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shorepig Samba Member
Joined: November 30, 2005 Posts: 516 Location: Vancouver, B.C.
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Posted: Tue Apr 26, 2011 7:12 pm Post subject: Pulsing brake pedal...why? |
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My 1985 west went in for a pre purchase inspection which included checking the wear on the brakes. When I picked the van up and pressed the brake pedal I could feel a pulsing in the pedal that was related to the rolling speed of the van. I brought it back to the mechanic and he said everything looked fine and the pulsing was nothing to worry about .
What could he have done that would cause this? I'm not happy with his response and would like to return to him with armed with more knowledge. _________________ 85 Westy
92 Mitsubishi Mighty Max 4x4 V6
74 Honda CB500T cafe racer
2013 ktm 690r
Sector nine pintail |
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joetiger Samba Member
Joined: January 27, 2005 Posts: 5078 Location: denver
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Posted: Tue Apr 26, 2011 7:14 pm Post subject: |
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He might have over-torqued the front lug bolts, which would cause the discs to warp.
Loosen them and re-tighten to spec ASAP and see if that works. _________________ Joe T.
'86 NAHT Vanagon GL Syncro/ supercharged ABA 2.0 "Pigpen"
'04 GTI 1.8T
'04 Golf R32
"get metaphysical with it. if it's simply a means to get to and from places, it will let you down. if it becomes your zen, it can't fail you." -dabaron
"Still, it's good to be afield."--VWagabond
Available Now! Vanagon to Louisiana--A Two-Lane Reckoning Through Past and Present
www.josephtrussell.com |
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syncrodoka Samba Member
Joined: December 27, 2005 Posts: 12005 Location: Santa Cruz, CA
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Posted: Tue Apr 26, 2011 7:21 pm Post subject: |
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Drive slowly and pull up the emergency brake lightly with your thumb on the release button. If the handle rises and falls them the rear drums are warped- not a uncommon problem.
Loosening the lug nuts and retorquing to the proper spec wouldn't be a bad idea either. |
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IdahoDoug Samba Member
Joined: June 12, 2010 Posts: 10248 Location: N. Idaho
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Posted: Tue Apr 26, 2011 7:28 pm Post subject: |
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If the test involved a braking test and the brake rotors were thin, or drums, then they may warp when subjected to a test stop. I don't know if that's part of the test.
Also, if the mechanics hands were greasy or similar, then a bit of grease or oil in the drum brake surface or the rotor brake surface will make the brakes pulse until it's burnt off. A shot of brake fluid would fix this one.
DougM _________________ 1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader |
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BushChicken Samba Member
Joined: March 11, 2010 Posts: 250 Location: California
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Posted: Tue Apr 26, 2011 7:57 pm Post subject: |
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IdahoDoug wrote: |
A shot of brake fluid would fix this one.
DougM |
Well....maybe brake clean would work better... |
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EvilDNA Samba Member
Joined: January 10, 2006 Posts: 116 Location: Salt Lake City, UT
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Posted: Wed Apr 27, 2011 12:26 am Post subject: |
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I had this EXACT issue happen and the culprit was improperly tighten lug nuts. I simply loosened and retightened the offending wheel and Bob's Your Uncle. _________________ 1990 4 Speed Orly Blue Multivan |
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BayrischerGTI Samba Member
Joined: March 10, 2009 Posts: 51 Location: Norfolk, NE
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Posted: Wed Apr 27, 2011 6:48 am Post subject: |
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BushChicken wrote: |
IdahoDoug wrote: |
A shot of brake fluid would fix this one.
DougM |
Well....maybe brake clean would work better... |
LOL would work MUCH better I think |
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IdahoDoug Samba Member
Joined: June 12, 2010 Posts: 10248 Location: N. Idaho
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Posted: Wed Apr 27, 2011 7:17 am Post subject: |
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Heh, indeed. Meant brake cleaner - just spray it on the front rotors liberally with the engine idleing and immediately drive off with the brakes applied for a hundred feet or so. That will get the product around the rotor under and on the pads before it dries, which it will do in 20 seconds. Won't edit my post just on general principle.... Heh...
DougM _________________ 1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader |
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Captain Pike Samba Member
Joined: December 30, 2003 Posts: 3341 Location: Talos IV, Piedmont Arizona
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Posted: Wed Apr 27, 2011 7:17 am Post subject: |
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If the (wrench) used a hammer to loosen the drums he most likely distorted one or both. Common mistake for a non Vanagon savvy wrench.
Do the above tests esp. the parking brake test. If all else fails then .....well....you paid to learn about not hitting the drum. _________________ LEARN TO SELF RESCUE
59 Panel bus, 1966 Single cab. 73' 181. 73 Westy. 91' H6 Vanagon 3.3L.
.....................All Current....................... |
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insyncro Banned
Joined: March 07, 2002 Posts: 15086 Location: New York
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Posted: Wed Apr 27, 2011 7:22 am Post subject: |
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Captain Pike wrote: |
If the (wrench) used a hammer to loosen the drums he most likely distorted one or both. Common mistake for a non Vanagon savvy wrench.
