Hydroboost help

[Frankie]

I do believe I have an issue with my hydroboost system, maybe, well we'll see. Unit was replaced roughly 8 years ago when peddle went to the floor and had zero and I mean zero brakes. Fast forward to 2 weeks ago, pedal went almost to the floor again. Checked brake fluid and rear reservoir was almost empty. Filled and checked for leaks and found none. Brakes returned to near normal with some intermittent pedal bounce. This past 4th while pulling a car in a parade the pedal went to the floor and had maybe 10% brakes. Enough to finish the parade and get home with lots of down shifting and long slow stops. Checked all fluids and they are full. No leaks. However while driving before the parade and slowing down for a turn the brake pedal got hard, very hard to push and the steering almost refused to turn. Almost like when you an engine cuts out and you lose everything. It came back after several seconds and was fine until it fully failed. I find that symptom very odd.

Best guess that the booster went out again. But could it be the ps pump? Although steering is fine at this point. Pedal will not pump up when not running either, won't build pressure. Just looking for ideas before I dish out the money for a new booster and labor. This is on an '89 (most parts are 87 which is why I am here) R3500, dually crew.

 

[bucket]

Sounds like the booster has issues, possibly a failing master cylinder as well. That missing brake fluid went somewhere.

It also sounds like you haven't had the best luck with hydroboost, lol. Was this last one a reman unit from the parts store?

 

[Nonstop]

Did you ever replace the master cylinder? That would be my first concern. Whether or not you have a working hydroboost, the brakes still should work. Reading into the post, it sounds like the master MAY have been the issue the first time (the fluid went somewhere and no leaks) but was never replaced. On top of it, you now have a bad hydroboost or pump. If you replaced the master cylinder, then I am wrong!

If it’s a parts store hydroboost with a lifetime warranty, might as well replace it if it will be free! If not, I would consider digging deeper in case it is the pump.

 

[highdesertrange]

yeah a bad hydroboost does not cause the peddle to go to the floor or the fluid to disappear. highdesertranger

 

[shiftpro]

If you slam on your hydro boost brakes and go through the windshield, they are working properly.

Here's some good info..
https://www.scribd.com/doc/6829161/Operation-Diagnosis-and-Repair-of-HYDRO-BOOST

 

[trukman1]

I had the same issue and a mechanic told me the bore in the master cylinder was worn and piston would sometime stick, fluid would bypass piston and walla, no brakes. Then brakes would come back. Went through three rebuilt masters before saying the heck with that and purchased a new unit. Problem fixed and lesson learned. I will never buy any rebuilt brake parts again.
My symptoms sound like yours, no leaks was the key. Mechanic new it had to be internal fluid bypass issue. Said he was sure it was the master cylinder and he was right. I'd try that first, at least that solved my issue and seems eerily like your problem.

 

[Mr Clean]

I have to agree with everyone here. I only run Hydro-boost on my trucks, like everybody has said it's your master cylinder. Like Trukman1 said don't buy a rebuilt, buy new... it is your life, and everyone else on the road

 

[idahovette]

Always new ---- brake parts and water pumps!!!

 

[MrMarty51]

What year is this hydroboost on ? My 2000 K3500 has an electronical controlled pressure valve. steering gets hard sometimes. I was told to remove that electronic controlled valve and replace it with a regular valve from an older unit.

 

[SquareRoot]

electronical

That's a new one.