Engine whine after a long drive
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Engine whine after a long drive
Howdy. I thought this was an AC compressor whine as the noise was not there all winter long. Today I noticed the whine on with ac on, so I decided to turn AC off but the RPM related whine is still there after an hour long drive. Its only there after a long drive.
Fresh trans oil service was just done. 123 k miles. 2008 s550 4matic. Trans and engine moujnts are fresh, MB parts. RPM related noise.
It does it in Park, or neutral, or in drive naturally. Mostly heard at low rpms.
Power steering pump? Alternator bearing? Ac clutch bearing? This only happens only after an extended drive. More often in warmer weather.
Fresh trans oil service was just done. 123 k miles. 2008 s550 4matic. Trans and engine moujnts are fresh, MB parts. RPM related noise.
It does it in Park, or neutral, or in drive naturally. Mostly heard at low rpms.
Power steering pump? Alternator bearing? Ac clutch bearing? This only happens only after an extended drive. More often in warmer weather.
Last edited by tbilisi79; Apr 13, 2025 at 05:49 PM.
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From: Phoenix
222 S-65
Be sure all fluids are full. Just had a trans service? Look there first.
Use a long screwdriver to find where the noise comes from. At idle... screwdriver on A/C compressor. Put an ear to the end of the screwdriver. Do the same for alternator, mounting points for idler bearings, water pump, power steering pump. You’ll find it.
Use a long screwdriver to find where the noise comes from. At idle... screwdriver on A/C compressor. Put an ear to the end of the screwdriver. Do the same for alternator, mounting points for idler bearings, water pump, power steering pump. You’ll find it.
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S500
is the 4x4 box the original ?
there was a bearing made of chocolate on the early ones - these days virtually all the real info about it has vanished from the internet - you'll find a few useless references to it, but little useful -
I believe its a bearing in the transfer box - that these days people have a source of, and a way to get a new bearing in there... howling growling noise was what Merc called it
in the day the bearing couldn't be swapped and either owners offloaded it or paid $7 to 9k for a new box - but eventually persistent owners in the USA got a free new gearbox, ROW got their wallets out
personally I wouldn't touch one, the reason to have an S class is so it drives right - adding more diffs and nasty shafts on the front completely stops any point of the S existing - its the same reason premium cars were only rear drive - better steering feel, better weight distribution, better refinement etc. (but cost a bit more and slower to build at the factory)
the change today meaning 4x4 are far more common place is across many areas
marketing has sold the dream of masculinity from good genes and exercise, in to a money making scheme for car manufactures
mostly terrible drivers with no idea how it ruins cars
nanny state, and congestion, means you can't really enjoy how proper rear drive cars handle anymore
summer tyres with zero grip in bad weather
all cars now are disgusting rubbish to drive, so a 4x4 no longer feels as awful as they did
lots of cars now have four times the power anyone needs, and the brain dead generation with a play-station mentality means for the rest of use to be alive - they need all the help they can get
.
there was a bearing made of chocolate on the early ones - these days virtually all the real info about it has vanished from the internet - you'll find a few useless references to it, but little useful -
I believe its a bearing in the transfer box - that these days people have a source of, and a way to get a new bearing in there... howling growling noise was what Merc called it
in the day the bearing couldn't be swapped and either owners offloaded it or paid $7 to 9k for a new box - but eventually persistent owners in the USA got a free new gearbox, ROW got their wallets out
personally I wouldn't touch one, the reason to have an S class is so it drives right - adding more diffs and nasty shafts on the front completely stops any point of the S existing - its the same reason premium cars were only rear drive - better steering feel, better weight distribution, better refinement etc. (but cost a bit more and slower to build at the factory)
the change today meaning 4x4 are far more common place is across many areas
marketing has sold the dream of masculinity from good genes and exercise, in to a money making scheme for car manufactures
mostly terrible drivers with no idea how it ruins cars
nanny state, and congestion, means you can't really enjoy how proper rear drive cars handle anymore
summer tyres with zero grip in bad weather
all cars now are disgusting rubbish to drive, so a 4x4 no longer feels as awful as they did
lots of cars now have four times the power anyone needs, and the brain dead generation with a play-station mentality means for the rest of use to be alive - they need all the help they can get
.
