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Engine Specific Info and Questions => IDI Engine => Topic started by: 92EcoDiesel Jetta on March 05, 2016, 05:24:59 pm
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92 Eco Jetta. Brake reservoir gets low every 2 months or so and I top it up. Must have added more than 2 qts over the last year or so. No leaks anywhere on the brake system that I can find... all dry. I suspect it is leaking into the booster. Anyway I plan on pulling the master cylinder and booster and have a look but want to have a master cylinder on hand if needed.
Anyone have experience with the KMM unit https://www.fcpeuro.com/products/vw-brake-master-cylinder-357611019bec?gclid=CjwKEAiApOq2BRDoo8SVjZHV7TkSJABLe2iD0O1t9ca3IqBfhh4e045ldQMDJkIlMDYqVRP6016hbRoC8TDw_wcB
An ATE is spendy more than 3X the KM https://www.fcpeuro.com/products/vw-brake-master-cylinder-cabriolet-jetta-golf-357611019
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Clutch slave cylinder is another possibility...
ATE is good stuff. For what it takes to yank the MC from the booster I'd do it first for an inspection rather than buying a quality part you may never need, or buying a cheap part just in case. The KMM one is probably serviceable but you probably would never have to replace the ATE one for the rest of the time you own the car as long as it receives good clean fluid.
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I had that issue, ended up 2 faulty master cylinders. They leaked into the booster. FWIW the booster worked fine it was just full of fluid.
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I had that issue, ended up 2 faulty master cylinders. They leaked into the booster. FWIW the booster worked fine it was just full of fluid.
Was this on the MK 2? How much fluid can the booster hold? How did you clean it?
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I think if you look back with the search function and use his ID and a subject like brake booster you will find his entry. I think he more or less took it off drained it, dabbed it out and rinsed it with some solvents and then soap and water wash.
Is that about right 92Eco?
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I dumped the booster as it was rusty on the outside and a great guy gave me a new one. If I were to have kept it I would have siphoned it out and ran it. I do not think the brake fluid hurts it at all.
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I'm thinking the later Rabbit and MK2 resevoir leak down the front of the booster instead of inside it.
You would see it.
Which compartment gets low? Front or back?
Leaking from inside the rear drums?
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020 tranny cable clutch no slave.
Leaking from front reservoir, not sure about rear. Will check.
Had rear drums off they were dry.
Front of booster is dry.
Will look closer again everywhere tomorrow.
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pretty common to get a bad mc out of the box. when my rabbits mc leaked it leaked down the front of the booster, but many leak inside of it.
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Isn't there an o-ring between the MC and the booster for a vacuum seal? If it is leaking brake fluid outside of the booster, then the vacuum in the booster is also leaking and thus not getting power assist?
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if anything, your not losing boost, if anything the airflow is going into the motor, crankcase, and if air is going in, its going to back up the vent(s). you may not feel the difference in the brake pedal, and if air is moving the vac pump will suck it in and it goes in the cc. or the boost your losing, you dont feel in pedal, but its pressurizing cc? possible.
the other thing was getting brake fluid out of booster, cause they are a junglegym to get out, after 1 or two you get used to it. i find if fluid gets in my booster, i have to take it out, and use softsoap, palmolive, dawn, with warm water, swish, rinse, swish etc, on a good warm day set up in sun to dry, some compressed air, helps. (clean up threads, etc.)
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Took MC out and as expected the booster was full of brake fluid. I used a 3 liter wine bottle made a sucker out of it and a 12 v vac pump got most of the fluid out. The bottle is about 1/5 full, that's a lot less than the 3 x 32 oz bottles of brake fluid that I used to top up with over last year and a half. Since I do not have any external leaks, all that fluid must have been sucked into the engine! How bad is that?
Ordered a new ATE MC, hope it gets here quick. In the mean time I have not decided if I will take the booster out to wash it out. Maybe I'll just use a garden hose to flush it out in place, then suck out most of it, blow it out with compressed air and put a 40 watt incandescent bulb under it overnight to dry it out.
