Rear Brakes grabbing after service - Rolls-Royce and Bentley Forums
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old 07-05-2016, 08:06 PM Thread Starter
Member
 
genemullins's Avatar
 
Join Date: Sep 2014
Location: Florence, Kentucky
Posts: 31
Garage
Rear Brakes grabbing after service

Need some guidance here....
Recently, I had installed on 72 RR SS LWB a new rear accumulator and a rear accumulator valve. A few months prior, I replaced the front accumulator valve.
After the install and the subsequent bleeding of the rear brakes, the bled the front, I took it for a drive and the pedal seemed to get harder and less play. Then the car/engine was struggling to keep speed up because the rear brakes were grabbing. Pulled over and noticed smoking from the rear brakes. I turned off the engine and just turned the key on and did the brake test multiple pumps 30-50 times to illuminate both brake lights, they both came on and relieved the brake pressure, heard a small thump and was able to drive a short distance and it happened again.

Any ideas why this would happen? Any suggestions?

Gene Mullins

Gene
genemullins is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 07-05-2016, 08:21 PM
Senior Member
 
Join Date: Apr 2012
Location: Wexford, Ireland
Posts: 375
Possibly seized piston in the calliper due to rust which stops the piston from retracting when the brakes are off.
shadow 11 is offline  
post #3 of 12 (permalink) Old 07-05-2016, 08:32 PM
Senior Member
 
guyslp's Avatar
 
Join Date: Aug 2007
Location: Staunton, VA - USA
Posts: 2,919
The two things that scream out as likely possibilities to me, barring what's already been suggested, is a restrictor valve that's partially clogged and creating back pressure and keeping the brakes engaged, or old hoses that are collapsing internally and not allowing the fluid to exit the caliper as it should when the brakes are released.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


guyslp is offline  
 
post #4 of 12 (permalink) Old 07-05-2016, 09:15 PM Thread Starter
Member
 
genemullins's Avatar
 
Join Date: Sep 2014
Location: Florence, Kentucky
Posts: 31
Garage
thanks for the input...

Gene
genemullins is offline  
post #5 of 12 (permalink) Old 07-05-2016, 09:16 PM Thread Starter
Member
 
genemullins's Avatar
 
Join Date: Sep 2014
Location: Florence, Kentucky
Posts: 31
Garage
Weird part is; fixing problems beget new issues. very trying.

Gene
genemullins is offline  
post #6 of 12 (permalink) Old 07-05-2016, 09:37 PM Thread Starter
Member
 
genemullins's Avatar
 
Join Date: Sep 2014
Location: Florence, Kentucky
Posts: 31
Garage
pardon what may be a dumb question. The restrictor valve you refer to; is it the Ride height restrictor valve? can't locate a brake restrictor valve on Flying spares.

Gene
genemullins is offline  
post #7 of 12 (permalink) Old 07-06-2016, 12:10 AM
Senior Member
 
guyslp's Avatar
 
Join Date: Aug 2007
Location: Staunton, VA - USA
Posts: 2,919
Gene,

See chapter G11 of the Workshop Manual for the two-series cars, figure G23. It's generally referred to as "the restrictor valve" though the documentation talks about the solenoid restrictor valve, which is a part of the fast/slow leveling that's triggered by the solenoid valve itself.

See also the catalog page for the UR17525SXR Solenoid Restrictor Valve.

Brian

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


guyslp is offline  
post #8 of 12 (permalink) Old 07-06-2016, 05:55 PM Thread Starter
Member
 
genemullins's Avatar
 
Join Date: Sep 2014
Location: Florence, Kentucky
Posts: 31
Garage
Thanks for your assistance, I think I'll start with this valve replacement and hope for the best...

Gene Mullins

Gene
genemullins is offline  
post #9 of 12 (permalink) Old 07-06-2016, 06:40 PM
Senior Member
 
Join Date: Apr 2012
Location: Wexford, Ireland
Posts: 375
Gene, It's usually a simple matter of removing the restrictor valve and cleaning the internals with methylated spirit and blowing with an air hose and checking that the small part in the very centre is free by rotating it, there is one seal in each valve and it would be recommended to replace the seal when reassembling. Sometimes when a restrictor valve is blocked you will hear a hydraulic knocking noise when you manually operate the height control lever on the height control valve, it sounds just like a banging sound in household plumbing water pipes. If there's blockage in the low pressure return restrictor valve the hydraulic fluid from the height control rams can't make it's way back to the reservoir and the pressure build up can cause the brakes to bind, good luck, Larry
shadow 11 is offline  
post #10 of 12 (permalink) Old 07-07-2016, 10:30 PM Thread Starter
Member
 
genemullins's Avatar
 
Join Date: Sep 2014
Location: Florence, Kentucky
Posts: 31
Garage
good info

Larry, Thanks for your input. This information I gather helps allows me to narrow the choices of repair. Really appreciate the info.

The seals you mention, are they available from a parts house such as Flying Spares? Is there a rebuild kit that you aware of?

Thanks for helping.

Gene
genemullins is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Rolls-Royce and Bentley Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome
 

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.

SEO by vBSEO 3.6.1