Coolant and Emission

[Hansome Rob]

I am new to the BMW world. I just came from FC3S (RX-7) land. I am thinking that i have a bad O2 sensor but not quite sure. My exhaust smells like rotten eggs (bad cats most likely) and my check engine light is on. At high RPMs under load i have hesitation. I have been doing some research and am i correct in understanding that the E36 BMW 325i has a precat sensor AND a postcat sensor? Also my computer is telling me to check my coolant level. I look at the semi clear bottle (I think it is the overflow tank for the radiator) and it is filled to the top. So i assume that i am good on coolant. What are your thought everyone?

[my_e36]

I am new to the BMW world. I just came from FC3S (RX-7) land. I am thinking that i have a bad O2 sensor but not quite sure. My exhaust smells like rotten eggs (bad cats most likely) and my check engine light is on. At high RPMs under load i have hesitation. I have been doing some research and am i correct in understanding that the E36 BMW 325i has a precat sensor AND a postcat sensor? Also my computer is telling me to check my coolant level. I look at the semi clear bottle (I think it is the overflow tank for the radiator) and it is filled to the top. So i assume that i am good on coolant. What are your thought everyone?


Depending on the year of your 3-series, earlier ones with OBD-I engine computer only have 1 O2 sensoe, where OBD-II have pre and post cat sensor like you said.

Overflow tank should only be filled around half way, there's a mark on outside that says "KALT", that's the correct level when the engine is cold.

[Hansome Rob]

My 325i is a 95.

[ImperialDuckM3]

I am new to the BMW world. I just came from FC3S (RX-7) land. I am thinking that i have a bad O2 sensor but not quite sure. My exhaust smells like rotten eggs (bad cats most likely) and my check engine light is on. At high RPMs under load i have hesitation. I have been doing some research and am i correct in understanding that the E36 BMW 325i has a precat sensor AND a postcat sensor? Also my computer is telling me to check my coolant level. I look at the semi clear bottle (I think it is the overflow tank for the radiator) and it is filled to the top. So i assume that i am good on coolant. What are your thought everyone?

First welcome to BMW's world :thumbup:

The rotten egg smell is in fact your Cat is dead. Also yes, you need to replace the O2 sensor which is located on your cat.

About your "Check Coolant" you have a sensor at the bottom of your reservior tank. Its a simple DIY and cost like $20 bucks. Now, thats if you don't have any problem with your coolant system.

[Hansome Rob]

WOW Imperial. Thanks for the knowlegable information. That is exactly what i needed to know. One more question about the cat thing. I have 2 cats and 2 "pre-cats". Is there only one cat that has an O2 sensor in it? Plus where is the best and also least expensive place to get the O2 sensor for the 95 325i? Thanks

Robert Stoddard

[ImperialDuckM3]

WOW Imperial. Thanks for the knowlegable information. That is exactly what i needed to know. One more question about the cat thing. I have 2 cats and 2 "pre-cats". Is there only one cat that has an O2 sensor in it? Plus where is the best and also least expensive place to get the O2 sensor for the 95 325i? Thanks

Robert Stoddard

Actually you only have one Cat but your b-pipe split ( hence you have dual exhaust). The 2 O2 sensor are located; One is at your exhaust manifold and the order is located on your Cat.

Price range depending if you getting OEM or aftermarket. But look somewhere between $80-129. Of course avoid the dealership as much as possible, unless you want to give your first born child to them.

You should check Bimmerzone.com or Bimmerparts.com they pretty cheap and most will offer free delivery if your purchase exceed $75.

Also a side note, Ford Mustang and BMW 3 series use the same O2 sensor (with a little work :D)

:thumbup:

[Hansome Rob]

Thanks dude.