300sd switchover bypassed

The purpose of this valve is to prevent an engine runaway. The valve vents the line to the ALDA whenever (hopefully never) the turbo boost exceeds 16 psi. The electric pressure sensor is on the top rear of the intake manifold.

Defeating this safety system creates the possibility of engine destruction if the turbo's wastegate (relief valve) fails to open at its

The valve gets dirty and may leak; that creates flat acceleration when the ALDA doesn't get the proper boost pressure. Or, the banjo fitting on the rear of the intake manifold gets clogged with soot (cleaning it is easily done with a straightened paper clip).

You can experience the effect of the ALDA by test driving the car without the banjo connected to the intake. The motor will run fine but acceleration will feel flat; the hissing noise is the turbo pressure blowing out of the banjo hole.

Thanks for the explanation T.G.

Sounds like I should get a new switchover valve, clean the banjo fitting and reconnect everything.

Again, thanks, Jeff

Has any heard of an engine blowing up from bypassing the switchover valve?

Jeff

No. But diesels have been known to do so for another reason - running (uncontrollably) on their lube oil.

And let's not forget that these 617.95X are now old machines and have weakened somewhat with age so no drag racing for them!

On Apr 16, 1:49=A0pm, "-->> T.G. Lambach