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secondary air pump

2K views 7 replies 3 participants last post by  Noodles 
#1 ·
here is what happened. Fan ran for several min after shutting off car, loud and noisy. check engine lite was on. I unplugged it for a while and plugged it back in and it didn't run. After getting advice on this site I put 12 volts on the pump and it didn't run, had to hit it with a rubber hammer a couple of times to get it to start turning. Bad fan motor so I replaced it. when I started the car cold the new fan ran for about 30 sec and shut off so I figured the relay was good. I didn't replace the relay and my new fan went bad after about 3 weeks. could the relay be intermittently sticking and burning out the fan? or maybe I just got a bad fan. I now have a new relay and lucky for me I can exchange the fan for a new one. but before I put the new fan and relay in.

My question is, the output ports of the fan go to some kind of valve looking round metal things. If those don't open or are plugged will that burn the fan out? should I be able to blow into the fan inlet side and blow air in. I tried that and just get pressure, no air movement. Do they open only when the fan is being called to run? If they are plugged or don't open wouldn't the fan air just get pushed back thru the inlet hose and not burn the fan out? I am hoping I just have a bad fan and it isn't some other deeper issue that will cause me to go thru fans or require a several thousand dollar fix. I got the fan on ebay from speed line concept for 150.00 and it says bosch oem. The dealer wants 800.00 for that thing, I assume its the same part even though it doesn't have the mercedes logo on the sticker.

And finally, if I do have an underlying problem that is causing fans to burn out and it costs grands to fix, is there any harm in just not fixing it. sound like its just an emissions thing.
 
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#8 ·
I should mention that failure of these seems higher on the M272 V6 and M273 V8 than on the older M112 and M113 designs. The shop I hang out at has replaced on average 2-3 per month on the newer engines and only about 1-2 per year on the older engines.

I do agree that anytime a component like this is replaced a new relay should be part of the process.
 
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