Last month when I took my XC into the dealer for state inspection, they told me my air pump was bad. I didn't even know this thing had an air pump (being used to belt driven pumps from the 70's and 80's I thought they had rocks in their head when they told me it was bad).

I eventually found the pump and when I popped the cap off the back of the motor, a good pint or so of water came out. The motor was junk (bearings locked up, burned up windings, full of rust).

The dealer quoted me about $781 for the replacement parts (no labor).

I found one online for somewhere between $300-$350.

Then I check out ebay and noticed that Pierburg makes a bunch of these suckers for lots of european cars. I took a chance and bought a pump from a VW 1.8 turbo Golf which had very similar geometry. Well when I compared them side by side the motor part was the same, the fittings for the intake and exhaust hose were different and the wiring connector was different.

I popped off the VW motor end cap and popped on the volvo one, perfect fit. The terminals for the motor were 1/4" push on QC terminals in the VW, the volvo had 2 different sized ones. So I had to cut off the smaller volvo terminal and put on the 1/4" QC. Snapped the rear cover on and test ran it, worked with no problems.

The intake port on the volvo pump is just a hose barb, the VW has some kind of funky plastic o-ring sealed tube thingie. I took a drill and drilled out all the rivets on the front part of the pump and put the volvo front on the VW pump so I now had a hose barb pointed in the right direction. Replaced the rivets with 6/32 stainless screws and nyloc nuts. The discharge pipe has the funky connector on it still and that part of the pump is not easily disassembled, so I sawed off the VW fitting and just hose clamped the volvo hose to the end of the pump.

The last step was the look at the water mark/rust stains on the inside of the old pump and find the lowest point on the pump. I drilled a 1/8" hole in the discharge tube at the lowest point of the pump housing. I picked the discharge tube for 2 reasons: the source of the water that killed this pump is water vapor from the exhaust, not splashing from the road, so the discharge side is where the water will be coming in (running down after condensing in the rubber hose). Also, if there is water in the unit, when it starts and builds pressure, it will blow out any road debris and water that accumulated in the hole, rather than suck in any debris that went into the hole if it was on the intake side.

While looking on ebay I saw that BMW also used the same pump in the 3-series cars. I talked with a guy at work who has a 3-series with the right amount of milage and this same pump and he said he's not had any problems and not heard of any BMW owners with this problem. His pump is located high up on the engine so any water that condenses in the tubing can run downhill back into the exhaust or back into the air intake. Volvo's choice of putting the pump at the lowest point in the plumbing is clearly why these pumps die like clockwork at 70,000 plus miles (my car has 82k miles or so).

Looking online with google, certain gm cars (chevy blazers) also seem to be prone to early failure. I also checked with the auto parts guys and these electric pumps don't seem to have made it into the aftermarket. They sell rebuilt air pumps (belt driven) but all the listings in his book for GM cars stop at 1994-95. Which is when GM seems to have switched to electric pumps.

So while the VW pump isn't an exact drop in, it was lots cheaper than a volvo replacement ($40 + 12s/h) and a couple of hours worth of work. I think the BMW pump is a closer fit (same fittings) if you'll be shopping around for a McGuyver replacement, make sure whatever pump you bid on has good pictures and matches up with what you have.

I'll see how this things runs and see if its happy now and if the check engine light stays out.