Catalytic question for '89 300SEL - PeachParts Mercedes-Benz Forum

cubanbaptist · #1 01-19-2006, 04:44 PM

Q: all inspections and Federal/State Laws aside.... would anyone reading this consider completely removing the Catalytic Converter (and pre-cats if applicable) from a 300SEL and simply filling in the gap with a filler tube?

Would this be bad for the car in anyway?

Moneypit SEL · #2 01-19-2006, 06:09 PM

Not bad for the car, but a violation of federal anti-tampering laws. We all breathe the same air...why you wanna stink it up?

#3 01-19-2006, 08:54 PM

I agree, what if we all removed the cats? pretty stinky indeed, i have actually installed cats where ther should be none, i updated the fuel injection system on an old BMW 733i, it had thermal reactors, i installed a cat and the injection system that has an oxygen sensor, ran much better, more efficiant and polluted less.

cubanbaptist · #4 01-24-2006, 12:48 AM

Well, it took me a few days to get the car up on a horse to get under photos. I got an oil change today and took advantage then.

I guess the photos show my problem. There are no more precats, so my mechanic says air travels too far and can't heat up fast enough before it gets to first cat. Not to mention the fact that one of these cats sits a bit 'low' so when I have 4 adults and some luggage, and happen to turn into the alley, or back out of the garage into the alley, it 'rubs' and both had to be replaced already due to cracked ceramics. Muffler shop says cats are fine and engine must have problems. Dealer sent me directly to this specific muffler shop (in good faith to save some money), so I didn't feel need to do much due dilligence.

I guess I'll just have to fork over $$ for factory cat and have that installed - maybe then it will pass inspection. It's already had valve job + new O2 sensor.

Thoughts.

Moneypit SEL · #5 01-24-2006, 08:27 AM

Quote:

Originally Posted by cubanbaptist

I guess the photos show my problem. There are no more precats, so my mechanic says air travels too far and can't heat up fast enough before it gets to first cat.

Find another mechanic. Either this one is stump-stupid, or he's deliberately misleading.

Quote:

Originally Posted by cubanbaptist

Not to mention the fact that one of these cats sits a bit 'low' so when I have 4 adults and some luggage, and happen to turn into the alley, or back out of the garage into the alley, it 'rubs' and both had to be replaced already due to cracked ceramics. Muffler shop says cats are fine and engine must have problems. Dealer sent me directly to this specific muffler shop (in good faith to save some money), so I didn't feel need to do much due dilligence.

How would the dragging exhaust be caused by engine problems? Or, is there an issue you've not mentioned?

Quote:

Originally Posted by cubanbaptist

I guess I'll just have to fork over $$ for factory cat and have that installed - maybe then it will pass inspection. It's already had valve job + new O2 sensor.

That might be the easy (but not cheap) way to handle it. I used a 'direct fit' aftermarket catalytic converter. it also had no pre-cats, and wasn't quite direct fit, either. We had to heat and beat it to get it into place, and then bend it some more to keep it from breaking those rubber exhaust hangers. Still, considering the cost of an OEM part, I can afford to take some extra time and bother getting this one to work.

cubanbaptist · #6 01-27-2006, 10:22 PM

Quote:

Originally Posted by Moneypit SEL

Find another mechanic. Either this one is stump-stupid, or he's deliberately misleading.
How would the dragging exhaust be caused by engine problems? Or, is there an issue you've not mentioned?

I probably didn't speak clearly about the dragging. However it happened, these cats 'rubbed' on something and I had to replace both of them. As for the mechanic. Well, I have alot of faith in him. Won't mention his name, but I actually found his name referred to (kindly) in this shop forum by someone else. I was referred to him by my service rep at dealer. The work he has done on my w126 is excellent.

Quote:

Originally Posted by Moneypit SEL

That might be the easy (but not cheap) way to handle it. I used a 'direct fit' aftermarket catalytic converter. it also had no pre-cats, and wasn't quite direct fit, either. We had to heat and beat it to get it into place, and then bend it some more to keep it from breaking those rubber exhaust hangers. Still, considering the cost of an OEM part, I can afford to take some extra time and bother getting this one to work.

I guess my problem is this:

issue: car doesn't pass inspection (I already threw out the data)
first solution: new cats as seen in fotos I posted. Not to mention valve job from 12 mo earlier.

next issue: car doesn't pass inspection (same numbers from computer output)
next solution: O2 sensor replaced, check for 'running too rich'.

next issue: car doesn't pass inspection (don't remember numbers from that test)
next solution: leave $50 bill on passenger seat during inspection. Got sticker I needed without further delay.

The only thing I think I may have done wrong is turn the car off while waiting for turn at inspection. Maybe cats didn't have enough time to light off. Maybe I should take 30 min spin on George Bush frwy then pull into get inspection immediately without turning off car.

I don't bat any eye at fixing problems on this car. In fact, I do it gladly. But this issue of inspection is too much and is getting stressful. I can't expect my mechanic to look at the car until he's blue in the face to resolve the issue without charging me an arm and a leg. The dealer will charge a fortune for any troubleshooting, too.

Hence, I'm tempted to simply remove cats, continue paying $50 annually extra for courteous inspection service, and put money towards other repairs and upgrades to keep the car going so I can get the next high mileage badge.

Quick question: does anyone else have a cat configuration like the one in these fotos?

Moneypit SEL · #7 01-27-2006, 11:24 PM

Quote:

Originally Posted by cubanbaptist

I probably didn't speak clearly about the dragging. However it happened, these cats 'rubbed' on something and I had to replace both of them. As for the mechanic. Well, I have alot of faith in him. Won't mention his name, but I actually found his name referred to (kindly) in this shop forum by someone else. I was referred to him by my service rep at dealer. The work he has done on my w126 is excellent.

The problem I have with your mechanic is this:
"so my mechanic says air travels too far and can't heat up fast enough before it gets to first cat"
Exhaust does not heat up between leaving the cylinder head and entering the converter. The distance the exhaust gas has to travel has no bearing on emissions, either. This guy may be an excelent mechanic in all other aspects of car repair, but I stand by my original statement with regards to emissions.

What can happen is a too-rich air/fuel mixture can cause the converter to overheat and melt down, or even cause it to never light up in the first place. A car with a new converter and reasonable air/fuel mixture should zero the tailpipe test.

Post the actual test numbers for your failure, and it's likely you'll find help here.

Kebowers · #8 01-28-2006, 01:13 PM

The exhaust gas is COOLING OFF before it gets to the cats. You will have to insulate the exhaust pipes to and between the cats to get proper performance.

They HAVE to be HOT HOT to work.

cubanbaptist · #9 02-06-2006, 04:58 AM

well, I'm stumped. I took it to inspect last Saturday and sure enough, it passed. I only wish I had last year's report to share with the forum.

see attached pdf of report.

Hit Man X · #10 02-06-2006, 05:53 PM

Big deal is you need to drive the vehicle around for a long while, freeway run is good... to get the cat to work properly. This goes along with a proper tune on the said motor.

I don't have a precat on my F150 anymore, just a single highflow unit... works fine provided I drive it to where it's quite warm. Simple city driving will not work.