14 Jun, 2009 07:01
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If the pedal is spongy then bleeding it will resolve it. If, with constant foot pressure, it gradually descends to the floor, then bleeding it will not resolve it. Ziptar, in your case a spongy pedal must have seemed like it kept descending as it is impossible for a constantly descending pedal to be cured by bleeding.
Hmmmm, now that you mention it libbybapa, I haven't really tried brute force constant pressure since bleeding the brakes. I'll have to see. If the pedal descends under pressure then Master Cyl. is bad, No?I bled the front brakes when I did the pads but the rear drums were untouched since I bought. So I went to bleed them and there were no nipples either side! Broken off? Damm now I need new wheel cylinders and a master cyl also. The number of things I'm finding wrong with this car is just too many.
DON'T GIVE UP!!!!!
Stick with it, while it may have issues from neglect or a doofus previous owner once you get an MkII Diesel up to snuff it'll probably out last you. I still have lots to do to to mine and probably another $4000 (or more) to spend but, I care. I own the simplest, most reliable, and durable car ever manufactured. I think others here will agree. While you may be finding stuff wrong, the MKII is so simple there should be relatively few.
My wife just rolls here eyes every time I say it but, I think MkII TD is a technological marvel and THE finest vehicle ever manufactured
. She just thinks it is "old". Well SO AM I!!!!! When my wife gives me a bit of torment about the work and money I've put into "Bubbles" (My daughters named it that.) I say to her "Look at this way, it is a 2 for 1 deal. I get a car and you get a coffin for me because I am driving this car to the grave.".
Ok, that being said and motivation aside.
After the bleed, how are the brakes? Do they work OK and you can drive safely for now The I suggest a plan, Upgrade to 10.1 fronts and rear discs. Since you need a master, and rear wheel cylinders anyway you might want to see if you can pickup a 10.1 brakes, 22MM master and, rear disk at a yard near you or cheaply on the vortex. The 10.1 fronts and master cylinder can come off any MkII GTI/GLI or an 4x100 MkIII, just look for "Girling 54" cast into the calipers, you'll need the knuckle and everything with it. Some are of the opinion that the rear discs are horrible on the MkII but I like them, mostly because I hate working on drum brakes. You can do the upgrade piece meal if you upgrade the Master cylinder first (pedal will stiffer until fronts are done). While there are more awesomer brake upgrades out there, for the money and simplicity, the factory 10.1" is unbeatable
Used stuff available in the vortex:
Rear calipers and carriers http://forums.vwvortex.com/zerothread?id=4397994
22MM master http://forums.vwvortex.com/zerothread?id=4417866
$10 22MM Master http://forums.vwvortex.com/zerothread?id=4353059&page=1
22 Masters on ebay
I'd get a new master but, that is just me, used masters give me the heebeegeebies. Either way, the upgrade (once bled correctly) is really nice. -
#6 by Ziptar on 14 Jun, 2009 18:52
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I went out and stood on the brake pedal today, no sinking!
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#7 by 92EcoDiesel Jetta on 14 Jun, 2009 20:07
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I went out and stood on the brake pedal today, no sinking!
Was the engine running when you stood on the pedal? Mine would sink only when the engine is running.
I have not bled the brakes yet. Have to put new wheel cylinders in first. Hey, thanks for the encouragement!
ps. are rebuild kits available for the master cyl? -
#8 by Ziptar on 15 Jun, 2009 02:30
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You are welcome on the encouragement, it's easy, since you own the best car ever!
The engine wasn't running when I stood on the pedal, I'll have to try it that way to. You might want to try just bleeding the front before you get wheel cylinders for the back, it'll help you diagnose what is going on also could make for improvement in pedal in the interim. It'll take all of 20 minutes and Brake Fluid is cheap. At least then you will have an idea of what is going on.
I haven't seen a rebuild kit for the MkII master cylinders (come to think of it I haven't seen one for any master cylinder in 20 years.) the price between the 9.4" and 10.1" master cylinders are pretty much the same The Stock 18 or 20mm Master on the Ecodiesel is $98.55 @ autohausaz they aren't that different, The GTI/GLI 22MM Master is $98.90 @ autohausaz
There are new ones cheap on eBay, $24.00 for the 22MM form this guy. I've never bought anything from him and have no idea on the quality. I am guessing based on the price and the statement in the description "This item comes unboxed due to the fact that we by these bulk at 150 units at a time!" they are made in China.