Brakes

[RacerBill]

Brake issues are giving me fits. Don't know if there is any real reason for concern. I bled the brakes yesterday, following standard methods. The right rear had some bubbles, but not bad. I would get a burst of bubbles if I pushed the pedal all the way to the floor, but did not get them if I closed the bleed screw before the pedal got all the way down.

After bleeding, the pedal was nice and firm. When I turned the engine on, and the power brake was active, the brake pedal goes almost to the floor, and is not as firm.

The car is an 83 Dodge Shelby Charger.

Any suggestions?

Thanks.

[charrbq]

On the safe side, get a new master cylinder. A new PB booster might help, but bubbles only come from air getting into the system. If that doesn't work, check out each of the wheel cylinders on the rear drums for cracks in the rubber. ( I assume the car has rear drums, not discs)

[Z3_GoCar]

Sounds like a leakey master cylinder. Your car's about the right vintage for that to happen from pitting with bad brake fluid, from the previous owner. I'd say get a new master cylinder should solve this problem. Let us know how this goes.

James

[lateapex911]

Another vote for a new master. often the cylinder walls become pitted where the piston rarely travels. Then you bleed them, pushing the piston into rarely traveld areas, scuff up the piston seal, and it bubbles forever. It's too important a part to not be on an auto replace whether it needs it or not schedule anyway.

[RacerBill]

OK - three to nothing for a new master cylinder. I know I have one somewhere in the boxes of parts that came with the car. Now, we will have to try a new task that we have not done before!

Thanks for the advice!

[JeffYoung]

I had this same issue - firm pedal with car off, soft pedal with car on.

New MC helped.

[zracre]

that is why I never fully extend the MC when bleeding if it is not brand new...all of my brake bleeding is done compressing the old fluid (and air) out of the calipers with the bleeder open then lightly hit the brake pedal (no more than half way) until they are pumped up then gravity bleed until clear. It is easy and works especially when you are alone. I have never had problems with brake fade or excessive air in the Integra brakes. I also use Valvoline Syntec fluid (cheap and works fine).

[Eagle7]

I also use Valvoline Syntec fluid (cheap and works fine).
[/b]

Ditto.

[lateapex911]

Bill, I would be VERY careful when using "new" used spare parts. You could find the same issues. Call your friendly NAPA store and get a price on a new or freshly rebuilt unit.
First, doing the job twice is just infuriating, and second peace of mind is woth a lot. It's money well spent.

[RacerBill]

Jake: Thanks for the advice. Actually, I priced new/rebuilt units, and your suggestion will both save me time and worry.

Question: If I replace the fluid with synthetic, I will need to purge the old fluid. Is the synthetic fluid a different color so I can tell when the old fluid has been cleared?

Thanks, again. To all who responded!

PS We're still havin' fun. The crew chief and CFO told me yesterday though, that the next car we get will be all set up. Don't know if she realized that the word 'next' implies that this car is not the last race car we'll own! Better shut up while I'm ahead!!!!

[zracre]

the valvoline is compatible with other fluids...I didnt run into any problems...

[lateapex911]

Yes. flush flush flush! Many syns are compatable, but...you still want to flush out all old anyway. It's not hard anyway. Certain fluids come in blue and amber...same stuff, diffo color, for just that purpose. Works great.

[Matt Rowe]

Bill,

I'll throw in another vote for a new M/C. Another thing I will warn you about on that particular car is the brake booster. At least in my case I have figured out the average useful life is 10 hrs on track before it's time to replace it because the two halves of the shell start flexing too much to be able to properly modulate the pedal. Next time you have your crew chief in the car have them press the pedal down hard while you watch the M/C for movement. On a new booster there is virtually no movement, after ten hours I see about a half inch of movement. You can guess what that does to brake pedal feel. It may just be me and my setup but I would suggest keeping an eye on it.

[Z3_GoCar]

....
PS We're still havin' fun. The crew chief and CFO told me yesterday though, that the next car we get will be all set up. Don't know if she realized that the word 'next' implies that this car is not the last race car we'll own! Better shut up while I'm ahead!!!!
[/b]

You do realize that "ready to race" is a psudeonym for "This race car is a used up, clapped out, piece of junk, that needs a total rebuild" :P I mentioned this to some vintage racer I know in front of my wife, and they were laughing about the "ready to race" motor that actually was ready to race. It was so rare that they had to put in a second set of gaskets after they had it disassymbled. It's helped cool my CFO down about the original state of my racer.

[RacerBill]

James: Yeah, know what you mean. I didn't want to tell her that no race car is ever 'finished' until it falls apart.

Matt: Good to hear from you, again. Havin a great time with the Shelby. Send me a PM with your address, and I send some video, and pictures.

[BAC]

Hi Guys....
I don't mean to HiJack the thread but can someone explain how to "bench bleed" a MC??

Thanks a TON !

~Brian

[JeffYoung]

I didn't do it on my last m/c change, and wish I had.

The instructions said to put the m/c in a vise on your workbench. Put fittings in the outlet holes and attach hoses to them to a drain cup. Fill the m/c with fluid, and work the piston slowly until no air comes out of the holes.

That's it. Again, wish I had done it. They say you can't really get all of the air out of the m/c by a standard on car bleed.

[Ron Earp]

Here is a link to that procedure. It is more for convienence and ease than anything else because it will make your life easier when you install - but it isn't "manditory" for a firm pedal. Idea is you plug the cylinder after bleeding and therefore when you install it it will have little air in it at all.

http://www.misterfixit.com/brakbld1.htm

You can do a perfectly fine job bleeding your master as a normal procedure, or, you can use vacuum on the lower end, or pressure on the reservoir if that makes you even more confident.

[RacerBill]

bench bleed - yeah, had a fit when I read about that in the instructions that came with the mc. Their instructions called for taking the proportioning valve off, attaching it to the mc, plugging the holes in the proportioning valve, fill the mc with fluid, and work the piston.

The only way the proportioning valve is coming off is if I replace all the lines (which I may do as a winter project).

Lucky the mc came with these two cute little plastic plugs that fit into the outlet ports on the mc. Plugged them up, filled the mc and worked the piston. Then mounted the mc, and reattached the lines to the pro. valve.

Took some time to get all the air out of the longest line - but at least I know there is fresh fluid through the entire length. Will get the other three lines tonight.

Thanks, again for the advice on the mc.

[BAC]

Thank you for the info guys!
It should save me some time.

~Brian