Last edited by BOTUS; Apr 14, 2025 at 04:55 AM.
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Botus I agree. I did not want a 4 Matic car, but the deal was too good and this was during Covid hysteria .
Since this noise was there last summer and summer before and was not there in non summer ( no ac) weather, I’m gonna assume it’s the ac compressor. I usually turn the ac compressor when it’s not needed. So I’m hoping it’s not the 4 Matic bearing like botus mentioned.
Im now learning the compressor is clutches. Today my stethoscope will arrive and I’ll be able to zero in the noise I hope.
if it’s the ac compressor making noise. Is it dangerous ? Can it grab are and throw a belt ? I’ve read that the pulley has a break away mechanism to allow it to spin even if the compressor locks up.
I got a trip coming up in late June and wanted to take this car.
unjust spent over $3500 taking care of other issues I’ve been putting it off. But with summer coming I’d like to make sure Ac works and won’t grande itself.
Forgot to mention. All belt pulleys and tensioner are new. Car was quiet from October till April when Ac compressor was off.
Since this noise was there last summer and summer before and was not there in non summer ( no ac) weather, I’m gonna assume it’s the ac compressor. I usually turn the ac compressor when it’s not needed. So I’m hoping it’s not the 4 Matic bearing like botus mentioned.
Im now learning the compressor is clutches. Today my stethoscope will arrive and I’ll be able to zero in the noise I hope.
if it’s the ac compressor making noise. Is it dangerous ? Can it grab are and throw a belt ? I’ve read that the pulley has a break away mechanism to allow it to spin even if the compressor locks up.
I got a trip coming up in late June and wanted to take this car.
unjust spent over $3500 taking care of other issues I’ve been putting it off. But with summer coming I’d like to make sure Ac works and won’t grande itself.
Forgot to mention. All belt pulleys and tensioner are new. Car was quiet from October till April when Ac compressor was off.
Last edited by tbilisi79; Apr 14, 2025 at 06:28 AM.
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S500
- the AC low gas noise sounds like fluid in the torque converter or gearbox rushing around - weirdly it seems to sounds worse if you swap between S or C (I forget which). But then you top up the AC gas and the noise vanishes
I would guess it must produce some wear - likely needs 500g of gas - everybody sells the top-up crap these days - its got a mix of O-ring reviver, the correct AC compressor lube and the 134A gas - shake the bottle - engine running AC on, connect up to the big pipe near the suspension turret and squirt it in whilst tipping can 90 degress every few seconds - if properly low the bottle will be gone in seconds - if you weigh the bottle before and after you’ll be able to work out how much it ate.... - you can't really overdo it as the bottles don't have enough pressure to harm things...
if its losing gas absolutely no point bothering with a full vac empty and refill - those guys and modern machine don't know what's going on anymore - the good machines are all fully automatic
got a mate with a garage - I couldn't believe the speed the modern ones work at - emptied the whole 1200g system (with rear AC) in about 30 seconds and refilled in even less time .... the vac and hold for 10 mins was the waste of time, claimed mines OK but its not !!!!
.
I would guess it must produce some wear - likely needs 500g of gas - everybody sells the top-up crap these days - its got a mix of O-ring reviver, the correct AC compressor lube and the 134A gas - shake the bottle - engine running AC on, connect up to the big pipe near the suspension turret and squirt it in whilst tipping can 90 degress every few seconds - if properly low the bottle will be gone in seconds - if you weigh the bottle before and after you’ll be able to work out how much it ate.... - you can't really overdo it as the bottles don't have enough pressure to harm things...
if its losing gas absolutely no point bothering with a full vac empty and refill - those guys and modern machine don't know what's going on anymore - the good machines are all fully automatic
got a mate with a garage - I couldn't believe the speed the modern ones work at - emptied the whole 1200g system (with rear AC) in about 30 seconds and refilled in even less time .... the vac and hold for 10 mins was the waste of time, claimed mines OK but its not !!!!
.
