That was dandy advice that I would have posted, if I had thought of it. Allow me to add a few observations. I only replaced one heater core while working for a very nice family-owned Chrysler dealership. It is the exact same procedure that also requires taking the AC system apart. It is real common to end up with a squeak in the dash once you have everything back together, even if you don't have three screws left over and a clip that you do not remember where it goes. I was the suspension and alignment specialist, but a friend / coworker was the main AC system specialist, and I watched him do this job on occasion. Every job included a few swear words, and he was often complaining that the job could not be done in the time allotted.
My next concern is evaporators do not typically corrode through in such a short time. Do you live in an area where salt water gets into the air intake? That would lead to corrosion. I live in the middle of Wisconsin where they throw a pound of salt onto an ounce of snow, and think that is going to make our roads safer to drive on. That salt caused my 1988 Grand Caravan to rust in half so only the carpet is holding it together, but the evaporator still never leaked. What a professional would be looking for is the cause of the leak, and he would try to do something so that does not happen again. There is not much he can do to prevent salt air damage because coating it with something could decrease its efficiency, but there could be signs that it was vibrating or sliding around on a loose mount. That rubbing could wear a pin hole into it. You would want to identify that and do whatever is needed to keep that from happening again.
You also need to check the condensate drain to be sure it is not plugged. The common complaint is the water that condenses on the cold evaporator collects in the drain pan, then, instead of dripping onto the ground by the right front tire, it overflows and makes a puddle under the passenger's feet. In a warmer state, that water might evaporate before it runs over, but the evaporator might still be sitting in it. If there is salt in that water, the problem is going to occur again if that drain isn't cleared. The clue that the drain tube is not plugged is you should see a steady drip on the ground under the passenger's foot area when the system is running.
You are still going to need a mechanic to charge the system once you're done. The laws vary by state, but here in Wisconsin, we are not allowed to charge a system that has a leak. We are required to recover the refrigerant. That is a really big deal, and the state sends people around with cars with leaks to try to catch us. If you do the repairs yourself, then the mechanic finds a leak, you can be expected to have to pay for the service, you get to do the job a second time, then pay for the charging again. When a mechanic does the work, the shop covers the cost of any remedial repairs. You only pay once for the job.
Also, be aware that refrigerant is extremely dangerous to work with. It can cause frostbite and blindness. We wear gloves and safety glasses, and most of us also wear a face shield. Be aware too that you are going to have the system open and air is going to get into it, along with the humidity in that air. The system needs to be pumped into a vacuum for at least a half hour just before the refrigerant is pumped in. In a vacuum, water will boil at 77 degrees, then it can be drawn out. It is standard procedure to replace the receiver/drier any time the system has been opened, but even a new one can only absorb a limited amount of water. Water and refrigerant combine to form an acid, and that will attack the metal parts and can result in another leak. Also, a single drop of water circulating in the system will freeze at the expansion valve where the temperature drops real low. That will stop the flow of refrigerant, and stop the production of cold air, for up to an hour when it melts and starts to circulate again. The symptom will be cold air, then hot air, over and over.
You also have to be aware of foam seals inside the heater box. If some are misplaced or thrown away, you can get a thumping noise when mode and temperature doors slam open or closed. The HVAC controller will have to be re-calibrated to learn the position sensor readings when the doors are in various positions. I don't know what is involved on your van, but on 1997 models the "cool down" test was extremely frustrating and could easily take twenty attempts to get it to pass.
It is also important to pump in the exact amount of refrigerant called for. If you need two and half cans of do-it-yourselfer cans, how will you know when to stop? The evaporator needs to be approximately half full of liquid refrigerant and half full of vapor. That is the exact point where it becomes very cold, where it is turning to a vapor. If you have too much in the system, that point of evaporation will be in the hose under the hood, going to the compressor. This is a case where more is not better. You'll feel a real cold hose under the hood, but have warm air inside, and of course you will assume something is wrong with the door actuators. If you have too little refrigerant, it will turn to a vapor before it gets to the evaporator. The cold spot will not be where the incoming air is blowing across it.
For decades only Chrysler used a sight glass on their receiver/driers to show when the system was fully-charged. With an under-charge condition, you'd see vapor bubbles flowing through the glass. Ford tried to copy that in the 1980's, but there were always still bubbles when the systems were full, so they didn't do any good. Any attempt to eliminate the bubbles by adding more and more refrigerant eventually led to having so much liquid, it could slosh into the compressor and destroy it. Refrigerant compressors can only pump a vapor. They cannot handle a liquid. Home refrigerators can be damaged with a two ounce over-charge. Cars need to be much more forgiving because of the bumps and angles they go through, but while they can tolerate some over-charge, at the very least it will negatively affect the system's performance. Professional charging stations pump in only the exact amount specified for each vehicle.
Be aware too that if corrosion caused this leak, chunks of aluminum likely broke off and are circulating in the system. There is about a fifty percent chance one of those chips can make it all the way around to the expansion valve and block its tiny orifice. There is no way to clear that other than to replace the valve. That will not occur right away. Most specialists will flush the lines, then install the new receiver/drier which does include a filter. If this does happen, it's nice if someone else provided a warranty, and will at least cover the labor. You can be expected to be charged for additional parts, like that expansion valve, but the shop will handle the refrigerant recovery and recharging.
As for renting a vehicle, most new-car dealers have rentals with reduced cost if they are working on yours. Many independent shops offer loaner cars, typically with the only requirement that you return it with the gas tank filled for the next person.
If I needed this job done, I would do it myself, but I have the special tools, some experience, and other vehicles to drive. I would still need to visit a friend with a charging station, but it's silly to pay someone else to do the same type of work I did for many years. I know when it is smarter to pay someone else to cut my hair, bake my cookies, and grow my food.
Steve W. Is right about getting the service manual. I prefer manufacturer's paper manuals, but those from online companies have the same information. Read through the many pages of instructions with line drawings and specs before deciding if you want to tackle this job. You will notice the only things included are procedural steps and a few warning disclaimers. None of the wondrous observations I presented here are included.
Tuesday, February 14th, 2017 AT 5:10 PM