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privera64

Sensitive Brakes

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I am both new to the forum as well as the Lexus world. I've been tinkering away on my '94 SAAB 900 for about six years now and frequent various SAAB forums for my repairs. So in short, I understand the frustration when a new member ceases to search the forums for their particular situation :rolleyes: and someone has to re-direct them. My apologies if in my forum searches I've simply missed a previous post regarding the issue below.

Here's the scoop:

About a year ago a co-worker of mine allowed me to start working on her '98 SC300--now mine (200k/runs great!). In the past 10 months I've replaced the starter, alternator, serpentine belt (done w/alt.), oil, etc. What I mean to say, is I'm a home garage mechanic at best. From day one I realized the car's breaks were pretty sensitive. Since the front pads and rotors had been replaced in June '09, and the previous owner felt she would simply adapt to them, I decided not to investigate the matter.

The car is now mine (some people just don't trust the dependability of "old" cars) ;) , and the rear brakes are ready to be replaced; it wobbles away when I push the pedal. Now that I'm replacing the rear, and can't handle the sensitivity of the front brakes, I'd like to find a cure for the sensitivity in them. I've replaced brakes before on 4 cars different in make.

So, could it be too much pressure in the line? Too much shim between the pads?

Thanks for any help!

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Welcome to the LOC! Since you mention that they have been like this from day one, it may also be that you're just not used to Lexus brakes. Try feathering brake application with a very light touch to start, then modulate progressively. You might find yourself getting used to them after a while. Can also compare with another sc. If after a comparison or after having someone familiar with the sc test drive your car, you determine that they are indeed grabby, then there are some things to check out. Assuming there's no contamination of the pads from oil, grease, brake fluid etc, you don't have ceramics, the rotors aren't badly scored, and you have no sticking/loose calipers, my guess is you have a faulty power booster or vacuum check valve. Vacuum lines could also be leaking or damaged. A corroded master cylinder bore could also be a cause. Start with the cheapest test, check the pads and go from there.

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Thanks for the response. I'll need to check the front pads and go from there, but in all severity the list of parts here http://www.lexuspartsnow.com/components/1998-lexus-sc300~brake-booster-vacuum-tube-47-03-4421.html isn't as bad as expected, especially when this car--which I had been working on all year for free beer and $$$--I bought for only $2000.

I know I'll lose a little fluid after bleeding the rears, thus I'll evaluate the pressure and then look at the fronts.

Another unmentioned note; the previous owner said the car didn't grab before the front brakes were repaired. Because she went to a local mechanic who didn't specialize in Lexus',I think the ceramic hypothesis holds some weight.

Thoughts?

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especially when this car--which I had been working on all year for free beer and $$$--I bought for only $2000.

Free beer & $$$ is always an incentive. Having worked on the car for the past year, you know what's waht and is also a good incentive for buying.

I know I'll lose a little fluid after bleeding the rears, thus I'll evaluate the pressure and then look at the fronts.

Just a reminder when bleeding to keep an eye on the reservoir level to make sure you don't introduce air into the system.

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