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928 brakes dragging and heating up one wheel, causing vibration !

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928 brakes dragging and heating up one wheel, causing vibration !

 
Old 05-21-2014, 12:21 PM
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Default 928 brakes dragging and heating up one wheel, causing vibration !

Guys,

As the 928 gets older we'll all be tending to more and more issues, and I wanted to share this one because I suspect there are others out there who will be seeing the same thing.

I would be running along and would eventually start picking up vibration caused by an overheating disc. I used a pyrometer to check and one wheel was always getting very hot. One then another. I wrestled with this for quiet some time, bleeding brakes, changing pads, type of fluid, and then rebuilding all the calipers.

The problem was the master cylinder had finally given up and run the bell (actually the booster is the part that was making the brake system operate like my foot was lightly on the pedal, not just the master cylinder, so all was replaced). This was determined by my friendly porsche guy who does the tough work on the car, and he is the one who replaced it for me following porsche directions of cutting an opening in the wheel well for access and then sealing it up properly after the work was done.

Now in finally reaching this final fix, I did have the pleasure of being outside and working on one wheel at a time regarding calipers, etc. Here are some photos for your viewing enjoyment.


My one front brake was 170 degrees and the other one was 350 degrees, and obvious sign the caliper was sticking.

<img src="http://ecx.images-amazon.com/images/I/41N5NyknHvL.jpg" alt="[linked image]">





Here's the crime scene. Not a pretty sight, but hey it was a beautiful day and this had to be done.
























Basically pull everything off, blow the piston out of the caliper with compressed air (low pressure please!), clean it all up, gently hone the cylinder bore, follow with 2000 grit sandpaper, spray everything down with cleaner, wipe it very very clean, use the brake cylinder assembly paste as a lube, apply the seals, press the piston in, add fluid, bleed, assemble the brake system, bleed again, test drive at 100 mph, all is well!

The discs were replaced at this time too, probably did not have to at the time but found a good slotted disc for a fair price so that worked out nicely.

Thankfully I live out in the country near (an airport) where I can see a long distance and have a nice straightaway for testing. The "28" is barely breaking a sweat at 100.


Regards,

P

Last edited by ...P; 05-21-2014 at 04:38 PM.
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Old 05-21-2014, 12:28 PM
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Ah...".This was determined by my friendly porsche guy who does the tough work on the car, and he is the one who replaced it for me following porsche directions of cutting an opening in the wheel well for access and then sealing it up properly after the work was done."
This is totally wrong !!! Your Porsche guy is a HACK, literally. The correct procedure is to compress the pedal and use a small strap and hose clamp to hold the plunger extended. The wheel well window is used to access the clutch master BUT NEVER was approved by Porsche.
And the failure of the booster locking of the brakes is an all to common every 20-30 years event Well documented in numerous posts.
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Old 05-21-2014, 01:01 PM
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Originally Posted by James Bailey View Post
Ah...".This was determined by my friendly porsche guy who does the tough work on the car, and he is the one who replaced it for me following porsche directions of cutting an opening in the wheel well for access and then sealing it up properly after the work was done."
This is totally wrong !!! Your Porsche guy is a HACK, literally. The correct procedure is to compress the pedal and use a small strap and hose clamp to hold the plunger extended. The wheel well window is used to access the clutch master BUT NEVER was approved by Porsche.
And the failure of the booster locking of the brakes is an all to common every 20-30 years event Well documented in numerous posts.

James, my lad, step AWAY from the caffine.

The fact that you or someone else has covered this already in the past has a bearing on what? I missed the point. That was then, this is now.

The tab is used when a decision has to be made about cost, time, and the recommendation of the advice given at the time. Had we known about your opinion at this time, we would have flown you into town so you could have supervised this. Why would an expert mechanic give me that advice? Because he is a hack, or because this is the way a 928 is fixed in the real world? I have to side with my mechanic on this one, sadly might be less than the perfect solution, but hey I'm a less than perfect guy and I'm on a budget most of the time. That is why I drive an old one.

best,

P
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Old 05-21-2014, 01:11 PM
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Here are a couple other photos of the brake system, for anyone who is contemplating doing this themselves.

Sorry for wasting anyone's time for those of you who already know all about this or have discussed it a thousand times before, lol. For those of you interested in doing this yourselves, I hope you enjoy the photos and find them informative.





The system before the work was done.






















regards.

P
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Old 05-21-2014, 02:22 PM
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Originally Posted by ...P View Post

James, my lad, step AWAY from the caffine.

The fact that you or someone else has covered this already in the past has a bearing on what? I missed the point. That was then, this is now.

