info Chevy P30 hydro boost brake/power sterring bleeding

[1530004]

I am looking for info on repairing & bleeding the hydro booting brake system by a mechanic on my 1989 Coachmen 23 ft. MH. He has replaced the leaking brake lines on the frame rail below the motor, replaced the rt. real wheel cylinder & master cylinder as well as replacing all the brake fluid and same wheel seal. Bought a bleeder system and used it but still can't bring the brakes up to snuff. Also I have a friend who is a retired certified Chevvy mechanic and currently teaching a DBSC and he is attempting to find an answer. I found a post by radardog 01/28/09 reffering to a post by "OLUSEDBEAR" to try turning the steering wheel back & forth with the engine off to prevent further problems?? I have not been able to contact either of them to gain further info. Thanks, Dick

[turbojimmy]

1530004 wrote:
Again thanks to all who responded. After much searching the mechanic and a fellow mechanic were able to find that the master cylinder rebuild sent out was the wrong unit but did fit the system. Proper one has been shipped from warehouse for installation tomorrow. Should solve the problem. Dick

Glad you got to the bottom of it. Hopefully the correct part will solve the problem. Looking at mine, I am NOT looking forward the the day I need to replace that master cylinder. It looks pretty tough to get at.

[Bugman114]

I've never bled any master cylinder and have never had any issues. I sometimes like to leave the lines to the master cylinder loose and pour the the fluid in, and wait for the lines to start leaking, then tighten them up. But if I've painted the master cylinder, I won't bleed it. Just hook everything up as its supposed to be, fill it with fluid, pump the pedal and watch the bubbles come up from the resivoir, and once no more bubbles, then just bleed it normally. I've never had any issues doing it this way, on any vehicle: 90 ford 460 class a, 85 Pace arrow chevy 454 hydroboost, 79 chevy truck 454 non hydrobost, 95 gm hydroboost, and various other makes and models (VW, porsche, honda, toyota, etc.).

[1530004]

Again thanks to all who responded. After much searching the mechanic and a fellow mechanic were able to find that the master cylinder rebuild sent out was the wrong unit but did fit the system. Proper one has been shipped from warehouse for installation tomorrow. Should solve the problem. Dick

[turbojimmy]

wolfe10 wrote:
Some confusion here.

Some are discussing bleeding the hydraulic brakes (i.e. brake fluid).

Some are discussing bleeding the hydraulic booster (ATF).

Both are important, but unrelated in terms of how it is done.

Yes! Someone made this point earlier. Based on the original post, it does not sound like the Hydroboost system was opened up. A brake line was replaced. Therefore, a standard brake bleeding procedure needs to be undertaken. Hydroboost or vacuum assist is irrelevant.

Again, it sounds like the MC was allowed to drain and air was introduced. The MC needs bled properly before proper pedal feel can return.

[turbojimmy]

Something like this might be more effective than plugging the lines:

http://www.amazon.com/Dorman-13911-Master-Cylinder-Bleeder/dp/B001SG8ZC0/ref=sr_1_1?ie=UTF8&qid=1406...

It's basically a bench-bleed kit, but "bench-bleed" is just a term for bleeding a new MC. You can bleed it while it's installed using this kit. As dakdave said, unhook both lines and install plugs - or in this case fittings to which you attach rubber lines. Route the rubber lines back into the fluid in the MC. Pump the pedal a few times and it will blow bubbles into the fluid until all of the air is dispelled. Replace the cap!! The seal of the cap will prevent the MC from draining itself again. Reinstall the lines and bleed normally (again, I would gravity bleed.

The pedal should be back where it was.

Just an aside, your "mechanic" should know this....just sayin'.

[wolfe10]

Some confusion here.

Some are discussing bleeding the hydraulic brakes (i.e. brake fluid).

Some are discussing bleeding the hydraulic booster (ATF).

Both are important, but unrelated in terms of how it is done.

