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Brake Pedal Push Rod Vs. Master Cylinder Preload
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Ian
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PostPosted: Thu Oct 28, 2010 11:00 pm    Post subject: Brake Pedal Push Rod Vs. Master Cylinder Preload Reply with quote

Hi Volks...bit of a stumper here, working on a 59 Bus with single circuit brakes...

I'm fixing a lot of issues with a previous brake job (by a hack) and trying to get things figured out. I replaced the M/C reservoir and went to reinstall the M/C and the brake pedal push rod is pushing the plunger of the M/C in before I can get it bolted, giving it a preload. As it's my understanding, there should be a empty space between the pushrod and the M/C plunger, right? I have the push rod screwed in as close as I can to where it pivots before it starts to bind where the threaded part meets the end of brake pedal. So...what exactly is going on here? I have one more pushrod for a Splitty and it's the same length. I think the solution is to cut 1/4" of the threaded part of the push rod off, but I don't want to be "that guy".

Thanks for any help!

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Andrew
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PostPosted: Fri Oct 29, 2010 5:34 am    Post subject: Reply with quote

Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.
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PostPosted: Fri Oct 29, 2010 5:52 am    Post subject: Reply with quote

Andrew wrote:
Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.


you are mistaken. a 67 rod is visibly different.
The left two are single circuit push rods up to 67 1/2. The length and diameter are different, as they are for different types of single circuit master cylinders that were installed on busses.
One on the right is for a 67 dual circuit master cylinder.
Image may have been reduced in size. Click image to view fullscreen.


Ian, yes, there is supposed to be about a 1mm clearance between the end of the rod and the plunger in the master cylinder. bend the stop tab, that's how you are "supposed" to adjust the pushrod clearance.
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PostPosted: Fri Oct 29, 2010 7:42 am    Post subject: Reply with quote

So it was correct before? You never took apart the master cylinder part? Weird for sure. Does it have the thick washer under the internal snap ring in the barrel? Is the snap ring in its groove?
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PostPosted: Fri Oct 29, 2010 9:18 am    Post subject: Reply with quote

BarryL wrote:
So it was correct before? You never took apart the master cylinder part? Weird for sure. Does it have the thick washer under the internal snap ring in the barrel? Is the snap ring in its groove?


It could have possibly been correct sometime in the 60's?

Unfortunately the last person to do the brakes did a piss poor job (glued the M/C reservoir, replaced 1 out of 4 rear brake shoes, installed bent brake shoes, installed bent adjusters, cut the e-brake cables and didn't reinstall the ebrake hardware in the drum). Luckily I have pics to document this person's "work". This person also replaced the brake pedal return spring(but left the nut on loose so the pedal wasn't even on the stop!!), so he was in there fat fingering the area and definitely fucked with the pushrod (notice new cotter pin). My customer was wondering why his brake job only last 100 miles. Rolling Eyes It's really ridiculous that the same person who disabled his e-brake, also did such a shotty brake job that the Bus has no pedal and no fluid in the reservoir. Very unsafe.

He could have swapped the pushrod for a different one?

I have 3 Bus master cylinders and the pushrod is too long for all three of them and gives each one the same amount of preload. I don't take the M/C's apart...

I'm going to grab some breakfast burritas then head to the shop and bend the tab and shorten the pushrod. Hopefully it works.
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PostPosted: Fri Oct 29, 2010 9:22 am    Post subject: Reply with quote

Andrew wrote:
Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.


I thought something like this but Jon's pic confirms that it has no 67 parts on it. The 67 has a shorter pivot piece and the pushrod is way different. The two I have are early style, long pivot straight rod same as the one on the left in his pic.

I'd like to find one like the middle, I think that is what would be in here originally because it is a shorter rod.

The coup de gras of the situation is that my customer took his 61 Bus to the same person for a brake adjustment...and now he has the scariest brakes ever!! On the first pump you get nothing, pump it again and only the right front wheel locks up!! It's scary! So this proves a direct correlation between the hack's work and no brakes.
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PostPosted: Fri Oct 29, 2010 10:23 am    Post subject: Reply with quote

If you removed a German MS and installed a Varga MC the push rod suddenly is too long.
You have to grind a little bit off the end.

grease the moving parts at the push rod clevis pin.
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PostPosted: Fri Oct 29, 2010 1:24 pm    Post subject: Reply with quote

You don't need to bend the tab on the body. That will acomplish nothing but making the brake pedal hit the bottom of the floor.

