The AC was blowing warm air last October on my ’05 Limited at 162,900miles. I did leak testing – vacuumed the system and it held. Recharged with dye, did not see any leakage using UV light but system was low again in May. Again, I did not see any dye - recharged and paid particular attention to the drain water from the evaporator but no leak was detected. I placed a white paper towel under the evaporator drain and let it run for a while and saw a very faint dye stain around the perimeter of the wet spot. Repeated twice and proceeded with the evap core replacement. After removal, I did verify the evap core leaked at two different spots. AC now working great again and I hope it lasts for another 17 years.

Along with the evap core, also replaced the AC expansion valve and condenser, drained the engine coolant and replaced the engine coolant thermostat and radiator cap. The cost of parts and supplies was $422.85 but $193.00 of that was the condenser which was not planned. The evap core and expansion valve were Denso and sourced from Rockauto along with seals and compressor oil. The old expansion valve was fine but since I was in there I thought I would replace it. The job took me maybe 35 hours over 8 days working at a very enjoyable, casual pace. Too much time I know but I only broke two clips, cleaned the inside of all the ductwork and ended up with no codes at the end so I was happy.

Observations:

1. I had the FSM doc’s for the job which was important. You can get a full FSM on CD from Rockauto for $25 or so. More Information for DAVE GRAHAM 03T4RUC
2. I used torque wrenches on the important stuff and noticed the conversion to ft-lbs and in-lbs in the FSM are wrong in a few cases – check them against the metric specs which are correct.
3. Toyota specifies their compressor oil ND-OIL 8 and the generic equivalent is PAG-46. The FSM says to lube the o-rings with the compressor oil but does not specify adding any when replacing AC components which is standard practice. I added 1.5 fl oz to the evap core and 1.5 fl oz to the condenser when replacing – total system capacity is supposed to be 4.5 fl oz. Lack of lubrication to the compressor could cause it to fail and I have seen a number of posts where folks did this job and subsequently had to replace the compressor.
4. I had purchased a new desiccant element for the receiver /dryer on the condenser, removed the condenser but the threaded nylon plug was seized.
   I ended up destroying it and never did get it out. Not my best day. I replaced the condenser with a Toyota part purchased locally as I could not get a Denso on-line fast enough. I removed the plug in the new condenser to add oil, verified it had a desiccant element installed, noted the o-rings were dry and lubed them. Perhaps this is why it seized on the old condenser which appeared to be original.

This is on my list for this summer. Mine is blowing hot right now. I've been riding my bike a lot to save gas so I haven't felt too rushed.

How do you know your compressor has enough oil? Do you need to remove it to drain the oil out?

I would not do that unless you were replacing the compressor. I would just add some back for each of the components that you replace. They say that too much oil can affect the cooling performance of the system but I think not enough is the bigger problem. The total capacity of the system is 4.5 fl oz so that is your absolute top end. In the absence of Toyota specifics, these are generic quantities to be added based on the component being replaced:
Condenser: 1 fl oz (suggest 1.5 fl oz instead as it includes receiver/dryer)
Evaporator: 2 fl oz
Hose : 0.3 fl oz

Was the service manual adequate or did you also use a write up post from here? I think we need to replace the evaporator in our 03 4.7 and it looks like the whole dash needs to be removed.

Yes, the 4th gen requires the removal of the dashboard and underlying equipment. You end up going all the way to the firewall. I looked at the writeups & video's in the maintenance sticky on this forum to get an idea of the magnitude of the work. The Service Manual is good but the procedure for the evap replacement references quite a few other sections so you need to have access to those as well.

I ended up tackling this job this last weekend. It took about 6 hours to remove dash, replace parts (evap core, desiccant, and heater core), and reinstall the dash. I didn't have the tools to recharge the AC, so that was done a couple evenings later, but all in all its not a bad job. It takes a long time, but if you are organized and watch a video or two it goes pretty smoothly.