burnin' smell and brake petal flutter....great

[231power]

Hey all - I'm looking for some insight on a Powermaster problem -
since I got the GN out ('87 w/ 48k) this April I felt some feedback or fluttering from the brake petal when stopped – and I see the brake lights are flickering in time with the pulse from the petal. I’ve had good luck with the PM brakes over the past 13 years – I think the only brake part I had to replace was the accumulator.

today I noticed some squeaking (from under the hood) when I used the brakes - the car sat all day after that and when I started it w/ the hood up, some smoke was around the PM right away. I decided to head home carefully (about 6 miles), and the brake light came on as I got home. The part below the master cyl was hot again, w/ burning smell and the brakes weren't there, just started to lose them. I pumped the petal with the car off, and when I started it again, it didn't lower the fluid in the pass. side part of the bowl like I noticed before driving home. I don't think the pump has been running steady, I never noticed the hum from it.

So I'm probably looking at the pump motor and/or switch? Maybe time to change to vacuum - it's just as cheap to do isn't it?

Any thoughts from the experts would be greatly appreciated!
I lost the only mechanic around here who had some GN experience.
__________________

 

[zeus87gn]

Powermaster Rules...

I wouldn't call myself an expert, but I have gone through my PM system from front to back, talked to many on these systems, and here is what I have figured out.

Typically, the first thing to go is the Accumulator. And it will go many times before the switch or anything else. The Acc won't help the motor build pressure, so the switch won't tell the motor to shut off. Therefore, the motor will run too long, get hot and possibly create smoke and usually blow the 30amp fuse. The motor isn't designed to run more than about 20 seconds at any one time. Sometimes the brake light will come on, sometimes it won't.

Your situation sounds typical, only the Acc went quicker than you could catch it before it caused damage. If the motor has created smoke, it's 'not long for this world'. Especially if it's not sucking fluid out of the bowl when it is running.

My opinion: You can replace the motor, switch and accumulator and get it going again, but you may end up taking the entire unit off to do it. If you go through that trouble, no sense in not having it operate 100%. The fresh motor and accumulator will put the cylinder seals to an early grave if they have not been kept up with clean fluid on a regular basis. These are your brakes, no place to skimp on $$.

If you want to keep the PM alive, keep the car original and don't want to do the work yourself, get the rebuild from Kirbans. If you would prefer to do the work yourself, get the book and tear into it. There are many procedures outlined on the gnttype.org website, but the book has more. Bleeding these systems can be tricky, so don't let 'Midas' do it.

There are many here that prefer the vaccum system. It works, and they have been proven to be quite reliable in our cars, but I prefer the PM. It's unique and works reliably well but must be properly maintained.

HTH

 

[Turbodan]

I just had the same problem. Felt the fluttering at my pedal and had a burning hot powermaster motor. Just had the powermaster motor replaced today with a new unit. My problem is fixed. Just driving it from my house to Aggressive Auto which is 2 miles away. I ended up with a super hot motor. After the new motor was installed i drove around for 15 minutes and new motor was not hot at all. If the motor loses it's ability to create pressure it will run to long.

 

[231power]

The next step is expensive

Thanks a lot for the info Zeus - I'm just not sure what you are describing here:
"The fresh motor and accumulator will put the cylinder seals to an early grave if they have not been kept up with clean fluid on a regular basis."

So TurboDan, how did you know you could replace only the motor to get it fixed up ?? I better check that fuse I guess also to see if it's blown. My fear is that I might replace the motor, then also need an accumulator. I'd be in for around $160 + $150 in parts then, so I might as well be paying for an entire rebuild unit at $420 - which will also be cheapest labour, since it's just unbolting off the firewall and dropping in a new one. Labour for bleeding will be there either way.

Does Kirban have the best price for the whole unit ??
Thanks guys - this forum is a goldmine.

 

[Turbodan]

Well the signs were pointing towards my powermaster motor. I never experienced any brake warning light problems. I had changed my accumulator 2 months ago to get rid of the flickering brake warning light. The motor seemed to be making a different noise. We changed the motor first then checked for a master cylinder internal leak. After we confirmed there did not seem to be a internal leak I took the car for a 5 minute ride and then pulled over to test if the powermaster motor was getting hot. It was not warm at all. Just went out for a ride this morning for 20 minutes. Motor was still cool. I did have a pressure switch put away just in case it was a switch.