As of about five years ago the Varga master cylinders have a different shaped bore, and you need to grind the push rod to have a sharper point on it (or cut it shorter) to get the proper clearance. If messing up the orginal pushrod bothers you, grab an 8mm piece of allthread and shape it to fit.
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PostPosted: Fri Oct 29, 2010 1:42 pm    Post subject: Reply with quote

campingbox wrote:
You don't need to bend the tab on the body. That will acomplish nothing but making the brake pedal hit the bottom of the floor.

As of about five years ago the Varga master cylinders have a different shaped bore, and you need to grind the push rod to have a sharper point on it (or cut it shorter) to get the proper clearance. If messing up the orginal pushrod bothers you, grab an 8mm piece of allthread and shape it to fit.


Greg's right, I've had to do similar things on a few different buses and it works perfect!!!
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PostPosted: Fri Oct 29, 2010 4:39 pm    Post subject: Reply with quote

hazetguy wrote:
Andrew wrote:
Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.


you are mistaken. a 67 rod is visibly different.
The left two are single circuit push rods up to 67 1/2. The length and diameter are different, as they are for different types of single circuit master cylinders that were installed on busses.
One on the right is for a 67 dual circuit master cylinder.


Thanks for the correction. It's been a while since I've looked at a non-'67 pushrod. Embarassed
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PostPosted: Fri Oct 29, 2010 8:11 pm    Post subject: PUSHROD LENGTHS Reply with quote

WHEN I REPLACED THE MASTER CYLINDER ON MY 1960 SINGLE CAB SEVERAL YEARS AGO, I RAN INTO THE SAME PROBLEM...I FOUND THE FOLLOWING INFO AND SAVED IT...

The master cyl fitted into the 1500 transporter has a shorter stroke than the cyl for a 1200 transporter...The pushrod lengths are also different. The dimentions are as follows:
1500 transporter piston stroke 1.181 inches and pushrod length 2.32 to 2.36 inch
1200 transporter piston stroke 1.417 inch and pushrod length 2.735 to 2.774 inch

Found on page 105 in the 1954 to 1967 Transporter Workshop Manual Autobook # 834 , Copyright 1974.
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PostPosted: Sun Oct 31, 2010 9:10 am    Post subject: Reply with quote

i cut the pushrod and all's well!!

brake job perfection is a must!
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PostPosted: Thu Aug 22, 2013 8:18 am    Post subject: Reply with quote

Just to revive a thread about this pushrod length thing.
Yes, the new Brazilian replacement master cylinders take a shorter pushrod.
I found a beetle pushrod in the junk pile which happened to have a shorter length, and guesstimated it would be about right.

Installed it, and set the approx. 1mm free lash with the brake lever all the way up and it worked perfectly.

So, you might not have to modify your old pushrod, you may just have the right one in your pile of beetle bits and pieces.
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PostPosted: Fri Aug 23, 2013 6:37 pm    Post subject: Reply with quote

hazetguy wrote:
Andrew wrote:
Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.


you are mistaken. a 67 rod is visibly different.
The left two are single circuit push rods up to 67 1/2. The length and diameter are different, as they are for different types of single circuit master cylinders that were installed on busses.
One on the right is for a 67 dual circuit master cylinder.
Image may have been reduced in size. Click image to view fullscreen.


Ian, yes, there is supposed to be about a 1mm clearance between the end of the rod and the plunger in the master cylinder. bend the stop tab, that's how you are "supposed" to adjust the pushrod clearance.
so, the shaffer and ate single circuit master cylinders took a different length rod?
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PostPosted: Fri Aug 23, 2013 7:37 pm    Post subject: Reply with quote

Same thing happened to me... I just put a spacer between the MC and the frame.. Works great.. Just a thought. Good Luck!! Bob King.. 63 EZ lOng Beach,, Ca
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PostPosted: Thu Jan 23, 2014 12:13 am    Post subject: Reply with quote

hazetguy wrote:
Andrew wrote:
Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.


you are mistaken. a 67 rod is visibly different.
The left two are single circuit push rods up to 67 1/2. The length and diameter are different, as they are for different types of single circuit master cylinders that were installed on busses.
One on the right is for a 67 dual circuit master cylinder.
Image may have been reduced in size. Click image to view fullscreen.


