[maxpower10]

I just bought a C320 4Matic with 90,000 miles on it. I noticed a ticking noise at idle. It gets faster as you accelerate and stays regardless of engine temperature. It sounds very much like a sticky lifter but does not go away. It is very noticeable but I would not consider it a knock so much as a tick.

Shortly after leaving the dealership (3 hour drive at 70mph) I slowed to about 35 mph. Just as I slowed the check engine light came on. I did fill up with premium (91 octane) fuel and was very careful about tightening the fuel cap. I tried starting the engine 4 times in a row as stated in the manual but the light remains on. I'm wondering if this could be related to the ticking noise.

The other thing I noticed was a considerable amount of road noise. Seems like a whirring noise from wheel bearings but I've never owned an AWD vehicle before so I'm wondering if the drivetrain is just going to be that lound.

The code turned out to be a PO432 and a PO422 Main Catalyst Efficiency Below Threshold, Bank 1 and 2. How would I know if I need to replace the catalytic converter or just the O2 sensors and how do I know which O2 sensors to replace?

The ticking noise does seem to be getting louder as I drive it and seems to be coming from the driver side of the engine. So far the loudest point I've found is when I listen directly to the driver side exhaust manifold.

Thanks in advance!

 

[rudeney]

It probably is bad cats, but I'd get a competent mechanic to check it. The error codes combined with the noises are classic symptoms.

 

[maxpower10]

It probably is bad cats, but I'd get a competent mechanic to check it. The error codes combined with the noises are classic symptoms.

So the ticking could be caused by bad cats? Why? Too much back pressure? What would be making the noise?

 

[Whosdis]

The element inside the housing is coming loose and rattling, if the ticking you hear is more a rattle than a tick.

 

[rudeney]

As Whosdis said, if the catalyst is physically deteriorating, it could be causing rattling noises as it bounces around in the exhaust system. However, if the cats are clogged, you can get leak at the manifold/exhaust pipe seal and that will sound like a loud tick.

 

[maxpower10]

Yes the loud tick is what I'm hearing. Seems like if I pull the cat off and run it the ticking would go away? That would prove a bad cat. I've seen the scottykilmer video of running a half gallon of pure lacquer through with a half a tank of gas to clean the cat. Alternatively taking it apart and soaking it in laundry soap over night. Any chance these ideas might fix it? Also, is there any harm in taking the belt off and running it for a minute to make sure it's not an accessory such as the water pump causing the noise?

 

[rudeney]

I would definitely not run lacquer through the engine! And I don't know anything about soaking cats in soap, either. But, there is no harm in removing the belt and letting the engine run for a few minutes to check for sounds on pulley-drive accessories. Just do it on a cold engine since the water pump won't be running.

If you think it might be an exhaust leak, you should be able to find it. Use an LED flashlight in the dark with the engine running cold to see tell-tale signs of exhaust.

 

[maxpower10]

What are your thoughts on removing the cats and welding in a straight pipe. I understand the effects on the environment, I'm not worried about passing emission tests. What are the effects on the engine and the sensors? I most likely would be stuck with a check engine light on for good I suppose. Removing the belt and running the car left the ticking noise in place so at least it's not an accessory.

 

[rudeney]

You can get an ECU tune (Kleeman, and others) that will "ignore" the downstream O2 sensors.

 

[sammy567]

What are your thoughts on removing the cats and welding in a straight pipe. I understand the effects on the environment, I'm not worried about passing emission tests. What are the effects on the engine and the sensors? I most likely would be stuck with a check engine light on for good I suppose. Removing the belt and running the car left the ticking noise in place so at least it's not an accessory.

driving with a check engine light will dump fuel $$$$$$$

ticking noise is sometimes the lifters opening a closing the valves, fuel injectors ...if it was a pulley problem ud have a different noise

effects on your engine would be fatal in the long run since your car is running rich and not getting enough air

 

[maxpower10]

Oil usage

I'm about 300 miles away from my first due oil change and the add 1 quart oil light came on. It doesn't seem to be leaking any which must mean it's burning oil. Is this normal for this car or something I need to look into?

 

[rudeney]

Yes, a quart between changes is not unusual for a mature engine. Both my C240 and CLK burn about half a quart between changes.

 

[maxpower10]

Bad Smell

Seem to get a bad small in the car. Almost could be that rotten egg smell. Leaning towards replacing the cats. If I remove them, the ticking noise should go away, then I know that was the problem and I can order new ones. How many cats are there and where are they located?

 

[dmac]

Did you ever find a solution to the ticking? I have a similar problem.