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Dads Mechanic
Dads Mechanic, RV Body Repairer
Category: RV
Satisfied Customers: 202
Experience:  I was a rockwood camper dealer for many years from 1970 on many years Servicing motor coachs, rv's and motor homes.
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I have removed master cylinder and checked Bendix power brake

Customer Question

I have removed master cylinder and checked Bendix power brake unit,refitted master cylinder connected brake pipe not bothered to blead brakes and got a perfect pedal that does not want to build up pressure,why?
The Brake people want a reason before exchanging master cylinder, and at $385.00 I cant afford to just buy another one.
Submitted: 1 year ago.
Category: RV
Expert:  Dads Mechanic replied 1 year ago.

Dads Mechanic :

Sorry for your trouble, why did you change the master cyl & power unit. Was there something wrong with your brakes? Have you corrected the other problems? Thanks for coming to Just Answers. Jim!!!

Customer:

The master cylinder was leaking bad, I have been talking to

Customer:

Ron, but wasnt happy with the answer

Customer:

I ordered a new Master cylinder from Alretta Truck and Coach parts in Massachutus, he would not sell it to me untill he talked to me on phone as copper top hat washers seal are not available and we wanted to make sure I knew. as John Deare only made the right amount as what was on the production line.

Customer:

we have checked the casting Numbers to check its the right one.

Customer:

We fitted the new master cylinder, blead the brakes with and oil can and then 3 pumps on each wheel like we always do.

Customer:

we change the brake fluid every year.

Customer:

So we set off for a week end away and we got about a mile from home and we

Customer:

had a pedal with 1" play for Bendix power Brake unit,and about an 1" before brakes went solid.

Customer:

the pedal seamed to be self bleading till there was no play and brakes were binding.

Customer:

the only way to release the brakes was to release some fluid and then we could travel for a bit then release some more and we got home

Customer:

so what I have done is in the first question

Customer:

PLEASE NOTE

Customer:

This is a Fleetwood Southwind on a John Deare Chassis with Ford Running Gear

Customer:

and we have owned it for 6 years

Full Size Image
Full Size Image
Full Size Image

Customer:

enclose photo of Bendix power brake unit which master cylinder to

Customer:

see what type of brake unit I am talking about

Customer:

as most people dont know this vehicle

Customer:

The other chap Rod just said faulty Mastercylinder not good enough for the people wher i brought the master cylinder

Dads Mechanic :

I had the same problem with the unit, I'm not sure weather you have an oil or vacuum assist unit. as far as the copper washers, are you talking for banjo bolts. Youu can buy an assortment at any auto parts store. sometime you will need to readjust the push bolt between the power unit and the master cylinder. If the adjustment is off it will not allow the fluid to return to the resivoier, kind of like pumping up the brakes and keeping the pedal partialy applied. if you want to test to see if this is the problem you can remove attaching nuts and put 2 or 3 flat washers in between power unit and master cylinder put the nuts back on and try it.

Dads Mechanic :

get back to me and let me know if this works, if so you are going to have to adjust the push rod. Jim!!!

Customer:

You cant put washers between bendix unit and master cylinder as it will push seal out on Bendix unit and you have TQF oil all over the floor.

Customer:

The copper washer have a tube attached to them ,they were turned on a laithe

Customer:

The system has a pump the same as power stearing which works the power brake unit

Customer:

The end of the Master Cylinder is re-sessed and the Bendix power brake unit fits into the end to stop it moving,

Customer:

With the master cylinder off and very lightly press the brake pedal you can watch the piston come out and return home fully no adjustment on it ,Thats the 1 of the photos I sent you

Customer:

I have tried with master loose because some one else told me to try this and had to put new seal into Bendix power unit

Customer:

The Biggest problem is no one understands this kind of power brake unit designed by John Deare

Customer:

The new cylinder is Identical to the old all measured and checcked with a Vernier to the thousandth of an inch

Customer:

I am an mechanic and an engineer but this has got me stumped,I can usually mend anything

Customer:

This system is Hydraulic TQF or ATF power brakes with dot 3 brake fluid in master cylinder

Customer:

Any time before when we have had brake fade when fluid get hot or brakes not wanting to stop as well as usual we just drain brake fluid and replace blead brakes and problem solved.

Customer:

this has got all new brake fluid in completely drained and refilled

Customer:

push rod not adjustable

Customer:

there's play on pedal linkage when brakes are on and binding,so its not adjustment at the other end

Customer:

the rod from the pedal in the cab only adjusts the power unit have tried messing about with adjustment on side of road to get me home

Dads Mechanic :

sound like possibly the master cylinder has been fitted with check valves, possibly for rear drum brakes. to release brakes do you need to open both lines or just one?

Customer:

one front wheel only to release

Customer:

disc's all round same calipers on front as back disc pads are universal

Dads Mechanic :

Realy sounds like the master cyl is is not releasing the fluid back to the resivior the second piston may be stuck forward or just not returning to the neutral position. Where did you purchase the master cyl? They realey shouldn't give you any trouble replacing the master cyl itt is a safety issue. If I can be of any help talking to where you purchase it I would be glad to help.

Dads Mechanic :

sorry i was at the car auction all day today.

Customer:

The Master cylinder was purchased from Geoffery Rosenburg, Alretta Truck Parts INC,BLD#5B, One , Watson Place,Framingham, MA. 01701 Tel (XXX) XXX-XXXX.

Customer:

My Name is William Blain,delivery address was 12,Coningsby road, Sc**thorpe,North Lincs, UK

Customer:

my te;

Customer:

My Tel 0XXX-XXX-XXXX

Customer:

order No 51766

Customer:

If you could explain your finding to Geoffery I would be very grateful

Dads Mechanic :

I will give them a ring today and see what i can do. Jim!!!

Customer:

thanks, XXXXX XXXXX to American shows allready

Customer:

Motorhome has graphix pictures all over it and they always put us in the middle of the show ground so missing the time out at moment.

Full Size Image

Customer:

And Americana biggest show of the years is comming soon

Customer:

Bill

Customer:

Did you manage to talk to Geoffery

Dads Mechanic :

Good afternoon. I just got off the phone with him. he is going to talk to the techs at the company that manufactured the unit and call you or email you about it. His sugestion is to look in the resivoier and make sure the ports are drilled in the proper place to allow the fluid to return to the resivoier. I'm not sure what he is willing to do about your master cyl. He seems to think you have a proporting valve on the side of it that may be yuour problem. I said you didn't have a problem just a leaking master cyl. lets see what he comes up with for you keep me in the loop.

Dads Mechanic :

Jim!!!

Customer:

ok thanks

Dads Mechanic :

he still thinks you may be doing somthing wrong, but give him a chance.

Dads Mechanic, RV Body Repairer
Category: RV
Satisfied Customers: 202
Experience: I was a rockwood camper dealer for many years from 1970 on many years Servicing motor coachs, rv's and motor homes.
Dads Mechanic and other RV Specialists are ready to help you
Expert:  Dads Mechanic replied 1 year ago.
Thank you! for the positive rating. If I can be of more assistance get back to me. Thanks for coming to Just Answers. Jim!!!
Customer: replied 1 year ago.

the two little spring loaded valves between master cylinder and reservoir were stuck


problem seems to have solved its self


will let you know when i road test

Expert:  Dads Mechanic replied 1 year ago.
Glad to hear you have solved the problem. You should see if the will give you some money back on the master cyl. Jim!!!

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