bgross88

Was wondering if anyone has ANY idea on this. I've searched the forums a lot, read some possibilities, but nothing sounds like it's this exact problem.

Some history: 2003 Audi A6 3.0 with 110K on it. Bought used a year ago. Had the timing belt service done at 106K. Car was throwing codes for both cats; replaced all 4 O2 sensors and cat codes went away. 4 weeks later, started throwing a misfire on cylinder 2. Replaced all the plugs, and the coil pack on 2. Misfire came back about 2 weeks later. Currently, it still has the misfire on cylinder 2--I hope to resolve that this weekend.

Now to the current problem: About a week or two after changing out the 02 sensors, I noticed the car smoking at start up. White smoke/not blue--and it only does it after its sat for a while(usually 6 hours or more).
Oil is NOT foamy or milky, and it's not consuming any more oil than normal. Also, temp is rock steady. Needle sits at mid-point and doesn't move. Smells of antifreeze when cold started, after sitting a long time. Obviously, I think the white smoke is antifreeze in the cylinders, but how?

Part 2 of the problem: this week I've also discovered this--it appears the radiator is NOT losing pressure as the system cools down. I popped the cap after it sat overnight, and it "hissed" as if it was under pressure. Car smoked when I started it, right after popping the cap.

Later that night, I popped the cap again before bed time(again car was cold, but system was still pressurized). Recapped they system, and let it sit over night. The next morning, I started it...and NO smoke. I've now replicated that scenario 3 days in a row(pop cap in PM when cold-release pressure, let sit overnight, cold start in AM..no smoke)

I did replace the radiator cap(hoping for an easy fix) in the middle of all this, and it has not changed the "pressure" issue. I've read about PCV issues, suction pumps, vacuum lines, etc. I've had previous cars with head gasket issues, and this doesn't act like them. Oil clean, no temperature spikes, no overheating, etc....

I plan on doing leakdown and radiator pressure tests this weekend to rule out/in the head gasket.

My question is: if it's NOT the head gasket, has anyone experienced this or have any idea what it is?

I can't get past the "pressure" issues that remain when the car cools down, but I have no idea what would cause that.

Thanks in advance for your help, and please let me know if I left something out or if there are any questions.

jcman

Are you loosing antifreeze?

jcman

Also keep in mind that this engine does have a secondary air injection pump aka SAI, depending on your location and the seasonal climate conditions of high dew points it's possible that you are seeing moisture condensing from the exhaust during start up until the cats heat up, I have also noticed this on my 3.0 during certain times of season changes in the fall and spring.

Just Me

Since i could not connect the previous dots, i'm tending to think this may be it...

bgross88

Yes, I need to add antifreeze about once a week. Didn't mention that before--that's why I don't think it's just condensation in the exhaust system. Plus, it's a LOT of smoke. It looks like I'm trying to kill mosquitos.

N_Jay

Head gasket or cracked head.

What did the plugs look like?

Run it till hot, shut it down.

Wait till cold, and turn it over a few times without starting.

Pull plugs looking for the one that looks damp.

jcman

Yep there is no mistaking that antifreeze "sweet" smell if you noticed, you should do a compression test first because the thing that is strange here is the coolant system holding pressure cold so a coolant pressure test would not show a leak down based on your findings, yes?

thall6594

I have been dealing with the exact same issue on my 02 3.0L, but mine sometimes throws misfire codes for 2 and 5, and mine only smokes at start up once in a blue moon. I've had mine pressure tested and it held steady. I loose a little coolant, and also only have to top it off about once a week. I really don't think mine is a headgasket either, but I can't figure out what it could be. No external leaks, and drives perfectly fine.

My mechanic told me there is some pipe on the 3.0 that has an o-ring that can leak causing coolant to get into cylinders 2 and 5 (causing a misfire at start up only).

I can almost guarantee you that the misfire on cylinder 2 for you is because of the coolant getting into it.

N_Jay

Are the intakes warmed with coolant? Is there any cross connection between the cooling system and the intakes?

thall6594

I remember my mechanic mentioning the intake manifold gasket, actually. Is that the same thing?