92 300SD A/C & Miscellaneous

[duronimo]

I'm retired and had some prior bad car luck, so I thouight I would go back to an older Mercedes. The 240D, 300D's were always dependable. I picked the wrong car. The 92SD uses oil, the turbo quit, cruise quit and the A/C went out. So I'm starting with the AC. I flushed the system, replaced the compressor (new Denso 20C)/drier etc. but I can't get any power to it. It's a the speed sensor in the bottom. Is there a relay or line fuse? Thanks

[sixto]

Originally Posted by duronimo

uses oil

Worst case is bent rods. Might be worth trying a new head gasket first. The head gasket section around main oil gallery feeding the cam bearings and lifters can fail sending oil into the #1 cylinder and out by the #1 exhaust runner. While the head is off, compare piston protrusion fore and aft at TDC. Should be the same ~0.7mm fore and aft. If the aft end is higher than the front end, the rod is bent. Not the end of the world. The new head gasket might reduce oil consumption to an acceptable level. If not, consider a 603.96 3 liter block as a replacement.

Could also be external leaks and/or worn turbo seals dumping oil into the intake manifold and exhaust pipe.

Originally Posted by duronimo

turbo quit

You'll enjoy more of your retirement if you convert the wastegate actuator from ECU/vacuum to mechanical/boost control. The bulk of this discussion applies to your 3.5 - Wastegate actuator swap for OM602.962?

Originally Posted by duronimo

the A/C went out. So I'm starting with the AC. I flushed the system, replaced the compressor (new Denso 20C)/drier etc. but I can't get any power to it. It's a the speed sensor in the bottom. Is there a relay or line fuse?

That vintage has its share of problems with evaporator leaks. Does the system hold a vacuum for several hours? There might be info at V12 Uber Alles | A site for Do-It-Yourself repair of the Magnificent W140 Mercedes Benz on AC compressor control.

Sixto
87 300D^2

[duronimo]

Thanks for the info on the turbo. I'm aware that a mechanical wastegate is the way to go. About the oil use. The engine has 235K miles on it and it runs very good -- it just uses a lot of oil. I have learned about the rod bending deal and I guess I'll have to see if Mercedes has a history of this car. I don't know if this is a replacement engine or not. About the A/C. The old compressor was shot. I flushed the lines, installed a Denso 20C. My problem is that I'm getting no power on the wire that plugs into it.