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After successfully repairing my r roof piston o ring and reassembling all the parts/panels etc. in the trunk area, I have noticed an electronic high pitch (intermittently) sound while driving. radio on/off position. could this be related to a poor antenna connection?
thanks,
roger
 

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Is it a high pitched whistle? Very annoying, and very deceptive as to where it is?
I had one - extremely difficult to diagnose. Turned out to be a vacuum switch behind the glove compartment that oscillated. It happened most often as I decelerated. After replacing the $40 part, I could blow into the old one & hear that annoying sound!
 

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Is it a high pitched whistle? Very annoying, and very deceptive as to where it is?
I had one - extremely difficult to diagnose. Turned out to be a vacuum switch behind the glove compartment that oscillated. It happened most often as I decelerated. After replacing the $40 part, I could blow into the old one & hear that annoying sound!
Is this the vacuum switch you're talking about? I've developed the whistle when I accelerate and decelerate...very annoying in stop and go traffic. :mad:

Vacuum Switch.JPG
 
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I have what sounds like an air leak behind the dash when the rpms are low and goes away on acceleration, I wonder if it is the same thing.
 

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I've come up with two part numbers so far:

0005409897 (I suspect is for '98-'00) and
2028000178 (Possible '01-'05 and the one pictured above)

Searching EPCnet yeilded nothing when looking up the 2nd part #, but I found it looking up the 1st one.

I'm going to drop the glovebox tonight and see which one I have and also disconnect it while the car is running. It's got to the point now where the whistle "arrives" when I sit at a stop light, but goes away idling in Park. So I'll set the emergency brake, put the car in drive, and examine from there.
 
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OK, well, I replaced the "Fresh/recirculating air flap switchover valve" (part no. 2028000178). Did not alleviate my whistle. :mad: Now, I'm looking at the "Vacuum Element" (part no. 2028001875). I'm just wondering if there's anyway of definitely determining this is the culprit of my whistle because there seems to be two parts to the device, the element (Item #95) and the mechanism the element attaches to (Item# 90 part no. 2028001376). It would be nice to replace the actual part instead of shotgunning it. :(

Edit: Sorry, I should have included this since I was referring to item #s.

Capture.JPG
 
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Sorry, I don't remember getting notified about new posts here, but I got this one!
I made a video back then to help others, since it was soooo elusive! I had my wife drive, and I poked around till I found what would caused/stopped it. It was a diaphragm in a vacuum switch that had deteriorated, as I recall.
I will hunt it down and post it - PM me if you don't see it soon!
 

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Sorry, I don't remember getting notified about new posts here, but I got this one!
I made a video back then to help others, since it was soooo elusive! I had my wife drive, and I poked around till I found what would caused/stopped it. It was a diaphragm in a vacuum switch that had deteriorated, as I recall.
I will hunt it down and post it - PM me if you don't see it soon!
Thanks! Was it item #95? (See above edited post)
 

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In diagnosing vacuum leaks, either pinch off the offending item's vacuum line going to it or disconnect the line. That should tell you if it is the problem or not when the whistling stops.
 

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In diagnosing vacuum leaks, either pinch off the offending item's vacuum line going to it or disconnect the line. That should tell you if it is the problem or not when the whistling stops.
Normally that would be a good suggestion, Jim, and one I have practiced. However, in this case, there is a vacuum line that runs serially between them. There really isn't a way to isolate one from the other without killing the vacuum to both. :(
 

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Thanks! Was it item #95? (See above edited post)
Oh that dreaded air flap!!! I remember it....
Check out this thread:
http://www.slkworld.com/slk-r170-class-diy/33742-air-recirculation-flap-inside-outside-cabin-air-problem.html
If it's part 95 then it's probably the rubber is deteriorated and causes air to leak.
When you're driving, and you shut off the air to circulate through the cabin by putting switch to position "0", does air still get through your vents? If yes, then it's most probably this flap.
Part 90 is just a simple mechanism that operates small door and part 95 (possible culprit) is what sets part 90 in motion.
 

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That link shows many photos of the part - it has 2 green vacuum tubes attached. I have 2 great videos that demonstrate the noise and show where it is located. I couldn't find a way to upload videos to the forum, so if you want me to PM it to you, let me know.
I ended up replacing the valve, about $40 from the dealer - never heard another sound again! I don't know the part number, but I'm sure it's there somewhere!
 

