[1980 Special Twin]

I'm currently spending a lot of time underneath my car, mostly to do an overhaul on the rear axles and related parts. I bought the w123 from someone who had parked it in the garage for 10 years and it needs to be restored.
I was lucky to get a relatively rust free car, which is quite unheard of in this part of western Pennsylvania but the car had previously lived in the south.
I would love to preserve its uncorroded quality as long as I can. I'm definitely going to brush and wash all of the surfaces I can, but is there any recommended way to clean and coat as much as possible so that it will stay unoxodized, even if I have to take it out in the salt and sludge next winter? The factory coating is mostly intact.

 

[silverspy0]

Find someone locally that sprays on Fluid Film or similar. Don't get the hard spray, keep to stuff that just wipes off.

 

[luisg92]

I’d recommend you don’t spray any undercoating or paint over the existing one. Instead, use something that can be applied yearly and keep the wheel wells, drains and jack holes clean & free of debris.

Problem is, undercoating in these cars is known to crack and trap moisture which rots things out without you noticing it until its too late. If you apply another layer of either paint or undercoating, that new layer will crack and come off allowing more moisture to be trapped thus making rust worse.

Just pay attention to the condition of the current undercoating and treat any crack that can exist or develop in the future and try to keep the car away from salt as much as possible. These cars are classics and really shouldn’t be exposed to road salt anymore.

 

[ianrandom]

Bilt Hamber stuff is really good, I use that yearly-ish. You can use the Dynax Wax which can be transparent.

Definitely do pay attention to the factory seal, it's extremely thick and durable but if it does crack then it hides rust.

Take off your bumpers and anything else like that for cleaning and wax behind etc. If you're able to borrow a ramp or makes a huge difference to finding nooks and crannies.

Applying any kind of wax like that is best done in the hot weather and the car should be bone dry.

 

[kevdupuis]

My preference has been to use oil/fluid based rust proofing, applied late summer and parked in a dusty breezy spot or a leisurely drive down a dusty road to create a very good barrier just like any vehicle that has had a slow long term oil leak, a pain to clean when you want to work on it but everything underneath is still in great condition.

 

[plinker17722]

Just purchase a few tins of silicone grease and a good brush and paint the under side with that ..dont use any grease if its petrolium based .