An elderly gentleman went into a dealership in Dallas yesterday, and traded a 1990 350SDL in on new Lincoln. Only has 51,000 miles on it. I grabbed it.

The belt tensioner appears shot, the belt is in bad shape and is banging around making all kinds of rumbling noises when car is idling. I was able to talk dealer down several thousand dollars because of it and couple of other problems.

I can't remember, but think I had read something about the tensioner. Tensioner is common problem on these cars, but was there some kind of recall on them or a redesign?

When I replace the parts, is there some kind of updated design, or just replace the worn stuff with new?

Don

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1991 350SD 265,000 miles
1981 300D 320,000 miles

1990 350SDL 144,000 miles (wrecked)
1991 350SD 225,000 miles (sold)
1985 300D 113,000 (sold)
1987 300SDL 183,000 (sold)
1984 300D 360,000 (sold)

Yup, mine is shot, too, at 70,000 miles. My indy says that it's a common problem. It would be great if there is a new design.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

I have mine replaced twice within months of each other, just recently. I am at 195k and the latest seems to be ok now. It seems to be a common problem - and the belt wear is horrible when they start going.

What kind of MPG do you get on your 350s?

I get approx 26mpg combined city/suburban driving.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

Whoa! I just pulled the service records out of the glovebox and went through them. The car has had excellent service history, or at least it has had lots of service done in its 51,000 miles. All at the Merc dealer where it was purchased. But the fan-belt/tensioner issues! This is unreal. Here is history of fan belt/tension in the records:

Sep 90 - Odometer 224 miles. Owner complains of vibration in belt. Replace vibration dampner.

Sep 90 - Next day. Odometer 239 miles. Owner returns and complains about vibration. At owner request replace sepentine belt and fan blade.

Jul 92 - Odometer 2578. In for oil change, owner complained of vibration. No problem found.

Sep. 92 - Odometer not recorded. Replaced serpentine belt. Not warrantied, $99.97

July 94 - Odometer 11978. Engine running hot. Replaced Fan clutch and serpentine belt.

October 95 - Odometer 17750. Fan belt failed. Replaced alternator, serpentine belt, idler pulley, belt shock. - Note at end of order. Belt shock pulled from stock bad. Replaced again with another belt shock.

July 96 - Odometer 22085. Serpentine belt failed. Replaced belt, belt shock bad. Replaced belt shock.

Nov 97 - Odometer 29287. Belt tensioner vibrating. Replaced serpentine belt.

Jul 98 - Odometer 32843. When AC on, belt shakes. Replaced belt tensioner, belt shock, serpentine belt.

July 00 - Odometer 39689. Belt rattling. Replace serpentine belt, replace belt shock.

Aug 01 - Odometer 43677. Serpentine belt failed. Replaced serpentine belt.

September 03 - Odometer 49445. Serpentine belt failed. Replaced serpentine belt, replace belt tensioner.

There are also two separate receipts for serpentine belts by themselves. Owner replace himself? Also, yet another new serpentine belt new in truck with fresh receipt.

Today, Odometer 51,100. I bought the car yesterday, the belt and tensioner vibrating wildly, making all kinds of racket. I can look at the idler pulley, and it IS cocked couple degrees out of line.

What do you think? What do I need to do with this car to fix this right?

Don

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1991 350SD 265,000 miles
1981 300D 320,000 miles

1990 350SDL 144,000 miles (wrecked)
1991 350SD 225,000 miles (sold)
1985 300D 113,000 (sold)
1987 300SDL 183,000 (sold)
1984 300D 360,000 (sold)

I can't get over 21.5 on the highway. Usually 19.5-20 around time. Can't figure out why or how to improve it.

Little frustrated, but it runs well.

Just in case someone comes across this ancient thread. I just bought a low miles 350SDL with a very noisy belt tensioner, same history Don Baker described with his. In a nutshell: these models were the first Diesels coming out with serpentine belts that offer greatly reduced slip VS traditional V-belts.

This setup causes dynamic momentum differences between the mass of the Alternator rotor spinning at high speeds due to its small pulley and the crankshaft at idle. The belt tensioner has to compensate for that, the hydraulic damper on my tensioner got so hot i could not touch it after a few minutes at idle. Mercedes was not the only car maker having issues with that on their Diesels, VW BMW had similar problems.
The solution are overrunning alternator pulleys. OAP. The pulley used with the E300 OM606 engine worked on my OM603 without modifications: URO-010663 Benz 847603071569. It has a slighter larger diameter but no impact on the charging performance. After installing that thing (30minutes job) my engine sounded like a charm, absolutely no more vibrations, for the first time this thing hit the road in 1991 ;-)

The OAP will also allow you to run a much larger alternator. I'm using a 150a alternator from an R230 SL.

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CENSORED due to not family friendly words

Hi guys, URO Parts Alternator Pulley 604 150 0360 is technically an OAD / OAP style pulley for Bosch Alternators on 1996-1999 E300.

We've actually discontinued the pulley due to low sales, but we do have 16 left in the warehouse, so don't wait if you want one. Some retailers might also still have some on the shelf, but Pelican doesn't appear to offer it, unfortunately.

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URO Parts online catalog: https://apaindustries.com/catalog

for sure use an OAP. If you're in the DFW area i have an alt off a 99 e300 that appears to be somewhat new i'd sell. Would be a slight upgrade to the stock 70a and has the clutched pulley.

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect