ep3_lol

So the last time I started my 2002 2.7, it blew coolant smoke out the exhaust for about 2 minutes before it gradually trailed off. It was definitely from coolant, not oil. It had the look and consistency of steam without a trace of the burnt oil smell. I've since pulled the spark plugs and checked the oil and coolant reservoir and see no sign of head gasket failure. I have seen signs of air/oil separator failure recently. While at the Porsche dealer picking up a new spark plug tube and O-rings (one tube had oil in it), I asked the guy at the counter if he knew what could cause the smoke aside from a head gasket. He informed me that some of the cars have a coolant line to the AOS and that when it fails it can cause coolant to go through the intake. This would be consistent with what I've seen, but I can't find anything else saying that a failed AOS will cause the coolant smoke I saw, or that coolant goes through the AOS. I'm away from my car this weekend so I haven't been able to look for myself.

The guy at the dealer was very confident that this is my problem. My question for you guys is, does this sound right? I have never heard of coolant going through the AOS and cannot find anything saying it does now, but again, if that is indeed the case then a failed AOS would explain every symptom I've seen from the car recently.

Thanks,
Robert

gfl

I've never seen it, and mine - a later 2004 car - did not have such a line to the AOS.

Maybe, but i think not.

The AoS is basically a still - vapor rises, oil and water fall back. Maybe a little water can get in, but this suggests you have a bunch of water in the crankcase - and you might ask why?

Has the AoS shown any other signs of failure - big puff of smoke momentarily under hard cornering/accel (typically a track thing), or blue / white oil smoke at start-up?

You are sure this was steam?

It dissipated nearly immediately?

Grant

extanker

iirc some are water cooled,look for a line going from the AOS to the expansion tank. i think it was/is a smaller od line than say a heater hose

Macster

My 02 2.7l engine is on its 3rd AOS. I cut one apart and barring the slim possibility Porsche changed the AOS design in this way after my car was built there's no coolant line/connection.

(The 996 AOS has a coolant line.)

If the vapor was really coolant and it was coming from the exhaust you've got problems.

Now the coolant could be coming from a failed coolant tank. When these finally let go they can dump coolant like nobody's business.

You say you checked the coolant but did you really check the level? You can't always depend upon seeing the level through the tank wall. After a while the wall gets a stain and can fool you about the level. Remove the cap and the screen and carefully check the level.

Take the oil filter housing off and pour the oil into a clean drain pan and let it sit for 12 hours. If there is any water (coolant) in the oil you'll see. If you see it you've got problems.

When there's a reasonable suspicion of a head gasket failure this is the time for a compression test and leak down test.

Remove all the plugs. Be sure you note which plug comes from which cylinder and not how they all look. Generally a head gasket is a bit bad before it turns into a gusher so the plug in the cylinder with the gasket leak is going to look different.

Also, I'd be inclined to drain the coolant from the engine too. This keeps the risk of contaminating the oil down and possibly damaging the engine.

Do the compression test.

The results will tell you if there is a head gasket leak (or some other problem with the cylinders and their integrity).

ep3_lol

gfl: Yes, quite positive. There was no trace of blue, no trace of the oil smell, and the smoke dissipated quite quickly. The car threw codes P1128 and P1130 (running rich) and had an inconsistent idle before this incident, both of which I understand can happen with a failing AOS. It also blew oil smoke occasionally at start up, which has gotten a bit more frequent recently but not close to every time. I haven't noticed any under hard acceleration or cornering.

Macster: How will the plug from the problem cylinder look different? The heads all look in line with each other. There is some carbon build-up on the base of the porcelain on the plug that was in the leaky tube, but the other 5 are clean. Otherwise they look exactly like I'd expect 40k mile spark plugs to look. Also, the coolant level is below the minimum level but still present in the tank in the trunk. I'm honestly not sure how much of a change that is from previous, or if it's a change at all. The car has never run too warm and the previous owner had it serviced by Charlotte's Porsche dealer rather frequently so I never checked it.

I'll check for a line tomorrow, thanks for the replies.

Macster

If you can't spot any differences between the plugs there is no coolant leak into a cylinder is my opinion.

Based on what you posted I think the engine has a bad AOS.

It probably (probably) has a coolant leak too. AFAIK the AOS does not have a coolant component so the leak is coming from somewhere else.

The only real leak I've had with my 02 2.7L is the coolant tank.

Oh, and a cap. The effects of a leaking cap can be substantial. Oover time -- approx. one month -- the coolant level dropped from at the max line to warning light time as the cap let vapor escape.