The tab is used when a decision has to be made about cost, time, and the recommendation of the advice given at the time. Had we known about your opinion at this time, we would have flown you into town so you could have supervised this. Why would an expert mechanic give me that advice? Because he is a hack, or because this is the way a 928 is fixed in the real world? I have to side with my mechanic on this one, sadly might be less than the perfect solution, but hey I'm a less than perfect guy and I'm on a budget most of the time. That is why I drive an old one.

best,

P
He is only an expert in your "real world" simply because he THINKS he knows more than you do..... I am curious what he cut away, am sure others would like to know, how about a photo of that bit of craftsmanship. And doing it right is pretty easy if you know how to do it , have and can read the workshop manuals or even take a few minutes to search here for brake booster removal...several excellent tutorials. Where the novice gets in trouble is first removing the pedal connection clevis then after unbolting the booster the rod projects too far to allow you to turn and remove it.... This is the first time I ever heard of ANYONE needing to cut a window for this repair. But it probably has happened as people have done some strange things to these cars.
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Old 05-21-2014, 02:34 PM
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Sure for anyone who wants to know how this is done, i'll be happy to spend the time to document it.

And for you, work on those interpersonal skills, they're self defeating.

best,

P
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Old 05-21-2014, 03:17 PM
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"And for you, work on those interpersonal skills, they're self defeating."

The hacking is neither necessary nor desirable, and doing the job the right way eliminates permanent damage to the car.

Being nasty to someone who helps as many people on this Forum as James does won't win you any admirers.
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Old 05-21-2014, 03:25 PM
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Originally Posted by ...P View Post
Sure for anyone who wants to know how this is done, i'll be happy to spend the time to document it.
James asked to see how the repair was done so we can judge how bad it really is and to show an example to others what not to do.

Nothing needs to be documented, just post a photo of what was cut away to remove the booster.
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Old 05-21-2014, 04:22 PM
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Originally Posted by WallyP View Post
"And for you, work on those interpersonal skills, they're self defeating."

The hacking is neither necessary nor desirable, and doing the job the right way eliminates permanent damage to the car.

Being nasty to someone who helps as many people on this Forum as James does won't win you any admirers.

hahaha, Wally, the good old boy club patting themselves on the back here, please read his initial postings and see the lack of respect he threw first. Just responding as prompted.

P
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Old 05-21-2014, 04:35 PM
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For anyone who cares to follow this thread any further, intended to be good natured and honorable, only to be jumped on like a 20-dollar bill being dragged through a trailer park.

Richeous indignation aside for my posting, your own forum is full of this info.

https://rennlist.com/forums/928-foru...inder-job.html

https://rennlist.com/forums/928-foru...-hose-job.html

https://rennlist.com/forums/attachme...ch-mc-hole.jpg

http://arnnworx.com/images/928/Clutch/x4.jpg

http://wordpress.sempca.org/wp-conte...r-cylinder.jpg


http://forums.pelicanparts.com/uploa...1325993542.jpg

Did you note the comment about the guy who tried for hours, and then did the deed quickly once the fender was open?

I looked at my fender at lunch today, it is very neat with no issues. At the time I think I was told something similar, like this is something that could take us hours but we normally cut the fender for this.

Upon hearing that I did not know any different so I said okay. So if you want to jump on me for not being informed, or perhaps not having someone spend hours at my expense for doing it a different way, so be it.

Today, armed with what I know now and the manner in which it was delivered to me on this forum, and having seen my fender, I would make the same decision now.

This could have been dealt with in the following manner:
"You know that is one way to fix these cars and we see it from time to time, but there is a better way to do it and here is how."

When you guys can elevate yourselves to that level when responding, instead of posturing yourselves as know-it-all elitists, you will get less crap back from people like me who post things with good intentions, and don't really appreciate the $hit we get back for taking the time to post things we think will be of value to others. Actually some of you should post something of value and/or interest. Since I have received more readership here on this forum today than anyone else, maybe some of you guys who have nothing to do but snipe on someone elses commentary can dream up something to post, that has not already been discussed lol.

best,

P

Last edited by ...P; 05-21-2014 at 07:39 PM.
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Old 05-21-2014, 05:31 PM
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Hey, it┤s all group dynamics. People with an attitude only get accepted here if they expose exceptional 928 knowledge. Guys with an attitude and poor knowledge disappear very quickly around here. They hunker together over at Pelican and complain to each other how unfair Rennlist is.

