Rebuilding my hydroboost!

[BR3W CITY]

IMAGES UPDATED DUE TO PHOTOBUCKET DISASTER. THEY ARE LARGE! Some images may be reuploaded in wrong order. If you see anything, please let me know and I will correct it. 8/28/17

Pulled this Hydroboost booster, master cylinder, and resevoir from a scrap yard the other day. Been wanting to add the hydroboost for a while, and finally got out the the yards to get one. I decided that I was going to do a light rebuild on it anyway, since its history is unknown, and its my brakes afterall. So that being said, here's what the heck I'm doing.

Pulled it out of the garage and hit it with some carb cleaner. It was caked with oil and fluid, much of it coming from the little weep hole on the bottom of the booster. Thats the most common point of failure, and its from one internal seal.

I started off by pulling off the res and hose, and then taking off the 2 bolts holding the master to the main booster body.















Then I took off the 5 bolts holding the 2 sections of the main booster body together, being careful not to let anything fall out as they seperated.





A larger spring might fall out first leaving you with the 2 halves. In one half, you have this peanut shaped seal, and the piston and rod, with this other little plunger inside. This seal will be replaced on the rebuild. If you pull the piston out a bit and see the spring and this little lever/clip. I left this all attached for now.



The other half has this little shaft (valve?) and spring. If you look into the hole, there is a seal on the outside of this hole (the lip is stuck up there in the middle...It'st still in place for now, Because I have this weird little plastic piece stuck in there...I gotta get a long screwdriver or something to pull it out, its a bit awkward, and I'm not sure exactly WHAT it is yet (my rebuild kit is still in the mail!)
You can pull the valve out with a light tug, and then shake out the little spring left in the small hole.






With it all apart, I started cleaning it all up to give myself a clean, easier to work with set of parts and hardware. I'm going to continue this rebuild when the rest of the parts arrive, and I'll probably toss some of the install stuff up as well...just need to wait on the mailman.....

[INSIDIOUS '86]

Sweet. What year hydroboost is this? As I recall they were all very similar units with diff bodies.

Get that body wire wheeled and no more rust and paint it with glyptal.
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[oldman3]

Nice review on the disassembly...Jim

[BR3W CITY]

Thanks guys, I found out the little star-shaped piece is the spring retainer, which I'll try to get out in one piece...I think I ordered the deluxe repair kit, which should include another, but you never know.

The unit itself was out of a 97-ish astro van. The angled bracket might get replaced, as I think it might put the booster at a strange angle. The rebuild kits for the Chevy/GMC/...and Dodge are all the same...apparently the hydro units on cummins trucks was the same basic design, with different master cylinders/resevoirs.

[BR3W CITY]

While I'm still waiting on parts;
Rebuild kits are a little tough to come by, as I can only find one company that actually makes the product, MBM brake boosters. They retail it through a few different diesel vendors and hot rod shops, but everyone has the same kit. Its around $40 for the complete kit, with a new spring retainer and every gasket.

When I called the diesel repair shop near me, he said many places stopped servicing them because things like the Gas Resevoir started to become a liability. I find this funny, as its a replaceable self-contained unit which doesn't really require anything special. Only other option I could find besides the MBM kit was a reman unit, ranging from $225 and up, not even counting the core or a master.

[BR3W CITY]

oops double post

[INSIDIOUS '86]

Originally Posted by BR3W CITY

While I'm still waiting on parts;
Rebuild kits are a little tough to come by, as I can only find one company that actually makes the product, MBM brake boosters. They retail it through a few different diesel vendors and hot rod shops, but everyone has the same kit. Its around $40 for the complete kit, with a new spring retainer and every gasket.

When I called the diesel repair shop near me, he said many places stopped servicing them because things like the Gas Resevoir started to become a liability. I find this funny, as its a replaceable self-contained unit which doesn't really require anything special. Only other option I could find besides the MBM kit was a reman unit, ranging from $225 and up, not even counting the core or a master.

Are you able to replace the resivior?
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[BR3W CITY]

Well there usually isn't a reason to replace it unless ifs physically damaged. From what I read service parts exist for them.
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[BR3W CITY]

UPDATED 8/28/17 WITH RELINKED IMAGES. WRITEUP IS UNCHANGED.
Got the parts kit in from Nelco Hot Rods on ebay. Its the MBM kit, the only one really around. I got the deluxe kit, but really only need a few gaskets to clean it up and make it serviceable.


