Hydroboost

[GloNDark2]

I had a hell of a time bleeding both the power steering and the brakes on my WH MOAB system.

There is a video I watched from AGR that worked very well for me. It took forever to get a good brake pedal out of it but it's awesome now.

https://www.youtube.com/watch?v=AMV_x9WEoqY

[CityHick]

Thanks, that's a whole lot more "cycling" than what I've done. I sure hope I don't have to open this system back up anytime soon... I will get back out there soon and play the silly game of cycling the steering and brakes for what will feel like an eternity. haha. If nothing else it confirms my suspicions that there's air in the system.

[GloNDark2]

Thanks, that's a whole lot more "cycling" than what I've done. I sure hope I don't have to open this system back up anytime soon... I will get back out there soon and play the silly game of cycling the steering and brakes for what will feel like an eternity. haha. If nothing else it confirms my suspicions that there's air in the system.

Right?? I've done mine twice now because I had to redo the fitting on the back of the power steering pump. What a pain.

[CityHick]

I went through the process from the linked video and I am convinced that I got all of the air out of the power steering/hydroboost lines. I still had poor-to-nonexistent braking performance even after bleeding the brake lines again. When I got back into the garage I pumped the brake pedal several times to see if I could feel brake pedal pressure building. I could, but on the last pump, the pedal went to the floor and stayed there.

My first thought was that I'd blown a wheel cylinder, but there's no brake fluid on the floor, no leaks to be found, master cylinder fluid levels had not changed. I pulled the master cylinder off again and went through the process to bench bleed it, expecting that perhaps there would be no return spring pressure, perhaps a failed master cylinder. I have plenty of resistance in the master cylinder, it feels exactly the same as it did when I first bench bled it, so I am pretty sure the master cylinder is okay.

This leaves me with one conclusion, that I received a bad hydroboost booster out of the box. It is as if the push rod is not compressing the piston inside of the master cylinder. I don't know what else to think at this point. I will be placing a call to Wild Horses on Monday to discuss my experience and hopefully identify and solve this problem. I am getting pretty frustrated, and trying not to drift towards dark thoughts about the quality of this kit.

Interestingly the first time when I called to ask questions about this kit, I was told that the booster is a Bosch unit off the shelf, but they could not or would not tell me what the application for the booster is. On my second call I was told that the booster unit is a hydratech booster and isn't necessarily an OEM off the shelf part.

I am holding back my usual thoughts about the quality of auto parts these days.. and as there's nothing I can do about this, I am trying to do anything other than think about my bronco today...

[stock74]

Not sure if this is the cause. Could it be that the master cylinder piston is not engaging all the way when installed on the hydro boost? Have you confirmed the correct “bullet” (spacer) is installed in the master cylinder? Also maybe the piston hydro boost unit that pushes on the master cylinder is not adjusted correctly?

[CityHick]

The bullet is installed as required. I don't see any way to adjust the hydroboost unit or piston. I'll take another look but I don't see anything that I can do about any of this. The pedal to the floor issue, and how it suddenly started, has me the most concerned.

[stock74]

Not sure if all of the hydro boost units have an adjustable output piston. I have seen some that are threaded and use a jam nut to lock it in place. How is the power steering working? Is it difficult to turn the steering wheel? Any noise from the power steering pump? It took a very long time to bleed the air out of the power steering on my Dad’s bronco with hydro boost. Sounds like you got it all out though. Sounds to me like it is an issue with the master cylinder not engaging or air in the brake lines. Also if you still have drum brakes; are they adjusted correctly? If they are too loose you could see similar symptoms. If you have ruled all of that out then it might the hydro boost.

Hoping mine goes more smoothly. I have the hydra tech system from Duff. It is installed but waiting to finish the new plumbing and wiring now that the engine is installed.

[CityHick]

The power steering is working the same as it did before adding the hydroboost unit. There's no noise from the pump, and the fluid doesn't have bubbles in it when running (it did before).
I do have drum brakes in the rear and they're adjusted properly. I should restate that I had plenty of pedal pressure while pumping the brakes in the garage right up to the point where the pedal went to the floor. I agree with you it would seem that there is air in the brake lines but after bench bleeding the master cylinder (twice now) and running more brake fluid through the system than I've ever done before, I can't imagine that I am still fighting an air problem in the brake lines. I am going to call WH sometime today when I get the time. Thanks for your input.. your thoughts on this matter match what I've come up with. I should also mention when I separated the master cylinder from the booster, there was a small amount of fluid in there. I am not certain which fluid it is.

[country_boy_72]

any updates? I am looking at installing the same system pretty soon, had a old hydro boost from a Astro van that worked okay ish. would blow fluid out of the hydro unit when it got hot. I am hoping the Moab is a good upgrade we shall see.... wish you luck on figure your issue out I would suspect the master cylinder as well.

[CityHick]

I am trying not to let my frustration guide my answer here...

