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Discussion Starter #1
I'd like to replace my master cylinder, but the bolts that connect it to the intermediate tube look rusted to the point that the threads are going to crumble when I try to remove the nuts. (see photo) And the bolts appear to be welded to the intermediate tube. Also, the bolts coming through the firewall that the intermediate tube goes onto are in bad shape too. (see photo). Even if I do get the nuts off them, I don't think I'll get them back on - the threads look terrible. These bolts also appear to be welded to the pedal cluster. So it's starting to look like I'm going to need to replace the intermediate tube as well as the pedal cluster (since the bolts are not removeable). Can you think of another way to do this without having to replace these parts? I haven't even been able to find these parts yet online. And it looks like replacing the pedal cluster would be an involved job. Any advice would be much appreciated.

Thanks!
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I would use a wire tooth brush and clean the surface rust off the nuts and exposed screw threads. I would soak the bolts for a day or 3 with PB-Blaster, or CRC Freeze-off. Spray them well, and do it about 3 times a day.

Using the proper articulating Gear Wrench or an air impact (electric works well too) and 6pt socket with an extension to get it out to get the socket on an extension, and remove the bolts. You can also try to carefully remove the RES, as they are almost harder to get than the other parts. Apply some heat to the nuts. then tap the nuts lightly with a small punch and try.

This isn't the proper wrench but a sample.
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They work well in weird spaces, and have the pivot offset. Do not use Brute force, but gently steady pressure.
Going back, Never-seize is going to be your friend.

Never seen a Rabbit without a power booster.
 

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Discussion Starter #3
Thanks for the tips. Maybe it's because I haven't had my morning coffee yet, but you lost me with "RES"... what is RES?

If I had to take off the intermediate tube, I've been thinking about installing a booster. It would be nice to feel a bit safer with the added braking power. But I don't know if that's an easy change to make or if it would be involved and require changing lots of other parts. Would you happen to know?

The only other idea that occurred to me is to cut the exposed parts of bolt off since the parts of the bolt under the nuts are likely protected and in good shape. So maybe getting the rusted part of the bolt out of the way would let the nuts come off easy. Then again, if I mangle it, it might make it harder to get the nut off. Maybe I'll stick with your method unless you have thoughts on this.
 

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RES "Reservoir" The plastic container that holds the Brake Fluid. Carefully pry that apart, I usually use a scrap piece of wood under the middle of the RES against the plastic tank and pry up with a rounded part of a screw-driver after shooting some wd-40 into the rubber grommets of the MC that holds the RES into the MC "Master Cylinder".

Taking that off while it is mounted to the car is a tad easier, and will allow you to use heat if needed without Warping the RES or melting it. Another good trick is to use a hair dryer on the rubber grommets after spraying them with wd-40 to re-soften them as they may have hardened....Get them toasty warm on all the sides and Gently pry up and off with something between your res and the pry-bar. Make sure that your res is cool to the touch prior to prying.
As the heat can also soften the plastic res.
 

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Adding a Brake booster to your car isn't undoable, but sourcing the proper Booster or a good booster is getting harder and harder to do. I think the booster is easier to find than the crack pipe with the check valve, then there is the possibility of having to source different parts such as the proper proportional valves and things. Since yours is a early version the year would be nice to know. I am assuming pre-westy built.
 

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Discussion Starter #6
Ah, I understand now about the reservoir. Thanks for the detailed explanation.

It's a '78 Rabbit 1.5 diesel, Wolfsburg edition. So it does have some of the earlier tech throughout the engine. Thanks for the info about the booster. Any more info you have about this particular model is welcome.
 

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The brake booster on a diesel is run off the vacuum pump, that you may or may not have as you don't have a booster, and or probably a/c. You can do it, but you would need a Brake booster, and the set up off of a 81 diesel bunny. It bolts to where the extension pipe is. I had Boosted brakes on my 81 diesel. Now that I know that you don't have a Gasser then the vacuum pump is needed. So add that to your list, as there are 2 types early pre-82,5 and post 82.5, one deing diaphragm operated and the other is vane operated. The hose to the booster, most any type of vacuum hose will work the check valve to the booster and the booster itself.

you can use the ETKA to source partnumbers but you probably would need to source the EUropean version as they have the older types still listed.
Volkswagen Parts catalog - ETKA Online, Volkswagen EUROPA, original Catalog Volkswagen EUROPA beware they are Right Hand Drive (RHD)
 

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Discussion Starter #8
I definitely don't have an A/C. And I don't think I have a vacuum pump. Is that vacuum pump used for anything else, or is it only for the booster? It's electric, I assume... or is it somehow belt powered? This is great info. Thanks for sharing.
 

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Discussion Starter #9
Oh, I see where the vacuum pump goes now. It's gear driven. That hole in my block where the vacuum pump would go is capped off. I always wondered what that was for. Does that go down to the oil pump somehow?
 

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yes, it is driven off the oil pump which is driven off the intermediate shaft.
 

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I recommend using 6 point sockets on any heavily rusted bolts & nuts. The 6 point will apply more torque than a 12 point before it strips the head. I frequently run into this on my cars from the 60's. It's better to spend up to 10 days with frequent applications of PB Blaster, Liquid Wrench, etc. before stripping / breaking the studs, heads or nuts. Also moderately tap the nuts with a hammer & punch before attempting to loosen - to break rust loose. Then slightly tight & loosen in very short strokes with liberal application of penetrating oil. Go slow. Heat the nuts to almost red hot if possible depending on location. Proceed with patience as that is much easier than breaking a stud or rounding a nut off. Going slow normally solves the problem.

I always reassemble all fasteners with at least low strength Thread Lock, for example Blue from Harbor Freight. This puts a protection coating in the threads that cures in the absence of air - degrease with brake cleaner first. If not available, then coast the threads with lithium grease which is somewhat water resistant. An alternative is paint the bolts & nuts with Por15 organic paint as it makes a very hard waterproof coating that sticks to rusty (not oily) metal - clean with brake cleaner first.

Take your time & reapply penetrating oil day after day. Those don't look as rusty as many I've worked on. Let us know the result.
 

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Discussion Starter #12
Thanks for the tips! I was able to get the nuts loose at the master cylinder end of the tube, so I was able to remove the master cylinder. I applied PB blaster several times and used a 6 point line wrench (because I couldn't get a socket in there) and slowly worked the nut back and forth, cleaning out debris as I went. Worked like a charm. I wasn't able to get the reservoir off first - I was afraid I was going to break it - so I didn't use any heat this time. I still need to remove the reservoir, but I'll tackle that tomorrow now that the master cylinder is on my workbench.

Thanks for the tips about keeping the bolts from getting more rust. I wasn't able to find an intermediate tube to replace this one, but I decided against the power brake upgrade for now, so these bolt threads will have to last many more years given that they are welded to the tube. I have Permatex Blue Threadlocker and POR15. I think I'll go with the Threadlocker this time. I also noticed some other bolts that I should have put Threadlocker on that are now starting to rust, so I'll make a point to go back and do them too.

While I have the master cylinder out of the way, I'm going to replace the selector shaft seal on the transmission because it's leaking. Found these great tips from Broke on how to do that:

Things are coming along nicely. Right now I'm focusing on all the mechanical repairs I can do because I'm not looking forward to the body work that needs to be done. I think it might finally be time to learn how to weld.
 
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