I bought my 300D in Florida and drove it up to New Jersey in a straight shot. On the trip, the rear of the car clanked the whole way. It would start clanking, like, 100 miles into the trip. If we stopped for any reason, the noise would be gone and then, 100 miles later, start up again. When we got it to NJ, I asked a mechanic friend what he thought was wrong and without even looking at the car, he said, "Fuel filter needs to be changed." I thought he was joking. We changed it and it stopped clanking. Now, two years later, we took it up to Boston and the same thing happened again. I'm assuming the fuel filter needs to be changed again. The question is, does anyone know why it clanks like this when it needs to be changed?

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84 300D, greasified.

Your fuel filter is in the front, find another mechanic, one with a high school diploma.

Bearings or rear axle.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Clanking in the rear, yeah cv joint. They can clank on and off and yes in my experience stopping will make the noise go away for a little while. Should be easy to tell which is the bad one...

But go ahead and change the fuel filter anyway if it makes you feel good.

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Sadly Benz-less

Fuel filters should be changed yearly at minimum. I actually change the filters basically every 6 months.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

When you stop the bearings cool down and the clanking stops.

It really depends on the clanking. It could also be that your diesel tank vent hose is plugged and your fuel tank is collapsing. According to the Mr Wizard episode I watched as a kid it made some "clanking" sounds.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I have almost no opinion on the fuel filter angle. Well I did say almost. Although if you change it the engine dynamics might just be different enough to stop the rear axel noise. A strange one if so and not totally impossible. (really, really close though in my opinion). That torque converter on the front of the transmission should have eliminated any odd effects. More likely senario with a standard transmission and clutch but still remote even then. The rear axels should be seeing a constant even power loading even if the engine dynamics change.

Since at one time you apparently did change the fuel filter and the problem stopped. Normal cv joints will not respond to changing engine dynamics unless something is marginal with them in my opinion.

I would change the fuel filter again. Lubricate the cv joints even if the filter change made the noise go away again. It is very important to mention on this site that changing the fuel filter alone eliminated the noise once again. Once you are sure post again. If it did not stop post as well.

That should get plenty of opinions put forth. It would mean for starters that of all the cv joints changed some cars just needed a new fuel filter. Hillarious in context unless you were one of the people that changed one out. Really just needing a new fuel filter. Needless to say since they changed the axels they will never really know.

I do know if you get some lubricant into those cv joints before they are really damaged they may still be good for awhile. If the boots are torn forget it though. Inspect them carefully.

All you have to do is loosen the inside clamp and inject some lubricant into each side. May need a new clamp to close the axle/boot seal again. The price is right to try this.

If you managed to identify the offending side do it only. If not do them both. Do not pospone this as the damage increases a little everytime you hear the noise. At some point it will no longer go away after stopping for awhile.

You have basically described a rear cv joint noise. The only fly in the ointment is if a cv joint clanked all the way home on your trip up from florida more than two years ago. The offending joint should have totally failed by now. This may mean it is something else but nothing I can think of would normally be effected this way by a bad fuel filter.

Why is it so strange? If you changed the filter and the noise stopped. Then you put that old filter on any other 123 diesel. It would not clank in my opinion.

After all the fun what got my curiosity up initially was the mechanic a couple of years ago mentioning to change the fuel filter for your noise and it appeared to stop it. If you at that time told the mechanic the noise was a clanking one It would not suprise me if changing the fuel filter fixed it again. Just do not ask how. Better minds than mine are needed to answer that but I would enjoy the attempts.

You know, I think I heard about some German engineers that tried to patent a clanking fuel filter alarm for the 300D's. I thought it was a myth, but maybe you've got one of those rare finds! They say to look for something that looks (and sounds) like a cowbell back there. I'm surprised that mechanic didn't tell you about it!

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"Knowing is not enough, we must apply.
Willing is not enough, we must do." Goethe

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1951 Chevy 3100

2003 Indian Chief Roadmaster

1983 GMC 1 ton Dually

1982 Chevy 1 ton Dually, service body (sold)

'90 GMC Suburban 6.2 "SS Veg-Burban"
(single tank WVO\diesel conversion) SOLD

'81 300D ~ Mama's car...my job (now my car)(but still my job) SOLD

'83 300sd ~ rescue car SOLD

2005 Ford Taurus (Mama's new car)(NOT my job!)