Hydroboost question?

[92landyacht]

Back story is that, ever since I've owned my 92 Land Yacht, I've had very weak brakes. Since then I've acquired a 2001 GMC 3500 Savanna van with the same hydroboost system. The van has much more sensitive and responsive brakes.

On comparison I've noticed that, when the brakes are firmly depressed, the van and motorhome have a very different feel. On the van it feels simply like I'm simply pressing down on a slightly compressible firm object. On the motorhome it feels like I press down and it tries to press back up on me. If I press down firmly and hold the peddle it seems like the system wants to press back harder then I'm pressing down, like it's building back pressure.

My conclusion is that I have a hydroboost problem but would like some feedback on this. Does this seem to be indicative of an issue with the hydroboost system or am I chasing a ghost?

[92landyacht]

Went ahead and purchased a rebuild A1-Cardone Hydroboost power brake booster part number 52-9383 from Amazon.com for $171.39 (163.39 +TAX) delivered. Looks like it fits all P30 motorhome chassis models from 1982 to 1994.

All the symptoms seem to point in that direction and I've already done the following with no great improvement:

New Dexter TAG axle brakes with new Prodigy P2 brake controller (old controller was water logged and I got a great deal on this one)
New front rotors (Old rotors were badly pitted and rusted)
New front calipers (Rock auto had a great deal @ $14 each rebuilt, loaded and delivered from Wagner)
New Wagner thermal quiet brake pads on all four axles
New brake flex hoses (Old ones had collapsed)
Previous owner replaced the master cylinder
Flush brake fluid with DOT4 synthetic

The fact that I feel a strange push back pressure at the peddle with no apparent power braking and no power steering issues indicates to me that it must be something related to the hydroboost unit its self and not the power steering system. I may go ahead and replace the return line as well since it's there, easy and cheap.

Not looking forward to doing the swap, so any input would be greatly appreciated. I think the biggest problem I'm going to run into is getting the power steering hydraulic feed and steering gear lines off the hydroboost unit. My suspicion is that this is the original 1992 hydroboost unit since it still has the blue accumulator attached.

[mayco]

► 24:48► 24:48

Replacing A Hydroboost Unit - EricTheCarGuy - YouTube

Dec 7, 2010 - Uploaded by EricTheCarGuy
Replacing A Hydroboost Unit - EricTheCarGuy ... to a hyrdo boost setup in my 1997 chevy ...

Not sure if this will help you out but surely the basic ideas are the same......maybe?

[92landyacht]

That video helps quite a bit. I know the unit is different in a motorhome but not by much. It may even be a little easier since all the peddle connections are outside in the wheel well and not under the dash.

Just picked up a good Snap-on 16mm/18mm flare nut wrench. I've never had good success using flare nut wrenches from off brand companies. They always seem to want to spread open when removing the nuts and just round them off. I've read that the only ones that seem to work well are from high end companies like Snap-on and MAC. In the past I've had to resort to using Vise-Grips on brake lines to get them off. The thing I'm concerned with is you usually have a lot more room around the calipers then where I'll be working around. Never can have too many good tools you know.

[mayco]

Ill be interested to follow your progress. Ive done the pads, flex lines, master cylinder, and flushed the system. My pedal still feels soft but i think thats a common complaint on these systems. I also flushed the power steering fluid. Mine is a diesel though so i have a mechanical PS pump.

[92landyacht]

Looky what just arrived:





Plan on getting started with the replacement some time next week. Right now it's 95 degrees out and expected to go up tomorrow.

[92landyacht]

Digging around I came up with this nice writeup on the Bendix Hydroboost system:

Hydroboost

Might help others in understanding the system and doing maintenance on it.