Btw: the left front wheel well shows a cut and bound wire. Is that the wear indicator or ABS?
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Old 05-21-2014, 05:38 PM
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Originally Posted by Leon Speed View Post
Hey, it┤s all group dynamics. People with an attitude only get accepted here if they expose exceptional 928 knowledge. Guys with an attitude and poor knowledge disappear very quickly around here. They hunker together over at Pelican and complain to each other how unfair Rennlist is...
This is true.
Like all things in life, temperance is a good thing.
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Old 05-21-2014, 05:41 PM
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Originally Posted by James Bailey View Post
Ah...".This was determined by my friendly porsche guy who does the tough work on the car, and he is the one who replaced it for me following porsche directions of cutting an opening in the wheel well for access and then sealing it up properly after the work was done."
This is totally wrong !!! Your Porsche guy is a HACK, literally. The correct procedure is to compress the pedal and use a small strap and hose clamp to hold the plunger extended. The wheel well window is used to access the clutch master BUT NEVER was approved by Porsche.
And the failure of the booster locking of the brakes is an all to common every 20-30 years event Well documented in numerous posts.
The master clutch cylinder replacement make a lot of sense, but not the master. the master is connected to the vacuum booster, and that's an EASY open the hood and replace, job.

I had this problem on a BMW. the brake master wouild drag the brakes. all sorts of other solutions were given by the BMW community, but as I suspected, it was the master. also an easy fix on that car.

so, why was there a fender hold cut for the brake master job??

I also had a master cylinder fail on the old black 79 beater 928 from the start. it would fill with fluid into the vacuum booster . after putting the new master on, it was fine. easy job
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Old 05-21-2014, 05:47 PM
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P - I'm sorry you felt James was jumping all over you and I know you were just trying to be helpful. However, please try to put yourself in his place: Just how do you inoffensively tell someone their trusted mechanic is a quack? Let's face it, when any of us have done something or had something done to our cars that we're proud of, there's simply no good way to say that what was done was wrong. There's no good way to say we've trusted the wrong guy. Few of us wouldn't take such a message -- no matter how carefully worded -- as an insult.

On the other hand, this forum is read by lots of people who are new to the 928. If James had been all diplomatic (a/k/a mealy mouthed) in the way he worded his response, many of those newbies might have concluded that what you had done was okay. After all, these newbies might conclude, you said it was the Porsche approved method. And, James -- a guy with over 15,000 posts -- seemed to think what you did was alright. He didn't say what you did was wrong. All he said was "some people with a lot of experience are able to make this repair without cutting a hole in the wheel repair, but there's always more than one way to do things...."

So, James could have worded things differently. Had he done so you still might have been pissed off and a bunch of newbies might have been misled. On balance, while I'm sorry your feelings were hurt, James made the right call.
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Old 05-21-2014, 07:36 PM
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Originally Posted by DKWalser View Post
P - I'm sorry you felt James was jumping all over you and I know you were just trying to be helpful. However, please try to put yourself in his place: Just how do you inoffensively tell someone their trusted mechanic is a quack? Let's face it, when any of us have done something or had something done to our cars that we're proud of, there's simply no good way to say that what was done was wrong. There's no good way to say we've trusted the wrong guy. Few of us wouldn't take such a message -- no matter how carefully worded -- as an insult.

On the other hand, this forum is read by lots of people who are new to the 928. If James had been all diplomatic (a/k/a mealy mouthed) in the way he worded his response, many of those newbies might have concluded that what you had done was okay. After all, these newbies might conclude, you said it was the Porsche approved method. And, James -- a guy with over 15,000 posts -- seemed to think what you did was alright. He didn't say what you did was wrong. All he said was "some people with a lot of experience are able to make this repair without cutting a hole in the wheel repair, but there's always more than one way to do things...."

So, James could have worded things differently. Had he done so you still might have been pissed off and a bunch of newbies might have been misled. On balance, while I'm sorry your feelings were hurt, James made the right call.
Thanks for the note, no feelings hurt. Absolutely understand the NEED for policing the info base here, as I do on my own forum. If I stated this was a Porsche procedure, then I was wrong and admit it. Understood.

You have misquoted James by the way, lol. I understand he meant well so I'll give him a break. The problem with these forums is the fact that the written word banged out on a keyboard comes off as a knee-jerk mouse clicking contest sometimes, and it often does not represent the intended tone.

I have not encountered the underlying attitude of superiority experienced on this forum for quite some time. You guys should not be proud of the fact you run people off to another forum, because it makes me think about what other people say behind our backs about Porsche owners, and there is no need to repeat it here.

If you own the car, know it's a two syllable word, and take good care of it with good intentions, you deserve due courtesy even if you ask a dumb question.

So yes, I see the validity of many of your comments and don't take issue with them at all. Thank you for your comments.

regards,

P
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