1994 Mercedes E320 wagon loud motor sound - PeachParts Mercedes-Benz Forum

dmorgan · #1 08-01-2016, 04:44 PM

My 1994 Mercedes E320 wagon has this loud motor sound and where does that loud sound comes from? Is it the exhaust, manifold, catalytic converter, muffler, losing compression, defective 02 oxygen sensor, etc? There is no check engine light (CEL) showing. However, on the self-diagnostic test (DSM) 16 pin, it shows the troubleshooting light of 4 only, meaning the MAF sensor. I had this issue of MAF for quiet some time but I don't think it is related to the loud motor sound.

When I started the car the first time, at first, normal, then driving a short distance and of all sudden loud noise coming from the engine? I cannot pin point the exact location of the loud sound. It sounded like a hot rod.

I do notice a difference in the rpm on the dashboard. When I floored the accelerator, normally the rpm at around 4400 would rattled which is normal. Now the rpm is free floating over to the maximum without rattling. Is it a rpm issue? If so, what would be the culpit? I am somewhat baffled by this issue and scratching my head as to what is the source of the problem. Any ideas anyone? I appreciated some feedback on this issue. Thanks.

dmorgan · #2 08-01-2016, 04:53 PM

Correction on the DSM above, it should be DM (diagnostic module) and quiet was misspelled for quite as in quite some time mentioned above. Sorry about that.

Sugar Bear · #3 08-01-2016, 07:43 PM

If it is a roaring sound it may be a fan clutch that is locking up early. When the noise occurs pull off the road and put the car in park, rev the engine and see if the noise is present. If yes see if it seems a though the fan is pushing a lot of air. Stay clear of the fan blades. I don't think it is exhaust or transmission because they would make the noise all of the time.

If you do replace the fan clutch, research which brand to purchase. Members recommend one brand in particular, I think it is Sachs???

Good luck and keep us posted!!!

dmorgan · #4 08-01-2016, 08:51 PM

Thanks for responding. I appreciated it. However, you are correct with fan clutch issue because I had that problem before and replace a new fan clutch. The fan clutch is not the issue. I should have mentioned earlier in regards to the above first statement when I wrote first start the motor then the noise kick in. Since then, the noise is always there, even when I start the motor. However, you gave me an idea that if I remove the serpentine belt and start the motor and if the noise is still there, then it means some internal part of the engine is the issue and not other parts that relies on the serpentine belt such as alternator/generator, fan, air compressor, power steering pump,etc. I will follow up on this.

Sugar Bear · #5 08-01-2016, 09:15 PM

Try unplugging the AIR pump on the passenger side if it has one to see if that changes anything. The pump comes on for about thirty seconds producing a fluttering air sound and then should disengage.

Also when you disconnect the serpentine belt roll each pulley by hand to check for noisy/loose bearings.

Good luck!!!

dmorgan · #6 08-01-2016, 10:07 PM

Are you referring to smog air pump as you mentioned above in your post

Sugar Bear · #7 08-02-2016, 12:28 AM

Yes

dmorgan · #8 08-03-2016, 06:00 PM

Just to follow on the issue. A friend of mine came over to lend an ear to find the source of the noise. He said that the sound is coming from the exhaust area, muffler, catalytic converter. I am going to the shop tomorrow to get a more accurate diagnosis. So far, it does not sound like an air/smog pump issue. Stay tuned.

dmorgan · #9 08-04-2016, 03:05 PM

I took the Mercedes to a shop nearby today. The mechanic told me the pipe that connected on the end of the catalytic converter fell loose or broken. The other end of the pipe that is connected to the front muffler is intact. I asked the mechanic is the pipe is welded or clamp between the catalytic converter and the muffler. He said both ends of the pipe are clamped. So, the only thing for me to do is to jack up the end or front of the Mercedes or both, get underneath the Mercedes and see what is exactly for sure I need to do. If the pipe is broken and needed to be replace, that is good. I am somewhat mechanically inclined. I just need to figure out what is the name of pipe (exhaust?) and part number to make sure it is the correct part. Possibly needed additional new clamps to hold and connect the pipe to the catalytic converter and the muffler. Feedback anyone?