(http://i1183.photobucket.com/albums/x480/Ecodiesel92/20160307_165508_zpspqnmwzoc.jpg) (http://s1183.photobucket.com/user/Ecodiesel92/media/20160307_165508_zpspqnmwzoc.jpg.html)
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Mine actually leaked through to the inside of the firewall a little too. figured this was your issue
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Mine actually leaked through to the inside of the firewall a little too. figured this was your issue
I'll look tomorrow and see if the inside firewall is wet. If that is where all the brake fluid went, shouldn't my carpetting be soaked? They aren't.
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googled "brake fluid in engine oil" and apparently the effect is it ruins engine seals. I put in a Teflon main seal when I did the clutch a few months ago so I am ok there I think. I'll keep an eye on the other seals and see if they start leaking.
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So there is an o-ring that seals the master cylinder to the booster on MK2s?
On the later Rabbit there is a seal inside the booster that seals when the peddle is up.
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So there is an o-ring that seals the master cylinder to the booster on MK2s?
On the later Rabbit there is a seal inside the booster that seals when the peddle is up.
Yep a pricey one too. p/n from the local dealer 357611243 $11
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ATE MC arrived. It was on sale for $100. It's made in the Czech republic and the body is Aluminum. Came with the $11 seal between MC and booster and 2 new mounting nuts too. Hope it's a good one and the last one I have to buy.
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Checked the identity of my caliper per this guide http://www.ate-brakes.com/www/download/ate_de_en/themes/qualitaet_und_tradition_en/download/pdf_documentation_tecidentify_en.pdf (http://www.ate-brakes.com/www/download/ate_de_en/themes/qualitaet_und_tradition_en/download/pdf_documentation_tecidentify_en.pdf) and it is valid (not counterfeit).
The MC is not marked where it's made, just the box label with the codes.
(http://i1183.photobucket.com/albums/x480/Ecodiesel92/20160310_201550_zpsddepwhpu.jpg) (http://s1183.photobucket.com/user/Ecodiesel92/media/20160310_201550_zpsddepwhpu.jpg.html)
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The ATE MC is in. Time will tell if it leaks or not (hope not). I did look at the pedal end of the booster and there is signs of brake fluid drip. It was just a tiny spot where it is dripping from and not a mess at all. The carpeting is not wet but it appears it is dripping on this thick foam sound insulation with fiber backing and the brake fluid soaked into the foam. The layers are foam/ fiber backing/ carpet. I think the fiber backing may be preventing the carpet from getting wet. When I get time, I will pull the carpet back to have a better look. The good news is all that brake fluid did not go into the engine.
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So there is an o-ring that seals the master cylinder to the booster on MK2s?
On the later Rabbit there is a seal inside the booster that seals when the peddle is up.
I thought all brake boosters has an o-ring to seal the vacuum side of the booster against the master cylinder. How are the later Rabbits different? Do you have a diagram?
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No, I don't have a picture either.
Autohaus shows one for an '82 with no place for an o-ring.
http://www.autohausaz.com/search/product.aspx?sid=oxdw4eyohogjl4zmzo3yerq0&makeid=800026@VW&modelid=1369942@RABBIT%20&year=1982&cid=14@Brake%20%26%20Wheel%20Hub&gid=1836@Brake%20Master%20Cylinder
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No, I don't have a picture either.
Autohaus shows one for an '82 with no place for an o-ring.
http://www.autohausaz.com/search/product.aspx?sid=oxdw4eyohogjl4zmzo3yerq0&makeid=800026@VW&modelid=1369942@RABBIT%20&year=1982&cid=14@Brake%20%26%20Wheel%20Hub&gid=1836@Brake%20Master%20Cylinder
Just looked in my 77 to 82 Jetta/ Rabbit manual and it shows 2 types of brake MC (w and w/o brake servos). The ones w/o servos has no o-ring (makes sense), ones w servos has what's called a Vacuum seal O-ring. Hard to tell from the MC pic of what linked to if there is a groove for an O-ring or not. My point is that there must be some kind of a vacuum seal (O-ring or gasket) between the MC and brake booster.
