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Bogboy

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Discussion starter · #1 ·
Okay, here is the deal. 67 Camaro, 4-wheel drums, power brakes, new master cylinder, new lines, new wheel cylinders. I have searched previous posts for answers and here is what I've concluded. I've bleed the entire system three times now. First two times with one of those one-way check valve bleeder cups, starting at furthest wheel from master etc. Last time, I used a hand held vacumm pump. The last time, I had a firm pedal until engine fired and vacumm applied. Then pedal went to the floor with front brakes only.

I have read that I may be sucking air in past the bleeder screw threads and that pipe thread tape may do the trick here. Also I've thought about gravity bleeding the brakes if that doesn't work, but have read you can't gravity bleed the rear brakes.

I've never had a problem bleeding brakes before, but this one is starting to annoy and as we all know, brake fluid can make such a mess.

Your suggestions please.
 
#2 ·
Did you banch bleed the master before you installed it?If not,this can be the cause of hard to bleed brakes.

------------------
67 RS RAGTOP # matching
4X4 Chevy truck
4X4 Suburban
 
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#3 ·
Sorry to hear you are having trouble.

Make shure the new master has the same depth pushrod hole in it as the origonal one.

Make shure the master cyl is bled at the fittings, and the brake lines have been tightened enough to seat the brass seats in the master. Sometimes they don't fully seat them at the factory.

When doing any vaccum bleeding use teflon tape around the bleeder threads to prevent sucking air.

Why did you replace the master in the first place? Were you having a brake problem, and what was it?

David

------------------
Check my web page for First Gen Camaro suspension info:
David's Homepage
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Can Am Vintage Racer
 
Discussion starter · #4 ·
Actually David, the master was freshly replaced when I bought the car. Since then we've gone the resto route and have had everything off and back on... you know the drill. The master was dri at one point though. I've just come in from vaccum bleeding the rears again, this time with teflon tape on the bleeders. Seem to go a lot better, but brakes are still way spongy when car is fired and vaccum is applied. I been able to get plenty of fluid through the system from master to each wheel cylinder, could the master still not be bleed properly though?
When I removed master, I tried to retain the fluid in it and cap off the holes.

If I do need to bench bleed the master, what is the proper procedure?

Thanks for all the help.
 
#5 ·
If you are getting a good fluid stream at the back wheels try this method,
Jack the front of the car as high as you can get it, Pump the pedal 4-6 times until it is good and firm, hold the pedal down over night by bracing the pedal with a broom stick or somthing. Remove master cylinder cap, Don't forget to disconnect the battery.
Any air in the system will rise upwards and bleed off through the open ports of the master cylinder.
One last thing when you try your brakes after bleeding are you driving the car? With a good booster the results you are getting could be normal, in reality you would never be able to push the pedal that far down while driving, you would be in a lock up condition befor the pedal goes half way down.
Also double check the adjustments of the shoes, there should be a slight drag at each wheel when rotated.

[This message has been edited by Rob.Canada (edited 08-31-2000).]
 
#6 ·
One way is to put the m.c. in a vice, fill it up. Put fittings with rubber hoses (usually supplied with m.c.)from the ports back to the resevore. SLOWLY compress the the cylinder back and forth untill all the bubbles are gone. Make sure to keep the hoses submurged.
Another way is to fill the master, wait 'till the fluid starts to trickle from the ports, seal off the ports with fittings(usually supplied with m.c.) then push the cylinder about 1/4-1/2 inch wait 15 seconds and repeat untill you can't push it in anymore, and all the bubbles are gone. Waiting 15 seconds allows the air to escape from the compensating port.

Ron
 
Discussion starter · #7 ·
Rob,

I am driving the car, albeit just in the driveway. The pedal simply goes way to far to the floor for comfort. I tried the stick method last night before I went to bed, however, I did not jack up the front of the car. I have not tried it again however, will this evening. If this doesn't work, I guess I'll have to pull master and bench bleed and repeat the procedure.
Yes shoes have been adjusted. I thought of this after the second bleed trial and all four are at the point of a slight rub.
Do you or anyone else feel this condition is being caused by the rear brakes and air, or simply air in the system period.
I racked my brain all night on this one looking for solutions. Thanks to all who reply...