Do the above tests esp. the parking brake test. If all else fails then .....well....you paid to learn about not hitting the drum. |
So true! |
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climberjohn Samba Member
Joined: January 11, 2005 Posts: 1840 Location: Portland Orygun
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Syncronoid Samba Member
Joined: January 21, 2012 Posts: 1111 Location: Stanford, CA and Bend, OR
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Posted: Mon Sep 03, 2012 9:04 pm Post subject: |
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Anyone know what the front spec torque is on a '90 Syncro Westy? |
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morymob Samba Member
Joined: November 09, 2007 Posts: 4683 Location: east-tn
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Posted: Tue Sep 04, 2012 3:33 am Post subject: |
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For sure i wouldn't trust anything or even go back to that 'mech ??' A tire out og bal and run in the front will cause a rotor to wear uneven ending up with a pulsing pedal, tire can cause same. Awhile back it took awhile to convince mgr of a courier i worked 4 of the circle u can get into with tires/rotors and NOT correcting BOTH tire and rotor problem at the same time. |
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Syncronoid Samba Member
Joined: January 21, 2012 Posts: 1111 Location: Stanford, CA and Bend, OR
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Posted: Tue Sep 04, 2012 7:31 am Post subject: |
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I had/have this problem right from the start with brand new, machined, Audi (VanCafe) big discs and new16" tires/wheels. Are big-discs more susceptible to this tightening-induced warping??
UPDATE: I loosened and re-tightened the front lugs to spec (123ft lbs)… nice and smooth braking now. |
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markz2004 Samba Member
Joined: November 13, 2007 Posts: 944 Location: Portland, OR
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Posted: Fri Nov 16, 2012 2:07 pm Post subject: |
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Can anyone explain to me why or how over-torquing the lug nuts would cause a rotor to warp?
I have the VC big brake kit. A few thousand miles ago, I had a rotor turned due to the pulsation, but it has now returned...
thanks,
Mark _________________ 87 Westy, 250k GW 2.4 - 2.0 , 16" wheels |
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markz2004 Samba Member
Joined: November 13, 2007 Posts: 944 Location: Portland, OR
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Posted: Tue Nov 27, 2012 1:17 pm Post subject: |
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- bump - _________________ 87 Westy, 250k GW 2.4 - 2.0 , 16" wheels |
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presslab Samba Member
Joined: September 29, 2008 Posts: 1730 Location: Sonoma County
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Posted: Tue Nov 27, 2012 1:55 pm Post subject: |
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markz2004 wrote: |
Can anyone explain to me why or how over-torquing the lug nuts would cause a rotor to warp?
I have the VC big brake kit. A few thousand miles ago, I had a rotor turned due to the pulsation, but it has now returned...
thanks,
Mark |
Over-torquing distorts the hub, and the brake rotor is mounted to the hub so that distorts too. I'd say that if you have over-torqued the lugs and run it long enough, the rotor will take a "set", so even if you fix the torque and machine the rotor, the rotor is still messed up.
Junky rotors can also warp a lot easier than good ones. The "frozen" rotors (cryo treated) supposedly don't warp. Another thing that causes pulsations is that the brake pad material can transfer to the rotor. The rotor isn't really warped in this case but turning the rotor cleans it up. _________________ 1986 Vanagon Westfalia EJ25
1988 Subaru GL-10 EJ20G --- 2000 Honda XR650L
2010 Titus El Guapo --- 2011 On-One 456 Ti |
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morymob Samba Member
Joined: November 09, 2007 Posts: 4683 Location: east-tn
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Posted: Wed Nov 28, 2012 5:58 am Post subject: |
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China rotors can and will wear uneven in normal use, hard ?, soft? spots in material??, chicken/egg choice, too bad U. S. rotors hard to find.Out of bal tire WILL cause rotor to wear uneven,replace bad tire and pulsing pedal from uneven rotor will do same to new tire, gotta do both at same time. |
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KLSteward Samba Member
Joined: November 28, 2012 Posts: 11
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Posted: Wed Nov 28, 2012 11:14 am Post subject: |
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morymob wrote: |
For sure i wouldn't trust anything or even go back to that 'mech ??' A tire out og bal and run in the front will cause a rotor to wear uneven ending up with a pulsing pedal, tire can cause same. Awhile back it took awhile to convince mgr of a courier i worked 4 of the circle u can get into with tires/rotors and NOT correcting BOTH tire and rotor problem at the same time. |
^ This. If all he can tell is you is to not worry about he obviously has no clue what he is doing.. |
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Cygnus Samba Member
Joined: March 14, 2006 Posts: 129 Location: Idaho
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Posted: Wed Nov 28, 2012 2:39 pm Post subject: |
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On my 85 I had exactly the same thing - pulsing on braking. Fronts were fine - turned out that it needed the rear wheel bearings replaced and the rear drums were wasted beyond turning as well. replaced all and its good as new.
-B _________________ '86 Syncro Timbertech Hightop "Cygnus" |
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