Yet Another Brake Booster Failure. Help Required.

marok · January 20, 2015

Hi

I have a 2000 (Pre-facelift) GS300SE

After getting warning lights (ABS, VSC, VSC (Off), I got the car scanned at my local Lexus dealer. They tell me that there is an open circuit in the brake booster solenoid and that the part will cost around £2000.
As I can't justify that on a 15 year old car (although it is still immaculate in all other respects), I will be trying Breakeryard.com for the part. Having read quite a number of posts here, re: brake booster problems, it would appear to be wise to replace the part with one from a post-facelift model (2001-05)
The problem I have is that the site works off a fixed menu system where you choose the part from a list and I'm unsure of what to order.

The options are:-

ABS Control Unit
ABS ECU
ABS Modulator
ABS Pump
ABS Pump Modulator combined

So, which one do I require?
I would be eternally grateful for any help with this problem, or any advice on an alternative solution.
In any answer you may give, imagine you're talking to a 12 year old child, and that will be about my level of technical expertise.

Thanks, in anticipation

ColinBarber · January 20, 2015

the normal fault is the ABS pump but that doesn't guarantee you have that issue, certainly not without knowing the error codes and symptoms.

ABS pump / modulator combined would be the safest choice which would look like the following:

http://www.2040parts.com/98-05-gs300-gs400-gs430-anti-lock-abs-brake-pump-module-controller-cylinder-i650758/

marok · January 20, 2015

Colin, many thanks for the prompt reply, and the image.

There are no other symptoms apart from the warning lights mentioned above, and the Lexus main dealer said that the only fault code was for an open circuit in the brake booster solenoid.

I will certainly go with your recommendation of the ABS pump / modulator combined. I'm just praying that I can get one from the breakers.

Many thanks again. You sir are an absolute star.

Hayne · January 21, 2015

Are you sure that its the ABS actuator module at fault? if Lexus told you its the brake booster, then are you sure it's the same part?

My understanding of a brake booster is the circular donut shaped assembly with a vacuum diaphragm mounted to the engine bay bulkhead behind the brake pedal which boosts pressure to the master cylinder. The faulty solenoid could be related to vacuum regulation.

Just a thought. I'd hate for you to buy the wrong part. It's just worth checking with Lexus that you are looking at the correct part.

Giles.

ColinBarber · January 21, 2015

Hi Giles, unfortunately the series II GS doesn't have anything so simple.

The braking system consists of a master cylinder/booster assembly which contains the fluid header tank, valve body, an electric pump, a high pressure gas accumulator, a pressure sensor, an actuator/solenoid valve body (black box on the side of the booster assembly), and a separate ECU controlling the ABS/VSC function.

I would not expect a breakers to try and separate any of those components. You want a complete unit as shown in the link I posted.

The pre face-lift system (1998 to Aug 2000) have a weak pump (not 100% confirmed as it could be a leak in the accumulator or faulty pressure sensor) which fails resulting in a loss of ABS and VSC along with a continuous alarm going off in the cabin. This isn't the problem in this particular case, sounds like one of the solenoids has burnt out. The Oct 2000 vehicles don't seem to suffer this issue, the valve body was upgraded and maybe a new pump was also used too.

marok · January 22, 2015

Thanks again for the extra info, gents.
I've managed to source one from a post-facelift GS300 for £318. It should be arriving tomorrow.
I read somewhere on here (and I can't find it again) that the pre-facelift car can't read the sensor on the post-facelift part, but apparently there is an easy way around it by using the sensor off the old unit and splicing it into the new unit.
Can anyone give me any further info on this procedure, please?

marok · February 16, 2015

Unfortunately, no luck with the replacement unit. The mechanic tells me that now, the brake pedal is like standing on a brick (didn't have that problem before the swap) + there's now an audible warning (that wasn't there before the swap).

Does this sound like the booster part of the replacement unit is duff?

As a backup plan, does anyone know of a reputable company that could repair the old unit?

I've seen a couple of companies on the net that say that they can but have horrendous customer feedback.

aviator888 · February 16, 2015

Very sorry to read about Your problem. Hope You get it sorted!

Is the work being done by indie? I would suspect something been put together wrong way. Decent mechanic should be able to tell you exactly where the problem is.

marok · February 17, 2015

Thanks aviator

Yes, the work was done by an independant that I've used for years. I consider the owner to be a friend now.
He tells me that the actual swap was an easy job, but he's stumped by the fact that there is now hardly any movement in the brake pedal (like standing on a brick), so I'm guessing it's not a brake-bleeding issue.
His conclusion is that the unit I got from Breakersyard is also faulty.
Unless someone can tell me something that he might have missed out during the swap, I'm going to have to send my baby to the great Lexus home in the sky.
This is particularly galling as the car with the original ABS unit was running faultlessly - I hadn't noticed any decline in braking power. Just those damn warning lights - so obviously it wouldn't pass an MOT (in 10 days time).

ColinBarber · February 17, 2015

if you are getting an alarm then yes it could be a pressure issue with the booster. When the ignition is turned on you should hear the pump starting, and if it runs too long without getting up to pressure then it will alarm. You should also be able to make the pump start by pressing the brake pedal, once the pressure drops below a certain point the pump will start up again.

Installation/commissioning procedure attached, not sure how easy this is without the proper Lexus tools

GS brake booster.PDF

marok · February 18, 2015

Many thanks yet again, Colin

As a last throw of the dice it's gone back in to the Lexus main dealer for diagnosis.

Which ever way it turns out I'll post the result on this thread.

marok · February 19, 2015

It's going to the great scrapyard in the sky.

The Lexus main dealer told me that there is a peg broken inside the ABS unit that I got from the breakersyard, which is non replaceable.

Immaculate inside and out and an excellent runner - heartbreaking. I've been offered £115 from cartakeback.com for it. Anyone used them or know of a better solution?

Thanks for all your help folks.

bubba1 · February 19, 2015

Break for bits or offer to another Lexus owner who may wish to break for bits, must be worth far more for spare parts!!

There must be other GS3000's off the road at scrapyards able to provide the required parts to fix, is this really not an option?

Good luck

Hayne · February 20, 2015

So sorry to hear that. If you want to sell it, put it on eBay as an auction. You will get much more than £115 for it.

Make a good advert with everything about the car and its condition and service history, etc, and 12 good photos and briefly explain the fault. Start it a £1 with no reserve and I think you will find it will sell for a good sum of money (certainly more than you have been offered).

I did this a couple of years ago with my wife's MOT failure, 15 year old, BMW 3 series and I got £400 for it. There was a lot more wrong with it than your car and it was in poor condition.

Well worth looking at eBay. Someone somewhere will have access to this part and will be willing to spend time repairing it, so it still has some value. See what similar GS300s have sold for which are spares or repairs.

Giles.