Date: Thu, 26 Mar 2009 15:27:09 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Pulsating Brake Pedal (Need Solution)
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response
a cheater way to check out of round of the inner surface of a rear drum is
to mount it on the axle flange backwards..........or inside out .......
so you can watch it turn while the engine idles in 1st gear.
Might not be a really 'true' test, but it's free and easy to do, and might
reveal something.
there's always swapping parts around to see if the problem moves to the new
location. Like swap rear drums side to side, then do the 'clamp off a brake
hose trick' to each side and see if you can find out which shoes/drum etc.
are causing the problem.
it 'should' of course, be an out of round drum or warped front disc.
Using just the parking brake makes only the rear brakes involved of
course.........the idea being to isolate parts of the brake system, like the
clamp off the hose trick.
I also like Dylan's theory and experience about some brake shoe material
getting stuck on a drum surface. I haven't seen that ever occur, but I
imagine it could all right.
----- Original Message -----
From: "John Rodgers" <inua@CHARTER.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, March 26, 2009 3:14 PM
Subject: Re: Pulsating Brake Pedal (Need Solution)
> Blake,
>
> From what you have described, logically speaking you have an eccentric
> inside the drum itself. Consider that the wheel and drum give no
> vibration when free rolling, nor when the brake line is clamps off.
> That is going to rule out bad bearings, bad wheel mounting , bad drum
> installation, incorrect torque on axle nut, etc. Somehow the problem is
> in the relation ship of the brake shoe to the brake drum. If the brake
> shoes and linings are right - i.e., no flaws, and the moving components
> of the brake shoe operation is free with noting sticking, then the drum
> almost has to be the culprit. I would pull the drum, and have it mounted
> on a drum lathe at some shop where they will let you look at it while it
> turns, and while they check it again for true. Then you will know. You
> might also try another drum, just to see.
>
> Good luck,
>
> Regards,
>
> John Rodgers
> 88 GL Driver
>
> Blake Heinlein wrote:
>> Hi everyone, so here's my situation.
>>
>> My 1984 Westy has a pulsating brake pedal and undulating slowing during
>> braking. I can actually see my leg move up and down while braking. I need
>> help troubleshooting my problem.
>>
>> I have been able to isolate the culprit it to the back right wheel. How
>> do I
>> know this? If I clamp off the rubber brake line to the right rear wheel,
>> the
>> brake pedal is perfectly smooth and the stop is smooth. That means that 3
>> of
>> the brakes are working perfectly.
>>
>> Here is the work I have done and in order that is was completed. I always
>> did the work to both sides of the van at the same time.
>>
>> 1. Replaced rear brake shoes about 1-1/2 years ago (Did not turn the
>> rear
>> drums at this time)
>> 2. Had a local repair shop replace the rear wheel bearings about 1
>> year
>> ago (This is the only work I hired out)
>> 3. Bleed brake system and flushed with new fluid (The rest of the work
>> was done in the last 2 months.
>> 4. Installed new rear drums and the pulsation was worse so I returned
>> them.
>> 5. Turned the original rear drums and installed them
>> 6. Installed new front wheel rotors and brake pads
>> 7. Greased and adjusted the front wheel bearings
>>
>>
>> Symptoms and/or current conditions of van:
>>
>> 1. There are no wheel vibrations while driving the van
>> 2. None of the brakes drag when the brake pedal is up (brakes off)
>> 3. The parking brake engages the rear brakes at 4 clicks. There is
>> free
>> play in the parking brake linkage when they are released.
>> 4. The brake pedal feel is firm and high and does not leak down. The
>> best
>> I've had since I've owned the van.
>> 5. The van stops quickly
>> 6. The drum brakes are adjusted so they just slide on and then I
>> backed
>> the ratchet off by 3-4 clicks.
>> 7. None of the 4 brake cylinders leak
>> 8. I have checked that all the rear brake shoe linkage is properly
>> assembled.
>> 9. The drum brake positioning bolts are installed.
>> 10. The drum brakes are free of dirt and grease at installation.
>> Lightly
>> sanded pads to removing any glazing
>>
>> Here are some of my thoughts about what might be wrong:
>>
>> 1. Axle is bent
>> 2. Hub (part with the wheel studs) is bent
>> 3. Something wrong with wheel bearings
>> 4. Something wrong with proportioning valve to rear wheel
>> 5. The axle nut is not torqued correctly
>> 6. Brake pads don't seat properly in the drums (i.e. the
>> curvature radius is different)
>>
>>
>> So these are all my thoughts. Now it's your turn to help solve the
>> puzzle.
>> Thanks in advance to everyone.
>>
>> Blake HeinleinSacramento, CA
>> http://blakeheinlein.googlepages.com/
>>
>>
>>
| 
