Why would a wastegate get stuck open?
 

Wastegates spend most of their lives closed. On occasion, when needed, they are opened. So I'm trying to figure out why it would get stuck in the open position....as mine is on my 91.

Also, assuming the actuator itself is fine, is it usually sufficient to spray PB Blaster on, let sit, move back and forth, rinse and repeat?

Answer to second question spray and work it manually until it moves freely. I'd recommend Kroil if you can get some.

Exhaust crud builds up in the shaft of the valve and the friction keeps the valve open.

False. ESPECIALLY on diesels. It is constantly moving to regulate boost pressure when the engine is loaded, especially when driving at highway speeds. On your 91 its moving even more frequent as the ECM commands it to help direct EGR flow.

If there is a spring in it, I believe the spring weakens with heat and time.

Interesting. I would have assumed that the actuator would simply pull it back to closed when pressure drops back down.

No spring on that waste gate only spring is in the actuator.

So with Kroil and enough movement and time, should that be adequate? Or are there times when it's so gunked up that it has to be take apart?

No spring on that waste gate only spring is in the actuator.

That is the wastegate spring.


Secondly, the springs in 617's that were being referenced don't "weaken". Stock boost is 9psi, but the service spec is 12psi, so some people think boost is low or there is a problem. When in fact, all OM617 shipped set at 9psi, no matter Garrett or KKK turbo.