brake master cylinder rebuild

herr_sparky · Post by **herr_sparky** » Mon Oct 29, 2001 10:35 am

well, I suppose it was inevitable. leakage. a steadily growing puddle under the pedals and its not water. are the service kits available? What about super beetle interchangeability? recommendations?

ray greenwood · Post by **ray greenwood** » Mon Oct 29, 2001 3:45 pm

That would be a nope, nope and nope. It is exceedingly rare to find kits at all. They have to be the right kit. Either FAG or teves. Sheafer made one for each. I can still find a complete NOS FAG cylinder...for $220.00...and its been on the shelf for years. Not the way to go. Old NOS kits on the shelf have the same problem. Flexibility of the rubber parts. Heres one answer. Get a flexhone of 3/4" or 19mm. This is one of those honeing brushes that has all of the little beads on the bristles. 320 grit works well, They are about 20 bucks. You can also usethen for lifter bores. If after honing the cylinder you have any pits or rust specs, hone it again. Still there? The cylinder is shot. A 320 grit hone takes very little metal out. Now after a succesful honing, buy a 73 type 3 dual circuit master cyl .kit. These seals and brass valve shims will fit your pistons perfectly. The new pistons...throw them away. They won't fit. The metering ports are in different places. The seals from a brazilian made (varga) 19mm golf/rabbit master cyl fit also. These are about 25 bucks. Again, discard the cylinder and pistons. Keep the hose bushings, seals, valve shims and boots. Use 2000 grit sandpaper to clean any and all corrosion from the face areas of the old pistons where the brass valves seat.This set up works great. You can also use the entire rabbit and type 3 master cylinder assembly if you make a bracket out of 2" wide by 1/8" thick steel strip with about a 3" bend in the end. Weld a small gusset across the top bend area for strength. Drill your two 12mm holes to mount where your master cyl does. Slot your holes for adjustment. Drill a 1 1/8" hole for the master cyl end to go through and two holes for the ears to bolt up. You will have the cyl. turned about 30 degrees so there won't be so much offset. You will need a 1" longer clevis pin to link up to the pedal and a couple of washers to bush it up and a c-clip. This will alllow you to have a complete master cylinder, replaceable, with the correct volume stroke. The type 3 and rabbit cyl. also have the correct # of holes for switches and brake lines. I havn't had to build this yet...but it shoud work fine. Ray

herr_sparky · Post by **herr_sparky** » Mon Oct 29, 2001 4:03 pm

ray, are you telling me that with a couple of homemade brackets and some hardware I can use a complete master cylinder for a rabbit? thats incredible. seems like the way to go to me. brake light switches will plug in, too? great! best news all day. thanks

ray greenwood · Post by **ray greenwood** » Mon Oct 29, 2001 6:38 pm

I will see if I can make a sketch with measurments in it during lunch tommorrow. Yes, with a few minor extra pieces of fabrication, you can use either a rabbit master cyl. (I'll see if I have a part # some where) or a late model type 3. The bracket should work fine. The type 3 has the exact same positions and light switch types. You will not have to move any of your brake lines. Just wait until you have to work on your clutch master and slave. The problem we have with our master cylinders in the 411/412 is that yes...they are protected better under the dash, but moisture builds up..because of no air flow, inside of the boot. It puts a rust ridge right inside of the bore that tears up the lip on the outer piston seal. Then it leaks a little...absorbs a lot more moisture...then rusts more. Ray

sean · Post by **sean** » Tue Oct 30, 2001 6:30 am

i have just got rebuilt slave and master and a nos clutch slave and rebuilt clutch master of jane terry here in the uk t3 and 4 club £45 ukp each no problems here . sean also ray forgive me for not replying to my post as i up to my neck in it trying to get the 4 sprayed before the winter starts

ray greenwood · Post by **ray greenwood** » Tue Oct 30, 2001 9:12 am

Sadly,there is no-one on this continent who rebuilds slaves....I do some of them, but finding the correct seal in the correct material is almost impossible. I use a standard nitrile U-cup with an extra tight inner circle to seal on the shaft (I usually destroy two fitting one) I also use a tight O-ring backer to keep it stationary. It works great, especially after a good honing...but the sealing friction is very high and gets only about 30K miles. But it cost less than two bucks for the gaskets. I am probably going to fix that by honing and having my cylinders hard anodised in a batch. Should get about 60K out of one then. The rebuild on clutch masters I do with seals out of a type 3 master cylinder kit and a good honeing. They work great also. Eventually I will probably build a bracket like that I described for the brake, to use a single circuit type 1 master cyl for the clutch. As long as the residual pressure valve can be fitted...it should work fine. Ray

