2006 Gs450H Seized Front Calipers

[Cavanman01]

Hello,

I just thought I'd document my experiences with seized front calipers on my 2006 GS450h. Apologies for the long post, but hopefully there will be some useful information in here. When I originally searched for information on seized front calipers, I didn't find too much information. Rear calipers seem to be more of a problem...

I bought my car in Dec 2014 so didn't have it that long. (I originally typed this up in April but only getting round to posting now...)

As these cars get older, I think this may become more and more of an issue, given how easily I think this can happen. Looking at some of the US sites, seized front calipers seem to be common enough for various Lexus cars in the US.

I could go into the whole story and background to this, but I don't think it would add to the usefulness of the post and would reflect badly on me, as someone with an interest in his cars and who should have noticed this much much sooner...

In summary... This process was prompted by a slight noise from the front left disk when turning left. What started out as a change of brake pads turned into new pads, new disks and two new calipers.

The first indication of the issue was that the inner brake pad was actually seized in the caliper on the left hand side. This is first time I have ever encountered this on any car I've had.

When I got the pad out (after much prising, cursing etc.) I found the pistons for the inner pad on the left hand side were also seized.

The reason why this was not noticeable when driving was, unbelieveable to me, that the right hand side was in exactly the same state; the inner pad was seized in the caliper and the pistons were also seized!

The biggest suprise was that I hadn't noticed any issue with the brakes until very recently when I began to think I had a warped disk.

I'd driven several GS450hs before buying mine and the brakes seemed to be no different on mine. I believe the pads were seized before I bought my car. Both sides had a seized pad, hence the braking effort was similar. Perhaps this a case where the brake actuator etc. really does provide a totally artificial feel.

The only symptom (in hindsight) was that at times, when the road was damp or slippy, I felt there was too much rear brake bias in the car. This I put down to excessive regeneration rather than brakes so never investigated further.

Note: there is no electrical or electronic switch on the Lexus to warn of worn pads. There is a spring on one pad designed to be very noisy when it touches the disk. This spring is on the inner (and seized) pads so there was no warning of worn pads in my case.

When I had looked at the service records for my car, the brakes were changed in a Toyota garage in 2013 so I had been confident the brakes were in good condition.

I think this problem arose because the outer rubber seals were damaged when the pistons were being pushed back when the brakes were being changed. In the seals for the affected pistons I noticed a small nick in each seal of approximately 2-3mm in each.

The pistons themselves appear to be mild steel with a chrome or hard coating on the piston walls. The pistons may just be highly polished with no other protective coating.

In any case the pistons themselves, where exposed, seem to have rusted very heavily and very completely. I believe this car might have lived beside the sea before I bought it, leading to even greater and more severe rusting. This rust seems to have moved from the top of the piston, which is uncoated, down under the side coating. This has made the sliding surface rough and has also been sufficient to trap the piston in the aluminium caliper.

I managed to extract one of the seized pistons and I've put a picture of it here. Given the condition of the piston, I would not be willing to risk reusing this piston and caliper on what is a heavy and quite fast car. If a piston is seized, I think it could be dangerous to push it back in without inspecting everything throroughly.

As I was under a certain amount of time pressure, I decided to go ahead and purchase two brand new calipers from Lexus. These were expensive but at least I know what I have.

I've had a chance to do some more searching since and I've seen rebuilt calipers for sale for $70 dollars or so each. Given the damage to the pistons on my caliper, including the pistons that haven't seized, I would only be comfortable if all pistons were renewed and all seals, inner and outer were changed.

[ColinBarber]

Thanks for the post, I'm sure it will be useful for some other members.

What a state those brakes were in! For people who are reasonable light on braking, they would probably never know how bad their brakes are as with a hybrid as most of the braking effort is provided by the electric motors rather than the mechanical brakes.

[C Mclean]

Now that's a heck of a lot of rust there...

[Cavanman01]

I think the GS450h is well overbraked in it's original configuration so the loss of half the braking force wasn't quite the issue it might have been. I wouldn't consider myself particularly light on brakes, but to be honest I noticed nothing wrong until I actually looked at the brakes themselves.

Given the mix between hydrid and mechanical braking I assume that the brake control system on the GS450h must be continuously managing the amount of braking required (as suggested by the pedal pressure) and the bias front to rear, based on the amount of regeneration occurring etc. It appears that it does quite a good job but does highlight that the pedal feel and response is purely artificial.

I was shocked at the amount of rust on the pistons and I would have thought that more protection, either through the material or through an appropriate plating tor coating, would be the safest route. The outer seal is much more than just a dust seal in this case.

When changing pads it would be important to push back the pistons using suitable packing pieces and a g-clamp rather than the big pliers that the Toyota garage must have used. I was amazed at the effect that just a small tear in the outer seal could have.

[cruisermark]

thanks for the write up

very useful and informative

[Animal Mother]

Both my front calipers had the inboard pads stuck in them, as I found when working on them today. Pistons are ok luckily. Both rear caliper slide pins were seized too. I've never known a car like if for brake issues.

[C Mclean]

I'm in and out multiple dealerships on a daily basis and it's the same thing for every make of car ranging from a cheap and cheery  Fiat to an expensive Mercedes. New discs and pads are the moneymakers for dealerships now..

[Verbout]

None of them get my hard earned for such a simple job.