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Oh that dreaded air flap!!! I remember it....
Check out this thread:
http://www.slkworld.com/slk-r170-class-diy/33742-air-recirculation-flap-inside-outside-cabin-air-problem.html
If it's part 95 then it's probably the rubber is deteriorated and causes air to leak.
When you're driving, and you shut off the air to circulate through the cabin by putting switch to position "0", does air still get through your vents? If yes, then it's most probably this flap.
Part 90 is just a simple mechanism that operates small door and part 95 (possible culprit) is what sets part 90 in motion.
I'll have to try the position "0" test. :)

That link shows many photos of the part - it has 2 green vacuum tubes attached. I have 2 great videos that demonstrate the noise and show where it is located. I couldn't find a way to upload videos to the forum, so if you want me to PM it to you, let me know.
I ended up replacing the valve, about $40 from the dealer - never heard another sound again! I don't know the part number, but I'm sure it's there somewhere!
I already replaced the pictured part (part no. 2028000178), and that didn't stop the whistling. I got it for $38 from mercedespartscenter.com PM sent for vids :tu:
 
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OK, it's not the flap. There is absolutely no air passing through the vents when it's closed. It's definitely got to be the vacuum element.
 

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Well, I'm a little puzzled (and a bit :mad:). I replaced the vacuum element (along with the pump)...and let me make this loud and clear...it DOES NOT go on as easily as it comes off. Oh sure, I managed to "twist" it back into position, but getting the lever reattached to the flap nub was a total pita. I eventually had to manufacture a small steel rod, bend an "L" at the end and notch it so I could get the lever in place over the nub that protrudes off the flap actuator. Then, I had to manually actuate the flap, while pressing the lever on the nub. I finally got it on, but not before contorting my hand into very painful positions. Anyway...that's not what has me miffed. While I believe the whistle is gone, the recirculate button doesn't close the flap now, OR leave it partially open when placing the fan control in the 0+ position. The flap closes when I push the EC button, but not when I push Recirculate. All day I spent trying to figure out what's wrong to no avail. Can anyone shed some light?
 

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Well, I'm a little puzzled (and a bit :mad:). I replaced the vacuum element (along with the pump)...and let me make this loud and clear...it DOES NOT go on as easily as it comes off. Oh sure, I managed to "twist" it back into position, but getting the lever reattached to the flap nub was a total pita. I eventually had to manufacture a small steel rod, bend an "L" at the end and notch it so I could get the lever in place over the nub that protrudes off the flap actuator. Then, I had to manually actuate the flap, while pressing the lever on the nub. I finally got it on, but not before contorting my hand into very painful positions. Anyway...that's not what has me miffed. While I believe the whistle is gone, the recirculate button doesn't close the flap now, OR leave it partially open when placing the fan control in the 0+ position. The flap closes when I push the EC button, but not when I push Recirculate. All day I spent trying to figure out what's wrong to no avail. Can anyone shed some light?
Yes, you need to have small hands to squeeze in that tiny place. Really stupid engineering idea to put it into an almost non-accessible area.
Hmmm... your setup is different. There's no EC button on my SLK... All I have is a vent switch (positions 0-5) and the inside/outside recirculation button. Can you post a picture of your front A/C module?
If the flap closes/opens when you push your EC button then it means it's connected properly. The flap will not work unless you start the engine, since the small grey tank doesn't get any vacuum from the engine. After you switch your engine, there's a leftover vacuum that lets you operate flap 2-3 times. And when you shut the engine off. The flap moves to position "." automatically - lets the fresh air in. Did you perform your tests with the engine running or not?
 

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Yes, you need to have small hands to squeeze in that tiny place. Really stupid engineering idea to put it into an almost non-accessible area.
Hmmm... your setup is different. There's no EC button on my SLK... All I have is a vent switch (positions 0-5) and the inside/outside recirculation button. Can you post a picture of your front A/C module?
If the flap closes/opens when you push your EC button then it means it's connected properly. The flap will not work unless you start the engine, since the small grey tank doesn't get any vacuum from the engine. After you switch your engine, there's a leftover vacuum that lets you operate flap 2-3 times. And when you shut the engine off. The flap moves to position "." automatically - lets the fresh air in. Did you perform your tests with the engine running or not?
All tests were made with the engine running. Does the vacuum canister (blue box) need to build up pressure? Maybe I'm just being impatient? Certainly wouldn't be the first time. :cool:

HVAC Control Unit.jpg
 
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