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Brake Pedal To The Floor

Raj Rupra

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I've been scouring the pages of this, and other Lexus forums but I cannot find a solution.....

About 2 weeks ago, while standing in traffic, my brakes required more depression of the pedal than usual. Over the following 24 hours the pedal travel was so long it began to touch the floor.

As I accelerated and drove normally, brake pressure seemed to build up. So much so, that a stop from 30mph felt as though the initial bite was ok and I had normal retardation, but if I pressed further, it made little difference.

Also if I backed off the brakes and reapplied them the pedal travel was extended considerably. After a couple of days, low speed/crawling manoeuvres required pressing the pedal to the floor.

There are no warning lights or buzzers to alert me to a problem. I took it to Halfords Autocentre and they said the brake fluid looked as though it hadn't been changed for years! They changed it for free and checked for any leaks but couldn't find any. They then said that my VSC system was faulty. Apparently they'd turned it off and the brakes worked fine, although the ABS/TCS would be disabled. I was advised that whatever was wrong could not be diagnosed by them, only Lexus, and that it would cost me a fortune to fix!

Upon collecting the car, I turned the VSC off and it made no difference to the brakes at all. In depair, I have given the car to a mechanic friend to look at. He's had it for almost 2 weeks (although he only works on cars in his free time). To date, he has found nothing in the system that could cause the problem. All brake lines and calipers have been checked. He had it hooked up to a diagnostic tool (not Lexus, I guess) and it showed no faults.

I am going to collect the car this evening and pass it to an auto-electrician to go over and see if he uncovers anything.

Can anyone suggest anything that I may not have had checked, and where's the best place for me to take it, apart from the overpriced Lexus dealership?

All help will be greatly appreciated.

NB. If it ends up being a prohibitively costly solution, I'm likely to break the car up for parts. It's a black 2000 GS300 SE with sat nav and rear spolier.

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Sounds like the brake booster (nitrogen accumulator) not working properly anymore. Not sure what faults they would throw, but the average code reader doesn't read anything other than the engine ecu, which won't hold brake system codes or airbag codes, that kind of stuff. Either that, or your power (alternator) isn't providing enough juice to run some of the electrics properly.

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Thanks Tigerfish. Much appreciated. I've read your earlier advice in Feb 2012 to another member on replacement of the brake booster. That too was helpful.

All the electricals are fine, as are all brake lines and calipers. There is no warning light so all that remains is to isolate the pump and check its function, along with the master cylinder.

Thanks again.

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I don't know why people are so scared of main dealers? Their not highway robbers you know. Sure they can be expensive but only if you just say yes to first quotations etc.. They will negotiate just like any other buisness!

If I had a problem like yours with my brakes I wouldn't have gone to the monkeys at Halfords! Take it to Lexus, get them to diagnose the problem correctly, get a quote from them and then go off to find it cheaper at an independent! :)

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  • 3 weeks later...


Halfords checked the system, bled and changed the brake fluid and then told me where the problem lay (brake booster). All without charge. And they were correct. Another mechanic clamped flexy pipes in turn and checked caliper pistons for jamming and found nothing wrong. Finally, I took it to another mechanic who has pretty comprehensive diagnostic equipment. He plugged it in and said that everything pointed to a fault with the brake booster.... as Tigerfish said. He reset a few things through his machine and was successful in restoring sufficient pressure for me to brake safely, although at crawling speeds it can be unpredictable.

Time to scour the salvage yards now. Number 2 mechanic is pretty skilled and says he'll take the job on if I get the part. I think it may need reprogramming by Lexus (according to Halfords) after fitting, but shouldn't be too costly.

Thanks for your inputs.

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I couldn't be bothered with it any more. The car was almost 13 years old now and I expect it didn't have many more happy and cost effective miles left in it. Bodywork was also a bit shabby in places where it had been vandalised. Mechanical and electrics were spot on though.

So.... I part-exchanged it for a 2006 450h SE-L.

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