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View Full Version : My Hydroboost to Vacuum boost Swap



toebee97
05-12-2010, 09:05 PM
Not sure if I posted in the right forum, but this seems pretty modified to me.

The Start
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1281

The hydraulic pump. We didn't really have time to take out everything, so I ended up leaving it for now. Just disconnected the power relay to keep from pumping Dot3 all over the engine compartment.
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1282

The original MC, Pressure Modulator, Pressure Accumulator, and Proportioning valve all came out in one piece, all we had to do was disconnect the brake lines from the Proportioning valve, uncouple all the power connections, and unbolt the four bolts on the inside of the firewall that hold the MC in place. Also had to remove the washer fluid reservoir for better access. Two screws on top hold it on. Make sure you mark which hoses and connectors go where if you have a rear wiper, otherwise it won't work right when you put it back together.
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1283

Removing the whole mess. Probably worth a bit in scrap, alot of heavy aluminum there.
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1284

Initial fitting of the vacuum booster. I scored this off Craigslist for $20, came with the proportioning valve and pushrod. Just had to get a one-way vacuum valve and about a foot of vacuum hose.
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1285

MC and Proportioning valve
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1286
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1289

Had to cap the front of the Proportioning valve, we forgot the first time we went to bleed out the system and things got a little messy lol. Also for some reason only the front right line from the Proportioning valve worked, so we decided to just cap the front left and just put a t-fitting in the front right line so it ran it to both front brakes. Then we bled out the entire system and put in new Dot3, and adjusted the rear brakes as well.
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1287

Finished. All the parts stores decided to run out of the one-way valve, so we just cannibalized the one on my buddy's S10 Blazer. A couple days later he called me to tell me he had one sitting right on top of his rollaway the whole time lol.
http://www.xjtalk.com/picture.php?albumid=156&pictureid=1288

We tried to re-use as many old lines and fittings as we could to minimize cost. I think the only thing we had to buy besides the MC/Booster was a couple fittings, and we rented a double flaring tool from Auto Zone for $30, and I got the $30 back when I returned it. Total cost was under $25, not including beer. :D

So that's pretty much it. It might not be the prettiest job, but it's a lot more functional than the old system. sorry I didn't take more pics, I kept having to remind myself to take some. If anyone has any questions let me know, I'll try to answer them the best I can!

LostSoul
05-13-2010, 02:20 AM
What did you have before? The new one looks like the single diaphragm? Did it stop better?

toebee97
05-13-2010, 04:51 AM
The old system was Bendix-9 abs. It's shown in the first few pictures. Horribly faulty system. Instead of a vacuum diaphragm it uses a hydraulic pump that runs fluid to the accumulator and pressure switch to provide power braking. It also has a pressure modulator or some crap. Everywhere I have read about it, people recommend getting rid of it in favor of a vacuum booster. It's supposed to be covered by a lifetime federal recall, but good luck getting Chrysler to do it. I even threatened to report them to the NTSA, and they still screwed me on it. And the parts are over $1000, even rebuilt. So I said screw it, and did the swap. I know I should have went with a 96 or newer booster, but I was on time constraints, so I snatched up that booster off a 86 Comanche. It was a screamin' deal, I would have been an idiot not to. It's only single diaphragm, but it has WAY more braking power than what I had, which was almost none. If I want to I can lock 'em up now, which I couldn't before. Plus, half the battle is already won if I decide to upgrade to a newer booster or a Grand Cherokee booster later.

toebee97
09-20-2012, 01:43 AM
So I figured I'd put this in my old thread even though I don't have the gray XJ anymore, just didn't want to start another thread about something that pertains to this swap.

So I just replaced my brake booster last weekend with a brand new one since the old junkyard one I put in to replace the Bendix ABS had a vacuum leak. Now the tranny won't shift into overdrive, rollin about 2500rpm at 60mph. Didn't mess with my kickdown cable or vacuum lines other than the big one that goes to the booster. All I did was unhook the little plastic bell at the end of the throttle cable from the pedal to make room under the dash for a ratchet. Anyone have any idea what I could have done to cause it?

cantab27
09-20-2012, 02:11 AM
where you been hiding mate.....

toebee97
09-20-2012, 09:23 AM
where you been hiding mate.....
I know I haven't been on in a while, don't have as much spare time since I started a new job 6 months ago.

Mudderoy
09-20-2012, 09:37 AM
I know I haven't been on in a while, don't have as much spare time since I started a new job 6 months ago.

Hope it's a good one!

toebee97
09-20-2012, 09:59 AM
It is... Driving forklift for Reser's fine foods at the Don Pancho tortilla warehouse, pretty good gig so far!

Sent From My G-Note

Mudderoy
09-20-2012, 10:55 AM
It is... Driving forklift for Reser's fine foods at the Don Pancho tortilla warehouse, pretty good gig so far!

Sent From My G-Note

http://youtu.be/KTnGZ37sZqM