But it was the coolant tank even before it gushed coolant out when hot and under pressure that was I believe the source of an antifreeze smell. The cap failed first. The coolant tank second. I do not recall how much time between them but it was thousands of miles and months and months of time.

ep3_lol

Well this took far too long. Between messing my back up and having trouble getting another ignition coil, I haven't had much chance to do anything with the car for the past two weeks. But I got the new coil in this morning and the motor is running fine. The idle was perfect and it revved up as it should (once it warmed up of course). It did spit out a clear liquid with deposits of dirt in it from the exhaust when I revved it, but I'm pretty sure that's just condensation mixed with soot. I did, however, still see a small amount of white smoke out the exhaust for several minutes. It didn't get worse with the revving and had no odor (I'm a bit congested though, my sense of smell may be compromised). I'm gonna let things cool down and replace the AOS. What's the procedure for clearing the codes and check engine light?

You can see the smoke a bit in this image, it was hard to really get on a camera.

Macster

The bit of clear water with soot is common.

As you guessed, it is just condensation that carries with it a bit of soot it picked up on its way out of the exhaust.

Often behind a vehicle that appears to have been just started -- the exhaust is emitting a bit of water vapor due to cold engine/exhaust -- when the vehicle accelerates a surprisingly large amount of water -- a cup or so -- can come out the exhaust outlet.

So what you saw was normal given the type of usage you have subjected the engine too of late. Just an accumulation of water in the exhaust.

The "smoke" I'm thinking is water vapor it is so light as to not show up on camera. I have a pic on my other PC that shows my Boxster smoking from an AOS and you can see the smoke from across town...

As for the smell even with a clothes pin clamped on your nose you could smell the odor. Heck you can taste it it is so strong.

Oh, for clearing the codes/extinguishing the CEL the scan tool should walk you through this. From memory using my Actron connect the tool to the OBD2 port. Turn on the key. Follow the menu to connect to the vehicle. Wait while the scan tool tries each protocol in turn until it comes to the one for your car. Probably ISO which has a long (done at 5 baud) protocol initialization procedure. Then once connected there should be a menu item to read DTCs, clear DTCs. Just select the clear and press the ok/enter/continue key and wait. Watch the CEL. You see it go dark. Done.

ep3_lol

So I got stuck trying to get this thing out. There's no way I can get the quick release thing off at the purple arrow without prying with a screwdriver and potentially breaking it.



Anyone have any ideas? There is not enough room to get my hand at it from the top, and from the bottom i can grab it but there is not enough space to actually pull it off. I think if I had someone wiggle the AOS from the top while I grabbed it from the bottom, I could get it, but would rather find a way to do it myself.

sjfehr

My 2004's AOS is a bit different than yours, but I didn't have issues with the purple connector; squeeze the knurled section on the top and bottom, and it should release pretty easily with little pressure required. A lot of it was very awkward from the side of the car; I had the best luck getting leverage by throwing a towel over the trunk and laying on the trunk, and reaching down that way. Don't be afraid to remove other crap that's in your way.

gfl

Mine simply has a clear codes section of the menu tree.

Oil smoke (AOS) is not white. I expect your "smoke" is simply steam or the pollution that results from rich combustion when the car is started cold.

Grant

ep3_lol

I know the connection is supposed to release pretty easily, but it's just not. The top one was stubborn as well but with all the extra space it didn't really give me any trouble. I'm going to go back at it this afternoon.

ep3_lol

So I got the old one off and with the help of some cable-extended clamp pliers the new one went on yesterday. I drove it ~30 miles down to Charlotte and the idle would hunt sporadically for a brief period of time, but it was not nearly as bad as it had been. I got the codes cleared in Charlotte, drove home last night, and drove the Boxster to work this morning. Not another hint of idle hunting, no notable smoke at any point, and the check engine light has stayed off. I think, unless another symptom pops up, that this issue is solved.

One annoying note- O'Reily's Advanced Zone of Auto Parts or whatever you want to call them would not just clear the codes and my normal shop I go to wanted $40.00 to do it to cover their own rear-ends. I have a friend with an OBD 2 reader and he let me use it to clear the codes. I was not expecting this at all, is there some risk associated with clearing codes?

Mighty Shilling

Nope. go to amazon, get a bluetooth obd II scanner, go to the android or iphone App Store and download an app called "TORQUE". you can scan and clear codes from your phone.

ep3_lol

That's what my friend had, actually. I plan on getting it at some point now.