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I missed toomanytoys diagram above. The bottom line is that when installed the piston and rod should have no clearance. Be careful when you start adjusting. You do not want the rod pushing on the piston to the point the piston is set past the feed hole in the bottom of the master. If that happens you will have good brake pedal but over time it will go down due to brake pad wear. That's because the master won't be able to refill the cylinder itself and compensate for wear.
I just replaced a MC and booster on my 1980 Bronco. Yeah I imagine they are a bit different but does yours look anything like this?
Mine required a bit of adjustment so I held the splined part with channelocks and turned the end with a box end. I had to go back and forth a few times until I hit the sweet spot.
OK, again a picture would be helpful. To start with if you look at your master the piston should be flush with the end of the cylinder minus the snap ring that retains it. There should be a shoulder on the master of about 1/2 inch or so to fit into the booster. Measure the distance from the tip of the rod to the opening on the booster and then measure the distance from the bolt boss on the master to the end of the piston. It should be the same.
FWIW, the booster should be hydraulic and starting the truck without the master on will not harm anything. Have you tried to press the pedal with everything installed and checking for end play? That much play should be pretty obvious.
My truck is a 2011 F250 Super duty XL 6.2L engine Flex fuel 4WD. The Booster is Vacuum and Not Hydraulic. It works off of Vacuum from the engine. All of the pictures that others have sent shows the master cylinder push rod protruding from the opening in the booster. Mine does not. The master cylinder has a lip that goes into the vacuum booster about 1 3/8 inches. I am now wondering if something is wrong with the booster although it tests good. and no vacuum leaks. I think most who are responding have older trucks which are different. maybe someone who has a newer truck or has worked on one like mine will chime in. Thanks to everyone who has responded. I will take some pictures and post.
Mel
Here are some Pic's I took this morning of the master cylinder off and on the truck. also a picture of the (I think is the ABS Controller)??
Mel
you can see the part that goes into the Vacuum Booster it goes in about 1 3/8 inches. and the push rod in inside the vacuum booster and does not protrude. no way to Be able to hold the rod for adjustment unless there is a special tool.
Master cylinder installed on truck.
I assume this is the ABS Controller ahead of and below the master cylinder..
If your booster were bad then you would have no brake assist but still have brake pedal. The connection to the diaphragm from the brake pedal to the rod pushing the master cylinder piston is solid. The booster does not do anything except help with brake pedal pressure. Again, measure the master from the bolt boss to the end of piston where brake rod connects to and measure the end of the rod in the booster to the bolt flange on the booster. It should be the same or very close.
The image I posted above is from the 2003 manual, every time a platform is changed there can be alterations. You really need to have the service manual for the vehicle being serviced.
The 2011-2012 booster may or may not be adjustable, again a review of the proper service manual would indicate this.
Examples of 2011 vacuum booster and master.
That is the ABS controller. Again a review of the service manual should show if there is a manual check if the valves are bypassing or if you need to go with proper scanners to check that isthe source.
The image I posted above is from the 2003 manual, every time a platform is changed there can be alterations. You really need to have the service manual for the vehicle being serviced.
The 2011-2012 booster may or may not be adjustable, again a review of the proper service manual would indicate this.
Examples of 2011 vacuum booster and master.
That is the ABS controller. Again a review of the service manual should show if there is a manual check if the valves are bypassing or if you need to go with proper scanners to check that isthe source.
I'm not sure if it's a optical illusion but the top pic of the master looks like the piston is recessed into the master. The next pic shows flush while the bottom two show a different master altogether. To the op, is your piston in the master recessed?
Edit to add: I noticed the distance (depth) of one master is shallower than the other. I wonder if he is getting the right master? Could be he is getting a master for a hydraulic unit instead of a vacuum unit. Again, I am not familiar with his year but it might make sense that he has the wrong one.
Do you have rear disc or drum brakes. The only time I ever saw a problem similar to this is when the rear adjusters weren't working and the shoes were worn down. If the adjusters are not working they cannot keep the brake shoes adjusted and you will get low a low pedal until they have been adjusted manually. It kind of makes sense when you say it goes almost to the floor when backing up.
