Failed brake test....42% imbalance.

[mike65]

I put my car through its bi-annual NCT here last week. It failed on two counts battery tray and rear brake imbalance of 42% - it needs to be less than 30%. Can this be fixed with new pads (they are thin and need replacing anyway) or is it new calipers/pistons.?

Mike.

ps the emissions test gave just 0.15%vol CO2 and 308 HC ppm which was a surprise

[ericnguyen]

Dear mike65:

You incorrectly stated the emission result for CO2. It must be 15%, not 0.15%. If your car actually gave 0.15% CO2, it would be in the junk yard already because its fuel mixture was so rich and the cat did not work at all.

Most gasoline cars in good shape should give at least 15% CO2 by volume, the higher the better.

However, your car gave 308 HC ppm, which is way too much beyond the maximum allowable HC ppm in California. In California, the maximum HC ppm is 85 at 15 mph, and 50 at 25 mph (new CA Smog Check II specifications since Oct 1, 2003.)

Regarding your rear brake imbalance: you should remove the 2 sets of rear brake pads and inspect their thickness as well as the thickness of each brake rotor. If there's NO noticeable difference in thickness between 2 pad sets/rotors, and no noticeable glazing on the surface of a brake pad set, you may have to replace the calipers/pistons. Otherwise, new brake pad sets should correct the rear brake imbalance.

Eric

[mike65]

Thaks for the feedback on the brakes as for the emissions the 190e has no cat as they were'nt introduced in EU market until '93 (when ALL cars had to have them) so 308 ppm is okay (the limit is 750)

Mike.