Mollys 70

2004 SL500 R230. 69,500 miles. I am having a hard time getting the check engine light to stay off. AutoZone scan tool says smog pump.
I had the smog pump replaced about a year ago.

If I disconnect the consumer battery to reset, the light will stay of for a few days before it comes back on.
I have even driven the car on a 500-mile trip with no check engine light. Drive around the city a few days & it comes back on. I unplug the trunk battery again to reset.
CEL light stays off for some days then comes back on. I'm puzzled.

My friend/mechanic said maybe it is carboned up? This is my mother's car & has been babied.
I figured I'd run some BG 44K fuel system cleaner though it. I don't know why, just trying anything.

Hoping someone may have some advice for me. My friend is a great mechanic & has his own shop for German cars.
I'm not scared to take it to the MB dealership. I just need to do some bend over stretches & buy some lube.

Any advice or questions would be great. Thanks in advance.

tonylinc

Why would you take it to a MB dealer? Already know they will lie, and will definitely try to rip you off. My 2007 SL550 had been driven by a little old lady for ten years and ran like a broken lawnmower. It was as if the car had never seen a tune-up in its entire life. I wondered whether I had made a bad purchase. My friend the engineer said to Seafoam it. Okay, what do we do? Bought two cans of Seafoam in the spray cans, spent half an hour slowly spraying it into the (warm) engine intake with me stepping on the gas pedal to keep the engine running. It's a two-man operation. Then shut off the engine and wait for 30 minutes. Then, start and drive. We had a freeway hill near us that went four miles upwards, we drove up that hill in third gear with the pedal to the metal at about 6000 RPM, then back down the hill and up again, a dozen or more times. Each time we did, massive clouds of smoke the size of a cathedral came out. Halfway through this procedure, the car ran even worse, but we kept going... Finally when no more smoke was coming out, the engine was purring smoothly. It was as if it just got a $1200 tune-up at a Benz dealership. That engine probably had not seen over 3500 RPM in ten years! Blew out all that carbon. This was exactly what the car needed. After doing this, I changed the oil. filters, spark plugs, engine mounts, and the car ran and drove as new. Never ran badly again. If you suspect carbon in the engine I highly recommend this Seafoam treatment, it t breaks all that loose and blows it out. You'll be amazed at the difference. These engines need to be run a little hard now and then to keep carbon buildup away.

tonylinc

If you do wind up replacing the smog pump, secondary air pump, whatever it might be, do not use a part bought at Autozone! They might be nice people, but you only want to use genuine Mercedes / Bosch parts on an R230. Previous owner replaced an alternator on my SL55 with a $89 alternator made by Duralast from Autozone, and it worked fine, until it didn't. Suddenly it output 30 Volts, frying the battery control module that costs over $600 and also a 100-Amp starter fuse I think that cost about another $100. Bad idea, when a new Bosch replacement alternator only cost about $300 anyhow. You have to look at it this way; it's a $100,000-plus car, not a chevy impala. Genuine parts or nothing at all. Mercedes parts can be bought online for cheaper that most dealerships might charge, there's a whole list of places to check when looking for a part. I've been saving money on genuine parts for over 20 years, since my very first Benz, buying $120 distributor caps for W124 300E's for $75 and the rotor for that, $25 instead of $50.Gotta be a smart shopper nowadays! I even buy spark plugs direct from NGK on their own website. And, with Mercedes, I never deviate from what spark plugs the owners manual says to use. No cross-reference BS. If your plugs have been in there a long time, it can't hurt to replace those. If you do replace the spark plugs, replace the wires too at the same time they are small and don't cost a whole lot and this way the job's done completely and done right.

Mollys 70

Thanks for the replies. I put some BG 44k in the tank today. Full tank of premium no ethanol. I will purchase 2 cans of Seafoam tomorrow. I will not be able to spend any time with the car for a week or two.
I need to enlist the help of a friend.
The smog pump was replaced. I did not know it had a secondary air pump. Genuine MB parts have been used though out.
My mother basically did nothing to the car for 20 years but buy gas, change oil, some tires & drive it less than 2500 miles per year.

Here's my list of work I have had done at my buddy's shop.
Valve cover gaskets.
Engine mounts
Transmission mount
Electronic/hydraulic struts
ABC Accumulators
ABC hydraulic hose (1 of 4)
Flush ABC system
New Gas Tank, baffles broke loose.
Batteries
Battery Tender charger/maintainer w/ extensions cords
Emissions Air pump
Engine Oil
Engine Air-filters
New Tires
4-wheel tire Alignment
O2 sensor
Hatchback struts
Center console strut.

I am thankful for any help or advice.