Hissing Noise When Press And Release Brake

[Ling_Joseph]

I recently bought a 2008 RX350. From day one I noticed small hissing noise when I gentally press the brake all the way down and then release it slowly. The same noise sometimes can be heard when I dirve slowly and release the gas pedal. Anyone had the same problem? Is there a fix? Thank!

[Junxus]

I recently bought a 2008 RX350. From day one I noticed small hissing noise when I gentally press the brake all the way down and then release it slowly. The same noise sometimes can be heard when I dirve slowly and release the gas pedal. Anyone had the same problem? Is there a fix? Thank!

I think what you are hearing is the brake relay for the led brake lights. It sounds like hissing but is buzzing!!!! It drives me mad. My 08 is doing the same, my Uncle has the same RX 08 and does not have the issue. Mine is going in for service next week I will post if they solve the problem.

Overall I feel this car is a piece of rubbish. I have wind noise, road noise and buzzing!!! I have grown to hate this car! I have tried to trade for an 08 GS AWD. The RX value is down $7k from the time I purchased it in October. 2050 miles!!! I will be going back to Benz.

[Junxus]

I reserached a little more around the net, and found several other are having the same issue. Some were 2009 models. I guy claims it is the Brake booster check valve not a relay. I will post when ny car returns from service.

[Ling_Joseph]

I reserached a little more around the net, and found several other are having the same issue. Some were 2009 models. I guy claims it is the Brake booster check valve not a relay. I will post when ny car returns from service.

Yes, it is more like a buzzing than hissing. I did take it to dealer and they also said it was the brake booster check valve, and they ordered the part and replaced it on my car. But it didn't make any difference. So I took the car back to the same dealer, and they verified the noise still exist, and said it is necessary to replace the entire brake booster, and let me use their rental car for a day while they work on it. But later they called me saying they called Lexus and they were told it is a known issue, replacing brake booster won't solve the problem, and there is no fix at the time.

By the way, the rental car they let me drive was a RX350 2007, I notice the same problem on the rental car. The buzzing does bother me, especially when I think of the price I paid for it.

Could you share the link that you found around the net if you still remember it?

[Nebraska99]

2009 models?

[Ling_Joseph]

2009 models?

No, mine 2008 module

[Junxus]

Well my car is still at the dealer. The noise is caused by the brake booster. Lexus is aware of the issue (why don't they fix it) instead of shipping cars with known defects. Lexus claims they have no solution at this time. "Some cars are louder than others" I drove a 08 Japan built one with 9 miles on it and it was louder than my 08, however the 08 loaner with 12K miles on it is 50% better. The vibration travels from the booster over the brake assy. and over to the brace under the dash down to the fuse / relay box under the dash where it ends as a noise. This is per the Lexus chassis engineer that was involved in resolving / identifying my issue. I will attempt to resolve the problem myself and if I do I will post my solution. Wish me luck.

'

[Ling_Joseph]

Thanks for the update. The buzzing on my car seems like a little lower in rainy days, but louder when the whether is dry and cold. Since there are still many other people think their RX350 is perfect, maybe there is a high chance of solving the problem by replacing brake booster.

Looking forward to see your good news on fixing the buzzing noise.

[stan4gigi]

My car is 08 RX350 and had the same noise. I was told the same answer by Lexus... Brake booster and no fix available. At the time, it was only 1 week or so after I bought the car. So, I expressed my disappointment to my sales person and his manager. Finally, they came up a solution.

Since the noise is noticeable in some RX350, not everyone of them, they let me try out different new ones on the lot and find one that doesn't seem to have the obvious noise. Then, they exchange the brake booster on mine with that one. After that, mine doesn't have the noise but the one on the lot.

It has been a week now and I haven't heard any noise so far.

[neoj]

My car is 08 RX350 and had the same noise. I was told the same answer by Lexus... Brake booster and no fix available. At the time, it was only 1 week or so after I bought the car. So, I expressed my disappointment to my sales person and his manager. Finally, they came up a solution.

Since the noise is noticeable in some RX350, not everyone of them, they let me try out different new ones on the lot and find one that doesn't seem to have the obvious noise. Then, they exchange the brake booster on mine with that one. After that, mine doesn't have the noise but the one on the lot.

It has been a week now and I haven't heard any noise so far.

the noise we are talking about is like " KA-KA, ki-ki" when you press the brake? i had this noise once last dec. when first snow arrived in nyc. that scared me, i thought my new rx350 break apart. however, it only happen once so far, (cross my fingers). also i heard some other people complain about the wind and road noise, from my experince, it was quite for first 1000 miles, and now (4000) i heard lot of noise too..does anyone has a solution for reduce those noise? :) thx

[Junxus]

I used a scope and found the noise to be coming from the brake booster check valve. The dealer agrees and will order one. I put some Dynamat on the Brake booster and the check valve. The noise is gone!!!!!! :) I am happy now!

[Ling_Joseph]

I used a scope and found the noise to be coming from the brake booster check valve. The dealer agrees and will order one. I put some Dynamat on the Brake booster and the check valve. The noise is gone!!!!!! :) I am happy now!

My dealer has replaced my brake booster check valve, but it didn't solve the problem. It's great to know it can be fixed using the Dynamat. I wonder if Lexus can do it for free if they don't have better solutions.

[KJ Nguyen]

I used a scope and found the noise to be coming from the brake booster check valve. The dealer agrees and will order one. I put some Dynamat on the Brake booster and the check valve. The noise is gone!!!!!! :) I am happy now!

Hi JunXus,

I own a 2005 RX350 and experience the same problem. I wonder if you could share how you resolved it using Dynamat. Perhaps posting a picture of what you've done. Appreciate it.

KJN

[Junxus]

Sorry for the delay in posting the info. I have been car shopping to trade the 08 RX for a MB or BMW. Well I did not take any photos but I can share my words. You need to apply some Dynamat Extreme or some other brand material to the top, side and front of the brake booster, (the large round part behind the master cylinder) also apply 2-3 layers over the check valve itself (the plastic "L" shaped piece with the rubber hose connected to it.) The strips on the booster are 2.5 in. wide x 7 in. long (sides 3 req.), 4 in. x 7 in (front 2 req.) and 1.5 in x 4 in on the check valve itself (2-3 req.). I had to remove the air filter housing (2 screws and a clamp, easy) to access the booster because my arms were to big. The whole job is no more than 30 minutes. If Lexus HQ reads this they should be able to implement a similar solution in production and give the dealers a TSB for RX already on the road!!!! :chairshot:

[KJ Nguyen]

Sorry for the delay in posting the info. I have been car shopping to trade the 08 RX for a MB or BMW. Well I did not take any photos but I can share my words. You need to apply some Dynamat Extreme or some other brand material to the top, side and front of the brake booster, (the large round part behind the master cylinder) also apply 2-3 layers over the check valve itself (the plastic "L" shaped piece with the rubber hose connected to it.) The strips on the booster are 2.5 in. wide x 7 in. long (sides 3 req.), 4 in. x 7 in (front 2 req.) and 1.5 in x 4 in on the check valve itself (2-3 req.). I had to remove the air filter housing (2 screws and a clamp, easy) to access the booster because my arms were to big. The whole job is no more than 30 minutes. If Lexus HQ reads this they should be able to implement a similar solution in production and give the dealers a TSB for RX already on the road!!!! :chairshot:

Junxus,

Thank You for your detail description of the solution. I will give it a try.

KJ