Bypassed ALDA switchover-- Why??? - PeachParts Mercedes-Benz Forum

neatokino · #1 03-13-2006, 02:22 AM

I was looking under the hood of a friend's '84 wagon, and I noticed that there were two things different from mine:

1) the Alda switchover valve (the one near the brake cylinder on the firewall) had been bypassed.

2) The black plastic transmission vacuum box on top of the engine (the one that contains the little white levers) had been removed.

Why would someone have done that?

Are those modifications potentially damaging to the engine or transmission?

Is there any reason for my friend not to gather the parts to put those things back the way they should be, and will there be anything particularly difficult about finding the appropriate parts and putting them in?

Thanks in advance,
Michael

Hit Man X · #2 03-13-2006, 02:42 AM

First one was probably plugged up and made the vehicle receive no extra fueling from the IP. Happens often. They're about $35 new and few dollars used if you can find a good one. I need a few more too.

Thing on top is for emissions, you don't "need" it... and it doesn't really do anything. Just had to be there when they were made back in the 80s.

boneheaddoctor · #3 03-13-2006, 08:28 AM

Thats not an Alda "Switchover valve" its an Overboost protection solenoid.

It will save you if something happens that will allow boost to rise above max fact spec.

Its best to fix it...its not expensive to replace and may save your engine.

Brian Carlton · #4 03-13-2006, 08:32 AM

The box with the little white levers is used to control the EGR on that vehicle. Removing it will cause no harm.........however..........the rocket scientist who did the job may.......or may not.......have made the proper vacuum connections after removing that box.

Old300D · #5 03-13-2006, 10:47 AM

Quote:

Originally Posted by boneheaddoctor

Thats not an Alda "Switchover valve" its an Overboost protection solenoid.

It will save you if something happens that will allow boost to rise above max fact spec.

Its best to fix it...its not expensive to replace and may save your engine.

My car was never equipped with one, being a 240D, and I had no inclination to add a piece that would just clog up eventually. With gas engines overboosting can be a problem, I'm not so sure about a 120hp diesel. Maybe long term.

boneheaddoctor · #6 03-13-2006, 10:51 AM

Quote:

Originally Posted by Old300D

My car was never equipped with one, being a 240D, and I had no inclination to add a piece that would just clog up eventually. With gas engines overboosting can be a problem, I'm not so sure about a 120hp diesel. Maybe long term.

well stock boost is 11-13 psi in the benz. The overboost solenoid energizes at roughly 15 psi. A stock Garrett T-3 can push 25 psi easily if the wastegate fales to open. Thats a healthy load to the head gasket , bearings etc.. but for a different reason than a gasser.

Old300D · #7 03-13-2006, 12:38 PM

I don't disagree, however a head gasket designed to withstand 400+ psi static compression plus the peak pressure of burning diesel fuel is not going to notice 10psi more. I hope I've got 10psi margin in my head gasket.