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rpmdiag, Tech and Instructor
Category: Lexus
Satisfied Customers: 7752
Experience:  Since 1975
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I have a 2004 SC430 Lexus - Since I bought the car it has a

Customer Question

I have a 2004 SC430 Lexus - Since I bought the car it has a small dull pop that occurs when the brake pedal is pressed and it comes from behind the cabin wall that is directly behind the brake pedal - When this sound is heard it is felt in the pedal - This happens when the car is just sitting without a key inserted - It also happens when breaking - I think it happens also at times when I am not breaking but it appears to come more to the left of directly behind the pedal - Two Lexus dealers, a Toyota dealer and an independent shop have checked this out, heard the sound but can not diagnose the problem - The Toyota mechanic removed for several days a spring that attaches behind the break
pedal - The sound did not go away - In fact it seemed to occur more often - It seems to happen always after the car
has been sitting for a while by just pressing the medal - Anybody have a
strong sense of what might be going on -
Remember this happens when the car is not even started - Thanks - Steven
Submitted: 1 year ago.
Category: Lexus
Expert:  rpmdiag replied 1 year ago.

Hi, I’m Ron and I can help you.
I have been in this business since 1975 and also teach automotive repair. I am confident we can resolve your problem together. Please understand that I don't know your skill level. I can't see, smell, hear, or touch the vehicle either, so it may take a few replies to get to satisfactory results. Please be patient!
I also try to give all of the information you may need, expecting a “positive rating” in return. I will also continue assisting you after you have rated me, if necessary. If there is any reason I cannot get a positive rating, please let me know why “in advance”, so I can go another direction for you. I am sorry you’re having this problem; I’ll help you through it.

That pedal attaches directly to the brake booster, and sound and vibrations tend to travel. The need to detach the rod from the pedal to the booster and see if it stops.

Thanks, Ron

Customer: replied 1 year ago.
Thanks for the reply Ron - So if I understand you correctly I need to disconnect the Rod from the plunger that goes to the
Brake Booster - At the joint there is a pin that slips though the flat rod that connects the plunger to the rod - The connection
is secured with a clip - There is also a spring that locks onto the end of the pin - If I was to free the connection what would I then do to see if the noise still exists - However, I am sure the sound is coming from downstream of the connection and behind the cabin wall through which the booster plunger passes within a rubber boot - Please advise -
Expert:  rpmdiag replied 1 year ago.

That's correct.

Thanks again, and please don't forget to rate me and keep this link in case you still need me later on.


Customer: replied 1 year ago.
Ron - Your reply only acknowledge my asking if I was correct in my understanding - If so, as you stated, the noise is forward of the connection of the flat pedal rod to the booster plunger, so detaching the two will not change any noise that is coming from downstream of the connection - Thus, the noise is coming from the booster as a result of the plunger moving or somewhere else - I still have no clue what do do - Thanks - Steven
Expert:  rpmdiag replied 1 year ago.

Sorry, the rod going to the booster needs to be disconnected.

Customer: replied 1 year ago.
OK - So I disconnected the rod and when I pushed in the rod to the booster the sound dull pop still occurred - It is coming
from somewhere on the front side of the cab wall behind the brake pedal
Expert:  rpmdiag replied 1 year ago.

Wish I was there, it should be easy to find now. Pushing the look pedal, no more noise bding disconnected?

Customer: replied 1 year ago.
I am sorry Ron but I do not understand what you are saying - Your wording is confusing "look pedal" ? and I assume you meant to say BEING disconnected vs. "BDING" The noise still occurs when I push in the booster plunger and it is not coming from inside the cab of the vehicle but rather on the Engine compartment side of the cab wall - This is not an easy condition to find or get to as far as I can tell - Thanks - Steven
Expert:  rpmdiag replied 1 year ago.

Trying to do this on the road from my phone. Sorry.

You need to disconnect the pedal rod going to the brake booster.



Customer: replied 1 year ago.
I already did that as stated above and the sound still occurs on the booster side of the connection but not necessarily the booster itself - It is impossible to tell exactly where the sound is coming from
Expert:  rpmdiag replied 1 year ago.

Agreed, it's even harder from my end :)

Customer: replied 1 year ago.
My first expert has nothing to offer - Any other "Experts" have an opinion ?
Expert:  rpmdiag replied 1 year ago.

Testing the system with a scan tool is what you need to do.

Thanks, Ron

Customer: replied 1 year ago.
Thanks but my first e mail indicates the issue has been looked at by 4 different shops - Two for sure, maybe three, used a
scan tool - Thanks - Steven
Expert:  rpmdiag replied 1 year ago.

I know, but it doesn't seem to a common problem or complaint. I'm really sorry they're not able to find this problem for you, and it really is more difficult to do it over the computer as well seeing that I can't see it. It's obvious they're missing something.

Thanks again, Ron