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Audi A4 K04 Turbo upgrade / replacement

November 23, 2010

Last January, I wrote about the P0422 OBD II code that led to turbocharger and catalytic converter replacement on the wife’s ’99 Audi A4 Quattro.    The upgraded KO4 and performance converter were a huge improvement.

Following that work,  the car developed a bad miss and I wound up replacing a cracked plastic elbow below the intake manifold, and the ignition amplifier, and finally resolved the Po304 by replacing a faulty #4 coil pack.   The car has subsequently been dependable, and aside from replacing the front outer tie-rod ends and doing an alignment this fall,  required nothing aside from the usual oil changes.

However, in September, my wife noted the car started smoking at a stop light and that it began to smell bad when she parked it.   Since it seemed to run ok while driving down the road, I hypothesized that one of the fuel injectors had some trash in it, and was leaking causing the car to run rich and smoke at idle.   In hindsight, that was a bad guess since there were no check engine codes , and they would be expected.   I tried two rounds of fuel injector cleaner, pulled the spark plugs (which looked clean) and found and fixed one vacuum leak, but still no joy.

The smoking got worse – it began as a white smoke at idle that looked like normal water vapor, yet left no condensation on your hand if you held it near the tailpipe.   The smoking would occur after the engine warmed up in about 5 mins of idling from a cold start.   After warm up, the white, and at times blue smoke would flow consistently at idle, and would increase in volume when the engine was revved, but if held at 2000-30000 rpm to simulate driving, it would clear up substantially.   I began to suspect oil and or coolant was being burned, but was still at a loss to explain why the spark plugs were still very clean.  I would expect them to be oil fouled – greasy & sooting in appearance.  They were not – still a light tan.

Aside from the contradictory evidence of the clean plugs, one would suspect a leaking head gasket.  I performed a compression test – 180 lbs on the first 3 cylinders and about 175 on #4.    Normal wear, or problem found?  If it were a really small leak, and one that only showed up after the coolant system were under pressure once things were hot, this might explain the symptoms I was seeing.  So,   I added a can of head gasket sealant (the kind made of small copper particles) to the coolant and idled the car, waiting for the smoking to abate.  It did not.    A mechanic friend had a CO2 tester, and we tested the engine coolant and found no CO2, so that indicated the problem was not with the head gasket.

Where else are oil and coolant present, but not run through the engine (because the plugs aren’t fouled), yet somehow still being burned?  The turbocharger.  Coolant and oil are fed to this model of turbo, and if the bearings & seals were worn out, they could be passed on either the intake or exhaust side.   I pulled an intake hose at the throttle body and found the expected minor oil film – normal.   If the leak were on the exhaust side, it would also make sense.  The oil and / or coolant were leaking into the exhaust and winding up in the catalytic converter mounted to the exhaust side of the turbo.  It would take five mins or so for the converter and the exhaust to come up to temperature where it would begin to burn off the oil, which was why the smoking was delayed.  Further, when the car was at speed, the exhaust flow was much higher proportionate to the rate of oil leakage / burning so it was diluted, which was why the smoke appeared to abate.

But, the turbo was less that a year old, so it was odd the bearings should wear so quickly.   I found a lot of discussion online about sludging problems with these engines, although I changed the oil every 3000 miles and have done so since we bought it with about 45K on the clock.   Still, if the oil feeds, and return lines were restricted with coked oil, perhaps the oil pressure was pushing oil past the seals?  I tried a quart of engine de-sludge, and idled for 5 mins and drained the oil.    After changing the filter and adding fresh oil,  I was rewarded with even more smoke.

I pulled the inlet hose off at the turbo and felt for play.  As expected, there was perhaps double the amount of lateral play in the shaft, and a significant amount of movement front to rear – thrust.   Ok – time to replace the turbo.  Again.

I found another unit on ebay, and $100 cheaper than the last one.  The seller said this one was new and warned against buying units with blue metal tags from other sellers because they were “cheaper units made in China”.   Hmm.   Isn’t almost everything sourced from China these days.  I bought what he was selling and was amused after unpacking the box, to find that the instructions were a poor translation to English.  I had to wonder if he ever checked the instructions on what he was selling – if so, how could he advertise as he did with a straight face.   No matter, I have nothing against Chinese manufacture.   While I was on ebay, I found a lot of people selling rebuild kits for these turbos  for around $40.   Hmmm.   I bought a kit and will rebuild the turbo I am taking off and will have it on the shelf in case I need to do this again – hopefully not.

