HBoost - "No Brakes" - Resolved

[Jerryl]

After 9+ months, parts and every damn google search, the brakes are still kicking my arse. Switchws from PM to HB and brake pedal is spongy, goes to the floor on EStop. Stopping power is mediocre at best at any time.
I need some ideas and enlightenment.

What is done thus far:
-Autozone Hydroboost compatible with 84 GN
-New stock ps pump hoses to/from HBoost
-5th Master cylinder (!!) - Now new Wilwood, bench bled.
-No external leaks anywhere
-New brake hose @ front/back
-Pretty sure no air in the system after 6 months and 4 qrts of rebleeding.
-Drums adjusted very tight.
-Brake light does NOT illuminate when this happens (Light does work)

Thoughts and ideas welcomed.

 

[turboclam]

I just purchased a new hydro from Tallon Hydraulics and the owner there, Butch is very knowledgable. I'd give him a call and tell him what's going on. Maybe he can help.

(906) 440-5100

 

[No disintegrations]

After 9+ months, parts and every damn google search, the brakes are still kicking my arse. Switchws from PM to HB and brake pedal is spongy, goes to the floor on EStop. Stopping power is mediocre at best at any time.
I need some ideas and enlightenment.

What is done thus far:
-Autozone Hydroboost compatible with 84 GN
-New stock ps pump hoses to/from HBoost
-5th Master cylinder (!!) - Now new Wilwood, bench bled.
-No external leaks anywhere
-New brake hose @ front/back
-Pretty sure no air in the system after 6 months and 4 qrts of rebleeding.
-Drums adjusted very tight.
-Brake light does NOT illuminate when this happens (Light does work)

Thoughts and ideas welcomed.

Toby goodmk had this happen. I think he had the lines reversed on the steering box? His lines were an fittings each the same size thus the mix up. I'll see if I can dig up that link.

Oh also about 20 years ago bisons brakes acted crappy like this. Iirc the rears were glazed. It amazed us how much braking was provided by those old drums. So if the friction was better perhaps your car would brake much better before maxing out the pedal.
And once I had a customer glaze brand new rears and they turned purple because they didn't have time to bed in before hard stopping. I know you are smart not trying to say it's so simple but just to consider it.

 

[Danster]

In my opinion getting the HB from AZ or any other parts place are a crap shoot. I went through like 2-3 until I found and bought a used from a GN and worked as expected the first time.

 

[Jerryl]

Thanks guys.
Keep the feedback comming.

I did have conversation with Butch who indicated that its probably air in the system. Bled the system yesterday and dumped about 14 oz. Never seen any air. I am stumped.

 

[Blkt6]

I remember readining a post similar some time back with the same symptoms. He had the PS lines reversed.

 

[turbo87regal]

Did you swap the brake lines from front to back on the Wilwood compared to the way they were on the power master? I have personally seen issues with 2 hydroboost swaps so far and both were using the Wilwood master, one was fixed by swapping the proportioning valve and the other one was fixed by pressure bleeding the brake system by a shop. That Wilwood master is a pain in the @#$ in my opinion but it does look nice.

 

[No disintegrations]

How is the pedal with the engine off? Still goes to floor?

 

[Jerryl]

Thanks gents.
I will try to answer some of the questions.
-The HB pressure lines are stock and can't really be hooked up backwards and confirmed correct. Steering works great an no pump whine at all.
-Engine off, brakes are spongy and not firm. Never had that nice firm feeling with this setup.
-Engine running, the pedal drops even further as expected, almost to the floor.
-Increased use of the brakes in 20 mph drive results in serious brake deterioration, to the point of pretty much no brakes. (Drops to the floor!) After months of thinking, the rear brakes are doing the work!

Completed some additional trouble shooting and wrenching this weekend.

Bled the master front circuit "in car". The front brake circuit is nearest to the firewall. Did about 15-18 pumps with a block behind the pedal, 10 seconds between pumps. Slow pressing, slow release. Never saw any air. Next step:

Data is power . . Disconnected the front circuit, hooked up a 600 psi pressure gage. Engine off, you can easily max the gage, and system holds pressure at constant pedal. Engine running required less force for same pressure. Brake pedal felt nice and firm. (Hmmmm) Next step:

Measured to ensure there is no power to the line lock. No difference. (Yes, the orientation is correct). Next:

Bypassed the line lock & reconnected the front brake circuit, bled circuit. No difference in "soft" pedal feel. No external leaks, calipers are not frozen. There is "some" clamping force on the disk but, obviously, insufficient. Next step;

Verified line lock "open flow" against brand new spare unit. Confirmed adequate. Reinstalled old unit, rebled front circuit. Still the same. Next:

Opened bleeder one at a time at front caliper and simulated a panic stop/hold down with a helper to test fluid flow - plenty of fluid flow out the hose.