My Old and the new Master cylinder are the same. The piston is flush. Depth of of the piston where the push rod goes is the same on both using a vernier caliper. The Booster that you show in the picture looks just like mine. I went out and started the truck and took a ruler and measured from the top of the pedal to the floor. It is 6 inches. when I depressed the pedal it went down to 3 1/4th inches from the floor. I then pumped it and the pedal came up to 4 inches from the floor. a distance of 3/4th of an inch. The brake travel is excessive I think. there still may be some air in the system. I cannot get any more air manual bleeding the system at the calipers using the 2 man system. This leads me to believe that there may be air trapped in the ABS unit. Possibly 2 problems here.
1. excessive brake travel.
2. possible air in ABS when the master cylinder was removed and reinstalled. or ABS is dumping.
I do have a scan tool with ABS not sure of the procedure to check abs. 50 years ago when I was a mechanic we did not have all of the junk that is on the newer vehicles now days. This one has me stumped.
Mel
Mel, I realize your background and the shop work done to it, but I have to ask this as twice before people were jumping through hoops with a similar issue.
Have you confirmed all brake calipers have the bleeder screws higher then the brake hose entry?
Mel, I realize your background and the shop work done to it, but I have to ask this as twice before people were jumping through hoops with a similar issue.
Have you confirmed all brake calipers have the bleeder screws higher then the brake hose entry?
Toy and others please read this all of the way for a overall picture of whats going on.
THanks
OK I went out and checked again. All brake hosed are about the middle of the calipers. all bleeders are above the brake hoses where they enter the calipers. the bleeders are on the top. Lets review a couple of things.
1. 9 months ago I bought the truck. While bringing it home I noticed that there was excessive brake travel and the brake pedal would pulse sometimes. This was in Utah.
2. While in Arizona while getting ready to Pull a 5th wheel trailer I was worried about the excessive pedal travel and the pulsing. I took it to the Ford Dealer and they Turned all 4 rotors and installed heavy duty pads. They did not have Ford pads so installed Wagner severe.
3. the day I picked up the truck while driving back to our trailer I almost A$$ ended another truck during a panic stop because the truck in front of me had made a panic stop in the middle of the road. The brake pedal travel was the same only the pedal went to within about one inch from the floor.
4. I went back to the dealer and complained about the excessive pedal travel to the service writer. He had me pump the brake pedal several times and said that he heard a funny noise that sounded like a bad brake booster. They took my truck to the shop and 45 min later they service writer came and said my truck needed a new brake booster. I did not believe that and still don't.
5. I went home and bleed the brakes. And all was fine except for the excessive pedal travel. The brakes just did not feel right. I took it to the ford garage here in Utah and the service writer took it for a test drive and said that the brakes were OK and that the pedal travel was like that on all super duty trucks he said that he owed a super duty and that was the way his was.
6. a couple of weeks ago while coming up on a stop sign I stomped on the brakes and the pedal went almost to the floor and then slowly sank while applying pressure. all the way to the floor. I barely got stopped. Maybe the ABS unloading??
7. I figured that maybe The master cylinder was Bypassing internally. So I got a new master cylinder and bench bleed it and installed it on the truck. While removing the old master cylinder I could see where the Ford Garage in Arizona Had removed or slid back the master cylinder, probably while checking the Booster. I bleed the brakes using a Vacuum Bleeder. Then I used a clear plastic hose and bottle with the hose attached to the bleeder screw and submerged in brake fluid in the bottle. Using speed bleeder screws I bled the brakes. I noticed one of the front bleeders was maybe letting air back in. So I installed a couple of OEM bleeders on the front calipers and bleed the brakes again Using a helper to pump and hold the pedal. I ran a quart of brake fluid through the system using this method. No air bubbles while bleeding any of the calipers. this while bleeding the brakes for the second time using this method. yesterday. Still have excessive pedal travel. brakes do not feel right and will pump up 3/4th of an inch.
