84 GMC 6500 "Hydroboost" Leaking

[nbkk43f]

Hi - this is my first medium duty truck and was purchased for hauling rock, dirt etc around the property.

The good:

Based on my research, the truck has a 366 or a 427 tall deck BBC and runs like a top, fires right up
The dump works great and there are no hydraulic leaks
5 speed with a two speed rear

Now with the bad - it has a severe leak at what appears to be the hydro-boost unit. No leaks on the inside of the firewall. This truck has a master cylinder, "hydraulic booster" of some sort and a brake booster - which I found odd. I'm not too terribly familiar with hydro-boost brakes, but find it odd that it has a brake booster in addition to the hydraulic unit - my 2013 duramax, along with other similar vehicles, just have the master and the hydraulic booster. Everything regarding the brake system in the 6500 looks factory...to me. As with most power steering pumps, it works great when it has fluid in it - but doesn't last long due to the leak. A few pics attached for reference.

I was thinking I would just rebuild the hydroboost unit, but can't really find much about it. The part number on the unit itself is 2623501 and doesn't appear to be an available item anywhere. The rebuild kits, where available and if compatible, are ridiculously priced and I've read in other places that it requires special tools to open up?

For those of you familiar with this unit, is it worth rebuilding if I can find a suitable kit?

This place in the link below may rebuild them, haven't called yet - but if there's a better bolt on option, I'd rather go that route.

DELCO DUAL POWER HYDRAULIC BOOSTER 2623501

DELCO DUAL POWER HYDRAULIC

www.powerbrake-drivetrain.com

Thanks in advance for any insight on the issue!

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[chevdude]

Had a 1 ton service truck with the hydroboost.
Had nothing but problems with it.
Even took it to a local gmc truck dealership and asked them to fix it.
Got charged good money only to be told that there is nothing wrong with it.
But there was nothing right about it.
I sold the truck.

 

[HotWheelsBurban]

I think many issues with the GM hydro boost units may be due to the system being improperly or not completely bled. I replaced the master cylinder on my C3500 Crew Cab back in April, and the system would not bleed properly until my neighbor and I did the correct procedure. If the front of the truck is jacked up until the wheels are off the ground, it will be easier but it's still time consuming. You have to run the steering wheel through three complete lock to lock turns, then pump the brakes; wash rinse repeat until you quit getting big bubbles out of the master cylinder. Technically the hydro boost is "not" part of the brake hydraulic system, but doing this process is the ONLY WAY we got it completely bled. It took several hours, and we'd switch off periodically (he'd watch and I'd crank the wheel, then swap) (he's a professional mechanic and very good at brake service).

 

[Trucksareforwork]

I think many issues with the GM hydro boost units may be due to the system being improperly or not completely bled. I replaced the master cylinder on my C3500 Crew Cab back in April, and the system would not bleed properly until my neighbor and I did the correct procedure. If the front of the truck is jacked up until the wheels are off the ground, it will be easier but it's still time consuming. You have to run the steering wheel through three complete lock to lock turns, then pump the brakes; wash rinse repeat until you quit getting big bubbles out of the master cylinder. Technically the hydro boost is "not" part of the brake hydraulic system, but doing this process is the ONLY WAY we got it completely bled. It took several hours, and we'd switch off periodically (he'd watch and I'd crank the wheel, then swap) (he's a professional mechanic and very good at brake service).

I just took a normal hydroboost apart and replaced a master cylinder at the same time.

I’m thinking you HAVE to be referring to bubbles in your power steering fluid (not master cylinder). There is zero way for bubbles to be caused in the brake master cylinder from turning the steering wheel lock to lock.

Your friend did you a solid but seems to have not explained it. Here is the hydro boost bleeding procedure from the Chevy service manual.

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