So to clean the expansion valve without removing the dash, I would need to flush the system from the firewall and flush the air/debris out the other end of the firewall? Any help is appreciated.

I'm replacing the condenser/drier, the compressor and flushing the lines with ac flush/air.

If your A/C system has been completely evacuated, and by that I mean, I busted the connection with a pole about 10 feet away, (was doing timing belt, oil pump and so on) and I never refilled my A/C with anything, including the oil that sprayed out as well. Could this cause a whining noise at start up, but goes away completely once warm? I can't figure out what the noise is, sounds like it's either my A/C, or my water pump, which I also replaced. Can't seem to pin point it but it goes away when the drive belts removed.

When you guys are flushing the lines, you are removing the AC line from the firewall too right?

There was some talk here about flushing the system should clean the expansion valve, how is this done?

Great write up! Gives me some confidence to do this DIY on my '98 GS400 with 217k miles.

My compressor began clicking loudly (periodically). Especially at engine start. I topped off the freon with a canister that came with guage. Stopped 90% of the clicking and driver/passenger were same cold temp once again. HAPPY!

After about 2 weeks, ac temp was blowing warmer, clicking returned often. After 2 days, clicking was almost constant. Also notice extreme engine lag at takeoff from a stop with AC on. With AC off, engine performed good.

Refilled with freon canister again. Worked for a few hours, then GONE. No AC, blowing hot, outside temp (105 today :-( )

So, I'm thinking compressor, condenser and dryer replacement. All 3 Denso parts on Amazon are about $410.00.

Think I am diagnosing this right?

Great write up. I was actually searching for a thread about condenser replacement and didn't find squat Will try this out soon!

Try maybe the AC relay switch,if not that then, replacing the parts is the best

Is the clutch engaging? Seized? That's what needs to be identified first.

I did this DIY. I replaced the condensor, compressor, O rings, flushed the lines,vaccuum pumped for 1.5 hours (removed all the moisture, and checked for leaks), rented all the tools from autozone (pump, gauges, flush kit can), put it all back together and the car is blowing ice *****. Car runs a lot quieter with the new ac pulley.

Thanks for the feedback! Compressor clutch seems to work. I can spin it when the engine is off. When started, if AC is off, clutch does not turn. When AC is on, engages and turns with no unusual noise (different that the loud clicking I was experiencing).

I'll research and check out the AC relay switch.

Thoughts?

Just to add...
The 300 gets a new (Rockauto) Denso compressor Saturday.

Old compressor with 210k miles has internal failure, high side stayed at static pressure 80psi or so and low side was fluttering at 80+ psi. No audible noise.

Frank, this Texas heat ain't no punk.

Rockauto has been great on prices.

and since i am doing AC work, to note, step #6-7 on this DIY for filling 134a is not proper practice. on an empty system you fill by weight as prescribed by the AC sticker on vehicle hood, my 2006 GX470 says 1.69lbs (~27oz) max., and 1.5lbs (24oz, two 12oz cans) is about middle of the allowable range per the sticker i have. its best if you follow the sticker or service guide, etc.

Correct...
Refrigerant should always be measured and added by wieght.
I use a digital kitchen scale and subtract the wieght of the valve and can. Not super accurate but within the broad factory tolerances.
I refilled the GS with just shy of 23 ounces, I would have added more if needed but I was getting 35* at the center vent with ambient temperature at 98* and 65% humidity.

since i am doing this as DIY i bought the harbor freight manifold set, i did initial inspection of the tool and its going back (cheap hard nylon seals that had nylon remnants like "chads", and the 134a couplers were cheap). i then bought a Yellow Jacket #49987 because it is 1) quality, and 2) allows you to evac the refrig line thus no need to remove any hoses to evac system and refill (unless you need to switch bottles, as i do, but i can evac the line after switching, etc). the YJ doesnt come with 134a quick connects so i also got CPS Products QC14SET. i will also use the YJ manifold on my home AC system. and then two bottle of 134a, using one 12oz and one 14oz of Interdynamics (ACP-102 and ACP-101).

oreilly has pag46 w/ dye in it for ~$9 in 8oz bottle, but i only need about 1.4oz of that.

i dont do any additives cause it slightly takes away from the freons reaction

but you'll need more than 2 12 oz cans cause you have to bleed that center section of your gauges a tad so theres no air in there.

with a YJ #49987 there is no bleeding, you can evac the charge line, its a 4 valve manifold. i will be charging with 26oz.