I’ve had the air conditioning system for my 1997 Toyota T100 serviced at least twice in the last 5 years. They always find that the coolant is gone, but are unable to find a leak.
While running the A/C last year, a blast of vapor came out the vents. I suspect that the problem lies in the evaporator core, since it is the one part of the system that is so hard to get at that they never check it.
I’m pretty sure that the dashboard has to come out to access the core. That is usually a time-consuming=expensive job. It also requires the knowledge of what to force and how.
I service scuba equipment and compressors for a living, so I’m pretty handy with a wrench. Should I take on this task, or spend the big bucks to have it done? Where is the best source of a service manual for the A/C or interior? Option 3 of just sweating it our, does not appeal to me.
Thanks, Charlie
You can do it, but you’ll need a service manual. Haynes is OK, but Toyota factory is better. Try Books4Cars.com for inexpensive used manuals.
Removal of at least part of the dashboard is almost guaranteed, but the manual will tell you for sure. This sounds worse than it is. Mostly it’s just a lot of time taking things apart. A manual will show the location of fasteners, etc, which sometimes are hard to find when you do a project like this.
If you have the time and a book you can save a LOT of money on this job.
When the AC was serviced they should have added dye to the system. This helps quite a bit in finding leaks.
You may be able to just remove the Cooler Unit out from under the dash. Take a look.
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800374bb
Tester
Don’t tear your car apart until you KNOW where the leak is…
Do you have experience working on AC? You need a fair amount of special equipment. Even though I’ve installed a unit, I’d take my car to a good shop for what you’re talking about.
good god MAN! dont jump to conclusions,hook up a gauge set and see what is really going on.
geezzz!
try a tech!
If this blast of vapor was the refridgerant charge there would have been quite a oily mess around the air deflectors (the discharge vents) was there?
Evaporators usually leak slowly,the sudden discharge, while possible troubles me.
In any case get a Factoty Service Manual, I own some for cars I don’t own,picked a FSM for a 91 Bravada for $10.00. It contained a OBD1 trouble shooting chart,it was worth it for that alone.
Tester is on the right track. Toyota typically puts the expansion valves next to the evap grid in the same housing. They designed the dash to make it easier to service. Remove the lower portion of the dash with the glove box on the passenger side, and you can access the screws that hold the evap coil housing in place. You need to first disconnect the lines to the evap coil under the hood. Then, disconnect the electrical connectors to the evap coil. At a minimum, there is a temp sensor to detect a frozen core. And, disconnect the drain tube. Then, remove the mounting screws, and pull the housing out as a complete unit. Pull carefully, but firmly, since there are seals you need to pull through. It should come out.
thanks, most helpful reply I got.
This is long past, but part of the diagnostic should be to use an electronic leak detector at the drain outlet with the system off, so the refrigerant pressure in the evaporator is at the highest level. If the core is leaking it’ll sound off when it’s held below the opening. Refrigerant is slightly heavier than air so it’ll follow the path that the water condensation normally travels, which should lead out to a hose under the car, usually at the bottom of the firewall.
Dyes and soap solution testing for bubbles don’t work very well with the evaporator only because it’s all covered up. They’re good for everywhere else though.
Your advice isn’t going to help the guy with the Toyota T100 . . . that was 8 years ago, he’s probably no longer even active on this website
The advice is sound for anyone suspecting an evaporator leak though.
So then we’re just going to keep rehashing this ancient discussion . . . ?!
Good grief
Well, the advice is applicable for any make of vehicle on the offchance that someone does a search involving evaporator cores. Ok, now I’m done hashin’… 
Thanks for the advice.
I know that this is old, but I am just now needing this info for my a/c on my 97 t100.
Thank you I’m just now looking at mine on my 1997 T100. It’s nice to find this old information on these older vehicles no matter what other people think