Thumping noise while braking

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Hello,

I have an IS 200 Sport (2001) with relatively new brake discs and pads. No grooves on the front rotors, some on the rear ones, but no substantial wear yet.

Lately there has been a slight thumping/thudding noise when braking while driving straight. I think it is coming from the front and is consistent with the wheels rotation. Apart from that, the braking is solid and the stopping is OK. There is noise only when pressing the brake pedal. No other noises from the brakes/suspension when driving over bumps or turning. I have had the car inspected and the lower ball joints replaced, but the issue appeared soon after that.

Is this a fairly common problem in our model? Are the calipers to blame, do they require servicing?

Thanks!

[ColinBarber]

It's a continuous noise whilst braking, not a single thump? Are you able to record the sound and post here?

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It is a rhythmic noise with every turn of the wheels, like "thump-thump---thump---thump------thump", but not very loud. In fact, it is too soft to be recorded because of engine and road noise. Also not audible when the music is on.

[ColinBarber]

Possibly just some pad material unevenly distributed on the rotor. Find a quiet bit of road and do six to eight 60-10 mph hard stops one after the other (don't let the brakes cool between runs) to re-bed in the brakes.

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I took the car to a garage. They found some corrosion spots on the rear rotors and, indeed, suggested to do some hard breaking to clear them out.

Curiously, the thumping sound itself is coming from or is amplified by the rear knuckle bushes, which are worn out. The vibration from the uneven braking is making them shake and knock.

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So, the rear knuckle bushes were replaced (with Febest bushes), but the noise remains.

There are corrosion spots on the inside of the rear discs. They are clean on the outside, but have become very grooved. The front rotors are OK on both sides.

Now there is also a light pulsation on the brake pedal, along with the noise. But the steering wheel does not pull left or right when stopping.

The shop now suspects that the rear calipers are corroded and not pressing the pads evenly, and suggested replacing them.

Can it be the rear calipers?

If I choose to rebuild them, is it enough to replace the seals and the o-rings, or better get the pistons and slides as well? I want to have everything ready before taking them apart.

[Linas.P]

Yes that sound fairly standard for stuck callipers, so when you brake only outside pad is actually doing any braking (these are common on mk2, but I assume mk1 has same issues). You can certainly refurbish the exiting callipers (in fact most of so called "new" callipers are just factory refurbished), but just replacing o-rings won't be enough, it is likely that slider pins are corroded and binding. I would say callipers would need to be fully stripped, probably media blasted, machined surfaces polished, slider pins mostly likely need to be replaced. Unless you have fully fitted workshop I would say that is job for professional. Not sure where you from, but in UK that costs ~£100-150 per calliper, which is slightly cheaper than "new" callipers (at least on mk2 they are like £220 per calliper).

If you have grooved disks (rotors is american), then you need at very least to resurface them, again depends on what it costs in your location, but at least in UK that was never an option for Lexus IS simply because resurfacing costs £80 per disk, whereas new disk costs ~£22-60 - so it is cheaper to buy new disks every time. Maybe on some more exotic cars it makes economic sense, but not on Lexus IS. One note - if you choose to resurface, then make sure you use service where they doing it on the car and not taking it off the car, because if there is any run-off on the disk or it sits just slightly uneven on the car, it will not be cured. As well this could be part of your problem - clean the hub as good as you can and then ask  mechanic to check run-off on the disk.

P.S. - would be good to move to mk1 sub-forum.

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Thank you!

Could the moderators move the thread to the Brakes sub-forum, please?

I am located in Bulgaria.

The refurbishing will be done professionally, but I would like to get the parts myself. I am replacing the disks with new ones anyway.

I can get an OEM repair kit with the rubbers/o-rings, but without the pins and pistons.

Can someone recommend quality pins sold on eBay or in the UK? I see Bigg Red are mentioned often, but cannot find the rear slider pins/bolts on their website.

[Linas.P]

As far as I know Lexus does not sell repair kits (which is kind of sad considering that this is part where it would beneficial). There are third party repair kits, but I can't say if they are good quality. Not sure About Bulgaria, but in UK that would not make sense - you would pay same price regardless if you provide the parts or not, so there is no saving and refurbishment places usually have their own suppliers where they get big discounts and bulk orders, so at least in UK the best way is to give the calliper to them and let them deal with it. 

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https://www.amayama.com/en/part/toyota/0447930231

This is the kit for the rear calipers. It is genuine Toyota, at least is labelled so. I suspect the quality is better than what our local garages have access to, which is Autofren, Frenkit or similar. It is a matter of quality, not price.

[Linas.P]

Yes you probably right, but as I said the seals not going to be your main worry (it is not like your callipers are leaking), the worn-out/rusted pins is key thing for stuck callipers. As well as mentioned I doubt they going to discount it at all for you even if you bring your own parts. and furthermore they may refuse to warranty the work if you insist on using your own parts. 

[note]

OK, I visited another mechanic. He replaced the brake discs and pads (with TRW) and inspected the calipers. In his opinion they were fine and did not need any work.

The noise was gone immediately. 400 miles later it has not returned, so I hope the problem is solved.

And, as we all know, the lesson is: drive your car every day or it will rust away 😁