Ian, yes, there is supposed to be about a 1mm clearance between the end of the rod and the plunger in the master cylinder. bend the stop tab, that's how you are "supposed" to adjust the pushrod clearance.


I'm hoping someone can answer a few questions about the pushrods:
1. I run a 67 only MC but have the pushrod on far left of pic. It was working fine for over a year. Is it ok to keep running this combination or should I try to find a 67 only rod?

2. I recently damaged my 67 only MC and replaced with a new one from Wolfsburg West. Do I adjust the pushrod length before or after bleeding? Can pushrod length be tweaked after bleeding?
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PostPosted: Thu Jan 23, 2014 12:36 am    Post subject: Reply with quote

Sidbus wrote:
hazetguy wrote:
Andrew wrote:
Is it possible that it somehow ended up with a '67 only pushrod on it? They're a tad longer than the earlier ones, but otherwise look the same if I'm not mistaken.


you are mistaken. a 67 rod is visibly different.
The left two are single circuit push rods up to 67 1/2. The length and diameter are different, as they are for different types of single circuit master cylinders that were installed on busses.
One on the right is for a 67 dual circuit master cylinder.
Image may have been reduced in size. Click image to view fullscreen.


Ian, yes, there is supposed to be about a 1mm clearance between the end of the rod and the plunger in the master cylinder. bend the stop tab, that's how you are "supposed" to adjust the pushrod clearance.


I'm hoping someone can answer a few questions about the pushrods:
1. I run a 67 only MC but have the pushrod on far left of pic. It was working fine for over a year. Is it ok to keep running this combination or should I try to find a 67 only rod?

2. I recently damaged my 67 only MC and replaced with a new one from Wolfsburg West. Do I adjust the pushrod length before or after bleeding? Can pushrod length be tweaked after bleeding?


I got my answer to #2 from Bentley…set for 1mm of play. That said, if I get 1mm play on the far left rod will it cause problems with a 67 only MC?
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PostPosted: Thu Jan 23, 2014 9:17 am    Post subject: Reply with quote

Sidbus wrote:
I got my answer to #2 from Bentley…set for 1mm of play. That said, if I get 1mm play on the far left rod will it cause problems with a 67 only MC?


It shouldn't cause problems as people make the longer rod when necessary. The ball head should fit inside the socket in the MC without binding. Put a dab of grease on the ball.
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PostPosted: Thu Jan 23, 2014 12:59 pm    Post subject: Reply with quote

Just to add to the conversation, when I replaced my MC with a german one from WW about 1.5 years ago, the MC sits a bit further forward than it should. You can tell by looking through the reservoir observation hole, the reservoir isn't in the middle of the hole. This caused the pushrod to put load on the MC before tightening as mentioned above, even with the push rod adjusted all the way in. WW denied this was possible, even after seeing the pic I sent them.

So instead of cutting the push rod and reshaping the tip (or making a spacer like rking6), I threw it in a die, added a couple more threads, and was able to get a proper adjustment on it. It's been working great for over a year so far...
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PostPosted: Fri Jan 24, 2014 10:30 pm    Post subject: Reply with quote

otis_bartleh wrote:
Just to add to the conversation, when I replaced my MC with a german one from WW about 1.5 years ago, the MC sits a bit further forward than it should. You can tell by looking through the reservoir observation hole, the reservoir isn't in the middle of the hole. This caused the pushrod to put load on the MC before tightening as mentioned above, even with the push rod adjusted all the way in. WW denied this was possible, even after seeing the pic I sent them.

So instead of cutting the push rod and reshaping the tip (or making a spacer like rking6), I threw it in a die, added a couple more threads, and was able to get a proper adjustment on it. It's been working great for over a year so far...


Otis,

You described the same problem I was having. Same replacement MC from WW. I got lucky and didn't have to cut threads…was able to get the pin back far enough by slightly bending back the pedal stop. It only took a tiny bit more space. I actually heard the pressure release and my front calipers let go of the wheel.

(and I still have clearance between linkage arm and bottom of floor)

BarryL,

Thank you for the reassurance…intuitively I couldnt' see a problem but it's always good to double check…or with brakes triple check.
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