1993 940 turbo in excellent running condition

the turbo suddenly for no apparent reason ceases to function . the car continues to drive normally in every other respect

that was 2-3 months ago

yesterday the turbo suddenly and as inexplicably started to work and continues to work normally.

nothing was done regarding the turbo or any upkeep was performed on the car from the time the turbo stopped working until it restarted yesterday


i would love an answer i can get my mind around

I think the wastegate was stuck open. For unknown reasons it has freed up and is now working normally.

Turbos don't seize and free up.
--
john

It is pretty impossible for the turbo to stop working and the car to work normally! How do you know it stopped working if driveability was not affected? A turbo spins or it doesn't; it is pushed by the exhaust gases and if it suddenly stops that would be due to some blockage and you'd know it... Were you just going by the gauge?

you are mistaken.

i repaired a 940 turbo some years back that had had the wastegate rod detach rendering the turbo for practical purpose non functional. the owner had driven the car in that state for at least 5 years according to him with no other dysfunction than a lack of power associated with turbo boost he had enjoyed when it worked.

he also said his gas mileage improved with it not working

"Lack of power" means that the car was not working normally! It could be semantics between "running" and running as designed, i.e. "normally". Still, if a turbo car is unaffected by the inoperation of the turbocharger, what's the point?

think of it this way. you are flying on a commercial airplane with multiple engines

one engine fails and is shut down.

yes, power is now lacking compared to what was designed yet the airplane remains aloft and lands safely at a nearby airfield.

on a 940 turbo the turbo merely enhances the engines output of horsepower..... that's all it does.

When the condition began--did you check to see if the turbine would spin? Now it's free? If the cause was something like a split in any of the flexible hose connections I'd think that would effect running in a radical (aside from not providing boost) way. -- Dave