Loud secondary air pump

stirring up old thread......

16valex, how are things with your SAP nowadays?

I noticed my pump a few times (many months ago) to be quite noisy on -some- occasions, not always (more of a loud electrical buzz than a choo-choo), but in recent months I've heard nothing from it. Maybe it is dead...

My car starts fine, runs fine, no CELs, nothing ... but the silence is worrisome. Time to diagnose but wanted to get some clarification with the Seafoam.

If you are running Seafoam through the valve, does it go straight into the cats (ex. manifold) and out the exhaust? Or into the cylinders/valvetrain at all?

Uh-oh!

I just went out and unplugged the fat plastic hose between the SAP and the valve. It has no major residue.

I will test the relay with a 12v source, and may try to clean the checkvalve (possible?) and dissect the pump. I have a new bearing that I bought sometime ago, time to go read CN90's rebuild thread again ....

This morning it was about as cold as it usually can get here in wintertime, just below freezing. I unplugged the pump hose from the diverter valve and cranked the car.

The flow from the pump is very strong and steady but the pump itself I cannot hear over the engine.

The diverter valve inlet has vacuum, but it is not anywhere as strong as the air blowing out the pump hose.

I suppose this means time to replace the valve. Thing sure looks clean and shiny but it's probably 12.5 years old.

My other car wants a battery.... I'm about ready to join a monastery, too much material controlling my life.

16valex said:

Pete, sounds to me your SAP is working orderly. The diverter valve's vacuum just enough to open the valve to let the air into the engine. I would not do a thing to it..

Click to expand...

Hummm well .... I guess I assumed the diverter valve vacuum should be a bit stronger.

Anyone around here ever autopsied these valves? Is the diaphragm itself some sort of metal material? I was intrigued by your (16valex) use of Seafoam on it. I've used Seafoam on a lawn mower but never in a car, and I'm still not clear on where exactly the air from the diverter valve is being sent....

When the valve fails, is it something akin to the diaphragm burning through?

Is it correct that the air going into the valve is being directed into the cylinders to produce a lean combustion state? Or is the air being pumped directly into the exhaust manifold to help protect the cats from overly rich exhaust emissions? If the former, does the system on these inline-sixes also fail due to carbon buildup?

Look at these pics from the m5board....

http://www.m5board.com/vbulletin/e3...-system-carbon-build-up-removal-pictures.html

Fudman said:

Neither. The injected air is used to increase combustion of unburned hydrocarbons. This link gives the best explanation to date as to why there are excess hydrocarbons.
http://www.bimmerfest.com/forums/showpost.php?p=6519023&postcount=8

It followed my link, which was based on a TIS bulletin.
http://www.bimmerfest.com/forums/showpost.php?p=6519020&postcount=7

Click to expand...

fudman, do you think this SAS could be impacted by carbon deposits? I saw the m5 engine photos and wondered if the system on these i6 engines could have the same problems? Or if carbon deposits or clogging could kill the valve and pump.