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There is.
It's inside the booster.
I think I posted that in this thread once already.
Any master cylinder leaks go down the front of the booster.
I think you can find more than 2 types of masters for the Rabbit.
Non-power and 2 types with power brakes.
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There is.
It's inside the booster.
I think I posted that in this thread once already.
Any master cylinder leaks go down the front of the booster.
I think you can find more than 2 types of masters for the Rabbit.
Non-power and 2 types with power brakes.
Hard to tell what you are trying to describe. "There is" meant there is an o-ring or there is a groove in the MC that you linked to?
I think you meant an o-ring, which is inside the booster (by the way, I have never seen a booster like that). If that is what you meant, then the booster must have an inverted cup where the o-ring seals against the moving shaft of the MC, rather than an o-ring seal against the body of the MC. Were you also saying such a MC would leak brake fluid down the front of the booster only?
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There is.
It's inside the booster.
I think I posted that in this thread once already.
Any master cylinder leaks go down the front of the booster.
I think you can find more than 2 types of masters for the Rabbit.
Non-power and 2 types with power brakes.
Hard to tell what you are trying to describe. "There is" meant there is an o-ring or there is a groove in the MC that you linked to?
I think you meant an o-ring, which is inside the booster (by the way, I have never seen a booster like that). If that is what you meant, then the booster must have an inverted cup where the o-ring seals against the moving shaft of the MC, rather than an o-ring seal against the body of the MC. Were you also saying such a MC would leak brake fluid down the front of the booster only?
"There is" is in response to your post; "My point is that there must be some kind of a vacuum seal (O-ring or gasket) between the MC and brake booster.
"
I actually should have posted "there isn't" that it isn't between the master and booster. It's inside the booster. Seals from the inside.
Nothing between the booster and master to seal it,.. if it leaks it goes down the front of the booster.
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There is.
It's inside the booster.
I think I posted that in this thread once already.
Any master cylinder leaks go down the front of the booster.
I think you can find more than 2 types of masters for the Rabbit.
Non-power and 2 types with power brakes.
Hard to tell what you are trying to describe. "There is" meant there is an o-ring or there is a groove in the MC that you linked to?
I think you meant an o-ring, which is inside the booster (by the way, I have never seen a booster like that). If that is what you meant, then the booster must have an inverted cup where the o-ring seals against the moving shaft of the MC, rather than an o-ring seal against the body of the MC. Were you also saying such a MC would leak brake fluid down the front of the booster only?
"There is" is in response to your post; "My point is that there must be some kind of a vacuum seal (O-ring or gasket) between the MC and brake booster.
"
I actually should have posted "there isn't" that it isn't between the master and booster. It's inside the booster. Seals from the inside.
Nothing between the booster and master to seal it,.. if it leaks it goes down the front of the booster.
I've been trying to visualize how a booster is constructed as you described and came up empty. Maybe I am just dumb. Can you help explain? Maybe post a diagram or a year and model where such a booster is used? Is the MC for such a booster made differently?
Here is a great video showing how a booster and MC work the way I am familiar with.
https://www.youtube.com/watch?v=bGKJOICWmFQ (https://www.youtube.com/watch?v=bGKJOICWmFQ)
You can see the o-ring that seals MC to booster briefly at 0:33 to 0:36 and 1:46 to 1:55 secs. At 2:22 secs. there is a diagram showing the complete system (they left out the o-ring in that diagram).
Can you tell me where the inside booster seal is (in the diagram at 2:22 secs) in the system you described and how it is constructed? The diaphragm has to move in order to push on the hydraulic rod and the vacuum side of the diaphragm cannot have any vacuum leaks otherwise there is no vacuum assist.
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The one I linked to at autohaus shows the difference,... no groove for the o-ring.
I can't show you the difference in the booster.
I wish I knew you wanted this info when I changed the master on the '82 Rabbit a couple months ago,
I'd have taken pictures.
