I'm trouble-shooting a secondary air injection leak and looking for some guidance.
VAG-COM says that there's a leak in the system (I think between the pump and the kombi valves). Here's what I've done so far...
Test 1: Start engine and look for leaks on flex hose, piping, and fittings...all look good.
Test 2: I unhooked the control line (vacuum hose) from the kombi valves to the solenoid and manually actuated the valves with a hand vacuum pump. When actuated, the vacuum level held steady, indicating they are not leaking. When dropping the vacuum, I could hear the valves softly clink shut, so I think they're working...one of them could be internally sticking though...
Test 3: I connected the vacuum gauge to the 'T' upstream of N249 (kombi control solenoid) and found that the vacuum level is lower when the valve is attached, and higher at a higher vacuum level when it's detached and hose blocked..
Test 4: removed the vacuum solenoid, and cleaned out with electronic parts cleaner. Put two drops of light oil into the hose barbs and actuated it on the bench and tested for flow / stoppage.. Observe that some flow across the valve is possible even when it's not actuated, and the black plastic mushroom at one end appears to be the location of the leak... It appears that the barb connecting to the kombi valves is vented to atmosphere when unpowered, and the barb that would go to the main vacuum line will still continue to leak some small amount if the hand pump is worked.
Here's the question...
Is it acceptable for the vacuum control solenoids to leak air any air into the system? Do each of them normally leak a little? How much is acceptable?
Is this even my problem? Are the kombi valves 'open' or 'closed' when un-actuated?