 

[zeus87gn]

I'm just not sure what you are describing here:
"The fresh motor and accumulator will put the cylinder seals to an early grave if they have not been kept up with clean fluid on a regular basis."

Meaning that if you only replace the motor and accumulator, the oring seals within the master cylinder may go south with fresh pressure on them. Not meaning it will happen, just be forewarned that it can. In practality, you should flush the fluid in the brakes and the PM once every couple of years (or every year if you want) to remove contaminants and old blackening fuild. If this has not been happening, your seals may already be in bad shape and fresh pressure will do them in.

Does Kirban have the best price for the whole unit??

Not really sure, but if it is all fresh than what I just mentioned above would not be an issue. I did my PM myself a few years back before the prices on these parts went through the roof.

 

[Turbodan]

can you buy new seals for the master cylinder?

 

[zeus87gn]

http://www.turbobuick.com/forums/showthread.php?t=177359

 

[231power]

fuse

I've parked the car till I have a handle on this PM issue, but I checked the 30A fuse and it was blown. After replacing it, the brake light is out now and from just testing the car in the yard, the pump will run and lower the fluid back down to the 'car running' level on the pass. side bowl. It didn't get hot in a few min's of running the car, but i suspect it will on a longer drive. If I pump the petal w/ the car off, at pump 9 or 10 I get a bit of fluid coming out around the cover...that baffle inside is tough to keep flat when you force the cover back on - I think that's how the fluid is escaping.
I doubt this changes much as far as replacing the PM unit though.

 

[zeus87gn]

I've parked the car till I have a handle on this PM issue, but I checked the 30A fuse and it was blown. After replacing it, the brake light is out now and from just testing the car in the yard, the pump will run and lower the fluid back down to the 'car running' level on the pass. side bowl. It didn't get hot in a few min's of running the car, but i suspect it will on a longer drive.

What makes the difference is how long and how frequently the motor runs. If it is blowing the fuse and getting hot, there is a problem. Run the diagnostics procedure detailed on the gnttype brake page. Have a stopwatch or a good watch with a second hand available and you can figure out what is going on.

If I pump the petal w/ the car off, at pump 9 or 10 I get a bit of fluid coming out around the cover...that baffle inside is tough to keep flat when you force the cover back on - I think that's how the fluid is escaping. I doubt this changes much as far as replacing the PM unit though.

If fluid is forced out when you depressurize, you have too much fluid on the pass side of the bowl. It should be just full when you get to that 9th or 10 pump when the pedal gets hard to push. Escaping fluid? Do you notice it getting low on a frequent basis or only when you are diagnosing problems? Or am I misunderstanding you completely?

 

[231power]

What makes the difference is how long and how frequently the motor runs. If it is blowing the fuse and getting hot, there is a problem. Run the diagnostics procedure detailed on the gnttype brake page. Have a stopwatch or a good watch with a second hand available and you can figure out what is going on.

If fluid is forced out when you depressurize, you have too much fluid on the pass side of the bowl. It should be just full when you get to that 9th or 10 pump when the pedal gets hard to push. Escaping fluid? Do you notice it getting low on a frequent basis or only when you are diagnosing problems? Or am I misunderstanding you completely?

Hey Zeus - I haven't had the cover off the brake bowl for a while, but the fluid level isn't overfilled and hasn't been changing. So I figured when I took it off a few days ago after the issues started, I didn't get that baffle inside placed right - cause now, on the last pump or so, there's a little bit of fluid running down the side of the bowl. Then when I open it back up, the baffle will be squeezed down on one corner and some fluid has gotten on the top side of it.....and I can't seen to get the baffle to sit in there right.

I bought a complete powermaster from 'Turbo27' in the forum here, and I have a mechanic lined up to do the swap, hopefully this weekend when I get the part. I told him I'd find the procedure online here on how to do the bleed, and warned him it's a little trickier than some.

This powermaster is supposed to be rebuild or brand new, so I'll be in good shape I think after this, and I'll be sure buddy follows the bleeding tips from here or from gntype.org.

Can you think of any parts I'll need handy when bolting on a new powermaster? I'm going to be at a mechanic's house in the evening so we'll need to have everything ahead of time.

Thanks again for the info!

