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Project Car Diaries: Deep in the Valley of Deferred Maintenance With My $925 Audi S4

The S4 needs new brakes, new CV axles, and a new auxiliary water pump. Let's get on with it, then.
2002 Audi S4
Peter Nelson

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The last time I checked in and delivered the news that my $925 2002 Audi S4 shockingly needed a little work, its biggest issues were quite apparent. Since then, its new auxiliary water pump showed up in the mail, as did two new CV axles, a mess of filters, fresh oil, and a lot of other bits and pieces the car desperately needed to undo years of deferred maintenance and bring it back to flawless running condition. Well, almost flawless.

I’m not going to lie, I had a little trepidation about diving into this project. Was I too confident? Is this old German sedan about to embarrass me? Was this going to turn into a Carrie-like scenario where the Internet plus all my family and friends collectively laugh in my face, and some crazed voice starts screaming they’re all gonna laugh at you?

Thankfully, I’m not covered in pig’s blood yet. There has been some colorful language, however.

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The Elephant in the Room (Or Rather, Valley)

Firing up the ol’ Bavarian steed for the very first time revealed a massive coolant leak. Some quick examination showed its auxiliary water pump was broken open and emptying the radiator’s contents.

Opinions vary on whether it’s a good idea to eliminate this component, relocate it, or simply replace it. I erred on the latter—when in doubt, stick to the factory setup. Though this job has a huge asterisk next to it: Getting to the pump is a pain in the ass.

You have to disconnect a bunch of vacuum lines, try not to break anything in the process, remove the intake manifold’s 5mm hex bolts, not drop them (I loosened them and then pulled them out with needle nose pliers), and then pull the manifold up high enough so that you can reach in and get to work.

Once I got underway, this job proved to be quite time-consuming as every single connector and vacuum hose fought me. I was prepared for this with a few feet of new vacuum line. But still, it took a while. My creative use of cursing during the process would’ve made the late Sam Kinison blush.

As I got deeper in, I discovered that the PCV vent/breather hose—better known as the spider hose among enthusiasts—was shoddily repaired at some point. It’s not an expensive part, nor is it hard to replace—and neither is the vacuum check valve on the driver-rear side of the manifold that I broke. Thankfully, I happen to live less than 10 miles from Pelican Parts so I had new replacements within a day.

2002 Audi S4
Check out that crusty, broken original auxiliary water pump. I taped up the intake ports so that dirt and debris wouldn’t fall down there. Peter Nelson

Once I finally pulled the manifold up I had ample room to get at the auxiliary water pump. I replaced one of the hoses that led to the pump and the pump itself, and put new clamps on both ends. I then replaced a nearby vacuum hose that was hanging on by a thread, threw in two new intake manifold gaskets, and buttoned it all up. Getting the gasket perfectly aligned took some effort, but I eventually got it, and torquing down the bolts was cake.

Finally, to complete the job and stave off future issues, I not only replaced the spider hose and vacuum check valve but also went about replacing almost all of the nearby tubing and buttoned it up with fresh screw clamps. All in, I devoted a whole three nights after work to this; breaking it up made it far less of a pain for sure.

Once I was all done I added back a 70/30 mix of distilled water and G12 coolant. The car took some effort to fire up, but once it did it ran quite smoothly; no warning lights, no vacuum leaks, and most importantly no more coolant loss. The car reached operating temperature and stayed there, and all other vital signs looked good.

2002 Audi S4

Fresh Oil and Filters

Pulling out the dipstick, I wasn’t too concerned—the oil level was fine and the color wasn’t scary. CarFax recorded an oil change in June 2022, but who knows what horrors can visit a sub-$1,000 car over eight months. Time for another.

Liqui Moly USA contributed seven quarts of fresh Molygen 5W-40 to the cause—major thanks for their assistance in making sure this complex, twin-turbo V6 is properly lubricated with full synthetic oil that exceeds Audi’s own standards. Draining the old oil revealed no warning signs, thankfully; no evidence of any coolant mixing in somewhere. Unscrewing the filter took some effort with a three-jaw removal tool, but once it broke loose I spun on a fresh OE Mann filter and called it good.

