Brake Master Cylinder won't pump up after rebuild.

This is the place to get help with technical matters concerning your M151 jeep

Moderators: rickf, Mr. Recovery, raymond, moose53

Brake Master Cylinder won't pump up after rebuild.

Sponsor

Sponsor
 

Brake Master Cylinder won't pump up after rebuild.

Postby Halfdunn » May 13th, 2018, 1:45 pm

Hi all, any help with the M151 master cylinder not maintaining pressure after rebuild kit installed. All parts were replaced in same order as removed, precharged the unit before install and have bled all wheels to remove any bubbles. no leaks observed after rebuild.

Pumps up okay but won't hold after release.

Looking for a diagram of the actual master cylinder parts breakdown and cannot find one even in the Tech manuals for parts.

Thanks,

Halfdunn
Halfdunn
Private First Class
Private First Class
 
Posts: 18
Joined: January 28th, 2018, 8:09 pm
Location: Rincon, GA.

Re: Brake Master Cylinder won't pump up after rebuild.

Postby rickf » May 13th, 2018, 3:30 pm

Was there any rust in the bore of the cylinder and did you hone the bore? It sounds like the piston cup got scored or cracked.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
rickf
General
General
 
10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership
 
Posts: 15376
Joined: November 26th, 2007, 12:28 pm
Location: Pemberton, NJ.

Re: Brake Master Cylinder won't pump up after rebuild.

Postby Mr. Recovery » May 13th, 2018, 3:31 pm

can't find a diagram right now so , here's a few photos of the last one I rebuilt.

Image

Image

Image

Image

Image

Image
1960 M151 Run 1
1963 M151 Willys DoD 10-63 in Baltimore
1967?? M151 MFD By Ford Motor Co?? SOLD
NRA Life Member
American Legion Post 275 Fl
US Army 6 years 2nd Armored Cavalry Bindlach Germany
Colorado Army Nat. Guard 5 years
Md Air Guard 15 years active duty on C-130's
Image
User avatar
Mr. Recovery
Brigadier General
Brigadier General
 
10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership
 
Posts: 2443
Joined: December 5th, 2007, 8:03 pm
Location: Port Richey Fl.

Re: Brake Master Cylinder won't pump up after rebuild.

Postby Halfdunn » May 13th, 2018, 5:44 pm

Thanks everyone for your assistance and pictures. My current M/C(Master Cylinder) was brand new with no scoring or rust encrusted parts. It would pump up but not hold. Depressing the brake pedal after resting momentarily, resulted in it going to the floor. I put a rebuild kit in the new M/C to no avail. Still would pump up but not hold after release going to the floor again. That is why I wanted to see a diagram to ensure parts were in the proper sequence in the M/C. I did install the parts of the rebuild kit in the M/C just like they were removed from the original M/C. Still bleeding the system at all wheels and no relief.

Halfdunn
Halfdunn
Private First Class
Private First Class
 
Posts: 18
Joined: January 28th, 2018, 8:09 pm
Location: Rincon, GA.

Re: Brake Master Cylinder won't pump up after rebuild.

Postby Hambone » May 13th, 2018, 8:13 pm

Halfdunn
Check out this video, it has a cutaway that shows how it is assembled, if needed, I can break one down for you.
https://www.youtube.com/watch?v=c3uNjEcICSw
Hambone
Colonel
Colonel
 
8 years of membership8 years of membership8 years of membership8 years of membership8 years of membership8 years of membership8 years of membership8 years of membership
 
Posts: 1431
Joined: September 30th, 2010, 11:19 pm
Location: El Dorado, Arkansas

Re: Brake Master Cylinder won't pump up after rebuild.

Postby rickf » May 13th, 2018, 8:39 pm

You have a problem with the front piston cup, either it is scored, torn or put in backwards. The fact that you can pump up the brakes would tell me it is installed correctly but damaged.. Air in the system would not cause as much problem as you are having after so much bleeding. You are following a proper bleeding procedure aren't you?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
rickf
General
General
 
10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership
 
Posts: 15376
Joined: November 26th, 2007, 12:28 pm
Location: Pemberton, NJ.

Re: Brake Master Cylinder won't pump up after rebuild.

Postby Halfdunn » May 13th, 2018, 9:24 pm

Thanks rickf.

Video cutaway shows my parts installed appropriately on my M/C. Following normal bleeding procedures as in the TM for brake bleeding. Will review cups for damage but did that prior to install. Both looked good with no cuts, scoring, etc.. M/c bore was clean with no damage from visual inspection.

Will attempt a redo of bleeding and see if that works.

Thank you again.
Halfdunn
Private First Class
Private First Class
 
Posts: 18
Joined: January 28th, 2018, 8:09 pm
Location: Rincon, GA.

Re: Brake Master Cylinder won't pump up after rebuild.

Postby miljeep » May 14th, 2018, 1:48 pm

Make sure you have the correct cup, I bought a re-build kit a few years back from a M151 parts dealer and he sent the wrong cup.... Scott O&O
miljeep
Sergeant First Class
Sergeant First Class
 
10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership
 
Posts: 235
Joined: December 8th, 2007, 10:29 am
Location: Allentown, PA

Re: Brake Master Cylinder won't pump up after rebuild.

Postby muttguru » May 14th, 2018, 2:41 pm

There's some interesting information about master-cylinder problems in an old series of posts which you can find here:-

http://forums.g503.com/viewtopic.php?t=289691

Ken
Kind regards....
Ken

Always wanted - Details and pictures of M416 Trailer data plates & M151 data plates & body-tags for my research. Thanks!

Contact address - - muttguru@aol.com

Notes for 2018...... Doing nothing is ALWAYS an option !
User avatar
muttguru
Colonel
Colonel
 
10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership10 years of membership
 
Posts: 1654
Joined: November 26th, 2007, 11:18 am
Location: Li'l ol' England.....

Re: Brake Master Cylinder won't pump up after rebuild.

Postby m3a1 » May 14th, 2018, 4:50 pm

And I'll throw this idea out there for good measure...

Are you SURE you have no leaks elsewhere?
m3a1
Colonel
Colonel
 
4 years of membership4 years of membership4 years of membership4 years of membership
 
Posts: 1430
Joined: August 7th, 2014, 5:36 pm

Re: Brake Master Cylinder won't pump up after rebuild.

Postby Halfdunn » May 14th, 2018, 9:07 pm

Thanks again for all of your suggestions. Previous threads were helpful. I believe all of my parts are installed properly but I will check the size of the new cup. No leaks observed any where else in the system and fluid only needs adding after bleeding. Everything is still dry even after all of the bleeding process.

I believe bench bleeding is what I did prior to install by filling reservoir and pumping the piston until only fluid comes out of the outlet.

Again, you guys are the best and I truly appreciate all of the assistance.

Halfdunn
Halfdunn
Private First Class
Private First Class
 
Posts: 18
Joined: January 28th, 2018, 8:09 pm
Location: Rincon, GA.


Return to Technical Discussion

Who is online

Users browsing this forum: No registered users and 5 guests

Customization by G838.org