RTL4878 Posted July 5, 2007 Share Posted July 5, 2007 My check engine light came on and diagnosis was 02 sensors (both off the manifold) which I changed. Also indicated all 6 cylinders were misfiring. Within a day, got the check engine light again indicating same problem. I noticed a small hissing sound and found that it was coming from the brake booster near where it goes into the master cylinder. I got the CEL cleared and detached the air line to the Brake Booster and put a bolt into the line to disable it. I drove the car around with no power brakes for a while and the CEL light does not come on again. Reattached the line and same problem with the CEL light, so it appears that there is a small leak in the Brake Booster. Someone suggested that this could cause the fuel mixture to be too rich, that the this could cause the fuel injector to not work properly. Does this make sense? I looked online and found remanufactured parts for 200-250 with traction control which I now understand is necessary. Will replacing the brake booster solve the problem or is it something else. Is it possible for the brake booster to have a small leak to cause this? On cold days, my brakes would sometimes go to the floor when first backing out of my driveway in the morning. If it is the problem, is this something I can handle myself or am I better off letting a repair shop do it? Thanks! Quote Link to comment Share on other sites More sharing options...
todd332 Posted July 6, 2007 Share Posted July 6, 2007 I know there was a Recall for the Brake booster Hose on that year. Quote Link to comment Share on other sites More sharing options...
RTL4878 Posted July 6, 2007 Author Share Posted July 6, 2007 Thanks, but this does not appear to be coming from the hose at all. It is coming out of the brake booster itself. Quote Link to comment Share on other sites More sharing options...
brijinder1 Posted August 13, 2011 Share Posted August 13, 2011 Hello RTL4878, I am getting error codes p0130,p0133,p0150 and p0153 on my 1997 lexus es300. Mechanic checked for vacuum leak and noticed smoke coming from brake booster. He told me its brake booster issue. Did replacing brake booster resolved your issue ? Did you received same error codes? My o2 sensors too replaced at 102K miles and car is currently having 116K miles. Please let me know Thanks, Brij Quote Link to comment Share on other sites More sharing options...
lexis lexus Posted August 14, 2011 Share Posted August 14, 2011 Makes little sense, smoke coming from brake booster, or for that matter, causing those codes. It's a mechanical air pumping device. Push the pedal down, this compresses air in the booster which then gives the brakes "power" and provides an ancillary source of vacuum when you lift your foot off. I had a bad hose on another car, which didn't cause any engine mgt problems, but did lead to the pedal feeling like a brick after the first stomp while stopping. There's usually a one way check valve in the brake booster vacuum line that holds the vacuum when you hit the pedal.RTL's experience of plugging the vacuum line might be a good experiment for you Brij, then clear the codes and see if they come back, (but be careful with the brakes, takes a lot more foot power to stop the car..). Do you see any smoke? If you do, it's prolly coming from somewhere else. LL Quote Link to comment Share on other sites More sharing options...
brijinder1 Posted August 14, 2011 Share Posted August 14, 2011 Thanks lexis for info. There is no smoke coming out and there is no difference in driving after this problem came. So you are saying to take out the air hose going into the booster and clear the codes ? Do I need to also block the hose which is going to the other side towards the engine ? Quote Link to comment Share on other sites More sharing options...
Mike B. Posted August 14, 2011 Share Posted August 14, 2011 I think there is a little bit of confusion here. A brake booster works because vacuum is constantly pulling on the diaphragm while you have atmospheric pressure on the other side. When you step on the pedal, you push the diaphragm towards the vacuum side. The vacuum then sucks the diaphragm in causing a force multiplication. The brake booster does not add vacuum to the engine... it can't. Typically when there is a problem it is caused by a puncture in the diaphragm. It's possible it's in the hose going to the booster as well. Assuming the check valve is doing it's job then I'd venture a guess the problem is in the hose. If you disconnect the hose and cap it off, erase the codes and take a short drive (carefully as you no longer have brake boost) and see if the codes return then the problem is likey in the hose but you need to check engine vacuum to verify. If the codes and problems do not return the the booster is the issue and needs to be replaced. Quote Link to comment Share on other sites More sharing options...
brijinder1 Posted August 14, 2011 Share Posted August 14, 2011 Thanks Mike for the reply. I removed the hose from brake booster and cap it and I drove it, it became very hard and it took to much of hard brake to stop. So I put it back. I am thinking for taking it to other mechanic for second advice. Quote Link to comment Share on other sites More sharing options...
brijinder1 Posted August 28, 2011 Share Posted August 28, 2011 Thanks Mike for the reply. I removed the hose from brake booster and cap it and I drove it, it became very hard and it took to much of hard brake to stop. So I put it back. I am thinking for taking it to other mechanic for second advice. What I did alternatively is cap the hose and read the live oxygen sensor voltage on obd scanner and noticed that voltage was switching between 0.4 to 0.5 at rapid pace and it was around 0.0015V and ultimately went to 0V when hose is connected to brake booster. Through this test, I was almost sure that brake booster is having problem. Today I got brake booster replaced and after driving 40-45 miles, the check engine light didn't come on. This problem was kind of hard to detect and I asked some really good mechanics that I heard in my area and they said that it can't be a brake booster issue and suggested me to change oxygen sensors instead, inspite of telling them that they are changed recently less than 14K miles and they are OEM toyota BTW, I purchased this Ecan scanner (http://www.amazon.com/ElmScan-Compac...4573805&sr=8-2 ) and used Easy Obd software with it and I really liked it. I will update the thread if CEL comes it on again. Quote Link to comment Share on other sites More sharing options...
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