Interesting observations:
-While simulating the panic stops, the fluid level in the rear curcuit dropped. (?????)
-The brakes felt a bit better but not where it should be. There is absolutely no way you could lock the tires in a slow or medium roll.

Guess I am making progress. Lol

 

[No disintegrations]

How about possible glazed drums or rotors?

 

[Jerryl]

Rotors have mayb50 miles on them. DS rear drums needs to be cut but not glazed.
Proportioning valve?

 

[No disintegrations]

Maybe prop valve as you say. Can you do a temp reading on the wheels with an infared thermometer?

 

[Jerryl]

Last time the temp was read by means of IR thermometer, front and back were both warm. I need to do this again and take better readings.

Do you think the propertion valve can cause all these headaches? The bleeder valve on the proportion valve moves freely out when the brake is applied, and, the brake light does not illuminate. (Circuit is active as the light comes on when using the line lock.)

 

[TexasT]

You say you have tries five mc, but were any of them the one for the Cadillac with the aluminum part and plastic reservoir? This is what is working for me. If it is going to the floor I think bad mc. Spongy pedal I think air in system. When bleeding are you placing a 2x4 block under the pedal to prevent it from over stroking the piston . Are you having your helper hold the pedal while you close the bleeder. Then let the pedal back up with the bleeder closed. Then open the bleeder and have the helper push the pedal down slowly with the bleeder open. I use a clear tube and a mayo jar so I can see the fluid come out . Have the tube below the surface of fluid in jar so you can see the bubbles or if it is just fluid coming out.
Old school but it is what I know.
Call me and we can discuss it.

 

[1952ray]

You say you have tries five mc, but were any of them the one for the Cadillac with the aluminum part and plastic reservoir? This is what is working for me. If it is going to the floor I think bad mc. Spongy pedal I think air in system. When bleeding are you placing a 2x4 block under the pedal to prevent it from over stroking the piston . Are you having your helper hold the pedal while you close the bleeder. Then let the pedal back up with the bleeder closed. Then open the bleeder and have the helper push the pedal down slowly with the bleeder open. I use a clear tube and a mayo jar so I can see the fluid come out . Have the tube below the surface of fluid in jar so you can see the bubbles or if it is just fluid coming out.
Old school but it is what I know.
Call me and we can discuss it.

Old school my ass , you are spot on!!!!

 

[Jerryl]

You say you have tries five mc, but were any of them the one for the Cadillac with the aluminum part and plastic reservoir? This is what is working for me. If it is going to the floor I think bad mc. Spongy pedal I think air in system. When bleeding are you placing a 2x4 block under the pedal to prevent it from over stroking the piston . Are you having your helper hold the pedal while you close the bleeder. Then let the pedal back up with the bleeder closed. Then open the bleeder and have the helper push the pedal down slowly with the bleeder open. I use a clear tube and a mayo jar so I can see the fluid come out . Have the tube below the surface of fluid in jar so you can see the bubbles or if it is just fluid coming out.
Old school but it is what I know.
Call me and we can discuss it.

Yes, yes, & yes.

 

[No disintegrations]

Maybe something is wrong with the assist unit behind the master cylinder? Could you send it back on warranty??

 

[Jerryl]

The MC circus.
All with new unopened DOT 3/4 Synthetic fluid:

1-Autozone rebuild - Did not hold pressure. Lots of black grit inside bowl after bleeding
2-Delco NOS. Did not hold pressure. Dried seals?
3-Online purchase (Forgot the name) - Saw fine aluminum glitter in the bowl after bleeding. Did not hold pressure.
4-Autozone - Incorrect bore size and damaged the retainer. Thats on me. Should have checked.
5-Wilwood - purchased incorrect part after discussing with tech.
6-Wilwood #2. Fits

 

[No disintegrations]

The MC circus.
All with new unopened DOT 3/4 Synthetic fluid:

1-Autozone rebuild - Did not hold pressure. Lots of black grit inside bowl after bleeding
2-Delco NOS. Did not hold pressure. Dried seals?
3-Online purchase (Forgot the name) - Saw fine aluminum glitter in the bowl after bleeding. Did not hold pressure.
4-Autozone - Incorrect bore size and damaged the retainer. Thats on me. Should have checked.
5-Wilwood - purchased incorrect part after discussing with tech.
6-Wilwood #2. Fits

Sorry,. What I mean is the booster unit. Isnt that sold separately from the MC? Maybe is getting cross talk inside?

 

[Jerryl]

Guys,
Thanks for the constructive brainstorming. Much appreciated.

There are no leaks to be seen on the HB. Had a Autozone replacement unit on order before my 30 second discussion with Butch 2 weeks ago. He stated they the there is air in the system basd on the description I gave. This is what started my focus on the MC. Very nice guy and knowledgeable guy btw.

This is what I am thinking. (??)