2002 Audi S4 oil filter

While underneath, I took my time looking up at the turbos and nearby hoses and surfaces. The turbos didn’t appear to have any external leaks, and the sides of the block looked generally clean. The trickle of oil I did find seemed to come from two clamped connections around the oil filter housing—I tightened them down and gave the area a good cleaning with brake cleaner. We shall see if that was the oil leak I mentioned in my previous diary entry, though I doubt I’ll be so lucky.

Up next, I changed out the disgusting old air filter for a fresh Mann unit, as well as the nearby cabin filter, and made sure to clean off all nearby surfaces along the way. The car once again fired up and idled smoothly without issue, so it was onto the next line items.

2002 Audi S4 brake fluid

New Car, New Braking System Annoyances

The S4 had very obvious signs of needing all-new brakes plus some fresh fluid. Its pedal travel was quite long and the pads and rotors looked pretty thin, so I ordered four new quality Zimmermann rotors—plus Brembo ceramic pads—for just $360 shipped to my door. I’d almost forgotten how cheap brake parts can be when all you want is slightly better-than-stock stopping power and aren’t concerned about track performance.

The overall job was easy at first, and a previous owner even installed stainless steel braided lines up front. However, the rear brakes were a different story.

2002 audi s4 new rear calipers

While attempting to push the single piston on the driver-rear caliper back, the rubber boot promptly gave up the ghost and started leaking a lot of fluid out at the seam, so the factory unit had to go. I sourced a set of fresh rear remanufactured units from AutoZone and threw them in without issue. Replacing the passenger side was extra work, but I comforted myself by imagining the original springing a leak at the worst possible time in the future. Crisis averted.

The S4’s four hubs don’t have provisions for rotor retaining screws, so lining stuff up and keeping the rotors pressed against the hub while bolting up the calipers was a massive pain in the ass. I bought a set of wheel hangers to make this easier for the next time I pull the wheels off.

2002 Audi S4 brake reservoir
I’m actually glad that the original reservoir broke, it definitely needed changing. Peter Nelson

Liqui Moly came through once again and sent me a few bottles of their DOT 4 brake fluid to flush out and replace the old putrid stuff. I broke out the power bleeder to do a full bleed, but the pressure it delivered blew out a seam in the worse-for-wear fluid reservoir. I picked up a new one from O’Reilly’s the next day and tossed it in without issue. Thank God that bit went smoothly.

Starting from the furthest corner, I slowly but surely pulled out all the old yucky, green fluid. It truly was disgusting, too—it looked like cloudy, algae-filled pond water and possessed the same slimy consistency.

Baby’s First Axle Job

2002 Audi S4 axle job
The order of operations was a little off, but I swapped the axles without enduring too much pain. Peter Nelson

While working on the front brakes I installed two new front CV axles since the old passenger side’s outside boot had clearly torn a long, long time ago. Might as well take care of both while I was in there. Tackling this solo was a little tricky at first, but once I utilized my floor jack to hold the tire while loosening and re-tightening the inner bolts, it just involved adding a few extra steps to my normal brake change process.

Looking back, I should’ve removed more components to pull the axles out. Some folks prefer just turning the wheel full lock with the brakes removed and suspension loaded with a jack and pulling them out from behind the hub. Others say unbolting a few suspension arms allows you to pull the axle straight out for a seamless removal. I did the former, but should’ve done the latter—the former takes too much finagling when you’re working on the ground with jack stands.

Once everything was buttoned up, the B5’s braking force was nicely restored and its pedal travel went back to what I’d call firm and confident.

2002 Audi S4
It’s driving well, but there’s still a good amount of stuff to tackle. Peter Nelson

Off to a Great Start

Knock on wood, my 2002 Audi S4 is turning out decently so far. It’s put up a fight due to its age, but otherwise, no weird issues have arisen yet. But then, there are a lot of interesting signs that previous owners actually cared about this car. A lot of the intake piping sports refreshed hardware, the diverter valves are upgraded OEM 710N units (a popular upgrade), and the valve cover gaskets look to be fresh as well.

I’ll continue taking my time getting to know it, making sure to get the oil up to temperature before putting its tiny K03 turbos to work, and continue to fix and mildly modify some things.

In fact, the next rounds are coming soon: replacing the timing belt, water pump, and thermostat, doing an automatic transmission fluid, filter, and gasket service, and refreshing the suspension. The valley of maintenance is long, but we’re moving through it just fine. So far.

2002 B5 Audi S4 engine


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