Overdue Hydroboost Brake Conversion Write up

[speaceman]

For the most part, there isn't anything the TJ guys, or even other ZJ/XJ guys on this board haven't done that is bigger, stronger or crazier than what I have done on my ZJ. Nevertheless, there is one buildup on my jeep that I can tell everyone about and some of you might actually be interested in it.

I was talking to Blaine awhile back and he related that he didn't know that I was happy with the brakes on my ZJ. I agree that I really haven't done a good job of letting people know about the braking system we ended up with on my ZJ. How we ended up with this system is part of a long, frustrating, and annoying story that primarily deals with me being the only ZJ in the world with an ABS computer that lost its mind once the tone rings were gone and specialty brake stop in long beach. But my pain, is your gain....

Anyway, here it goes.

We ended up ripping out the stock booster and master cylinder. In it's place, we installed a corvette master cylinder with a hydroboost booster. The hydroboost is run by your power steering pump. It stops the jeep really well. Locking up on road is easily accomplished. Further, the brakes offroad will easily hold the jeep, even in 4-low, even down hill in reverse. Stopping is not an issue with this system.

The pros of this system are as follows:
1. It stops. Well. You can lock up 33 inch MTRs at half pedal pressure at driving speed. I forgot what amount of pressure the hydo boost system puts out, but I think it was well over 1200 lbs per inch measured at the end of the line (ie the calipers).

2. You do not have to change any braking componants other than the master and the booster. You can leave all your stock calipers and lines in place.

3. It is afforadable. $717.50. I will list the final price of all parts below along with a parts list.

The cons of the system are as follows:
1. You end up with two systems you have to make sure to bleed right. You have to bleed the brakes, as well as your power steering system. Neither of these are super tricky, but if you don't do it right, you will not have good braking.

2. The hydroboost taxes your little stock steering pump. This can be aleviated by building out the pump or getting a bigger pump. I had shims removed so that the pump put out a higher rate of flow. Plus, you can install a power steering cooler which helps a lot.

3. The pedel feel of your brakes will be changed. The hydroboost is much stiffer. There is no squish like there is with a pneumatic booster. If you are the type of person that is bothered by stiff pedel feel, take this into account.

For me, the Pros, especially the fact that the jeep stops really well, far outweigh the cons. I just wanted everyone to know what they were instore for if they do this conversion


The intall is relatively easy, if you know how to bleed brakes and power steering correctly.

The install goes as follows:

1. Purchase parts:

Hydroboost $375 (Vanco Brake Supply 213 563-1588)

Corvette Master Cyl (any brake or parts store)$60.51

P/S metric o-ring conversion fitting (for hoses) $25.80 (Lee Manu 888 698-6679). You need two 18mm -6 fittings and two 16 mm -6 fittings.

5 or 6 feet of medium pressure hydralic hose with three 90 degree fittings and one straight (may be different for your jeep) $56.19 (Orme Brothers 818 885-1414

Rebuild P/S pump for max output. Sorry, I couldn't find my invoice for this. It cost $110, but Blaine might be in line to getting a stronger pump than what I ended up, which would improve braking even better. I'll post if I end up with it.

P/S cooler $68 (with fittings) form Baker Precision in Long Beach. (You can get a smaller and cheeper one from anywhere, and I would recommend doing so on a ZJ since there is little room in front of the radiator).

Misc parts, such as a t junction and the recycle line on the P/S system and hose clamps $30 max.

That's everything. The grand total is $717.50

2. Install.

Remove brake lines from master cylinder. Remove high pressure P/S hoses from pump and steering box. Leave recycle lines in.

Remove stock master and booster.

You will need to bore out the holes in your firewall that the booster mounts too. The hydroboost has slightly thicker studs. You may also have to make one or two metal shim plates to angle the hydro boost up to match your stock booter angle. This helps a bit with the pedal feel. You can look at mine to see what I am talking about.

Mount hydroboost and new master.

Remove old P/S pump. Carefully install resovoir tank on new P/S pump. Install new P/S pump, with tank

Install fitting on output of P/S pump and intake of hydroboost. Install fittings on output of hydroboost and intake of P/S box

Assemble P/S hoses, cut to length, determine directional placement of 90 degree fittings.

Install p/s hoses. 1 goes from P/S pump to hydroboost. 1 Goes from hydroboost to steering box.

Install P/S cooler

Install extra recycle line from hydroboost. Use t-junction to join it with the steering box recycle line. Run both into cooler and cooler back into the resevoir of the P/S pump.

