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Vanco Hydroboost Brake Conversion

NOTE:  This conversion alters one of the safety devices (the brakes) on your vehicle.  If you should decide to undertake this conversion, it should be performed by personnel who are competent to conduct such alterations to a vehicle.  This conversion can result in changes to your vehicle's handling and braking ability.  This is not a step by step set of instructions on how to do it, but rather a summary of the various things I did to accomplish my conversion.  Any similar conversion work performed on your vehicle is done at your own risk.  If in doubt, consult the services of a professional. 

I had been running 35" tires for a number of years now and I always wondered just where my braking really was in comparison to a stock TJ.  It has been years since I drove a stock TJ and trying to recall what it felt like just wasn't working.  A couple of years ago, I installed Grand Cherokee disc brakes on my D44 rear axle and put Performance Friction pads on my front calipers.  I also replaced the factory front rotors with good quality Autospecialty Premiums when I installed my Warn hub kit.  I had done about all I could to make my TJ stop reliably given the circumstances. 

My meeting up with the folks from Vanco Power Brake Supply was kind of a fluke.  I got an e-mail from one of the employees (Bree) who asked if I might have some off-road pictures.  That led to more e-mail exchanges and I finally ended up talking to Vanco about upgrading my braking system.

The Hydroboost is a hydraulic booster that replaces your factory vacuum booster.  The booster is that big round thing that is bolted to the firewall on the driver's side of the engine compartment.  When you press the brake pedal, the booster amplifies the pressure you generate and applies it to the master cylinder.  As you know, the master cylinder pushes brake fluid to your front and rear brakes to stop your vehicle.  Whereas the factory booster receives its operating power from the engine's intake vacuum, the Hydroboost relies on hydraulic pressure and flow to make it work.  For the TJ, we reroute the output from the power steering pump and use it to power the Hydroboost and still handle the power steering demands of the vehicle.  This increased demand means the pump gets upgraded too.

Vanco has done CJs and YJs for a number of years but has had limited experience with the TJs.  To be truthful, my first attempt at getting the Hydroboost to work in my TJ yielded less than the expected results.  It worked but not as well as I hoped.  I had installed a higher capacity power steering pump along with the new booster and master cylinder.  By this time, I was working directly with Van himself and he was doing everything he could to help get things working on my TJ.  Van immediately sent another system (hydroboost and master cylinder) after we exchanged information about how it was performing.  The second unit performed worse than the first and I was baffled as to why things were not working.

I spoke with another Jeeper who had recently installed the Vanco setup on his TJ and he was completely satisfied with the results.  I spoke with Van again and updated him on the situation.  Blaine Johnson, my friend in CA who had helped with my rear disc conversion and rear shock relocation, had done a couple of booster installs and I talked with him a bit about what I was experiencing.  At some point, Blaine and Van hooked up to exchange ideas and comments.  After a lot of discussion, it was decided that I was suffering from low power steering fluid flow to the hydroboost (which we later determined was true).  What we didn't know was that there was a manufacturing defect in the second master cylinder I had tried, a brand new Wagner unit.

By this time, Van was pulling out his hair and I was feeling pretty down in the dumps.  I had put my stock pump and factory booster back into the TJ so I had a Jeep to drive again.  In the mean time, Van made arrangements to drive to Phoenix (he lives in CA) with a trunk full of parts in hand.  Toys by Troy had installed a couple of the Hydroboost units too and their results were mixed as well (some really good, some just average).  Troy donated some space in the shop and I met up with Van on a Monday to work on my TJ.  I took Tuesday off from work just to be safe and to help Van with an XJ install assuming we got my brakes working on Monday.

The time between my second install and Van' arrival at Phoenix, he had some lengthy discussions with his power steering pump supplier.  To make a long story short, the high flow pump that I got for my first install wasn't flowing enough fluid.  When that same pump was hooked up to the second Hydroboost install (with the defective master cylinder), it simply made the situation worse.  No wonder install #2 was the pits. 

Van arrived in Phoenix on a Sunday and I met him at Troy's shop bright and early on Monday.  The third install worked like a champ!  Another pump with verified flow specs was installed in my TJ.  We took a new 3/4 ton Hydroboost and new Wagner master cylinder and attach them to the new pump.  The results were better than I had seen to date but we were still not quite there.  Troy had loaned me his brake pressure gauge kit when I had started this project.  After each install, I would check the front caliper line pressure to see how things were shaping up and take the vehicle for a couple of test drives.  Van decided we should try a beefier Hydroboost.  Out came the 3/4 ton booster and in went the 1 ton unit.  A quick bleed of the power steering system and we were ready to look at the pressure gauge numbers.

"Houston, we have brakes!"  Oh yeah, finally I was seeing the results that Van kept telling me I would see.  It was great.  TJ Hydroboost brakes feel so much different than vacuum booster brakes.  The first thing you notice is the firm pedal.  It moves ever so little to apply the brakes.  I let several friends that happened by Troy's shop take a test drive.  They were totally impressed with the way it stopped.  The best comment was "Oh, that is what brakes are suppose to feel like!"  The 1 1/8" diameter bore on the master cylinder is larger than the factory master cylinder.  If one simply attached a bigger bore master cylinder to the stock vacuum booster, you would actually see a decrease in brake performance.  However, when the larger bore master cylinder is coupled with a higher pressure booster, you will see more pressure at the calipers (along with less pedal travel and effort). 

