Ragunarok

When I got the car back after an engine oil and filter change I noticed the exhaust sounds muffled/quieter, noticeable on overrun and the downshift bark is gone. Anyone else experience this?

Thanks

skullbox15

Not normal... did you check the oil level? Not that that should impact what you're describing.

Ragunarok

Yes, when checked hot the oil level is below the full level. When checked cold (left overnight), the oil level is covering the full level raised tab but not the entire upper tab

W205C43PFL

Any chance any updates were installed, assuming the oil change was done at the dealership. Probably not, eh?

Diabolis

An oil change affecting the loudness of the exhaust is about as possible as it changing the temperature setting on the thermostat in your living room. In other words, there is no mechanism in place that could possibly result in what you are describing. The W204 does not have a valvetronic exhaust, so even if they applied various software updates it would still be impossible for it to affect the loudness of the sound coming out of the tailpipes.

Ken Keith

Is it possible they crushed the exhaust some how? Either with a lift arm or lowering the vehicle on a tool cart that was forgot about under the vehicle?

Ragunarok

Thanks everyone

Oil was changed by Indy - no software updates were done.

The car is going back tomorrow to get checked.

chrisridebike8

Maybe they put your rear seats back up when you normally have them down?

Ragunarok

Update - happy to report car is back to normal. Mechanic took some engine oil out and changed out the fuel. So it was either a little too much oil or bad fuel.

Diabolis

If some idiot had filled it up with regular instead of premium and the ECU was pulling back the timing to compensate for the poor fuel quality so that you don't blow up your engine, then yes, I can see how that could affect the sound (and I would be pretty pissed at whoever did that and would make sure they never go anywhere near the car again). The oil had absolutely nothing to do with it.

W205C43PFL

I see. Learned something thanks.

W205C43PFL

Hmmm OP had the oil done by an Indy, there is no reason why there will be regular fuel (low octane) in the fuel tank unless the vehicle was driven a while before returning to OP therefore the fuel level was lowered and they had to fill it up back to the original value or had been taken for a joy ride (hope not). OP, any chance your oil change service includes free fill-up, nope right? Hmmm, I don't understand then. Obviously the easiest way to tell is if there a lot more klicks on the odometer.

Diabolis

"Mechanic took some engine oil out and changed out the fuel" sounds rather alarming for two reasons. First, unless someone put in the wrong fuel or it has been sitting for many (like 5+) years and the fuel had Ethanol in it that has absorbed plenty of moisture over the years resulting in phase separation, there is no need to change out the fuel - so something somewhere has gone wrong. And, overfilling the oil is also a no-no as it results in excessive crankcase pressure and can blow out the rear main seal, or at the very least result in excessive foaming - both of which are a great way to damage or destroy your engine life. Maybe the mechanic is a bicycle mechanic, not a car mechanic.

W205C43PFL

Shoot I missed that part, my bad thanks for mentioning it.

Ragunarok

The mechanic did put miles on the car, invoice says a test drive was done. the car was there all day before I could pick it up. I didnt pay attention to the miles so I dont know how many were done...

The oil level was only slightly over (did not go above the top red tab, but slightly above the raised notch on that tab which I understand is the full level). I was assured the oil level wasnt problematic and Mercedes have tolerance built in...now I'm worried.

Should I take the car elsewhere for a check up ? It's driving fine now as far as I can tell and I haven't seen any leaks

Diabolis

If the oil was only slightly over and/or you didn't push it hard, chances are it is fine. The PCV would have puked up the excess into the intake and you would have burned it up. And, judging by your original post, i.e. the exhaust sound not being what it was, the ECU was pulling back the timing because of bad fuel so again likely no damage done unless you have a tune on the ECU that can't properly compensate for low octane fuel... there's enough of safety margin in the OEM ECU software to get you from point A to point B if you can't get premium fuel.

The only thing that's not fine is the mechanic... if I were you, I'd find a new one for all future work.

chrisridebike8

Well if the oil was overfilled, could it have dumped oil into the intake and reduced the effective octane being ingested? That might be the root of everything.

Diabolis

Very unlikely at the minute amounts that would have possibly been ingested. Besides, based on the description, he was only about half a liter too high... foaming would have been a bigger issue.

My bet is on the fuel.

Madcow554

half a liter to a liter surely isn't enough to cause foaming? Surely that amount doesnt move high enough in the engine to contact the crankshaft

Diabolis

When I was regularly tracking the C63, I was told to never fill up above the halfway mark on the dipstick (but obviously above the minimum) by someone from Daimler who knows the M156 engines intimately. Otherwise it will indeed foam up when you are revving the snot out of it.

Ragunarok

Hi, thanks Diabolis, Madcow554 and chrisridebike8 for your replies. I do not have a tune on the car - ECU is stock. The entire car is stock.

I have attached a photograph of a C63 dipstick. The first black line is where the oil level shows when checking hot, after oil was brought up to operating temperature, 5 minutes after engine shut off. The second black line, slightly below the raised notch, is the oil level about 15 minutes after the first reading. With all the oil in the sump (i.e. car left overnight and checked next morning when cold), the oil is not above the upper red tab.

Is this the correct oil level? I have asked the Mercedes Dealership near me and I was told where the level is showing on my car is OK but I'm not sure, and I'd rather trust the advice of fellow owners who know the car. I do not track the car but I do take her on spirited drives.

I'll certainly be on the lookout for a new mechanic.

Madcow554

honestly this is why I do oil changes myself, because I can measure exactly what comes out and exactly what I put in and don't have to play guessing games hoping some mechanic did the job right. Maybe you should invest in a jack or some ramps.

W205C43PFL

Alternatively, I wonder if the MityVac will be able to get all the oil out if OP doesn't want to go the traditional route of dropping the drain pan.

Diabolis

On a W204 C63, the difference in the amount of oil that gets extracted through the dipstick tube vs. completely draining the oil pan is less than 40mL. Measured several times by the shop foreman at the corporate dealership next to Mercedes HO in Canada with a beaker when I used to track the car and did oil changes every two track events (as in every month). In other words, completely insignificant for all intents and purposes.

On a diesel ML with the OM642, the tube extraction method actually gets MORE oil out than draining it from the sump.

W205C43PFL

Good to hear, thanks for sharing your experience!