300SDL Trans and AC questions
 

Hello folks. I recently acquired a 86 300SDL. I've been searching awhile for an MB diesel, and came across this one. I was looking for a project, and something different than what I'm used to (I've been into Mazda RX-7s, Mazdaspeed 3s, Jeep Wranglers, and motorcycles). Well, lets just say that this Benz is definitely a project (that I overpaid for, but hey, it was an emotional decision).

The car had one foot in the junkyard when I bought it. Not even roadworthy. Well, I've replaced the tires, rear brake rotors, right front and right rear brake calipers, master cylinder, all soft brake lines, front lower ball joints, guide rod bushings, LCA bushings, passenger tie rod and drivers outside tie rod end, and shock all away around. It rides smooth, except for the transmission.

When I got it, the transmission shifted hard and short. Not hard as "break neck" or "tire chirping", but a definite clunk. It also shifted around 2000, leaving nothing but 4th gear to get you moving. The PO has all the vacuum lines coming off the check valve by the brake booster. The smaller line on the vacuum pump was capped, and EGR at least disabled. I've since routed lines as needed to be as the diagram (except EGR).

I've adjusted the Bowden cable, so now it is shifting a little later and just how I like it, however I get bad flaring from 3-4, and sometimes a little from 2-3. The output of the vacuum amp going to the tranny is 15" at idle, and goes down with throttle (don't have exact, I'm just using a mityvac under the hood). The output of the VCV is about 9". So from my reading, it looks like everything vacuum related is working right. However, the VCC is turned all the way CW (can't lower vacuum any more). If I disconnect the vacuum line to the transmission, it shifts a little hard, but too soon. Can't really figure out where to go from here.

Second neither the AC or heat work. The PO converted to 134, not sure how well of a conversion he did, but it has the fittings for 134. The compressor engages, but that's about it. There's some hissing noises that don't go away by the expansion valve. No change in temperature occurs. The high pressure side going to the condenser is hot, the cold side is ambient (good). There are bubbles in the dryer, so it isn't 100%. But no change in air coming out the vents.

Turn the temp to hot, nothing changes. Maybe... just maybe.... the temp coming out the defroster vents goes up, but maybe.

Also, the different buttons really don't change the air coming out the vents. It's all coming out the defroster and vents, nothing even comes out by the floor, no matter what button is pushed (except off, and going to EC does kick the AC compressor off). Haven't spent much T/S here, as I've been focusing on the drivability of this fine machine.

Anyone have any ideas? Much appreciated, and glad this forum exists. I've spent a lot of time learning from everyone.

hissing from the expansion valve usually means the system is undercharged. r134a needs to be right on the money to get cooling.

the climate control needs vacuum to work the vents. if its been disconnected it will default to safe mode, which is side vents and defrost only.

Thanks, I'll look into it. The low pressure side when the compressor is running is about 30 psig. What should it be? I also get air out the center vents. All the vacuum hoses going into the comapartment are connected, I haven't tested the 7 valve manifold yet though. I'll look into it tomorrow or the weekend.