tmandel

I've just acquired a '99 E320 4matic wagon. I haven't owned a Mercedes for almost 2 decades, and I'm delighted. A great car to drive.

Only 95,000 miles and a full Carfax report showing a more or less uninterrupted history of dealer service ("for better or worse" I suppose I should say).

A few little problems to take care of, mostly minor cosmetic issues. But one mechanical symptom I thought I'd ask about: when my foot is on the gas pedal there is a slight whine, which seems to come from the front of the car. Take my foot off the gas, and the whine goes away.

My guess is that this is from the front differential. But you all will know more and better than I. Any thoughts?

tmandel

This is when driving, I should have mentioned. I.e. not in neutral but rather when power is being delivered to the wheels.

tirona

congratulations on the purchase and welcome to the forum. good place to start is to replace differential fluid both for front and rear. i have heard from other member noise dissappearing after replacing old differential fluid with synthetic fluid. mobil1 75w90 synthetic can be easily found at any autoparts stores and i think is recommended by mb also. i think the front differential on the 4-matic doesn;t have a drain plug, only a fill plug, so you would have to suck the oil out.
the rear differential should have a drain plug and a fill plug (always open the fill plug first, then the drain plug).
also your car has a transfer case which uses automatic tranny fluid, but i'm not sure how you check the fluid there.
franasia and loubapache are forum members who have a 4-matic wagon, they are way more knowledgeable on the matter and hopefully will see your post.

tmandel

Thanks, Tirona -- I'm planning to replace the differential fluid next week. I will definitely do both front and rear.

It's a good idea no doubt to check the transfer case as well -- perhaps franasia and/or loubapache will advise me whether it's advisable replace the tranny fluid in the transfer case.

Thanks again. I'm loving this car.

tmandel

Over at benzworld, I see recommendations to use Mobil 1 Synthetic 75-90 when changing front differential oil. Since I see many of the same names there as here, shall I assume that's the right thing to do?

Franasia

Hello tmandel, congratulations for your new purchase and welcome to the forum.

I doubt the noise is coming from the front differential. It's very easy to replace its fluid though. There's a DIY by yours truly at benzworld on the stickies. I used a Mityvac vacuum gun and worked great.

Rear differential is easy as well. As far as the transfer case goes, I have yet to replace fluid on mine. The Mityvac would be the extractor to use here as well. Here's a link to an interesting thread:

http://www.benzworld.org/forums/w210...-question.html

Hope that helps,

Cheers

tmandel

It's a steady whine occurring only when my foot is on the gas and the car is driving in a forward gear. Comes from the front.

Franasia

what it could be. I would start with the wheel bearings.

tmandel

Huh... I would expect wheel bearings to continue to sound even when I remove my foot from the gas or to change if I brake slightly while continue to gas.

I owned a couple of Subaru SVX's (great car!) that had repeated wheel bearing problems; this doesn't have that 'round and round' sound I also associate w/ wheel bearings.

But, we'll see -- it'll be up on the lift today.

Musikmann

Went through a bad wheel bearing with my Toyota. I agree with the 'round and round' noise you described. I heard that all the time, coasting, accelerating, etc. Don't remember what the sound was when braking, but it chaned slightly when I was turning right vs. turning left.

tmandel

Well, we changed the front differential oil, and the liquid was *full* of metal shavings -- am going to replace front differential soon. That was where the noise was coming from.

Looking at the car while on the lift was reassuring. A lot of good maintenance has been done and there are really no apparent problems. Looks like a new front driveshaft was fitted at one point, though I see no mention of this on my Carfax report.

We got the gas cap off -- that's good; now I can fill up! -- and I'll have to work with it until the Blau cap I ordered arrives next week. I'll have to be careful not to turn the current cap on too tight. Seems like a *really* silly problem for a car to have, I must say...

Franasia -- thanks for the link to the Benzworld thread, which was very helpful.

Franasia

with that front differential. Something bad happened to that car before. That axle replacement might have had something to do with it. Far from being a 4Matic expert, but there's never been issues with front diffs reported in four years on these forums.

OTH, do not trust Carfax that much. Actual dealer/indie service records is what you can really trust. Good luck with that repair and keep us posted.

Cheers

tmandel

Yup, my mechanic and I talked about that. A replaced front driveshaft may point to a previous situation that gonzo'd the front differential.

Musikmann

Agreed! You have a much more detailed CarFax report than I've ever seen. In my limited experience, routine services are seldom a part. Just remember to take those with a grain of salt because not all shops report to them. I bought my last MB with a clean report that had been in an accident. I'd be asking myself why the driveshaft was replaced. Does your mechanic have a guess there?

tmandel

I don't think he has any speculation about what might have led to replacing the front drive shaft. I can't imagine why myself.

In any case, we'll swap out the front differential and take it from there.

Franasia

is a common occurrence on 4Matics if an outer CV joint boot gets torn and damages the CV joint. CV joints on this system come in one piece with the axle, so that might explain the new axle.

As to what caused the differential problem, I'm clueless.

Cheers

tmandel

It's driveshaft not axle -- but in fact the it does look like the cv joints were replaced after torn boots.

I don't think I'll get to the bottom of this -- just replace the front diff and enjoy the car.

Hope you all have a nice holiday; you deserve it!