Brakes Problem - please help!

[ChrisF]

I have an 86 GN - standard stock brakes, functioning powermaster (I think!) new rotors and pads, new S-10 shoes and drums, no hydraulic leaks anywhere.
Hydraulic system has not been opened since before this problem began.

When driving, when 1st hitting the brakes (especially quickly) the BRAKE light on the dash flashes for a second. It is occurring more and more often, and the pedal is starting to feel low. The brakes do grab but the pedal does feel low.

I am thinking the master cylinder is on its way out. Am I correct?

1) Where do I get one;
2) What procedure do I have to go through replacing the master while making sure the powermaster has fluid and it is all bled out properly?

Thanks in advance!
Chris

 

[XLR8]

There is a fair chance it is the accumulater ball. At least it was when my car did what you are describing. I am not sure where to get one now.

 

[POWERBRAKEBOB]

Hydroboost conversion

We recommend replacing that troublesome Powermaster with our NEW Hydroboost unit. This unit will outlive the car. Even after 200,000 miles, they can be rebuilt. It runs off of the P/S pump, and needs no vacuum or electricity. It is completely reliable, comes with a 1 year warranty, and a replaceable master cylinder. It bolts right in. If you read othe posts from guys have have converted, they are all happy with it.

 

[jdpolzin]

Or you can get a stock 84-85 GN rebuilt Hydroboost set up from the parts store for $200.

Hydroboost unit $149.99
Brake lines hydroboost to pump, hydroboost to gear box $49.99
Master cylinder $14.99
5' 3/8 hydraulic hose $5
3/8 "TEE" fitting $3.99

Use your stock powermaster pedal.

 

[POWERBRAKEBOB]

Hydroboost conversion

We offer rebuilts also, as we have been in that business for 60 years. We like the new because we know it's history. Rebuilt units have some wear on the spool valve and the bore, and there is no way to test it, especially for long term use. The units, like you say, are 25 years old already. There is no way to sleeve the spool bore. The first design Hydroboosts with the internal accumulator (the external has the gold cylinder on the side of the casting) have been experiencing loose spool bores and sometimes do not hold pressure. We can supply either, but we do not sell the internal accum units anymore. Some guys have problems bending the 84 hose onto the 86-7 pump. Our stainless hose simplifies that.

 

[jdpolzin]

Are you a vendor on this board?

 

[IrvJr]

Check the fluid level first. With the key off pump the brakes til they get hard, maybe 10-12 times. Then pull the lid and see what the level is. Do not add to the fluid level before emptying the accumulator, which is what the pumping of the pedal with the key off does. Secondly there is a troubleshooting guide for these, flowchart style that works well. I like my powermaster and have heard both good and bad about the hydroboost and vacuum conversions. I think you should find the trouble with what you have and hope its a simple fix then throw money at it with a new setup. Accumulator is usually the first suspect, switch is next. Does your brake pedal go down when you are sitting still or has it just gotten lower til you get some braking action?

 

[ChrisF]

Where is this troubleshooting flow chart everyone keeps mentioning?

Today I used a baster to get all the old fluid out of the reservoir and replaced it with new. The pump kicked on and pressurized the system, and then shut off.

The pedal is (and has been) low and squishy. Not a ton of effort needed to actually get the brakes to work, but the light coming on more and more surely indicates a problem of some sort. It is acting like a hydraulic failure of some sort, at least that's what the symptoms would be on a typical vacuum assited G Body. I am going to completely bleed the entire system and then if it persists, replace the ball next.

Rich Clark talked to me on the phone and was nothing short of extremely cool in helping me, and offered to test my accumulator ball for me. He sounds like a Power Master expert.

If the bleed out and a new ball do not fix the problem, I may be going vacuum or hydroboost. I just can't wrap my head around several hundred dollars to have a working power master again.

 

[aminga]

Low squishy pedal is air in the lines not the powermaster just like every other brake system.

Bleed it Well starting at the wheel farthest from the MC and work inward.

It does sound like the accumulator may be going bad but bled it too and see. Pump it down with the pedal and allow it to run do this until there is no more tiny bubbles in the passenger side of the reservoir.

 

[zeus87gn]

Chris,

Squishy pedal is air in the system.
Flashing light is low pressure in the accumulator.

Bleed the system and remove the air. Then go through the diagnostics and time your pump. The diagnostics are here. I have a link to my bleeding procedure in my sig. It is another method that you can use if you like.

From your description, it sounds like your accumulator may be on it's way out. It is usually the first to go. But after you cycle it to get the air out, you need to time you system to determine if you have internal leaks.

A low pedal can be a number of things. If the pedal is firm once it gets to that point, don't worry about it. Be sure your rear brakes are adjusted correctly and you have plenty of pad on your shoes.

HTH,
Z

 

[yrlessbob]

Chris,

I have the issue with the brake light but have hard pedal. The AC Delco part number is 18M754 for the accumulator ball. Can't seem to find it using the AC Delco web site so stopping by store tomorrow to see what they can do for me.

 

[aminga]

Chris,

I have the issue with the brake light but have hard pedal. The AC Delco part number is 18M754 for the accumulator ball. Can't seem to find it using the AC Delco web site so stopping by store tomorrow to see what they can do for me.

I believe it's out of production. Some of the supporting vendors have repop versions though.

 

[ChrisF]

So if I never opened the system - where did the air come from?

I agree with this being typical behavior for that problem - but how does air just "get in" ?

 

[aminga]

So if I never opened the system - where did the air come from?

I agree with this being typical behavior for that problem - but how does air just "get in" ?

Leaks in the lines to the wheel cylinders.

 

[yrlessbob]

FYI - GBodyparts.com has accumulator balls but are $189. They also have rebuilt power master unit for $650.

 

[ChrisF]

Okay guys, bled the system out fully, no better results. Had the system professionally vacuum bled, it's marginally better if at all. The car stops but certainly not the way it used to, and the light still flashes.

I am now going to pull the accumulator ball out and send it to Rich, he offered to test it for me. He offered to test the whole thing but that is a lot more work pulling the whole thing out and everyone seems to be leaning towards the ball, so I am doing that next.

I am going in order of least expensive to most as I have a limited budget planned for this season, and never planned on spending it all on brakes!

Any sources for these accumulator balls would be great, as it looks like I might need one!

Thanks again everyone!

 

[IrvJr]

Maybe find someone near you with a spare and see if that really is the problem.

 

[GNX243]

Accumulator

Maybe find someone near you with a spare and see if that really is the problem.

Chris,
Kirban sells reconditioned ones for $180...I believe Rich Clark does the mechanics and tests them before sale.

 

[ALVAROG1983]

reply

Okay guys, bled the system out fully, no better results. Had the system professionally vacuum bled, it's marginally better if at all. The car stops but certainly not the way it used to, and the light still flashes.

I am now going to pull the accumulator ball out and send it to Rich, he offered to test it for me. He offered to test the whole thing but that is a lot more work pulling the whole thing out and everyone seems to be leaning towards the ball, so I am doing that next.

I am going in order of least expensive to most as I have a limited budget planned for this season, and never planned on spending it all on brakes!

Any sources for these accumulator balls would be great, as it looks like I might need one!


Thanks again everyone!

so did you fix your problem.

 

[ChrisF]

I shipped the ball to Rich Clark (again, this guy is really nice) and he's testing it for me. I am leaning towards it being bad based on all of the good advice here. I wanted to test before just tossing money at the problem, and he was kind enough to help. Limited budget this year, need to get my alky kit on, my THDP installed, and get the 2-3 shift fixed. Sucks the trans was just rebuilt last year.

Thanks for asking, and I will keep you guys posted!