thisisludicrous Posted August 13, 2007 Share Posted August 13, 2007 This will be my third set of front rotors (always OEM replacements) in a little over 4 years of ownership, about 60k miles. I complained to my indie mechanic and he suggested it might be something wrong with the master cylinder. I know ZERO about the master cylinder, can it possibly be set too tightly, to squeeze too hard, creating too much heat that warps the rotors? He can diagnose this somehow? I live in the mountains, yes, and drive slightly faster than most, yes, but 3 sets in 4 years just seems wrong. The wife's Toyota Sienna minivan has had only ONE brake job in more than 5 years of ownership, and she drives just like me. Anything else that might be out of place to cause the extra heat/warping? Axle? Sticky calipers? Many thanks in advance for any input. Quote Link to comment Share on other sites More sharing options...
wwest Posted August 14, 2007 Share Posted August 14, 2007 This will be my third set of front rotors (always OEM replacements) in a little over 4 years of ownership, about 60k miles. I complained to my indie mechanic and he suggested it might be something wrong with the master cylinder. I know ZERO about the master cylinder, can it possibly be set too tightly, to squeeze too hard, creating too much heat that warps the rotors? He can diagnose this somehow? I live in the mountains, yes, and drive slightly faster than most, yes, but 3 sets in 4 years just seems wrong. The wife's Toyota Sienna minivan has had only ONE brake job in more than 5 years of ownership, and she drives just like me. Anything else that might be out of place to cause the extra heat/warping? Axle? Sticky calipers? Many thanks in advance for any input. Left foot just "resting" on the brake pedal, maybe? Quote Link to comment Share on other sites More sharing options...
SRK Posted August 14, 2007 Share Posted August 14, 2007 Check the slider pins on the front calipers. They will seize up over time. I just repaired an LS400 with a stuck pin on one of the rear calipers. Chances are the master cylinder is fine. Quote Link to comment Share on other sites More sharing options...
etex Posted August 14, 2007 Share Posted August 14, 2007 I can think of no way the master cylinder could cause warping of the rotors. Quote Link to comment Share on other sites More sharing options...
thisisludicrous Posted August 15, 2007 Author Share Posted August 15, 2007 Many thanks again for the responses, I'll ask him to take a very close look for sticky slider pins, etc. I'm afraid my driver's ed teacher left us effectively scarred with several bits of dogma, one of them being to never drive with your left foot in an automatic trans car, so no, not "resting" left foot on brake. But I like alternate solutions being considered! Quote Link to comment Share on other sites More sharing options...
wwest Posted August 15, 2007 Share Posted August 15, 2007 Many thanks again for the responses, I'll ask him to take a very close look for sticky slider pins, etc. I'm afraid my driver's ed teacher left us effectively scarred with several bits of dogma, one of them being to never drive with your left foot in an automatic trans car, so no, not "resting" left foot on brake. But I like alternate solutions being considered! But what about your dear "other's" driver's ed teacher? Quote Link to comment Share on other sites More sharing options...
W201 sweden Posted August 15, 2007 Share Posted August 15, 2007 Hi there! Sounds pretty abnormal, if you ask me. (Used to be professional car tech.) Master cylinder does not seem likely, from your description. Try to eliminate the following possible sources (general for all cars): -bent/warped hubs. Next time you remove the rotors, check the hubs for warping. Some 1/100 of a mm is acceptable - not more. Then mount the new rotors, and check them in place - same criteria. -excessive heat buildup on new rotors. Cycle brakes (heat up/cool down a number of times) before you take full use of the new rotors. -sticky pistons or pads. This can also cause the brakes to overheat, if the pads keep dragging on the rotor surface. -too old brake hoses can also cause the exact same problem. If worn out, hoses become "one-way-valves" keeping a constant pressure on the pistons, even when pedal is released. Good luck! /Alexander from Sweden Quote Link to comment Share on other sites More sharing options...
jsteb Posted October 5, 2007 Share Posted October 5, 2007 Kind of late but just read this, believe it or not the number 1 cause of warped brake rotors is improperly torquing the lug nuts. My 99 LS calls for 76 ft lbs and all vehicles should be done in a cross pattern. There are untold hundreds of not so honest shops that will over torque lugs on purpose. The thing with the improper torque is; you don't get warped rotors right away, they typically will warp after a fairly hard stop which causes them to get good and hot. I'm not sure this is your cause but I'd have to agree that the master cylinder doesn't sound logical to me either. On the other hand frozen caliper pistons could cause it but typically you will notice the car pulling when you apply the brakes and believe it or not it will pull to the opposite side of the frozen caliper. Good Luck Quote Link to comment Share on other sites More sharing options...
