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Discussion Starter #1
Hey guys,

Haven't posted here in quite a while. After a great year with my SLK32 AMG, it's starting to do the whole "when it rains, it pours" thing!

First, I'll start off with some advice. Attached below is a diagram of the SLK32's pulleys and belt route. In the past 3 months, I've had to replace both #4 and #6 pulleys, along with two belts. #4 exhibited way more signs than #6 . With #4 's failure, I thought I'd head some grinding noises a few times while driving, then one day I was pulling into a plaza (luckily) with the top down and heard a very loud grind, followed by silence and lack of power steering.

#6 went somewhat suddenly. There was one strange sign the day before in which it almost sounded like some engine noise came through the cabin then went away. The next day on the highway, I felt a little "slipping" feel in the wheel that felt like I'd run over something smooth like a tire shred, then I went around a curve and suddenly found my power steering gone, temp gauge immediately headed skyward. This small pulley failure sheared my belt as though it went through a cheese grater, up and through the center of the engine cover and blew the circular M-B cap/logo right through the middle, never to be seen again.

Both of these failures were a result of bearings failing inside the pulleys. I got pulley #6 off Amazon for $25, pulley #4 was around $50ish.

Which brings me to my next question. The same day that I replaced the second pulley and belt, I drove around with a nice, quiet car for about 30 minutes until my car started to develop an odd, high-pitched chirping sound. Soon after, it threw code P0410, Secondary Air Injection System. Temperature stays normal, oil level is fine.

I'm not sure if the sound and the code are related or not. The sound almost seems like a pulley sound, which was my greatest fear, but it's strangely inconsistent. When I first start the car cold, the belt/pulleys spin along quietly and remain doing so for 30-50 seconds after the idle settles down/warms up. Soon after, the chirping sound begins quietly at first, then builds up to a consistent, loud, high-pitched chirp. Raising RPMs has no effect on the sound or its consistency. At first I was convinced that the chirping sound was another pulley. I inspected all before installing the new belt and the #8 water pump pulley has a light but audible grinding sound when spun manually, but this is a hollow pulley with no bearing and I have no coolant loss that would indicate water pump failure. #9 tensioner pulley also was a little noisy when spun manually but it doesn't seem to have any wobble.

From what I've been able to find through the last 48 hours or so of searching and reading endless topics related to the secondary air system, this system acts like an EGR system and re-circulates air into the exhaust system to warm up the catalytic converters. The vacuum hoses that attach to the lines in this system have to be pulled in order to remove the #6 pulley, which was the one that I changed the SAME day this new problem developed. However, I've inspected the lines, tried to push the metal pipe in a little further, and no luck. The vacuum tubes are still flexible which does not indicate that they're drying out and prone to cracking. Also, I think that a vacuum leak would normally make a constant hiss, instead of a "chirp, chirp, chirp", unless maybe the valve opening/shutting could be causing the break in-between the noise.

I am not sure whether or not this system is inactive below a specified engine temperature or not, but if this sound and code are related, that's my only theory as to why it starts up quiet then the sound appears soon after. Again, I'm not even sure if these two symptoms are related at all.

Any help or suggestions would be greatly appreciated!
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Administrator 2009 SLK 55 AMG/Founding Member 2006
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97,206 Posts
I have no hair. flattop
 

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Discussion Starter #7
You guys are hilarious! So, after spending the last several hours sweating my a$$ off in the Florida heat, making trips to Advance Auto and Lowes, cutting my hands up, and dropping my iPhone-turned-flashlight down into the engine compartment several times, here's what I've got.

The two problems were unrelated. It looks like the PO had the water pump replaced at some point and whatever idiot replaced it only put one of the bolts on. I didn't see the single bolt last time the belt was off because it must've been turned out of my view. This time, it was one of the first things I noticed. I pulled off the belt, pulled the bolt out of the pulley, and took the bolt to Lowes, where I got 3 bolts as close as possible (they were 1/2" long whereas the original is about 1/3" but adding a nut fixed the length problem). Re-installed belt, ran it idle for about 10 minutes and the problem didn't return. Gave it a good run down the highway a couple exits and back and it's running smooth and quiet.

As for the P0410, I did a twice-over on all rubber tubing again. Pulled all the rubber, inspected the metal lines, and disconnected the electrical connection to make sure there wasn't any apparent corrosion. All looked okay but I found that there's a recall or service bulletin on the relay that controls it. Going to see if I can lose the CEL within the next few days or I'll call up M-B to see about the recall/TSB.

I'll let you guys know how it goes! No more chirping!
 

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I had the P0410 code. Mine would come up intermittently, once every few months at the beginning; always during normal driving and never when cold (which is when you'd expect it). After a lot of research, and a year later when it was coming up every week or so I decided to do something about it. The first thing I looked at was the K40 relay module and luckily that's what it turned out to be (dry joints), although that isn't the main supply relay. An easy fix for me. Hopefully yours is just as easy to find and fix. It seems a coincidence though that it appeared when you were fiddling with the vacuum hoses. There's lots of information on this code. Try this one: Air injection system DIY??? - Page 3 - Mercedes-Benz Forum or this one P0410 Secondary Air INjection System Malfunction - Page 5 - Mercedes-Benz Forum
By the way, the indy I took it to at the beginning told me it was the oxygen sensors (which is also what my carsoft says). It wasn't.

Good luck. And let us know what you find.
 

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I had the dreaded chirp and quickly fould out it was the grooved idler pulley. Ordered a new belt and pulley and had it done in 20 minutes tops. One of easiest fixes on any car ever! When you first look down it looks like a long job, but pop the top cover off, disconnected the fan wire connection, pull off 2 clips that hold the fan, lift out the fan, and your there. I think I spent as much time doing that as I did changing the pulley and belt.
 
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