GL Class (X164) 2007-2012: GL320CDI, GL420CDI, GL450, GL550

water/condensation in secondary air pump?

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Old Feb 19, 2020 | 08:20 PM
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2014 GL450
water/condensation in secondary air pump?

Hi,

I have a 2012 GL450. In April 2019, I had the secondary air pump replaced by a garage because it was broken. It has been 10 months and it failed again. The dedicated 40amp fuse for it is blown. I checked the resistance of the air pump, it is like 0.1 ohm. When I disconnect it from the electric plug and directly applied 12V to it, the air pump won't run. So it is bad again.

I removed the air intake hose from the pump end, and I noticed there is a little water or condensation in both the rubber pipe and the opening of the air pump that the pipe connects to.

Is this normal? Based on my research, it looks like the one way check valve is in poor shape so it allows exhaust gas to entering into the secondary air pump and causing moisture. Based on this article, https://autoservicecosts.com/obd2-codes/p0410/, which says that if the temperature is too low and the water/moisture in the air pump froze, it will cause the pump not able to run when it should, so it will overload the circuit and pop the fuse. I guess this explains my situation. Last time when I had it fixed at the garage, they didn't replace the check valve, hence the pump will gradually get moister in it. And we just came back from a ski trip and it was cold, so the water in the pump must have been frozen, causing the problem.

Actually I suspect even last time the air pump went bad was due to the same reason, it went bad near the end of skiing season.

Is replacing the secondary air pump and the check valve a difficult job? I just replaced both the front struts of my GL450 myself, and fount it wasn't hard. I am wondering how hard it is to replace the air pump and the check values (there are two). Looks like it is not a hard DIY project? Anyone has experience?

thank you very much!
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