Maybe if you can find a pic of the '82 booster is will show you how it's sealed.
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Does your booster look like this http://www.partsgeek.com/7vtbltt-volkswagen-rabbit-brake-booster.html?utm_source=shoppingcom&utm_medium=pf&utm_content=dc&utm_campaign=PartsGeek+ShoppingCom&fp=pp&utm_term=Volkswagen+Brake+Booster ?
Here's what fcpeuro has on an 82 Rabbit master cylinder https://www.fcpeuro.com/Volkswagen-parts/Rabbit?year=1982&e=961&m=20&keywords=master%20cylinder
There is a grommet which serves the same function as the o-ring. Did you replace the grommet? How does it go in? I assume the small diameter end goes into the MC and the large end goes in the booster? If so there must be a drain of some sort in the grommet for any MC fluid leaks to drain out the front of the booster? What I do not understand is how it could drain out the front of the booster only and still provide a vacuum seal.
The one I linked to at autohaus shows the difference,... no groove for the o-ring.
I can't show you the difference in the booster.
I wish I knew you wanted this info when I changed the master on the '82 Rabbit a couple months ago,
I'd have taken pictures.
Maybe if you can find a pic of the '82 booster is will show you how it's sealed.
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When you say "it" could drain from the booster what do you mean?
I believe that grommet is to seal around the reservoir,.. so yes I used it. Of course the rebuilt master cylinder had it's own grommet but I've heard of them leaking and that was the case with the new grommets on my rebuilt master,... so I reused the ones from the old master.
The top link to the partsjerk booster shows you real well how the seal looks inside the booster and it even has a little divot for the brake fluid to leak down the front of the booster if the master starts leaking. Kind of hard to get an o-ring to seal with a deep dent where it rides.
Oh if you send a postal money order to partsjerk they will wait 3 weeks before sending your part,... that info isn't on their website.
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"it" is brake fluid, what we were talking about all along.
Now that you have pointed out the divot on the booster, I see what you mean that brake fluid (as well as air) would drain out the front of booster, after the booster is filled 1/2 way from a MC leak. I still cannot picture how a seal inside the booster would look like. Seems not possible.
As for the grommet, my ATE MC came with 2 grommets installed (for the reservoir- and it didn't leak) as well as a vacuum o-ring seal. I assumed the single grommet shown on the same page as the 1982 MC goes between the MC and the booster to provide a vacuum seal, not for the reservoir (where 2 grommets would be required). Was my assumption wrong?
Anyone else know anything about this? We are not getting anywhere. My 81 Rabbit pickup should have the same brake setup as the 82 Rabbits. I have not had to do any MC or booster work on mine yet. When I do, I will have a chance to have a look and maybe answer my questions.
When you say "it" could drain from the booster what do you mean?
I believe that grommet is to seal around the reservoir,.. so yes I used it. Of course the rebuilt master cylinder had it's own grommet but I've heard of them leaking and that was the case with the new grommets on my rebuilt master,... so I reused the ones from the old master.
The top link to the partsjerk booster shows you real well how the seal looks inside the booster and it even has a little divot for the brake fluid to leak down the front of the booster if the master starts leaking. Kind of hard to get an o-ring to seal with a deep dent where it rides.
Oh if you send a postal money order to partsjerk they will wait 3 weeks before sending your part,... that info isn't on their website.
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The booster is sealed internally, it does not rely on the MC to booster junction for sealing in any way. The seal there is a dust/moisture seal only.
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As I see it that divot would keep fluid from leaking into the booster by allowing it to drain down the outside.
I think assuming your '81 is the same setup as the '82 might be reaching.
I've already pointed out; I think your assumption that the gommet goes between the master and booster is wrong. Again, I think it goes between the resevoir and master.
At some point; some of the boosters were set up so any fluid leaking from the back of the master doesn't fill the booster,... it runs down the front.
The lack of o-ring groove in the master as well as no good place to seal against the front of the booster,... in items you linked, to confirm this.