Problems after replacing master cylinder
in [Technical]
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From: jim on 6 Apr 2010 10:31 lugnut wrote: > > On Mon, 5 Apr 2010 18:33:16 -0700 (PDT), Mark > <muffi74(a)hotmail.com> wrote: > > >Hi, > > > >I have a lexus es300 with 128K miles. I had taken my car to the > >mechanic as I felt the brakes needed work. I had to press the brake > >pedal all the way down to stop the car. The mechanic suggested > >replacing the master cylinder which I did. > > > >Now, I have 2 unique problems and I am looking for advice here to > >educate myself before I take the car back to the mechanic. > > > >1. The brake pedal sometimes works just by a little pressing, and > >other times I need to press it all the way down. In other words, > >sometimes it brakes just by a slight touch of the foot and sometimes > >it doesn't. The brakes work, just that the "firmness" of the pedal > >keeps changing. > > > >2. The car starts vibrating after driving for about 10 minutes on the > >highway. The vibration doesn't start right away. There is vibration in > >the car and the steering. When I brake, I get the pulsating feeling > >with the brake pedal. All the passengers in the car can feel the > >vibration. After about 15 minutes of driving, the vibration goes away > >and doesn't come back during the same ride. If I park the car, let it > >cool and drive again, then the same pattern repeats. This part sounds like a stuck caliper. What happens is when you apply the brakes, the pressure is being applied to only one side of the rotor because the caliper can't move freely. That means even the tiniest amount of run out in the rotor causes pulsation. If the caliper weren't stuck it would float with the sideways movement of the rotor. If the caliper can move freely a small amount of runout wouldn't cause pulsation. It also sounds like when things get warmed up the problem disappears. That would mean the problem is related to temperature. If your description is accurate as things start to warm up the problem gets worse before it gets better. This is unusual and I can't think of a reason that would be happening, but possibly something wasn't assembled correctly. if you have a stuck caliper things could be getting extremely hot. That could explain the intermittent pedal to the floor if you are getting things hot enough to boil brake fluid. -jim > > > >Could the experts here give some insight into what the possible issues > >could be? The advice here has always helped me in the past and look > >forward to your opinion. > > > >Thanks and regards, > >Mark > > Your problem sounds like the booster is not releasing which > results in your brakes being partially applied. This > explains both the low inconsistant pedal and the brake > pulsation after driving a couple of minutes. You may be > able to use your toe and lift the pedal to clear the problem > until you apply the brake again. If the master cylinder was > replaced, the mechanic may not have been able to effectively > bleed the system to purge air from it. > > As an aside, it is usually best to replace both the booster > and master cylinder if one fails and they are essentially > the same age with significant miles on them. In you rcase > at this point, I would have the booster replaced and the > hydraulic system purge following the procedure in the > manufacturer's service manual to be sure the ABS system is > cleared. That year model may also require a scanner to > correctly purge the ABS controller. You may want to have > the brake pads checked for heat damage, glazing, cracking, > disintegration, etc. to make sure the brakes are good to go. > I had this happen on my CV a couple of years back right > after a brake job. The pads were destroyed in less than 50 > miles after the problem began. > > Lugnut
From: Bill on 6 Apr 2010 11:24 Did you follow the procedures for bleeding in the FACTORY SERVICE MANUAL, particularly for the ABS? "Mark" wrote in message > Hi, > > I have a lexus es300 with 128K miles. I had taken my car to the > mechanic as I felt the brakes needed work. I had to press the brake > pedal all the way down to stop the car. The mechanic suggested > replacing the master cylinder which I did. > > Now, I have 2 unique problems and I am looking for advice here to > educate myself before I take the car back to the mechanic. > > 1. The brake pedal sometimes works just by a little pressing, and > other times I need to press it all the way down. In other words, > sometimes it brakes just by a slight touch of the foot and sometimes > it doesn't. The brakes work, just that the "firmness" of the pedal > keeps changing. > > 2. The car starts vibrating after driving for about 10 minutes on the > highway. The vibration doesn't start right away. There is vibration in > the car and the steering. When I brake, I get the pulsating feeling > with the brake pedal. All the passengers in the car can feel the > vibration. After about 15 minutes of driving, the vibration goes away > and doesn't come back during the same ride. If I park the car, let it > cool and drive again, then the same pattern repeats. > > Could the experts here give some insight into what the possible issues > could be? The advice here has always helped me in the past and look > forward to your opinion. > > Thanks and regards, > Mark
From: chuckcar on 6 Apr 2010 14:07 Mark <muffi74(a)hotmail.com> wrote in news:e52c66b9-90a0-4583-a493-0671bdd934d6(a)w17g2000yqj.googlegroups.com: > Hi, > > I have a lexus es300 with 128K miles. I had taken my car to the > mechanic as I felt the brakes needed work. I had to press the brake > pedal all the way down to stop the car. The mechanic suggested > replacing the master cylinder which I did. > Why that as opposed to the pads or bleeding the air from the lines? -- (setq (chuck nil) car(chuck) )
From: Tegger on 6 Apr 2010 16:51 Mark <muffi74(a)hotmail.com> wrote in news:f4392a29-ced5-4ae9-80c7- c5a948f4c2cd(a)s9g2000yqa.googlegroups.com: > On Apr 5, 10:07�pm, Tegger <invalid(a)invalid.inv> wrote: >> Mark <muffi74(a)hotmail.com> wrote in news:e52c66b9-90a0-4583-a493- >> 0671bdd93...(a)w17g2000yqj.googlegroups.com: >> >> > Hi, >> >> > I have a lexus es300 with 128K miles. >> >> What year? >> >> Does it have ABS? >> > > Sorry, should have mentioned in my post. It is a '97 es300, and yes it > does ABS. Do you have any freeplay at the pedal? Push the pedal with your fingetips, as lightly and gently as possible. You should feel the tiniest bit of very easy movement before it hits something solid and effort becomes much greater. You're looking for something like this in the first 1/16" or 1/8" or so of pedal travel. -- Tegger
From: Mark on 6 Apr 2010 21:58
Thanks everyone for your replies. I'll take the car back to the mechanic and have it checked again. I'll also have him look into the suggestions made here regarding proper bleeding, checking the vac booster, the caliper and rotors. The pads and rotor were fine at the time of replacing the master cylinder. As a side note, I had the tires rotated and wheels balanced a couple of times, but that didn't fix the problem. I have also been getting the check engine light with code P0446 (Evaporative Emission Control System Vent Control Circuit Malfunction). I didn't think it could be related to the problems I am having, but wanted to mention it, just in case there is a possibility of it being related. Tegger: I will check for the freeplay in the brake pedal and report back. Thanks for your help, Mark |