I was looking back though the 420SEL's documentation. It has some engine work done in the past.
-Both cam shafts and rockers were replaced at about 140K.
-One of the heads had its head gasket replaced at about the same time.
The $3500-4500 quote was for the full job to be done by the shop. I would not be doing anything other than dropping it off.
I had to take some half-day vacation Thursday and Friday so I dropped by the shop to check out my 300D and have them look over the 420SEL to see how the underbody looks.
They were quite impressed with how solid it was and how old it was. They didn't see any major show stoppers. There were two spots that they would like to address that I had ****tily attempted to patch up 6 years ago. They said that they would not hesitate to put money into the car. It's going to be around for quite sometime. Case in point my green 300SD lasted 10 years with significant rust on it even when we first bought it was a rolling/running parts car.
Beyond that I talked to them about doing the valve stem seals as a short term solution until I save up for the valve job. They were actually doing a similar job on a VW in the next bay over.
We did see a significant oil leak coming from both valve cover gaskets. It coated a lot of engine's underside. No leaks in any of the areas that I had previously sealed up (oil pan/sensors).
I also mentioned the A/C leak issue and how I'd replaced all these seals and the condenser, dryer, injected dye but couldn't find anything. Compressor is only 5 years old if that.
He took out his UV flash light and a pair of sun glasses and probed all over the car above and below. He was telling me that if it was the evaporator usually you would see some of the UV dye in the drain tubes as the condensation would tend to wash it down there. He saw nothing in them.
We walked back over to the a/c compressor and found a good amount of dye around all three sections of the unit. He said there may be more up against the engine block. He said that was a pretty common leak point for that style of compressor.
So I think most of my major issues on the 420 are addressable. I am going to have him do valve stem seals ASAP. I am going to park my freshly painted 300D (when he is done with it) for the winter as I have a few other engine things to take care of before I put it back on the road..which means I'll be daily driving the 420SEL..and burning oodles of oil.
I took a bunch of photos too.
2016-12-09 W126 420SEL Underbody Inspection - Album on Imgur