Chevy Hydroboost possible issue?

[wander2039]

Anyone with know how when it comes to Chevy Hydroboost brakes? Got to say the RV on a 04 Chevy Express 3500 chassis isn’t liking Alaska one bit. It’s throwing curveballs out of no where.

Ever since we got it 11 years the brake pedal has always had maybe 1/4 of play before the brakes started activating. On average I’ve changed the brake fluid every two years and suck out the ps reservoir every oil change, lately with Dex VI. Nothing changed it just thought that’s how it was since it stopped fine. The ps pump does sounds awful though. And it was low after this.

I’ve had a couple abs activations prior to this due the frost heaves but in Anchorage I really had to lay on the brake in traffic. Since then there’s no more play in the brake pedal.. it’s on and right now! I’ve checked temps and nothing is dragging. I don’t mind it except the pedal is squeaking now, guess due to the new location on the pins or bore.

So did it finally bleed itself after 100k? Or is there an issue I’m overlooking with this type of brake? At 110k wouldn’t think this old dog would have new tricks.

 

[Snagglefoot]

You really should be using GM power steering fluid, not Dex VI. Screen shot attached. I would suspect your issues are with the master brake cylinder. It can be removed and replaced quite readily. I did that on my 2008 Chev Suburban 3/4 ton with the hydro-boost system.

I have 260,000 miles on my hydro-boost unit. If you do replace the master brake cylinder I recommend new GM hydraulic hoses. I found they need to have the proper bends where they attach to the power steering pump and hydro-boost unit.

 

[c502cid]

Rock hard brake pedal is a done Hydroboost unit. I agree with Snagglefoot on fluid and hoses. I'd replace everything though. P/S pump, hoses, hydroboost unit, master cylinder.

 

[BrendanC]

i work on a fleet of these trucks and have owned 3. hard pedal could be a dying pump or booster. test the booster by getting up to about 15 mph on a straight safe road then shut the engine off. the accumulator on the booster allows for one powered stop after loss of pressure. if this doesn’t feel right replace pump and booster. try to get atleast gm rebuilt parts. also as already mentioned. ONLY and i mean ONLY use the GM power steering fluid. it makes a massive difference and won’t foam. change every 2-3 years.

 

[wander2039]

Well that’s not what I wanted to hear 4k miles from home! I did run power steering fluid for a couple years but didn’t notice a difference.. don’t think it was GM fluid though. When and if I get home I’ll plan on ordering everything and replace. Easier than on the on the road as I see it. With the new random misfire and overheating when I turn on the heater starting question if it time for an upgrade.