Just had my wife call AAA to bring our 940 turbo home on the flatbed since she just started to see some white smoke. This started with what she called a muffled pop on the freeway & a loss of power. Coolant type exhaust vapor started shortly there after but there is no evidence of coolant loss or coolant in the oil or compression pressure build up in coolant reservoir. I don't understand the intercooler system (YET) Is there somehow that turbo failure could produce these symptoms? TD

 

Well, catastrophic turbo failure on a water cooled turbo could allow coolant to flow thru the turbo and then into the combustion chamber. Your heading in the right direction. The two fluids in a car that generate white smoke are coolant and automatic transmission fluid. The soft pop makes me think a charged air hose leading to or from the intercooler blew off or burst. This would cause a major loss of power. Still, the white smoke is worrisome. Coolant entering the combustion chamber would not show in the oil and a smaller leak may not necessarily pressurize the cooling system. I would have a chemical test done on the coolant to detect byproducts of combustion. A blown head gasket on a 17 year old car is not uncommon, especially a turbo. Keep posting as you investigate!

 

Finally had a chance to drive it today. Runs & accelerates normally. Minimal white emission when idling but smells bad, not like just coolant. The turbo is functioning under hard acceleration but leaves a cloud behind which I think is more oil than coolant. This car has never burned oil before. Are there seals in the turbo that could have failed causing this? I'll do the chemical test on the coolant next and then perhaps a leak down test.

 

Sure there are seals that fail,; to the extent it will luff blue smoke at idle. The oil seals generally don't go all at once though. No seals for the coolant. So...no loss of power?

 

I don't sense a loss of power. At the time of the "incident" my wife was traveling 60-65 on I-5, 30 south of Portland. Her description was a noticeable "puff sound under the hood and perhaps associated with a puff of visible vapor (?)." On the next grade she felt as if the car wasn't as gutsy as normal, otherwise no problem. About 40 miles later the car was parked for a couple hours. As it was being driven about 5 miles back to the freeway is when the noxious emissions occurred, so much so that she noticed pedestrians staring at the car.

Any head-gasket event causing a puff sound or vapor would surely be evident under the hood somehow and be major enough to effect idle or acceleration.

I'm a retired quasi Volvo mechanic <http://www.oregrownmusic.com/anoldvolvo.htm> but never got into the newer cars of that day with turbo issues. They were all still going to the dealer in those days. I've been told there is a nationally know turbo guru (Bell Turbo) in my area so my plan is to speak with him Monday morning.

 

Spoke with a very knowledgeable turbo rebuilder & also a good European car mechanic. Consensus is it's a pcv/turbo issue. Since the turbo oil drains via gravity and this has likely been impeded by poor pcv flow, carbon build up is/has been allowing oil to pool up in the turbo and be pushed out the exhaust. My guess is the "event" that brought this on so suddenly must have been either dislodging of some crud in the pcv system or just reaching critical mass. Because the copious blue smoke is intermittent, disappears after coming off the highway, then re-appears big-time after the car sits for a short time, I think the head-gasket is not suspect.

Cleaning entire pcv system should test this theory and if it holds, I plan on having this turbo rebuilt while it's still good.

 

Well, yeah...blue smoke is indicative of completely different issues than white smoke. Dino oil will coke all through the turbo over time. Once you get that squared away, synthetic is highly recommended. Too, turbos have a bad rap in the USA simply because we Americans as a whole are horrible about changing oil routinely which leads to worse coking than would otherwise be the case. When the crankcase ventilation is stopped up, the loosened oil filler cap will jiggle rather than simply sit there when the engine is running. Also, the small vacuum nipples on the intake manifold will clog up, blocking all flow. I've seen them so completely clogged that I've had to use a tiny drill bit and drill the crud out.