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87tdwagen · #23 10-13-2020, 01:54 PM

Finally, it's done, after parts delays and mis-shipments, I'm cooling again
A few notes of what I found and some observations hopefully that can help others.

I believe, my undercooling and the hissing sound at the compressor originally stemmed from the over pressure relief valve on the compressor likely due to way too much oil in the system. Having only added/topped off the system in the nearly 20 years I've owned it, and not knowing how long before that when the PO did the original conversion and or how much oil was originally put in, but whoa, the amount of oil that came out was crazy, if I had to estimate, 12-15 ounces worth in a system that calls for 5oz per the FSM. Spilled a bunch on me removing the old compressor....and it's still full. The evap and condenser flush pulled about 5 ounces, dont know how much was in the old drier, but even the barrier hose leaked another oz or 2 on the floor. Either way it was overloaded. The original compressor may still be good as I noted no refrigerant leaks prior to removal, so will keep that as a spare for now.

My observations, lessons learned for others:

First, the Compressor, new units are still available from Denso and will likely as mine did INCLUDE the MB manifold, so you may not have to swap the old one to the new compressor, just connect the barrier hoses. The compressors come pre-charged with Denso oil N8, which is PAG46.

Barrier hoses, tried 2 4 Seasons and ACM, both required modification to make work, I chose to stay with the ACM one as fitment was slightly better, but even so only one of the 3 mounting brackets aligned, the other 2 had to be cut off to make it work. Some minor pipe bending will also be needed.

Condenser. My original was tight and sealed, but was original to the car and had likely never been opened prior to the R134a conversion. The only 2 black R12 O-rings I found in the system were at the 2 condenser connections. My low side nut was fused to the condenser. I tried PB blaster 2 day soak with no success. Heated up the nut with a torch, but would not budge. Carefully cut the nut off with a dremel tool only to find out after reassembly that the low side condenser fitting pipe had cracked a solder joint right at the condenser in the process, and now would not hold vac or pressure. Took it to a local radiator repair shop for a quote to fix....$175....$200 for a NEW ACM parallel flow condenser....went with New.
New ACM condenser also required "fitting" removing unnecessary brackets and adjusting the bends in the connection fittings to align with the hoses, not a straight plug and play.

Expansion valve access is limited as others have noted before. Removing the cowl gutter and fresh air intake screens provided excellent access to facilitate install. Only takes about 10 min to remove the cowling plastic but will save you tons of time and frustration given the cramped space the expansion valve is in.

Also, remove the drivers headlamp assembly, this facilitates greatly access to the drier, condenser high pressure line and the top most bolts of the compressor. Takes less than a couple of minutes to remove the headlight assembly and makes life easier.

So far the system is running good. Initially, after first run, I'm getting a slight momentary whine under acceleration, sounds like it's from the compressor, not sure if it's just the need for the system oil to circulate fully throughout or if I may need to add a little more oil. Will keep an eye on it and see if it goes away or not after a couple of days of running.

Thanks again to all for your help.