Pat
 
#8 ·
Having been a student of this site for some time now, it seems that it is imperative that you bleed the master cylinder if it goes dry or is new. I would bet a big mac this is where your problem is. NAPA or any store sells a kit that contains fittings that screw into the master cyl. ports and then have lines that hook over the top of the master cyl. and down into the reservoir to help bleed and keep the mess down. It just sounds to me like you know what you are doing and have bled all the brakes lines as you are supposed to, but you need to bench bleed the master cylinder on it's own first. Let us know what worked!
 
#9 ·
No need to removed the master cylinder to
bleed it. I just ran a hose from the bleeder
screw in the master cylinder and back into the resvour. Loosened the screw and slowly pump the brakes until all the air is out.
Tighten the screw and do the other 1/2 of the
master cylider. Then use the hand-held pump to bleed the brakes. It worked for me and it took me about 30 minutes to do mine....
 
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#10 ·
The rear brake line is fairly large and may allow a bubble of air to stay near the master cylinder.
Bleed the brake lines where they come out of the master cyl.

Press on the brake pedal and crack open the brake line flare nuts, one at a time, until straight fluid comes out, no air.

If you have bleeder screws on your master like the later 69 type you can use them. But I'm shure your master doesn't have the bleeder screws on it.

Your master cyl has a residual pressure valve behind the brake line seat and this may prevent all the air from bubbling up into the reservoir. Air can get trapped in the rear brake line near the master cylinder.

I've seen a lot of posts here about the same type problem you are having, you are not the first or the last to have this trouble. Hang in there.

Make shure to check the brake shoe adjustment and the parking brake adjustment.
If you have a stuck self adjuster the pedal would go down like you are experiencing.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Homepage
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Can Am Vintage Racer
 
#11 ·
Bench bleeding is the way to go, but I also had problems once after bench bleeding.
From an old post of mine:
"The rest of the folks may scoff at this comment, but it sure solved my problem. I put on a new master cyl and tried multiple times to get rid of the spongy feel to no avail. My next door neighbor is the local Smog Referee and he came over to help. He suggested that we disconnect the master cyl from the power booster and tilt the master cyl forward with all the tubing attached so that the master cyl was completely level. Then we used a 4" x 1/2" bolt to depress the piston on the master cyl while bleeding the brakes as Curt suggested. Once the brakes got firm we reattached the master to the booster and the brakes worked perfectly. Apparently there is some cavity in the master that may not fill up due to the extreme angle that the cyl normally sits at against the firewall. I thought putting the car on my sloping driveway would give me enough angle to circumvent this master cyl detaching, but even my steep driveway wouldn't put the master at a level position. I know it sounds like a lot of extra work, but it you have checked everything else, this might work for you like it did for me."
 
Discussion starter · #12 ·
Thanks everyone for the suggestions. I just bench bled the master, reattached it, depressed the brakes slighty to with lines loosely attached to master to rid of any more air and tightened everything down.

I then did the wheel cylinder bleed drill in proper sequence using a hand held vacumm pump.

I have now placed a stick on the pumped up brakes and left the cover off over night for any final bubbles.

I'm not sold though, the pedal still felt spongy when pumping them up for the stick treatment.

Thanks Bone for the suggestion, I'll see what I've got for brakes tomorrow morn and post back.

Any other suggestions appreciated.

Pat
 
Discussion starter · #13 ·
I'm back again. After doing the entire drill once, I did it again. Bench bleeding etc... this time taking even more care not let any air into the lines when attaching the master. I first vacumm bled each wheel cylinder then with the loving assitance of my wife, I bled them the old fashioned way. Pure fluid...

I took the car up and down the block today and the brakes are there but the pedal goes way down. Have I just not driven this car for so long, I've forgotten the feeling of power drum brakes? Or do I need to further adjust each shoe to a closer tolerance to the drum? Maybe I'm spoiled by today's new cars and I've just forgotten the way these old beauties feel?

