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Bcollier9253 · 07-27-2013, 08:35 AM

I have a 91 Southwind P-30 chassis. 454 engine, 4 wheel disc brakes. I flushed the power steering system and brake system before installing a new hydraboost and master cylinder. 4 new calipers, new hoses new front rotors. The reason I did all this is because the front brakes were getting hot and locking up. I have bled and bled all systems to the tune of 5 quarts of fluid thru the brakes. I kept getting a soft pedal, I just figured with a new hydraboost I just had an abundance of power assist, not the case. I just test drove the thing and the brakes go all the way to the floor to the extent of the brake pressure light coming on. I'm to my wits end with it, all out of ideas. Any ideas out there what the problem could be?

trackman · 07-27-2013, 09:35 AM

Where the fluid comes out of the master cylinder to the first split could be the problem. That valve could be letting just enough fluid to seem like you are bleeding. I do not know what that first block is called but that is what they replaced on my brother's unit

ChasA · 07-27-2013, 10:18 AM

Sounds like you got a bad master cylinder. Some have a switch to light a warning lamp to warn of different pressure between front and rear. If you have such a system, it could that.

YC1 · 07-27-2013, 10:20 AM

If you are bleeding by pressing the brakes a bubble in a high spot of a hose will never leave. There are some special tools to help. I had a vacuum device for my airplane brakes. With clear brake lines I could see the bubbles and they drove me crazy.

Bcollier9253 · 07-27-2013, 10:30 AM

Quote:

Originally Posted by ChasA

Sounds like you got a bad master cylinder. Some have a switch to light a warning lamp to warn of different pressure between front and rear. If you have such a system, it could that.

Brand new, not reman master cylinder

Bcollier9253 · 07-27-2013, 10:31 AM

I have found the valve that the lines from the mc go to, it has an electrical wire going to it. I'm going to assume the wire us for the brake pressure light

Bcollier9253 · 07-27-2013, 10:34 AM

Quote:

Originally Posted by YC1

If you are bleeding by pressing the brakes a bubble in a high spot of a hose will never leave. There are some special tools to help. I had a vacuum device for my airplane brakes. With clear brake lines I could see the bubbles and they drove me crazy.

I used a vacume bleeder and had good fluid, no bubbles

YC1 · 07-27-2013, 04:18 PM

It has been several years since my hydroboost rv. I recall having to raise the front wheels and turn the steering wheel clock to clock with the engine (off?) and with the cap off the fluid reservoir. Had to do it slowly to not bubble fluid out. Could have been with engine on but it seems I remember working up a sweat.

jerichorick · 07-27-2013, 07:45 PM

By chance do you have seized or sticking calipers? This is a common problem on many cars I have worked on. I guess it could be true on a coach too.

Nick-B · 07-28-2013, 12:04 AM

Master cylinder while new, could still be bad. Exchange for another new one.

Bcollier9253 · 07-28-2013, 04:03 AM

Quote:

Originally Posted by Nick-B

Master cylinder while new, could still be bad. Exchange for another new one.

Going to pull the mc off today and bench bleed 1 more time. Also going to install a new proportioning valve as well. Thanks everyone for your inputs!! Hope this does it, it's all that is left.

Bcollier9253 · 07-28-2013, 04:06 AM

Quote:

Originally Posted by YC1

It has been several years since my hydroboost rv. I recall having to raise the front wheels and turn the steering wheel clock to clock with the engine (off?) and with the cap off the fluid reservoir. Had to do it slowly to not bubble fluid out. Could have been with engine on but it seems I remember working up a sweat.

Yessir, ben there done that too !! Lol

Bcollier9253 · 07-28-2013, 04:08 AM

Quote:

Originally Posted by trackman

Where the fluid comes out of the master cylinder to the first split could be the problem. That valve could be letting just enough fluid to seem like you are bleeding. I do not know what that first block is called but that is what they replaced on my brother's unit

Going to replace that today if I can find the part in stock. Thanks!

iRV4FUN · 07-28-2013, 04:54 AM

In general, I would not touch my hydroboost without going to the Workhorse repair manual for proper procedure. People in general need to be very careful not to introduce air into the hydroboost system. Just saying... the repair manual is very definite about the procedure involving the hydroboost. Trust but verify!