Last edited by BOTUS; Apr 14, 2025 at 07:27 AM.
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- the AC low gas noise sounds like fluid in the torque converter or gearbox rushing around - weirdly it seems to sounds worse if you swap between S or C (I forget which). But then you top up the AC gas and the noise vanishes
I would guess it must produce some wear - likely needs 500g of gas - everybody sells the top-up crap these days - its got a mix of O-ring reviver, the correct AC compressor lube and the 134A gas - shake the bottle - engine running AC on, connect up to the big pipe near the suspension turret and squirt it in whilst tipping can 90 degress every few seconds - if properly low the bottle will be gone in seconds - if you weigh the bottle before and after you’ll be able to work out how much it ate.... - you can't really overdo it as the bottles don't have enough pressure to harm things...
if its losing gas absolutely no point bothering with a full vac empty and refill - those guys and modern machine don't know what's going on anymore - the good machines are all fully automatic
got a mate with a garage - I couldn't believe the speed the modern ones work at - emptied the whole 1200g system (with rear AC) in about 30 seconds and refilled in even less time .... the vac and hold for 10 mins was the waste of time, claimed mines OK but its not !!!!
.
I would guess it must produce some wear - likely needs 500g of gas - everybody sells the top-up crap these days - its got a mix of O-ring reviver, the correct AC compressor lube and the 134A gas - shake the bottle - engine running AC on, connect up to the big pipe near the suspension turret and squirt it in whilst tipping can 90 degress every few seconds - if properly low the bottle will be gone in seconds - if you weigh the bottle before and after you’ll be able to work out how much it ate.... - you can't really overdo it as the bottles don't have enough pressure to harm things...
if its losing gas absolutely no point bothering with a full vac empty and refill - those guys and modern machine don't know what's going on anymore - the good machines are all fully automatic
got a mate with a garage - I couldn't believe the speed the modern ones work at - emptied the whole 1200g system (with rear AC) in about 30 seconds and refilled in even less time .... the vac and hold for 10 mins was the waste of time, claimed mines OK but its not !!!!
.
will report back.
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S500
there are two - posh kit connects to both so you get pressure readings on both side of the mess -
the top up things ONLY connect to the large one by the strut - the sizes are different so you can''t go wrong - you'll only get gas in with it running
the top up things ONLY connect to the large one by the strut - the sizes are different so you can''t go wrong - you'll only get gas in with it running
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A quick fill using W134 shouldn't cost even ten bucks. At that price, you might as well try it and see if the noise goes away after a top off. I found results best to fill W134 on a cold engine. Keep us posted on how much it took and if the noise is solved.
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Well we’re one can. Psi was at 30 which is close to low.
After adding a can the psi went up a tiny bit. The noise is bearable now, but I only drove for 20 minutes so I can’t be sure if it’s fixed. But if it is I am ok with this low level noise.
https://youtube.com/shorts/LdB_H-i-xHI?si=HGduz9NBsgPRQmET
After adding a can the psi went up a tiny bit. The noise is bearable now, but I only drove for 20 minutes so I can’t be sure if it’s fixed. But if it is I am ok with this low level noise.
https://youtube.com/shorts/LdB_H-i-xHI?si=HGduz9NBsgPRQmET
Last edited by tbilisi79; Apr 14, 2025 at 04:13 PM.
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2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, 2017 Mustang GT, 2023 300C, and a 2019 Lincoln
Sounds like progress to me. At only 30+ psi, I might be tempted to top off again on a cold engine and see if the whine reduces again.
I have to top off my Corvette, a garage queen, every season. It takes me about three or four fills each on a cold engine to get the pressure well into the green. After that I am good for the rest of the year until it goes back into storage where I am sure it leaks out over the Winter. At $10 a can of W134, it can leak all it wants.
Consider one more fill on a cold engine and keep us posted if the whine reduces.
I have to top off my Corvette, a garage queen, every season. It takes me about three or four fills each on a cold engine to get the pressure well into the green. After that I am good for the rest of the year until it goes back into storage where I am sure it leaks out over the Winter. At $10 a can of W134, it can leak all it wants.
