Secondary Air Pump Running Frequently
Thread Starter
Junior Member
Joined: Jan 2012
Posts: 25
Likes: 0
From: New York
2016 GLC300 4MATIC
Secondary Air Pump Running Frequently
I have a 98 ML320 which has had a CEL and error P0410 on and off for quite some time now.
It's been into Mercedes 3 separate times, and they've replaced the relay, pump, and valve, and cleaned the heads the best they could without actually removing them from the car. The CEL is still coming on, and they're saying the next course of action would be to remove and clean the heads.
What I've noticed though is the air pump seems to come on frequently for short periods of time, well after the car has been running. Every time the CEL has appeared, I've been stopped at a red light. I heard the pump come on for a few seconds this evening while at a red light with the window open, and the car had been at operating temperature for some time. When I got home I left the car running and stood outside for a few minutes, and the pump went on and off brielfy several times.
It's my understanding the pump should only come on when the car is cold, shortly after it's first started. Anyone know what could cause it to come on so frequently? I'm starting to wonder if what's causing the CEL is the fact that it's running when it shouldn't be.
It's been into Mercedes 3 separate times, and they've replaced the relay, pump, and valve, and cleaned the heads the best they could without actually removing them from the car. The CEL is still coming on, and they're saying the next course of action would be to remove and clean the heads.
What I've noticed though is the air pump seems to come on frequently for short periods of time, well after the car has been running. Every time the CEL has appeared, I've been stopped at a red light. I heard the pump come on for a few seconds this evening while at a red light with the window open, and the car had been at operating temperature for some time. When I got home I left the car running and stood outside for a few minutes, and the pump went on and off brielfy several times.
It's my understanding the pump should only come on when the car is cold, shortly after it's first started. Anyone know what could cause it to come on so frequently? I'm starting to wonder if what's causing the CEL is the fact that it's running when it shouldn't be.
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
Likes: 765
From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
Under normal operating conditions the AIR Pump runs whenever the coolant temp. is less than 40C and other things and will run an additional systems check during that trip.
In both your cases the AIR Pump runs at different times because the prerequisites have not been satisfied. The reason you keep hearing the pump run is the system knows that a problem exists and will keep trying to do that.
The most common problem with the AIR system is that one or both of the heads gets clogged with carbon. To check if this is so:
1. Remove hose #53.
2. Remove vacuum hose #119 from valve #5.
3. Remove vacuum hose #107 from valve #41.
4. Remove the one bolt holding down valves #35 and 41.
5. Remove the valves and the gaskets.
6. Start the engine and feel that there is exhaust coming out of the holes where the valves were.
Whichever hole does not produce exhaust, that head is clogged and this is the cause of the problem.
In both your cases the AIR Pump runs at different times because the prerequisites have not been satisfied. The reason you keep hearing the pump run is the system knows that a problem exists and will keep trying to do that.
The most common problem with the AIR system is that one or both of the heads gets clogged with carbon. To check if this is so:
1. Remove hose #53.
2. Remove vacuum hose #119 from valve #5.
3. Remove vacuum hose #107 from valve #41.
4. Remove the one bolt holding down valves #35 and 41.
5. Remove the valves and the gaskets.
6. Start the engine and feel that there is exhaust coming out of the holes where the valves were.
Whichever hole does not produce exhaust, that head is clogged and this is the cause of the problem.