It still doesn't feel right though... I'm off to readjust shoes to drums and try it again tomorrow.

Thoughts?????
 
#14 ·
Bogboy,
I have a 67 with drum brakes, non-power. I had the same problem you are experiencing. No matter how well I bled the brakes, the pedal went to far to the floor for comfort. I solved my problem by lengthening the rod that goes from the brake pedal to the master cylinder. It is adjustable by loosening a jam nut, then threading it out or in. By lengthening the push rod, the brakes begin to apply much sooner. I have never been able to find this procedure in any manual, so I'm not sure if it is an acceptable thing to do or even safe for that matter. If not, I wonder why the rod is adjustable though? Maybe someone else can tell us if this is an advisable thing to do. I would not suggest doing it until you confirm that it is safe and there is nothing else wrong with the rest of the brake system. I could not resolve my problem any other way. An earlier post on this thread mentioned something about the master cylinder plunger depth. Does that have something to do with the fact that the push rod is adjustable?

Rich
 
Discussion starter · #15 ·
Interesting Rich... Since I've had the car down to nothing at one point in time, I do recall the adjustment on the rod. Good suggestion... I very well could have moved this. Does anyone know if there is a proper procedure for this? Or if it is even recommended. Obviously there is an adjustment.

??????
 
#16 ·
On a manual system the pushrod should lightly contact the master cylinder pushrod and be between 1/16" and 1/4" clearance from the brake pedal arm to the rubber pedal return stop.

The power brake pedal is a much lower pedal position and can be adjusted higher as long as there is no pressure against the booster.

The main thing to remember is to allow a clearance to permit the master cyl piston to return fully. If this does not happen the brakes could pump up and lock, or the piston might not uncover the replensihment orifice. This would prevent fluid from entering the master cyl bore and cause a low pedal when brakes are applied and would prevent proper bleeding.

Bogboy,
You are shurely getting to be a pro at bleeding brakes!

One way you can test weather the problem is on the rear brakes is to carefully clamp off the rear brake hose. If you get a really high pedal then, the problem must be a rear brake problem, not the master cyl.

I have used a needle nose vice grip pliers with the straight jaws. I pad them with thin aluminum or cardboard like used in cereal boxes to prevent damaging the brake hose. I clamp kinda lightly just enough to squash the hose without damage, then try the brakes.

It's sounding more like a rear brake shoe adjustment problem. If the rear brakes are loose, it would use up a lot of travel.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Homepage
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Can Am Vintage Racer

[This message has been edited by davidpozzi (edited 09-03-2000).]
 
#17 ·
How did the brakes feel before you did the work? The only other thing I can think of is the drum size. If a drum is over sized, the shoes will have to open up more at the top even if they're adjusted out at the bottom.

Ron
 
#18 ·
Bogboy,
As the owner of a brake shop I can tell you I cant count the number of times I have had do it your selfers bring thier cars to me with the same problem you describe. It is imperitive that the shoes be adjusted to within 3/32 of the drum. A good adjustment should very lightly drag on the drum. If 1 out of 4 is out of adjustment the pedal will be terrible.
 
#20 ·
Bogboy,

I recently converted my 67 from drum to disks all the way around, including new lines, MC, booster, etc...and experiences many of the same frustrations. I just re-read this thread from beginning to end and you have received all the same suggestions I got. I must have redone everything 3-4 times but I think I finally got it. I say "I think" because while the pedal is firm, I don't have the car running yet.

What I think finally did it for me was a re-tightened every connection in the system. Then I just let it sit for a while, like a week+, then I bled it one more time, making sure I had good seals around the bleed screws.

The "sitting" part may sound silly but I had read that if you are doing too many things, and especially if you get a little frustrated and rush, you can foam up the fluid in the system and this takes a long time to work out.

Hang in there. You will get it.


------------------
Mark M.
Red 67 Convertible
Red Deluxe Interior
383/Tremec 5 Speed
4 Wheel Disk
 
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