DoubleA4

At start-up I am getting a whining noise from the engine bay. Sounds like my dentists drill. I just had the 75K service done and although there was some minor whining before it is now a full minute or two of this before it dissipates. My assumption is that the noise is coming from one or both of my turbos... anyone out there have any experience with this and what it could be and how to make it go away?

lawdogg

Stock turbos are journal bearing, right? So when they go bad, they will leak oil and whine under boost. If you don't have a smoke screen behind the car, you're probably fine. Also, if the whining goes away, you're probably fine - a bad turbo wouldn't 'get better' after a few moments.

In any event with the whining on start-up, mine does it too, but I think it is the secondary air pump / valve.

DoubleA4

Thanks for the reply. I was getting nervous. I will keep an eye out for smoke. I did notice that the oil lines to the turbos had some oil around them but nothing terrible.

Pchelka01

Like it was mentioned, it's your secondary air pump, not your turbos

Prospeeder

that would be the secondary air pump. if its getting loud its going to need replaced.

Mr. Timewise

Replace (or re-build - do a search for the DIY here or elsewhere) the secondary air pump. If you don't, the "Kombi Valves" will also need replacing and they're $ and a B!TCH to replace.

See:

https://www.audiworld.com/forums/sho...47&postcount=1


FYI...the secondary air pump only runs for the first minute or so when the engine is cold. The whining you hear is the bearings inside the pump (top center back side of engine) starting to freeze up. When they do, and the rotor of the pump cannot turn, the 40 amp fuse protectingthe circuit will blow. A new fuse is about $7...it's under the cover where the ECU is located on the upper left side of the engine bay below the wide plastic cover in front of the windshield.

Kristopher

Agree with the SAI diagnosis.

I remember reading something about somebody drilling a small hole in the plastic motor housing and spraying some wd40 or silicon lube inside to temporarily stop the noise. I've read it's the 'lower' bearing making the racket and the lube should make it's way down there.

Checking the combi-valves for leakage seems easy enough. Replacing the SAI sounds like a PITA so can a guy buy a bit of time until he gets all the parts and downtime figured out?

Mr. Timewise

Don't bother, the bearings are already worn out

The SAI pump takes 15 - 20 minutes to change. Changing the combi-valves can take several hours because of the difficulty in reaching the bolts. You've got to remove the pump to gain easy access to the combi-valves. I guess you can put some flexible hose on the combi-valve "input" (SAI pump side)and try blowing into that hose. With the combi-valve closed you should not be able to blow air from the SAI pump side into the exhaust manifold.

lawdogg

What does the secondary air pump actually do? Is it necessary to have or can it be deleted?

Mr. Timewise

The SAI pump pushes fresh air into the exhaust gases for the first minute or so during start up. During this time (i.e., while the SAI pump is operating), the combi-valves are opened (via a solenoid which applies vacuum to the combi-valves' control ports). The open combi-valves allow the SAI pump air to flow into the exhaust down pipes. This extra air allows the cats to burn off unused fuel so the emissions are lower as the engine warms up. After the first minute or so, the SAI pump turns off and the combi-valves close. At that point the entire SAI system is just dead weight.

The problem with keeping a "dead" SAI pump in place is that during the time the engine is warming up, the combi-valves are opened and exhaust gases can flow backwards through the open valve.

Yes, the entire SAI system can be deleted. Search for a DIY.