Today when I started up the 1996 vanden plas 6cyl I noticed steam-moisture coming from only one exhaust, the left side.After driving to work only one of the exhaust tips and rear muffler was hot, the left side. It seemed to drive ok but in the winter with slick roads I drive a lot more conservatively.

I did have a p0420 code a month ago but the engine had been running cool because of an old thermostat that I replaced. Engine is now running at normal temp. according to guage on dash. I cleared the code and it has not returned.

I think one of the primary cats. is plugged. I will be taking it past the muffler shop to find out, the car has 93000 miles. I am preparing for a big bill!

 

Not sure how cold it is but in 2014 when we had 10ft of snow in boston, water froze in one of the pipes and I had to defrost it with a kerosene heater.

 

The exhaust comes from each manifold, through the first catalyst in each down pipe, then goes into a single pipe, splits into the underfloor catalysts then continues rearwards through a resonator, overaxle pipe, muffler and then tailpipe.

Good news is your downpipe cats are probably ok, likely something after the single pipe. Could be a catalyst, but also could simply be a baffle in the muffler has rusted and collapsed.

 

Thanks for the replies, I found that the problem was water or ice inside the right muffler. When I put my ear to that exhaust pipe I could hear gurgling from inside the muffler, I thought to myself that's a new one, a water cooled exhaust system!

I do not drive a long distance to work everyday and I guess water had built up. After a long high speed drive on the local by-pass no more water problems. That was a cheap fix!

Do the mufflers on our cars have drain holes? I need to check to see if mine are plugged or maybe drill a small hole at each end if they have none.

 

There are no drain holes that I know of and I'm not sure introducing a hole is a good idea. For some reason the water collects and unless you drive it for at least a half hour it collects and doesn't evaporate. I only had this problem when it was below 32F for many days in a row and did short trips. I've had my car since 1999 and 2014 was the first year I ever had this problem. I think it was below freezing in Boston for the entire month of February.