Been sort of quiet around here lately, mostly haven't done any Jeep stuff besides the last week or so. The flywheel swap was done back in December, and then it got too cold to drive. Plus the brakes still needed attention anyways.
Starting to warm up outside again and so it's time to dig back into the YJ and deal with what's left. The biggest issue at this point is/was the brakes. Not going to go over the history, but the brakes are back to stock as of a few years ago. Stock size reman booster, new (sat a few years on the shelf) Raybestos master cylinder, and new calipers and lines/hoses.
Keep in mind I have not driven the YJ in years, besides the short around the block test drives. The brakes were nearly nonexistent. I could stop, but barely. I had to push the pedal all the way to the floor to stop on my slanted driveway. I started to investigate and found a few things:
- Raybestos MC was leaking fluid out the back
- Reman booster pushrod was adjusted too short - measured with a booster pushrod adjustment tool
- Reman booster didn't seem to be built correctly, the pushrod piece was able to easily pull out, unlike other boosters.
SKP is now offering brand new boosters for the stock application, so I decided to pick one up, along with a Centric stock master cylinder on RockAuto. The parts arrived and look good. The SKP booster appears to be nice quality. It's very similar to stock, and a bit different in some areas. Overall fitment was good, quality seems solid.
I painted the MC, due to them being well known to rust. My paint job is not pretty, but it works. Mainly just wanted to keep it from turning rusty brown. I knew that as soon as my brake fluid covered gloves started touching the paint, the paint job wasn't going to be perfect anyways, so just the fact that it's covered in paint is good enough to me.
New booster:
The SKP booster comes with a boot on it that does not work for the YJ single diaphragm booster application. The rubber boot that comes installed is more for applications like the dual diaphragm boosters in the 1995 4.0 YJ or any of the TJs. The single diaphragm booster in the 87-94 YJs uses a plastic guard that slides over the booster tail housing, and butts up against the firewall.
I removed the plastic guard from the reman (which came from my original stock booster), and installed it onto the SKP. I don't have any photos of mine, but here is an example from eBay. Essentially, the booster has a felt pad as an intake filter on the pedal pushrod. The guard goes over the pushrod and slides onto the tail end of the booster, and compresses the felt filter to hold it in place. The guard then mates up to the hole in the firewall to keep the guard secure.
I removed the ACDelco reman booster and installed the new SKP. Things were uneventful for the most part. The booster went right into place and hooked up without any drama. The brake light switch did need slight adjustment. The brake lights were on all the time until I adjust the switch closer to the pedal. All is good now.
The master cylinder pushrod was a bit weird. The pushrods on all boosters including stock are adjustable. They usually have resistive threads so that the adjuster doesn't unthread and create a gap between itself and the MC, or so that it doesn't thread outwards and push against the MC. The problem with the new booster is that it used a jam nut to secure the adjuster, and that doesn't work. The threaded sleeeve is longer than stock, putting the correct place for the adjuster with the jam nut, to be basically all the way threaded in. Well, then there is no way to secure it. I removed the jam nut and secured the adjuster with Loctite 609 on the threads. The green stuff. Should hold well. I adjusted the length using a brake booster adjustment tool. Hopefully that makes it idiot proof for getting the length correct.
I bench bled the MC and installed it. Then allowed the calipers/wheel cylinders to gravity bleed. Doing a pedal test, the brake pedal feels MUCH more normal now. It is still relatively easy to get the pedal to the floor if I push hard on it, but I think that's normal? It's been a long time since I had stock brakes.
Planning to fire it up this evening and go for a drive around the block and see how it does. I can keep tinkering with bleeding and such if needed, but at least I think the booster and master cylinder can be left alone at this point. In reality, the only unknowns at this point are how the pedal will feel once the booster is boosting, and if the brakes work "properly", meaning the ability to lock the wheels at speed.
