Can overfilling brake fluid affect brake booster? (2 Viewers)

[scottaskinosie]

Hey everyone,

First off, thank you all so much! Everyone on the forum has been so helpful to me in the past, either directly or through your all's amazing tutorials.

I have a question about my 2001 Toyota Land Cruiser. I brought it in to the dealership here in Austin for a routine brake fluid flush and shortly after I left the brake light came on and then a little later the brake light, ABS, VSC TRAC and VSC OFF light came on with a loud high pitched alarm. I looked under the hood and my brake fluid was filled all the way to the top. In fact, some squirted out when I removed the cap.

I managed to suck enough out to get it back in range and my brake light went off but the other lights and the alarm keep coming on periodically. I brought it back in and they told me the brake booster is shot and I need to replace it. It should take about 3 weeks and cost about $3,500. I suggested the overfilling and the issues I am now having might be related but they played it off as a coincidence. They said the extra fluid could not affect the booster.

Is this accurate in your all's opinion?

It seems a bit too much of a coincidence to me but I don't know enough about it to say anything definitive. SO I thought I would ask the masters

 

[JunkCrzr89]

Overfilling is a problem for these boosters, which is why the FSM, owners manual, and even the reservoir cap all provide specific instructions for filling the reservoir. But it’s going to be nearly impossible to tie that to the booster failure. If the booster was new, sure it would be easy. But I’m guessing yours is 21 years old and has simply reached the end of its lifespan.

 

[Njck22]

Overfilling is a problem for these boosters, which is why the FSM, owners manual, and even the reservoir cap all provide specific instructions for filling the reservoir.

It's not like the techs will care either way. I picked my 100 up from service and while in the pickup/service writer area, opened the hood checked the level knowing they over filled it, pumped the pedal and had it over flow right in front of them. Service writer brought the tech over and he said "well you'll never pump the pedal 20 times like that" After showing him the explicit instructions on the lid.

 

[OEMGUY0720]

I think it does. That void space was designed to hold air in respect with fluid behavior specifically when it gets hot. All fluids expand when there’s heat. So maintaining the fluid level with the thresholds of the manufacturer is crucial for a reliable breaking system to function.

 

[scottaskinosie]

Overfilling is a problem for these boosters, which is why the FSM, owners manual, and even the reservoir cap all provide specific instructions for filling the reservoir. But it’s going to be nearly impossible to tie that to the booster failure. If the booster was new, sure it would be easy. But I’m guessing yours is 21 years old and has simply reached the end of its lifespan.

Thank you @JunkCrzr89!

Yes, you are correct. It has not been replaced to my knowledge. It may have just been the extra pressure may have just been the final straw...

 

[scottaskinosie]

It's not like the techs will care either way. I picked my 100 up from service and while in the pickup/service writer area, opened the hood checked the level knowing they over filled it, pumped the pedal and had it over flow right in front of them. Service writer brought the tech over and he said "well you'll never pump the pedal 20 times like that" After showing him the explicit instructions on the lid.

@Njck22 Yes, that was similar to my experience as well. When I brought it back in they did acknowledge that it had been overfilled but also said that it wouldn't cause any issues

 

[TexLexican]

@Njck22 Yes, that was similar to my experience as well. When I brought it back in they did acknowledge that it had been overfilled but also said that it wouldn't cause any issues

What would Toyota do if they find out their techs aren’t following the FSM? I get dealerships won’t do jack, but if you escalate this to corporate then surely the dealership’s insurance could cover their mistakes. Hopefully you have something in writing.

 

[2001LC]

Brakes ...... Overdue write-up.

First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems. With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake...

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