Consider one more fill on a cold engine and keep us posted if the whine reduces.
Thread Starter
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Joined: Aug 2005
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Sounds like progress to me. At only 30+ psi, I might be tempted to top off again on a cold engine and see if the whine reduces again.
I have to top off my Corvette, a garage queen, every season. It takes me about three or four fills each on a cold engine to get the pressure well into the green. After that I am good for the rest of the year until it goes back into storage where I am sure it leaks out over the Winter. At $10 a can of W134, it can leak all it wants.
Consider one more fill on a cold engine and keep us posted if the whine reduces.
I have to top off my Corvette, a garage queen, every season. It takes me about three or four fills each on a cold engine to get the pressure well into the green. After that I am good for the rest of the year until it goes back into storage where I am sure it leaks out over the Winter. At $10 a can of W134, it can leak all it wants.
Consider one more fill on a cold engine and keep us posted if the whine reduces.
Thanks, should I be worried about overfilling it?
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S500
the whine comes on the later variable rate compressors - older cars pre 2005 with the noisy electromechanical clutch systems, just switch off on a low pressure trip (at around 50% fill)
I don't think you need to worry about over filling - you should have a gauge and go gently... but if its making the noise its a minimum of 350g short of what's required
get some decent cooking scales, weigh the bottle before, give it thirty seconds (engine running AC on), weigh the bottle again...
if really low it might have eaten 400g in that short time, there is no harm doing it many times - nothing changes - just make sure the unions are all spotless, road grit inside is not healthy
I forget the small std fill gas quantity - its on the label - usually when the pressure in the system drops enough, most small leaks stop losing any more gas - thus many end up about 50% full, but whining
so if its a 900g system, anticipating 450g missing is quite a sensible rule of thumb - so top up 300 to 400g and see where you are
the big bottles 330mm x 65mm only have 650g of gas inside, leaving about 850g as the weight of an empty bottle - I have never managed one of these common sized bottles to get in to a high pressure territory - they don't have enough to do it
store the bottle upside down - the oil resists the gas walking off, so you can top it up another time down the road
.
I don't think you need to worry about over filling - you should have a gauge and go gently... but if its making the noise its a minimum of 350g short of what's required
get some decent cooking scales, weigh the bottle before, give it thirty seconds (engine running AC on), weigh the bottle again...
if really low it might have eaten 400g in that short time, there is no harm doing it many times - nothing changes - just make sure the unions are all spotless, road grit inside is not healthy
I forget the small std fill gas quantity - its on the label - usually when the pressure in the system drops enough, most small leaks stop losing any more gas - thus many end up about 50% full, but whining
so if its a 900g system, anticipating 450g missing is quite a sensible rule of thumb - so top up 300 to 400g and see where you are
the big bottles 330mm x 65mm only have 650g of gas inside, leaving about 850g as the weight of an empty bottle - I have never managed one of these common sized bottles to get in to a high pressure territory - they don't have enough to do it
store the bottle upside down - the oil resists the gas walking off, so you can top it up another time down the road
.
Last edited by BOTUS; Apr 15, 2025 at 05:36 AM.
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YES.
Variable displacement compressor AC systems must be charged by exact weight as designed. The use of AC pressure gauges to determine proper charge does work here because there is solenoid, electronic control valve, continuously adjusting load and pressure behind the scenes.
If you already determined your problem was low refrigerant, evacuate the system, test for leaks using vacuum, if nothing found the likely and common issue are the Scharder valve themselves which the vacuum test cannot pick up. Then, charge by weight as stated in the sticker/label.
If you have XEntry, you can monitor how the solenoid adjust the load if curious.
Variable displacement compressor AC systems must be charged by exact weight as designed. The use of AC pressure gauges to determine proper charge does work here because there is solenoid, electronic control valve, continuously adjusting load and pressure behind the scenes.
If you already determined your problem was low refrigerant, evacuate the system, test for leaks using vacuum, if nothing found the likely and common issue are the Scharder valve themselves which the vacuum test cannot pick up. Then, charge by weight as stated in the sticker/label.
If you have XEntry, you can monitor how the solenoid adjust the load if curious.
