# Catalytic Converter and Brake Pads



## knicks05 (Jan 5, 2013)

I recently purchased a 2002 Altima not even a month ago from a used car dealership. My Service Engine Soon light came on about two weeks ago and my BRAKE light came on 3 days ago. I took it to a Nissan Service Repair Center and theyre telling me I need a new catalytic converter and brake pads with increased brake fluid. I called up the dealership and they told me not to trust them and bring it in to them. I'm fairly new to cars and Nissan is telling me the total cost will be around $1500 and the catalytic converter cost about $700 alone. Does both prices sound right? Do you guys think I should just take it back to the dealership and not have Nissan fix it? Thanks


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## kupothechocobo (Jan 6, 2013)

Hey, I just shopped around for cats on my 2000 Nissan Altima, and without a brake job, I was quoted over $1,000 for both the front and rear cats (there's two on your Altima). I ended up buying the cats, flex pipe, and O2 sensors for under $300 on eBay.

My recommendation is to buy the upstream and downstream O2 sensors and replace them yourself. There's a tool that Nissan sells to put on or take off the O2 sensors and it cost me $13 in an auto parts store and it's worth every penny - it's a deep socket with a groove cut out for the wire. To get at the upstream O2 sensor, pop the hood and look at the exhaust manifold. You have to disconnect the wire (which is easily accessible) and then put the special Nissan socket I mentioned on the O2 sensor and take it out. The new one is just as easy to put in.

The downstream O2 sensor is the same story, except you'll need to jack your car up and look at the exhaust. It's located roughly behind the front wheels, except towards the center of the car where the exhaust runs through.

I would do this before replacing the cats.

As for the brake fluid comment... increased brake fluid? Do they mean you have air in one of your lines? If so, add fluid to the reservior under the hood, pop each tire off and bleedin new brake fluid through each of your lines. This consists of using a cheap hand pump that you attach to the bleeder valve. Here's the bleeder:
Brake Bleeder and Vacuum Pump Kit

I would do both of these repairs myself and also get the check engine wiped before paying a shop to do anything else.

EDIT: I forgot the 2002 was a new body design. My advice for installing the O2 sensors came from working on the previous body design. I checked another post and it seems that this information is still accurate - your model has two O2 sensors.


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## knicks05 (Jan 5, 2013)

Thanks I just got back my altima from the shop and on paper it says I need new front brake pads and rotors meanwhile now the BRAKE light is off. You think they're trying to take advantage of me?


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## smj999smj (Jan 1, 2006)

As the brake pads wear, the caliper piston extends more and displaces fluid from the reservoir. As the level reaches a certain point, the fluid sensor will cause the brake light to turn "on." Depending on how worn the pads are, topping off the fluid and/or replacing the brake pads will turn the warning lamp off. 

As far as catalytic converters, usually in a system that has front and rear converters, it is rare that the rear converter needs replacement. One reason is that the front converters act as sort of a filter (for lack of a better term) to the rear filters, as most of the exhaust emissions will be converted going through the front converter and any debris or oil will get caught in the front converter. Also, the ECM used the front and rear O2 sensors to monitor catalyst efficiency. These are placed before and after the front converters to monitor those converters for efficiency. Most rear converters are installed after the rear O2 sensor, so they are not monitored for efficiency. The big concern on a 2002 0r 2003 Altima QR25DE is the history of those engines burning oil. When replacing the front catalytic converter, it is important to look for signs of burnt oil on the catalyst honeycomb. If it exists, then you will need to correct this problem or the same will happen to the new converter. This usually means rebuilding or replacing the engine. Aftermarket catalytic converters and O2 sensors are an option to the high cost of Nissan parts, but make sure you stick with a reputable name, such as Bosal or Walker for exhaust products or NTK, Denso or Bosch for O2 sensors. Check Rockauto.com for good prices.


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## knicks05 (Jan 5, 2013)

smj999smj said:


> As the brake pads wear, the caliper piston extends more and displaces fluid from the reservoir. As the level reaches a certain point, the fluid sensor will cause the brake light to turn "on." Depending on how worn the pads are, topping off the fluid and/or replacing the brake pads will turn the warning lamp off.
> 
> As far as catalytic converters, usually in a system that has front and rear converters, it is rare that the rear converter needs replacement. One reason is that the front converters act as sort of a filter (for lack of a better term) to the rear filters, as most of the exhaust emissions will be converted going through the front converter and any debris or oil will get caught in the front converter. Also, the ECM used the front and rear O2 sensors to monitor catalyst efficiency. These are placed before and after the front converters to monitor those converters for efficiency. Most rear converters are installed after the rear O2 sensor, so they are not monitored for efficiency. The big concern on a 2002 0r 2003 Altima QR25DE is the history of those engines burning oil. When replacing the front catalytic converter, it is important to look for signs of burnt oil on the catalyst honeycomb. If it exists, then you will need to correct this problem or the same will happen to the new converter. This usually means rebuilding or replacing the engine. Aftermarket catalytic converters and O2 sensors are an option to the high cost of Nissan parts, but make sure you stick with a reputable name, such as Bosal or Walker for exhaust products or NTK, Denso or Bosch for O2 sensors. Check Rockauto.com for good prices.


this is my first car what are some signs of the engine burning the oil?


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## knicks05 (Jan 5, 2013)

And also my BRAKE light no longer shines bright on te dashboard. Nissan didn't do any repairs yet you think there problem no longer persists?


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