FWIW, my vehicle is a 2007 4-Runner 6-cyl Limited 2WD, but this topic seemed general enough not to locate in a specific Gen forum. My question(s)/discussion are more about what to do for my situation than specifically how to do it, for instance I see the very comprehensive write-up from @y=mx+b re: condenser replacement. What I am interested in is advice or suggestion as to what to do, and if one of them is replacing the condenser during this process, then I'll definitely use that excellent how-to write-up.

Over last few summers when my AC system seemed to be struggling during hottest periods used some of the easily available and well reviewed "top-off" products, e.g. AC Pro whatever. But apparently the "Stop-Leak" additives they include/tout are no bueno for most (maybe all?) AC systems. So I think I want to evacuate/purge system completely and replace with new/fresh refrigerant.

So my main question is since I have system open/purged, what else should I do? Replacing the receiver drier is a no-brainer, but some other thoughts:

-- Use system flush just because (even if I don't replace compressor)?
-- Add some leak detection dye when I recharge with new refrigerant just so I can look around later?
-- Go ahead and replace condenser since it is fairly straight forward and not horribly expensive?
-- Go ahead and replace expansion valve since it is fairly straight forward and not horribly expensive?
-- What about replacing compressor on a prophylactic basis? While I don't drive this car very hard at all (normal driving; drive it maybe 8K miles a year at most; sometimes tow a utility trailer), car is 17 years old and I am getting old enough that doing some of this in 5 or 10 years from now would be a problem for me, so that's a real consideration.

I don't want to do anything that is truly useless or just to say I did it, but I honestly am not sure what qualifies for that vs. "should do".

BTW, I've noticed that a lot of OEM/Denso products are on near permanent backorder nationally. RockAuto has other manufacturers listed for AC parts, but I've never heard of them...for instance here are the suppliers listed for a new condenser:

2007 TOYOTA 4RUNNER 4.0L V6 A/C Condenser | RockAuto

Any thoughts or recommendations as to which is preferred?

Replace filter/drier if it goes the whole system goes.
Condenser, what does it look like? I'd change it, it old.
Compressor, your circumstances maybe/probably.
Expansion valve maybe later, 96Red 22 yrs. only reason I changed was drier went took it with it.

Struggling, things to check if you haven't.
Check Site Glass for bubbles. If low add with leak dye.
Has condenser ever been thoroughly cleaned to point of between it and radiator.
Has Evaporator ever been cleaned.

This is all great...just the type of thoughts I was hoping for.

While I am really good at dealing with my HVAC related maintenance on house and appliances, it never occurred to me car-wise for some reason. I am pretty sure it is not included on Toyota scheduled maintenance guide, or I would have done it. So...sigh...no, the evaporator coils (a bit of a ***** to access) nor evaporator fan box/area nor condenser coils nor radiator fins have ever been cleaned (at least by me while I've owned it). My bad...but I have plans in place and products ordered to deal with.

I am planing to go into where I do my car work tomorrow and hook-up some manifold gauges and inspect the system. I can't clean/make a mess there, but I will be able to assess state of refrigerant and any potential leak(s).

Because the expansion valve is directly attached to the evaporator in gen-4 4-runners, it will take an act of god for me to decide to deal with that. But I will strongly consider replacing the condenser "just because". I am a little grumpy as it seem like Denso (OEM) condensers are on some sort of national out-of-stock, back-order status.

Anyhoo, based on your comments and some other insights I've gained, my current plan of attack is:

1) Hook-up manifold gauges and generally assess system, e.g. pressures and level of refrigerant and whatever. Inject some dye and maybe top off refrigerant.

2) Clean whatever I can: coils, fan box, cabin filter and re-assess system efficiency if called for.

3) Order, gather parts (O-rings, condenser, filter/drier, new refrigerant, etc.).

I have to think about compressor...it involves dinking with serpentine belt and other connections, and I am not sure if I want to take that all on and risk it if it is not obvious there is a problem, or unless known lifespan of compressor has been reached.

4) Once all is ready, get system professionally evacuated.

5) Remove/re-place new parts (condenser, filter/drier), pull a vacuum, and refill with new refrigerant (and probably some dye again).

I hope this all sounds reasonable. Of course, I am still open to suggestions and cautions and pitfalls.

Not sure if you're aware..but there is a OEM Toyota foam cleaner that you spray up into the AC condensation drainage hose to clean the evaporator .

toyota ac evap refresh kit - Google Search

There maybe a cheaper aftermarket version out there somewhere.

Don't forget Pag Oil!

Yep! I was gonna use this:

TSI-Supercool-P46-8D-Accessories-Fluid

No worries about using a product that mixes the two, I assume? I am open to suggestions if this seems sketchy.

What are you going to be mixing? Pag brands?

Evac and extended time vacuum after parts change not much/if any original oil in system my experience.

I hadn't quite thought that far, yet. I tend to use whatever Toyota uses or the dealership. Barring that, whatever seems to be "hearted" on Rock Auto.

I also assume as long as it was a PAG 46 product, I didn't really need to worry? Not correct? Denso uses ND-oil 8 for its R134a type refrigerant compressors, I read here and on Denso website, which is a PAG 46 oil.

I am now unclear on just how much oil I should add for just changing out the condenser and receiver/drier plus complete refrigerant replacement. I was going to use this guy's guidance:

https://www.toyota-4runner.org/3000329-post5.html

But you appear to be of opinion I will need to add more. What would you advise?

Also, I really appreciate your willingness to share experience and knowledge. Thanks.

@aa040371 Gotcha on mixing now, is wise to choose good replacement parts.
134A & Pag46/ND8 like peas and carrots.
TheDurk a good resource here never known for bad info, those numbers are
for 3rd Gen's 4th may or may not be different look to 4th Gen FSM to confirm.

Disregard "not much/if any original oil in system my experience" too much my technique my rules of thumb applied.

How much Pag to add go with FSM specs for what you've replaced you're good. It easy job.