I spoke with Wild Horses earlier in the week. They agreed to send me a new hydroboost unit given that I described my situation given that I removed the master cylinder and re-bled it, reinstalled it and still had the issue of the pedal going to the floor and not coming back. The master cylinder had plenty of return pressure at least on the bench, but still no return pedal.

The new booster came, I installed it, went through the procedure to re-bleed the system, regained the expected function of a brake pedal that returns back from being depressed. But still, no front brake pressure. Rear brakes lock up with authority, fronts not at all.

Fast forward to today - I had some help. Figured two sets of eyes and two brains might come up with a new conclusion. We re-bled all 4 brakes, rears continued to brake like never before, fronts not so much.

So... I removed the master cylinder (again) and sent it north with my helper who lives closer to Lodi than I do. I am going to call WH to discuss the situation on Monday, and hopefully get a replacement master cylinder coming back this way soon. They will receive my suspected bad booster and my master cylinder after we speak on Monday.

I am frustrated; I do not want this to turn into any kind of vendor bash; I can understand WH's perspective that I may be unique in having bad parts come to me, and my pragmatic nature believes that there's a possibility that I did something wrong to cause at least some part of this problem, but I cannot imagine which part of it I could have caused. For now I am ruling this as bad luck. I will update again once I have resolution.

This has been about the biggest pain in the ass I've dealt with in the 16+ years I've had my bronco.

[pippinmader]

Wow, what a bummer! I am no expert, but as I understand it the brake feel on a hydroboost system is based on pressure in the rear brake circuit. Are you still using the stock bronco proportioning valve? Could there be an issue with the valve that is making it work weird? For what it is worth, I eliminated the stock proportioning valve and just added a wilwood pressure regulator for the rear. Hope you get to the bottom of it soon!

EDIT: I see that your FANCY Moab system comes with a new proportioning valve and related wizardry - I would definitely look hard at that part of the system...
https://www.wilwood.com/PDF/DataSheets/ds715.pdf

[CityHick]

There's a new master cylinder heading my way this week. The wilwood proportioning valve would be the only remaining thing to look at should the new master cylinder not solve these problems. I'm not going to spend the brain cycles on the proportioning valve topic until after I install the new master cylinder (maybe today).

For what it is worth, the proportioning valve instructions say to start with the valve all the way out, and gradually tighten it until you get the rears to lock first, then back it off until they do not lock first. One of my tests was to tighten that valve down further and further and I did notice that the rear brakes were locking sooner, but I never got the fronts to even engage, at least not to the point where they were doing anything. So, the "adjustable" aspect of that valve clearly does work. From my understanding, the front lines just "pass through" and are not affected by the knob.

[904Bronco]

Tony, I am sorry that you are having to jump through these hoops...

Upgrades are supposed to be easy, especially since you bought a kit and didn't source parts from various sources. Keep working through it... Hopefully, WH's has been supportive.

[CityHick]

It has been a process, though WH is doing the right thing for me. I don't want to cast WH in a bad light over this, they just happen to be the intermediary between me and whoever manufactured these parts.

I am trying not to kick myself too hard over my decision to spend a little more in the interest of simplicity, to have this completely backfire on me in this manner. This could have happened had I gone the other route. What frustrates me the most is that I've not identified any clear smoking gun, root cause. but hopefully that changes here shortly.

[CityHick]

Some followup for anybody who may be interested.

The first problem appeared to be a bad hydroboost unit. Wild Horses sent a new one to me and it no longer displayed any of the symptoms of the first one.

The second problem seems to be not so simple. I went through many gyrations trying to get the brakes to work as they should, and was never able to get consistent pedal pressure. Wild Horses exchanged my Wilwood master cylinder for a new one. I bench bled that master cylinder, installed it, bled all brake lines and while I definitely noticed improvement (I can build pedal pressure and can come to a screeching halt with the rears locked up and tires smoking), but the front is still not locking up. There's not enough pressure going to the front brakes somehow.

Frustrated, I called Wilwood directly today and described my problems. I then stepped through a couple of exercises for them and they recommended that I install a 10lb residual pressure valve on the rear brake line. He states that the wilwood master cylinder that I have does not have one built-in whereas my previous OEM style master cylinder likely did. He came to this conclusion after hearing me tell him that (with the engine off) I have to pump the brakes 3-4 times to build pressure. After describing the extensive amount of brake bleeding I've performed, air in the lines is extremely unlikely and perhaps we just need to hold more pressure on the rear circuit at all times.

Long story short, I have a residual pressure valve coming to me from Summit; it should be here on Friday. If this ends up solving my issue, then I will be calling Wild Horses with this feedback, that the residual pressure valve might be needed for broncos in my configuration.

I will certainly update again with my results from this additional step!

...fyi I ended up buying a reverse brake bleeder tool today and I really like it. Thanks for the recommendation earlier in this thread!