I am wondering it the booster push rod for the master cylinder can't be adjusted if this is why the ford garage in Arizona wanted to sell me a new brake booster. Every test I've made says the booster is good. The only thing would be the push rod adjustment. I am at a loss as what to do. I have a chilton manual for my truck, but it does not explain a test for the ABS says to take it to a shop with the proper equipment. It does say excessive brake pedal travel can be master push rod adjustment. I don't want to spend money for a new booster if that will not solve the problem and I want to make sure everything else is up to par. What are you thoughts?
Any help or suggestions are appreciated.
Mel
I don’t think that original shop did anything but picked from column A, then went to B without diagnosis. Thirty years in brake engineering and occasionally interfacing with shops, they won’t diagnose.
Chiltons is a poor example of a service manual, spend the $35 or whatever and get a Ford Service DVD for your truck. For this or any other issue.
ABS today is way to complicated to try to diagnose without the software, whether it be Ford IDS, Auto Enginuity, or FORScan laptop or cell phone. If you don’t want to spend the money, get FORScan or Torque app on a cell phone with an adapter is a monitoring system any vehicle owner should have.
As a vehicle owner with one vehicle experience, go take some used 2011 gas motor Superdutys at dealers or used car lots for a test drive so you have experience in similar vehicles and know how the pedal feels. You’ll have a comparison for this situation and the next service writer won’t be able to BS you.
If I bought that vehicle I would have done a master first off. The booster situation is kind of low on the probability list for me. If the ABS controller does not have the inspection ports as I’ve mentioned before there’s only one stupid thing you can try other then the proper electronics interface. Pull every fuse listed related to the ABS, or pull the connector off the ABS controller module. All vehicle speed readings since 2000 are done through the ABS, including speed, odo, engine and trans control. It will operate poorly, it will set codes, and it will set dash lights. Depending on the failure of the ABS controller, it may or may not show where the problem lies. But if your hesitant to take it to a shop to read the ABS, it’s your only shot.
I don’t think that original shop did anything but picked from column A, then went to B without diagnosis. Thirty years in brake engineering and occasionally interfacing with shops, they won’t diagnose.
Chiltons is a poor example of a service manual, spend the $35 or whatever and get a Ford Service DVD for your truck. For this or any other issue.
ABS today is way to complicated to try to diagnose without the software, whether it be Ford IDS, Auto Enginuity, or FORScan laptop or cell phone. If you don’t want to spend the money, get FORScan or Torque app on a cell phone with an adapter is a monitoring system any vehicle owner should have.
As a vehicle owner with one vehicle experience, go take some used 2011 gas motor Superdutys at dealers or used car lots for a test drive so you have experience in similar vehicles and know how the pedal feels. You’ll have a comparison for this situation and the next service writer won’t be able to BS you.
If I bought that vehicle I would have done a master first off. The booster situation is kind of low on the probability list for me. If the ABS controller does not have the inspection ports as I’ve mentioned before there’s only one stupid thing you can try other then the proper electronics interface. Pull every fuse listed related to the ABS, or pull the connector off the ABS controller module. All vehicle speed readings since 2000 are done through the ABS, including speed, odo, engine and trans control. It will operate poorly, it will set codes, and it will set dash lights. Depending on the failure of the ABS controller, it may or may not show where the problem lies. But if your hesitant to take it to a shop to read the ABS, it’s your only shot.
To many toys I really appreciate all of your input to this thread. All of my trucks in the last 50 years have been ford trucks and the last three trucks have been f250 super duty. a 2006 super duty diesel, a 2008 super duty gas and now a 2011 super duty gas. I have also had 2 ford rangers and a f150 in the past couple of years. I do know how the brake pedal should feel especially in a super duty as I've pulled several trailers with them. I have pretty well made up my mind that I will take it to a shop that has the proper equipment to test everything. If it is the Booster I will buy and change it myself. If it is the ABS then I will let them do it. I will post the results after it is done and the brakes are working like they should.
Thanks for all of yours and others help and information in regards this thread.
Mel
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Vacuum not hydralic
