Hello,
I’m chasing P0410 code (Secondary Air Injection) in W140 – 1997 S 500 (2nd gen). So far I’ve changed the plastic tubing to the switchover valve. I’ve checked the switch over valve itself. Now I got the smog pump (secondary air pump) on the bench (000 140 35 85- updated electric pump) The pump spins up and blows plenty of air. I’ve attached it to a pressure gauge it was 2 psi steady. I’ve noticed a small leak where the body of the pump separates. I’ve tightened the 6 screws on the perimeter and the pressure increased slightly to 3 psi. I can still hear a little air hissing in that area, but don’t want to over tighten / crack the plastic.
These pumps are quite pricey, so your help is very appreciated.


How much pressure should the pump produce?
Can anybody recommend a good sealant (silicone, glue) to stop the hissing?
Is there a company that rebuild these?

And one more question: My neighbor has a spare pump from a car he sold (I believe it was E420- but I’m not 100% sure)
What is the difference between 000 140 3585 (my pump) and 000 140 3785 (neighbor’s)? They appear to be identical. Is there a difference in the pressure / volume?
Thank to everybody!

The pump should produce a lot more than 3 psi.

The pump your neighbor has is designed for the M113 engine & should work IF it fits.

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pump failure not very common. check for voltage/ground at the pump connection during cold start. i cant remember if this car has "kombi valves" that are vacuum operated to allow the air to flow in to the exhaust. if so the vac diaphragms can fail or the passages can get clogged. i think the most likely is air pump relay.

Thank you guys,
For r.e.wing fc3s,
I should have been more specific. My secondary air pump (000 140 35 85) works, but I’m still getting P0410 code.
I’ve changed the vacuum lines to the switchover valve (and tested for leaks),
I’ve removed and checked the switchover valve itself. It works fine (no hole in the diaphragm).
I’ve changed the connecting rubber hose between the smog pump and switchover valve.
I've changed the O2 sensors,
but still getting the same code.

Now I have the pump on the bench and is hooked up to a gauge (it’s a combination vacuum / pressure gauge, but worked great for me in the past). I’m getting only 3 psi when connected directly from the pump to the gauge.
I’ve sweet talked my neighbor and borrowed his smog pump (000 140 37 85) . His came from 98 E320 (V6). At a first glance the pump look identical, but the position of the ‘exhaust pipe’ is different (different angle).
When I hooked up neighbors pump to the gauge, it was producing only 2psi. I know he got this smog pump just as a spare. He used it for about two months in his car to make sure it works OK and than took it out and it was sitting in his garage. It still looks brand new.
My next test will be to try to measure actual airflow from these pumps. I’ll have to think of same reliable / readable set-up first.

My question is: How do you know if the pump is good or bad? It runs, it produces what appears to be plenty of air...
Did anybody tested any smog pumps? How much pressure should they produce?
Thank you everybody!
Any input is appreciated.
Mark.

manually operate the switchover valve and find a way to blow air into the valve to check for carbon buildup/obstruction in the passages that feed the air into the exhaust. its possible that only one bank is clogged and you might just be blowing through the open side. i might also suggest teeing in a vacuum gauge as close to the valve as possible to confirm the presence of vacuum opening the valve.

Since I have no Cats,can I delete pump,or use it to pump up intake manifold?

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Have you made any progress with this problem yet.I am chasing the same issue.I am thinking about dropping the exaust to see if I am getting air out of both banks.If these cars had true dual exaust this would be easy to troubleshoot by blowing air and smoke into the secondary air injection pipe going into the cyl block on the rt side. good luck john.....................

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