If you find that you are having to do this job, here are a few suggestions I have that may save you some time.

1) Remove the headpipe hanger bolt at the transmission and loosen the two bolts at the slip joint in the exhaust pipe after the braided flexible section.   Remove the four  bolts on the two hangers on either side of the muffler at the rear of the car, but leave the hanger at the rear axle and the other one just forward of the axle.

You can now slip the exhaust system to the rear and separate from the headpipe.

2) You can unplug the two oxygen sensors at the firewall – remove the 3 screws and set the coolant tank off to the side to reach them.

3) Remove the 3 nuts that hold the converter to the turbo and slide the converter, headpipe and O2 sensors down and to the rear of the car.  This saves separating the converter from the headpipe and fighting to remove the O2 sensors unless you need to replace them.

4) Drain engine oil and coolant.  There is a plug for the coolant on the water pump housing on the bottom toward the front of the engine on driver’s side.

5) Loosen the two allen head bolts holding the tensioner roller for the AC belt.  Tap the roller upward with a hammer and slip the belt off.  Unhook the one wire for the AC clutch.  Remove the 4 bolts holding the AC compressor and lower it carefully to protect the lines.  I hung it  from the sway bar, using some heavy wire. (It can be seen hanging below the passenger side of the car.)

6) Loosen all the band clamps and remove the turbo inlet and outlet hoses together, dropping them out the bottom of the car.  These are interconnected at a number of points and will stay together.

7) Remove the turbo support clamp and the oil drain line to the oil pan.

8) Remove the band clamp and the coolant return line from the turbo to the engine block.

Here the AC compressor is removed from the bracket, and the oil return port can be seen just above the drain plug on the oil pan, indicated by the lower red circle.  The other red circle denotes the coolant return line from the turbo to the block.

9) Remove the 3 screws and 2 bolts that hold the black breather pipe to the valve cover.

10) Remove the 2 bolts that hold the oil line and heat shield to the side of the heat.  Pull the heat shield toward the front of the vehicle and remove it.

11) Loosen and disconnect the coolant and oil feed lines on the top side of the turbo.

12) Remove the three, 17mm bolts that hold the turbo to the exhaust manifold and be ready to catch the turbo as you do so.  The turbo can now easily be passed forward and rotated down to exit the bottom of the vehicle.  (Last year, I left all the intake ducting in place and wrestled the turbo out the top.  It can be done, but is much more difficult.)  Soak these bolts with penetrating oil to loosen them – they will be difficult to remove and you may break one of them off.

13) On the bench, transfer all the fittings to the new turbo, taking time to clean each one.  Clean all the ducts and parts that you have removed before re-installing them with the new part.

It is a good idea to remove the oil feed line and clean it out – soaking in carb cleaner, or running solvent from a part washer through it will help remove the accumulated oil crud.  Clean the drain line as well.  Many guides suggest replacing the oil feed line instead of just cleaning it.

Installation is the reverse of what I’ve outlined here.   Of course you want to use fresh coolant, engine oil and a new filter.  It is probably a good bit of extra insurance to do a short interval oil change – perhaps 500 miles, or at least to replace the filter and top off the oil    Having the system open, there is always the risk of introducing debris that can find it’s way into engine or turbo bearings.

6 Comments leave one →
  1. Tim permalink
    November 23, 2010 3:30 am

    Good instructions Mark! It sure must be nice to have a lift in your back yard 😉

    What is this headpipe you speak of? The pipe between the tubo and the cat is generally called the downpipe. The pipe between the exhaust manifold and turbo is generally called the up-pipe. 🙂

    And man, I thought working on my engine was a pain!

  2. November 25, 2010 12:14 pm

    Nice job Mark.

  3. December 12, 2010 3:06 am

    good job for you !

  4. October 17, 2011 5:33 pm

    nice looking garage you got there Mark.


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