300SD Squealing

[Ray R]

Since I bought my 79 300SD back in October, it's had this squealing noise coming from the car. It occurs under partial throttle/load, like 1/3 to 1/2 throttle. The best way to describe it is like a REALLY loud bearing noise, but it behaves like a vacuum or turbo issue.

I went through and changed a bunch of stuff. Belts, pumps, turbo, etc..  I couldn't figure it out. So I tool it to a local shop that specializes in older Benz cars. The car spent 6 weeks with him trying to figure it out. What ended up being the root cause? The exhaust system!  He happened to have the same car onsite for parts and swapped out his exhaust system for mine. That fixed it!

There must have been something in the resonator or muffler that was loose or flapping, restricting flow, and causing the noise.  I think he may cut them open at some point just to figure out what it was. My car has only 88k miles.

I post this in case someone else has a similar issue and is pounding their head against a brick wall trying to figure it out.