350 SDL Hammering at Idle - Replaced Delivery Valve O Rings
 

I recently replaced the delivery valve o rings and washers on number 1 and 2 positions (cylinders) on my 91 350SDL. I had a small leak.

I swear there is increased clatter - more like what some describe as hammering - it also seems to smoke more (whitish/blue) and rougher idle. It runs absolutely superbly at speed and after a moment or two - still noisier at idle, I think.

I would immediately just think this is the death of another 603, but it runs great all the rest of the time - 122K on it. And, it has always been rough just after startup.

Any ideas?

George

Re: 350 SDL Hammering at Idle - Replaced Delivery Valve O Rings
 

George,

Is the car running rougher and noisier after the o-ring/washer replacement? If it is, retorque the deliver valve housing pipes again per Bosch instructions. The torquing instructions of these housing pipes have to be very carefully followed, otherwise, you may end up with a noisy system or a damaged FI pump.

You may have a problem with the injectors too. But the best way to attack this problem is to test the fuel injectors first (need the injector tester). Just to be sure they are working properly before working on the FI pump.

David

George,

This brings back some difficult memories for me. A compression check will help define the problem and eliminate the prospect of bent rods and out of round cylinders if it is ok. Mine began to knock a little and smoke at idle, but ran great at other than idle, and always jumped to life starting. I presumed the oil consumption was just an indication the valve seals and guides had deteriorated at 162,000 miles. Was I surprised when I was told I had two bent rods and would need an engine rebuild or a new engine.

I am still irate over the design defect that Mercedes foisted on me and others with this car. By the way mine, with less than 10,000 miles since the rebuild is now burning oil again, which the dealer attributes to a turbocharger oil seal failure. Which, of course cannot be repaired, you have to replace the turbo at $1800.

This has been the absolute worst car I have ever owned. I am questioning my 30 year relationship with Mercedes as the time to turn in my wife's 1999 C230 Sport comes near (December). Maybe a VW CDI. Too bad the Passat is no longer available with the Diesel engine.

Good luck, Jim

Jim has a good point. The 350 engine is known to have these kind of problems.

David

I would take the car to someone who knows these engines problems etc.........probably your loacal MB dealer
when my engine failed I was afraid of a rebuild...especailly since MB only offered a 1 year warranty ......
I went with a completely rebuilt(by MB) long block assembly...not really a lot more than a rebuild and you get the peace of mind of a 48 month 50K MB parts and labor warranty
I Spoke with a gentleman the other day in PA who has a 1995 with 75K who experienced hammering at idle...and it was bad news.....he caught it early though and his oil consumption problems had not started as of yet...and MB is covering some of his fix

bottom line...take the car immediatly to have a compression and leakdown test

good luck

Warren
1992 300SD 120K
Columbus Ohio
turner@greif.com