Bleed brakes, then bleed P/S. (This you'll have to aske someone else about, because I'm still not good at either).

Finally, I HIGHLY recommend performance friction pads for the front if you don't already run them. Plus, make sure you change your front and rear pads at the same time as doing this install. It will help even out your breaking and helps a lot with pedal modulation and stopping.

_________________________________________

That should be everything. I don't think I left anything out. The above may seem like a lot of steps, but most of them don't take much time. Assembly of the hoses is about 15 or 20 minutes. Cutting them to lenght is the hardest part about that step. And removing everything isn't hard or long either. The steps that take awhile are the bleeding, and installing the hydroboost to the firewall. You have to contort to get to the 4 nuts that hold it in place and it can take awhile.

I'd say if you have all the parts together and had everything ready and you are a fairly skilled shady tree mechanic, you could probably do everything in 4-6 hours. If you are less skilled or slow, it will probably take you close to a whole day.

Feel free to email me with questions.
Shalom

[Bruce David]

excellent write up Shalom.

I need to do something with the brakes in the CJ and
this is one of the options I was considering.

My only concern is if you loose your power steering
pump, you loose your power asst brakes also.

Did you do any research on 'high performance' vacuum boosters ?

[Jeff Weston]

I don't know about Shalom's setup but I'd guess that it's similar to the factory Hydroboost brake setup in my wife's Mustang GT. After turning off the engine you still get a few assisted pumps. After that it's hard to press but you still have braking abilities.

[speaceman]

Originally posted by Bruce David
excellent write up Shalom.

I need to do something with the brakes in the CJ and
this is one of the options I was considering.

My only concern is if you loose your power steering
pump, you loose your power asst brakes also.

Did you do any research on 'high performance' vacuum boosters ?

I did a bit of expirementing and Jeff is right, if you lose the P/S pump (i turned the engine off), you get a couple of pumps and you are down to pure manual braking. The vehicle is stoppable, but distances are obviously increased and it is damn hard to slow down.

This is no different than the stock set up though(mine at least), since if the engine turns off, you lose your vacuum assist on the pnuematic booster and the same result occurs,

As for researching "high perfomance" vacuum boosters, that is how I ended up with this system. I got sucked into a big, expensive, and utterly frustrating situation with a specialty brake shop down in long beach. The guy had no clue and was supposedly building me out a larger custom pnuematic booster. Nothing ever worked right, and it kept getting more expensive, and everything he tried worked worse. (the system he built me stopped the jeep worse than a fully loaded 18 wheeler. NO JOKE. I had to stand on the pedal with all my might to gradually slow down for stop signs at 25 mph.)

So I can't say there isn't a solution out there for a "high performance" vacuum booster, but I can say that I didn't find it and that this system works pretty well, is way cheeper than what that guy is long beach was trying to charge me, and is fairly simple to install and keep track off maintenance-wise.

There were a couple of stages left out of the write up. For example, Blaine and I started using the stock P/S hoses and one from a 1971 GMC pick up or something like that, becuase we couldn't find the metric o-ring adapters to build our own hoses. It worked for awhile, but the stock hoses weren't up to the task and started ballooning and leaking. Blaine hooked me up with Lee Manu. for the adapters and Lee hooked me up with the Orhme bros. for the high pressure hoses.

They work much better. I have much smoother pedal feel, and better braking with them in.

Anyway. Everything in the write up above works well, and is the best choice out of the options I had. The only thing left to make better out of everything is to get a better P/S pump and even that is not a big deal. The built out stock one works fine for everything except long periods of rock crawling. I had no issues with steering lag and non at all with the brakes on the Rubicon, except for one section where I had a lot of tight turning and 3 point turns while doing heavy braking to control speed on rocks. The steering started to lag at that point and got heavy.

The nice thing abou the system though, is that the hydro boost is in line in front of the steering box, and so far, the brakes haven't suffered, even when the steering started to lag. I'll take crappy steering for a bit on a hard trail over crappy brakes any day.

You can drive the Jeep around next time I see you if you want to get a feel for the system. It might help you make up your mind

ps-- In case any of you are wondering, I would have never thought to take on anything like this myself. Thank you again Blaine for all the footwork on getting the parts together and for the install. Thanks also to Scott for the extra set of hands while installing the new hoses before the rubicon.

[Bruce David]

Shalom,
Thanks for the info.

I have a call into Vett brakes to see what they have to say.