pishta Posted October 6, 2007 Share Posted October 6, 2007 Kind of late but just read this, believe it or not the number 1 cause of warped brake rotors is improperly torquing the lug nuts. My 99 LS calls for 76 ft lbs and all vehicles should be done in a cross pattern. There are untold hundreds of not so honest shops that will over torque lugs on purpose. The thing with the improper torque is; you don't get warped rotors right away, they typically will warp after a fairly hard stop which causes them to get good and hot. I'm not sure this is your cause but I'd have to agree that the master cylinder doesn't sound logical to me either. On the other hand frozen caliper pistons could cause it but typically you will notice the car pulling when you apply the brakes and believe it or not it will pull to the opposite side of the frozen caliper. Good Luck Do Lexus use a residual valve in their M/C's to keep a little pressure on the front calipers to keep the seals seated? I would jack up the front, start car, apply brakes a few times and then try to spin the front tires. Do they drag? What are your rotors doing, warping? Are you using an approved brake pad compound? I know some cause more heat than others. Quote Link to comment Share on other sites More sharing options...
oldskewel Posted November 6, 2008 Share Posted November 6, 2008 Do Lexus use a residual valve in their M/C's to keep a little pressure on the front calipers to keep the seals seated? I would jack up the front, start car, apply brakes a few times and then try to spin the front tires. Do they drag? What are your rotors doing, warping? Are you using an approved brake pad compound? I know some cause more heat than others. I've got a potential brake dragging problem. In this test you suggest, how much dragging is acceptable? I did the test, and when kicking down on the front of the tire, trying to spin it as much as reasonably possible, each front tire spun about 1 revolution before stopping. Would you call that dragging? OEM pads, no noticeable rotor warping. Just dragging, and it pulls to the right slightly when the brakes are not applied, after alignment. Thanks, Ed Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted November 7, 2008 Share Posted November 7, 2008 Sticky slider pins as has been noted in the earlier posts are your most likely culprits. Try this test, Drive the car from a cold start for as long as you can without applying the brakes (5-10 minutes), now apply the brakes firmly, stop and notice the temps of the rotors. Now drive for another 5-10 minutes, then stop and once again notice the temps of the rotors. If they are noticeably hotter after the second stop, then your pins are sticking. Another indication is a marked difference in the pad thickness from the left side of the rotor to right and/or left wheel to right wheel. Get the caliper kit and clean them out. Quote Link to comment Share on other sites More sharing options...
SKperformance Posted November 7, 2008 Share Posted November 7, 2008 95 does not have slider pins , they have 4 piston calipers. You need to lube each piston behind the seals on every service . Also make sure the seals are not cracked. This makes it feel as though you have warped rotors by pedal feedback but the pistons are being unevenly applied instead. Common for mechanics not to do this but a technician should know better . Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted November 8, 2008 Share Posted November 8, 2008 Of course the 95 doesn't have slider pins. My bad. In the 1st gen, Lexus used a floating caliper with two pistons. When the hydraulic pressure is applied to the caliper piston, it forces the inside pad to contact the disc. As pressure increases the caliper slides to the right and causes the outside pad to contact the disc. Both the the slider pins and pistons can stick if they're not cleaned and lubricated. Evidence of sliders sticking can be seen in excessively uneven wear of the pads on either side of the disc. In your 95 as SK correctly points out, the calipers were changed to fixed calipers with 4 pistons, two on each side of the disc. These pistons and their seals require regular service to keep them from sticking. You can see evidence of sticking pistons by uneven pad wear from left to right wheels. Also remember not to overtorque the lug nuts. Quote Link to comment Share on other sites More sharing options...
steve2006 Posted November 8, 2008 Share Posted November 8, 2008 Nobody's mentioned this one so I will. Make sure the hub flange mating surface is perfectly clean if required use a wire brush to remove rust deposits. Quote Link to comment Share on other sites More sharing options...
Randy&Bonnie Posted November 8, 2008 Share Posted November 8, 2008 .. Quote Link to comment Share on other sites More sharing options...
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