dmorgan · #10 08-05-2016, 05:36 PM

Upon inspecting underneath the vehicle, I noticed the end pipe of the center muffler broke off. The clamps on the other end of the broken piece of that pipe that connected to the rear muffler remained intact. Will replace the center muffler and hopefully will resolve the noise issue. Stay tuned.

Ferdman · #11 08-06-2016, 07:22 AM

dmorgan, recommend taking your 1994 E320 to a custom muffler shop that is equipped to weld components. If you have a hole in an exhaust pipe, with sound metal on either side, a tech can weld a patch. Replacing the muffler or catalytic converter assembly will cost hundreds of dollars, and may not be necessary.

dmorgan · #12 08-06-2016, 08:13 PM

Fred Hoelzle, Thanks for your above comments. I appreciated it.
Perhaps I made myself not clear on my last post. I apologize if there is any confusion on the issue.On the center/ front muffler, there is a total break, leaving the broken pipe end of the center muffler intact with clamp connecting to the exhaust pipe. The exhaust pipe, itself, is fine. On the front center muffler (connecting to the catalytic converter), another two clamps holding the center/front muffler.
I don't know if it is worth to weld that big gaping hole that is on the end of the center/front muffler. the hole itself is about 3 inches in diameter, I think. I also think the hole left little room to weld back the other end of the broken pipe of the center/front muffler. I am tempting to buy a replacement front/center muffler. I can simply remove the center/front muffler by loosening the bolts on the two clamps that is on the catalytic converter. Also, removing the clamp on the other end of broken pipe of the front/center muffler (connecting to the front end of the exhaust pipe). Remember, the exhaust pipe end connecting to the rear muffler and so far, both the rear end of the exhaust pipe and the front end of the rear muffler remains connected and intact. I wish I had a camera to post a picture of the issue. I have not done anything yet. I don't know if all the clamps are too tight to remove the front/center muffler. As far as I can tell, I don't see any welding connecting the catalytic converter, front/center muffler and the exhaust pipe. I hope I made myself clear on the issue.
I came up with two front/center muffers that specifically fits my Mercedes E320 wagon. One is Bosal 175-291 muffler. The second is Eberspaecher 23.191.82 Muffler. Are they both good front/center mufflers? Is there any preference on one over the other? Any comments, feedback is greatly appreciated.

dmorgan · #13 08-06-2016, 09:09 PM

Just a thought. If I am able to remove the center/front muffler from the catalytic converter and the broken end pipe of the center/front muffler from the exhaust pipe, then I could take the center/front muffler and the broken end pipe to the welder/muffle r shop and have both welded back together again.

Ferdman · #14 08-07-2016, 06:40 AM

dmorgan, recommend pricing mufflers at your local MB dealer and at MB dealers online because their prices may be as affordable as aftermarket mufflers. Apply some PB Blaster to the exhaust system nuts/bolts before attempting to loosen. The nuts are copper and should unthread without too much effort.

dmorgan · #15 08-10-2016, 11:59 AM

My friend found the problem with the exhaust loud noise issue. It turns out the sleeve goes inside the exhaust pipe that connects to the middle/front muffler was cracked and some of the areas of the sleeve had some holes as well. Both mufflers are fine. He removed the sleeve by prying with the screwdriver, hammer, and plier. I bought a new sleeve that matches the old one along with new clamp. He also has to weld the sleeve into the hole of the front/middle muffler. Also, the exhaust pipe that is connected to the rear muffler was bent due to dragging. He had to bend back to the original shape so the sleeve will go inside the middle/front muffler. Total cost was much much less. The only replacement was the sleeve and new clamp.