[dakdave]

remove both brake lines from master cylinder and install plugs in cylinder ports.Barely press pedal down have someone warch for bubbles in cylinder,release pedal just after bubbles.
Repeat this untill pedal is rock hard and right at top,you now have bled master cyliner and can quickly reattach lines making sure cylinder does not go empty.
Then bleed brakes as usual

[Gjac]

turbojimmy wrote:
I replaced both calipers on mines a couple of weeks ago and "gravity" bled them. I just open the bleeder valves on the one farthest from the MC. Wait until just fluid comes out with no air bubbles, and repeat on the other side. It works fine. If the pedal isn't returning to normal, I'd look into a possible problem with the master cylinder. If it was allowed to drain empty while replacing the line, it might need bench-bled.

This is how I do mine also just jack up the front first.

[turbojimmy]

I replaced both calipers on mine a couple of weeks ago and "gravity" bled them. I just open the bleeder valve on the one farthest from the MC. Wait until just fluid comes out with no air bubbles, and repeat on the other side. It works fine. If the pedal isn't returning to normal, I'd look into a possible problem with the master cylinder. If it was allowed to drain empty while replacing the line, it might need bench-bled.

[wolfe10]

Contact info for Roger Haag (old used bear): oldusedbear@gmail.com

One issue that can lead to inability to bleed the PS system is an autopark brake that is out of adjustment. Too much slack/clearance between brake shoes and brake drum can require the use of so much fluid to release the brake that you drain the PS reservoir of fluid. So air is re-introduced to the system.

[1530004]

The proper model may be C 30 ?? Dick

[1530004]

Thanks for the info, still having problem, driving mechanic up the wall. Unable to get brake pedal to assume normal position after repeated bleeding and drive/stops. Dick

[Bugman114]

I've never bled the hydro boost system on any chevy when replacing the lines. Simply steer to both sides and that's it. The brakes I just have someone pump the pedal several times, hold it, then I crack a bleeder open, and close it just before the fluid stops. And repeat as needed. I always start at the rear, it takes a while before you see bubbles at the rear, since the line is so darn long. I've tried using vacuum and pressure breeders but they just don't work as well as the pedal method for me.

[More_To_See]

Just a general comment. You are dealing with two isolated systems here that mechanically work together to provide your braking.

One is part of the power steering system and uses power steering fluid. The other, then, used brake fluid. Since you had only worked on the brake fluid part of the system I'd not think you would have to worry about the PS part. But here is the bleeding method:

There is a very specific method to "bleed" the power steering part of the system. First you be sure to bring your ps fluid up to proper level and after that is established you turn the front wheels (while off the ground) back and forth just barely hitting the stops at each end of range.Check and add PS fluid if necessary. Continue that till no more fluid is required.

Then lower the vehicle and turn the wheels from lock to lock. Stop engine. Check fluid. Add if necessary.

If the brake fluid is extremely foamy allow the vehicle to stand for a few minutes and then repeat the above procedure.

= = = = =

Then to bleed the brake fluid part of the system you can use either the old conventional manual method or a pressure method. The pressure method requires a special tooling.

For the manual method, you first have to bleed the master cylinder. That's just about the same as doing a wheel cylinder. There is one line out for the front wheels and one line out for the rear wheels.

Loosen the forward (front) brake line fitting and move it just enough so that brake fluid flows out of the master cylinder. (Keep adding fluid to the master cylinder when doing any bleeding.)

Let fluid flow out that open port a little bit and then put the forward brake line back on but do not snug down the fitting tight. Slowly press on the brake pedal to force air out but snug down on the fitting before the pedal reaches the floor.

Let up on the pedal and wait 15 seconds. Then start pressing on the brake pedal again as the fitting is loosened on the forward brake line. Tighten the fitting before the brake pedal hits the floor. Keep doing this bleed process until no more air comes out. Then move over to the real brake line and do the same thing there.

Then do the wheels: right rear, left rear, right front, left front.

It's not mandatory that you first bleed that master cylinder but apparently it can make things much easier. If fact they generally recommend bleeding that master cylinder while it's still on the work bench.

This is just a very general over view but maybe will help you with your project.

Good luck.