herr_sparky · Post by **herr_sparky** » Tue Oct 30, 2001 3:27 pm

great suggestions. ray, a part number would be excellent for when I go to the parts counter. Ill be tearing into the brake system of the 2-door also, and I just might luck out with the condition of its cylinders & pistons. Im pessimistic though, as the calipers are froze in place, engaged. If the bore in the caliper is corroded, wouldnt it prevent the piston from retracting? One thing at a time I guess. Maybe Ill track down a digital camera and post some pictures.

ray greenwood · Post by **ray greenwood** » Tue Oct 30, 2001 5:05 pm

Yep, a stuck piston will do that. Don't dfespair yet though. It doesn't take much clearance to actully get the caliper off. Use a prybar against the rotor...since the yare probably shot anyway. Don't lose the calipers. Let them sit with penetrating oil on both sides of the piston for a day or two, then get them warm...not too hot, put a block of wood between them...get some safety goggles and pop the pistons out with compressed air. I say don't lose the calipers, because the ycan probably be rebuilt, and you want to make sure you can get calipers to match what you have. Calipers, steering knuckles and control arms ned to be exchanged as a set from 411 to 412. They are different. I will try to get the part #'s in tommorrow as well as a sketch...works been crazy. Ray

herr_sparky · Post by **herr_sparky** » Thu Nov 01, 2001 7:12 pm

Ive removed the calipers now, pistons removed, and both pistons have a polished mark on them opposite eachother, as though they've been crooked. Normal? The boots are missing the circular spring clip on the outside, and the cylinder wall inward(towards the rotor) of the sealing ring is fairly rusty. The seal itself is fine. Two of the four bolts that hold the caliper together have sheared off inside their threaded holes and the heads are gone. Also, how do I reinstall the pistons while ensuring they slide in square to the cylinder? Its a tight fit as is. thanks

Chris Percival · Post by **Chris Percival** » Fri Nov 02, 2001 9:45 am

Ray, you really should write some of your knowledge down into a web page...

ray greenwood · Post by **ray greenwood** » Fri Nov 02, 2001 1:57 pm

Thanks Chris...if I can find the time soon I might. Herr sparky...The rust ring at the outboard side is normal. This area is larger diameter and does not contact the piston. The polished area is normal. Split the calipers. Do not lose the tiny black seals. They are to be reused. Start with medium steel wool. Finish with fingers and 1000 grit sandpaper...then 2000. Same for the piston...until it shines. Do not hone these. there is no piston ring to working about breaking in. The seal is stationary, so all you are looking for is very smooth travel. Ray

herr_sparky · Post by **herr_sparky** » Sun Nov 11, 2001 6:04 pm

ray - what are those part #s for the master cylinders? by the way, my calipers rebuilt nicely, shined right up. Yep.

Post by **Tom Notch** » Sun Nov 11, 2001 6:29 pm

Hmmmmm, just helped a friend bleed the brakes on his 412, he just put a NEW master cylinder in it. He got at the local Shuck's Auto parts store.

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Tom Notch
Tom's Old VW Home

ray greenwood · Post by **ray greenwood** » Mon Nov 12, 2001 2:20 pm

I'll see if I can get them in tonight sparky...I'm in the wrong car right now. Wow Tom...NEW. I can occasionally find one. The problem I have been finding is seal deterioration due to sitting on the shelf...ie. short life. They havn't made new ones in a loooong time and they fit nothing else. Rebuilding them is actually easy using type 3 seals...as long as there are no serious rust pits. One of my sources tells me that Lucas/girling in England has taken over almost all of the rebuilding business on cylinders like these. Especially clutch slave. He tells me that they will rebuild cltuctch slave and master...with a core...on demand in 3 weeks. The cost is ugly. The last quoted price for a 44mm slave rebuild was $219.00....with Lucas former rep for reliability issues...I'm not about to pay that and wait three weeks to boot. I'll ask what the situation is now. Ray

3rd_slow_411 · Post by **3rd_slow_411** » Thu Dec 13, 2001 7:33 pm

Tom,
Do you wanna? go back to that local Shuck's Auto parts store, and see if they have more? Sometimes they?ll have a pile on that ever-present mystery parts shelf. A new rusty core is better than an old, used rusty one!!
Clay