Anyway, before I get into the install procedure, I just wanted to relate my experiences in getting this project completed.  A very big thanks to Van for the unending support and effort he expended to help get my install problems resolved.  I learned a lot during this process and I know that Van will apply this experience to his 20+ years of doing brake systems to produce an excellent and reliable TJ Hydroboost kit for everyone else to enjoy.



OK....to the install details.  When the box from Vanco arrived, I pulled everything out to have a good look see.  The master cylinder was already bolted to the hydraulic booster.  Two AN-6 terminated high pressure hoses (one goes from the power steering pump to the booster and the other goes from the booster to the steering gear box) are included with appropriate adapters.  The remainder of the kit consists of several feet of pre-cut low pressure return hose with a "T" fitting and hose clamps and a pair of pre-flared 3/16" steel brake lines with appropriate fittings. 

The hydraulic booster puts an additional demand on your power steering pump.  Since I was still running the stock pump, I upgraded my pump to a 1500 PSI unit that flows about 3.4 GPM of fluid.  Vanco also included an in-line power steering fluid filter to be used with the new pump.  The install instructions from Vanco was written for pre-TJ vehicles but I knew that before the box of parts arrived.  With only a few hoses to attach, it wasn't difficult at all to figure out what went where. 

The first step of this project was to get real world data that could be used in the "before" part of our project.  Remember, this project is suppose to help me get back to stock braking performance (or better) and I wasn't going to be happy with a "it sure feels better" kind of comment when all was said and done. 

MikeW came over on a Saturday morning and we headed over to the west side of the valley where some freeway construction provided us with a dead end asphalt 2 lane highway.  Such a road would be perfect for doing some 60 MPH deceleration tests.  So, with video camera in hand, we jumped in the TJ and headed off to do some "panic stops".  The last three stops were the best (it took me a couple of times to get the feel of mashing the brake pedal for all it was worth) and yielded distances of 147, 138, and 136 feet.  In contrast, the first stop was right at 180 feet.  There was approximately 5 minutes of time between each braking period so I don't think we saw much in the way of brake fade, etc. due to heat build up on the rotors.

Next, I wanted to see just just how much brake line pressure I was getting before I changed anything on the TJ.  I wanted to see just how much force was being applied to my front calipers.  With the engine at idle (max vacuum for the stock booster), MikeW pushed the pedal to the floor a few times and we were able to record 2000~2100 PSI as max pressure at the front calipers.  With the last of the pre-project number gathering out of the way, it was time to get on the actual installation.

Note:   Since my install, I've been able to test a couple other TJs to see what kind of pressure their stock systems were generating.  An '04 automatic equipped model came in at 1500 PSI and an '00 automatic was putting out 2000 PSI.  In contrast, the '91 XJ that Van and I did an install on measured just 1100 PSI with the stock booster.  The single diaphragm vacuum boosters of that era do put out less pressure than the dual diaphragms used in the TJs. 

MikeW and I decided we needed a break from my 8" lift so we drug out the floor jack and got busy.  We removed both front tires and lower the axle down onto the shortest jack stands I had in the garage.  While not perfect, it was much easier to reach in to the engine compartment.  In fact, the milk crate I stood on last week, while replacing my water pump, was just about the right height now.  With that out of the way, we made some work space in the engine compartment by removing the radiator overflow container and the windshield washer reservoir.  With them removed, access to the power steering pump was much easier.

For complete details on how we performed the power steering pump replacement, see this write-up.   If you already have a 1500 PSI, 3.5 GPM rated pump, you won't have to worry about upgrading your pump to meet the increased demands from the Hydroboost.

NOTE:  Since this write-up was done, now a year ago, I recently installed a new pump with a remote reservoir.  If you are replacing your stock pump with this configuration, check out this write-up for details on how I did mine.  Obviously, the information provided in this write-up in regards to hooking up the return lines to the stock reservoir will be different.  The write-up for this new pump installation includes that information.


In addition to the steps outlined in the PS pump write-up, the pic above (taken below the driver's side headlight, on the inside of the frame rail) shows the high pressure line on the steering gear box that is removed and replaced with a hose from the kit.  The factory hose that originally connected the pump to the gear box is not used.  Take the hose and stuff it into a plastic bag (the one that the new pump came in would work just fine) and keep the hose on your parts shelf.  Some Saturday afternoon, when the dealership parts counter is closed, your buddy will call you and ask if you still have that old hose (because his started leaking and he has a night run coming up in just 2 hours!). 


One of the supplied AN-6 fitting adapters is inserted into the steering gear box.  This adapts the new hose to the steering box.  Of the two supplied hoses, you will be using the longer of the two hoses for this connection.  The other end will be connected to the hydraulic booster's output port.  While you are down here, you will notice that the low pressure return line (the other fluid connection on the steering gear box) goes up to the reservoir on the power steering pump.  Remove the hose clamp and then the low pressure hose from the steel section of the steering box's line.  You will later replace this return line with that provided in the kit.


After the power steering pump was installed, we turned our attention to the removal of the factory booster and master cylinder.  The picture above shows the connection of the booster rod to the brake pedal (taken from under the dash).  I had removed the small metal clip that kept the booster rod secured to the brake pedal when I snapped this picture.  The booster rod can be moved slightly to the right and slipped off of its mounting point on the brake pedal.  There are four bolts that surround the pedal rod where it comes through the firewall.   Once you have removed the lines from the factory master cylinder and disconnected the prop valve mounting bracket, these nuts will be removed and the vacuum booster can be removed from the firewall.

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