 

[zeus87gn]

...when I took it off a few days ago after the issues started, I didn't get that baffle inside placed right - cause now, on the last pump or so, there's a little bit of fluid running down the side of the bowl. Then when I open it back up, the baffle will be squeezed down on one corner and some fluid has gotten on the top side of it.....and I can't seen to get the baffle to sit in there right.

Sounds like that baffle has had it. Fluid shouldn't be getting past it. It's really a bowl seal and not a "baffle".

I have a mechanic lined up to do the swap...and warned him it's a little trickier than some.

Tricky may be an understatement. Just remember to take your time and don't rush it. The accumulator side is the tricky part. If you see frothy fluid (sometimes called microbubbles) in the bowl during the bleeding procedure, stop and wait until it clears up. Then go at it again. If you don't see it, your Ok.

This powermaster is supposed to be rebuild or brand new, so I'll be in good shape I think after this...

I'll keep my fingers crossed for you. Can't say I'm familiar with the person you bought it from, but just remember that you are still dealing with an unknown until you get into it. That's why I did mine myself.

Can you think of any parts I'll need handy when bolting on a new powermaster? I'm going to be at a mechanic's house in the evening so we'll need to have everything ahead of time.

Parts? Can't think of any right off. Worst problem I can think of, as you will have a complete PM setup, is if the brake line fittings get destroyed. You can get new lines from any local parts store but will probably nee to have them bent to fit properly.

Thanks again for the info!

You're welcome. I hope the knowledge is helpful.

 

[86gngirl]

You can bench bleed those units then put them on the car. Its less hassle.

 

[zeus87gn]

You can bench bleed those units then put them on the car. Its less hassle.

Yes, that's true for the wheel side of the master cylinder. I usually do my bench bleeding on the car because I don't have a vice.
But when it comes to the high pressure side, the pump needs to be hooked to the electrical system to operate. I had to go through pressurize/depressurize a couple of times to get all the air out of the freshly rebuilt cylinder and new accumulator. Got a littly frothy the first two times on depressurize, but it cleared up the third time.

Just a trick I learned...but have never read about.

 

[231power]

Well, I got the Powermaster on there this past weekend! When we put power to it, there was fluid escaping around the pressure switch - had to give it a 1/4" turn, but I see today it's still just a little bit wet at the threads - will have to try and tighten a bit more.

I know my ears are tuned in to the pump sound now, but it seems to be running on every 3rd petal push. ... sometimes after 2. And it seems to stop with a more audible click than what I was used to. Maybe I'll still need to do the troubleshooting flow chart?

We also changed the diff and pwr steering fluid and found some loose valve covers. Got a great price on parts and labour both.

 

[zeus87gn]

Well, I got the Powermaster on there this past weekend! When we put power to it, there was fluid escaping around the pressure switch - had to give it a 1/4" turn, but I see today it's still just a little bit wet at the threads - will have to try and tighten a bit more.

Don't tighten it too much, you'll strip the threads out of the cylinder!
If memory serves, there is an oring on the threads of the pressure switch. Smear a little dab of white lithium grease on the oring - or, if you feel outgoing, take the oring off and give it a good coating of white lithium and put it back on. If it breaks during removal, it isn't any good anyway. Any local auto parts store will have a replacement, just be sure to get one that is close to the same physical dimensions.

I know my ears are tuned in to the pump sound now, but it seems to be running on every 3rd petal push. ... sometimes after 2. And it seems to stop with a more audible click than what I was used to. Maybe I'll still need to do the troubleshooting flow chart?

Don't think that's a big deal as long as the motor doesn't run more than a few seconds. If you haven't bled the entire system yet, don't worry about it until you do. You have air in the lines and it will take a lot of pressure away from the accumulator.

 

[231power]

GoodDay Zeus,

Got a chance to move the O-ring from the old PM unit to the new one tonight....think it was missing off the new one, so that should be fixed.

I think we did a good job of bleeding the system - my mechanic followed the procedures.
We let some brake fluid sit in there for a while, then bled the frt/rear connections to the M.Cylinder, and bled at each wheel in the right order. I don't have a spongey petal.
I didn't get much chance to road test after putting the O-ring in.....I was told that small leak being sealed would keep the pump from running as often, but I'm not sure that's the case yet.
Thanks!

 

[zeus87gn]

Excellent!
Good to hear you got it going.