Started off by looking in the main oriface and pulled out the small piston seal seated into it, then working in the new seal. It takes a second to work it in even (not pinched!), and I cleaned everything with some rubbing alcohol to make sure nothing affected the seal.








Then I pulled out, cleaned up, and replaced the "peanut" gasket.


Put the little spring and the valve back into the unit, then re-install the star-retainer from the other side. After that, put the rod and spring into the piston, making sure to seat the locating pins into the channel in the top of the valve.




Then fit the halves together, putting in a couple bolts and tightening them slowly to help pull the piston into the new seal.


And thats pretty much it so far. I need to clean and re-attach the master, then get it all bolted together and move onto the install phase.

[Vova]

Well done. Thanks for sharing...
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[BR3W CITY]

I'll put some of the installation stuff on this thread as well, so its all in one place. It was nice and warm, so I worked on it a while today.

Starting with my old manual master cylinder. Started wuth pulling the bolt off the pedal (no clevis) to release the rod and allow it to come out in the cab (has no physical attachment to the master like some do).





The old rod I have, and the new rod on the hydroboost unit have a very similar end. The picture is a tad deceiving, but the hold in the rod end appears to be the same size. If I run into any problems getting the stroke correct (due to the different mounting depth and pedal style/attachment), my backup plan is to either cut and tap or cut and weld the old end onto the rod, giving me the old rod's adjusting capability.




Pulled the master off, to reveal the old-style 2 bolt mounting point, which won't work with the 4 bolt setup I had.



I had two choices; either measure and try to cut/fab a 2 bolt bracket for the booster, OR drill new mounting holes and possibly massage the old opening to fit. On top of that, the astro van bracket mounts at a steep angle, which would put the rod in a rather steep angle that I felt just wouldn't work (and it would look goofy underhood). I decided to try to kill two birds with one stone (and NO material haha). I would run the 4 bolt bracket for the security of the extra bolts, but mod it to fit a level position and dept.









My battery got low so the cam was on charge for the welding. I just used the old removed metal to form a filler piece. and ran two alternating concentric circles of weld holding it in place, and reinforcing anywhere that was cut or scored while I hammered it flat. The filler piece is also supported with stitched welds from the back. The result is a free basic mounting place that already has the scalloped holes for the studs, and the keyed hole for the booster. Then a dry mount of the booster. Starting on more assembly and lines tomorrow.




I'm looking forward to wiping all my alignment markings, penetrating oil, and dot 3 residue off all this so my hard work doesn't always look like its never been washed haha. And YES it will be bolted in all the way, the single half threaded bolt probably won't do much for mounting strength

[jjzepplin]

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[oldman3]

Nice write up...Jim

[THE "10" SILVERADO]

Found this an unfortunately the images are no longer available. Does anyone have another write-up or diagrams that show how this is done? Gonna be pulling a hydro-boost off of a crusty 78 that I would like to rebuild to put in my 77.

[BR3W CITY]

Originally Posted by THE "10" SILVERADO

Found this an unfortunately the images are no longer available. Does anyone have another write-up or diagrams that show how this is done? Gonna be pulling a hydro-boost off of a crusty 78 that I would like to rebuild to put in my 77.

The photos on most of the tech stuff got wrecked in the Photobucket hostage crisis. I have all of them in a folder, but they aren't hosted anywhere yet, until I can somehow relink 7 years of stuff.

[DieselSJ]

Dang, would love to see this. Have gone through 4 rebuilt units before I got one that worked correctly. It has a small leak around what appears to be a plastic plug on the upper front of the unit though. I really do not want to pull it and go through the hassle again. Wondering if there is a seal on that plug that can be replaced while in the vehicle?

[BR3W CITY]

Alright guys, I found most of the old pics and got the re hosted. I did my best to get the right images put back into the right parts of the original posts for continuity sake. Hope this helps some of you out. Please let me know if anything is out of order or if you have any questions. A few images are missing, and may not be recovered.

[DieselSJ]

Pics are a bit big...lol.

Can you post a link to your imgur page?

[BR3W CITY]

I think this should be the link to those pics, they are in their own album. I'm not used to Imgur yet though.

http://imgur.com/a/sbspX

[DieselSJ]

Awesome! Yep that link works great.

Question - when looking at the front of the booster, right above where the master cylinder mounts, there is what appears to be a white plastic plug. Does the kit come with a seal for that? Do you know how that plug is removed? That is where mine is leaking from.

Thanks so much for sharing!

[BR3W CITY]

This help?

[DieselSJ]

Originally Posted by BR3W CITY

This help?

That is awesome. Thank you!!