tj90

OK -
With new evaporator in hand, I decided to DIY evaporator change on my car. I hope these instructions help anyone wanting to tackle this job. I would also like to thank the Rennlisters that pointed me to helpful links that gave me the confidence to tackle this job. I will attempt to document the procedure I followed to do this job. If there are any holes or something plain wrong, feel free to comment.

As you may / may not know the 993 A/C system is practically like the 964 system of the early 90s. If you search "evaporator" in the 964 board, someone posted a comprehensive instruction in removing the evaporator. I used this as a blue print in removing the 993 evaporator. I did find that there are differences betweent the 2 cars that I will try to highlight.

Overall, it is a job that takes time. I estimate I spent close to 15 hours from start to finish including drier installation, evacuation, oil and charging of the AC system.

My impression from this DIY is that you need to be mechanically inclined and have a few specialty tools that makes the job easier (see below). I would say that the toughest part of the job is working under the dash and dealing with all the subcomponents of the airbox.

Grab some popcorn and follow me through the most "fun" Ive had on my p-car to date!

tj90

The evaporator is deep inside the air box between the dash and the firewall. Its essentially a radiator that gets really cold from expanding freon. Air is pulled through the evaporator, heat is removed from the air, and cold air comes out your vents. There is another component, called the expansion valve, that creates the pressure differential of the freon and hence cooling of the evaporator. This assembly is inside the airbox that sits directly below the air intake just behind your hood.

I learned the hard way thats its a good idea to replace the expansion valve at the same time the evaporator is replaced. The expansion valve is a $50 part that (in my case) can go bad and lead to to cooling problems as well.

Go ahead and order a replacement drier too - it contains a decisscant that must be protected from humidity. The drier is located behind the driver side front wheel behind the wheel well cover.

It is also recommended that everytime you crack open an AC line, replace the o-ring. Make sure the orings are designed specifically for AC systems and that they are oiled and clean using the compressor oil (PAG)

To do this job, you will need to remove the gas tank, loosen fuel pump, remove components in the dash, remove and disassemble the air box and finally remove DS wheel well. Plenty of opportunities to forget to connect things etc. so take plenty of pictures as you go. I referred to my camera pics many times during assembly. Also, I found it helpful to store bolts, screws etc in baggies to keep things organized. I labeled the bags "fuse box", "glove box" "top airbox" etc. Without doing this, I would have been lost.

tj90

Below is a picture of the tools that I used for the job. You will need to jack up the front of the car to access the fuel pump. Robins site outlines how to jack up the car properly.

I want to highlight a few of the tools.

1) Magnetic pickup tool - used plenty of times when retrieving screws - I dont know how I could have done the job without it. Magnetic tray is especially handy when working under the dash to prevent screws from falling under front seats or off the fender when your under the hood.

2) Mirror - great for under dash visibility.

3) Fender guards! I used 2 - one for the side to rest tools and fuse box and another on the front bumper to protect paint finish as you climb in and out of the hood.

4) Catch pan for fuel that must be drained.

5) Stubby wrench and universals for tight access, metric sockets and wrenches.

6) Metric allens

7) T-10, 15 torx wrenches.

8) Torque wrenches and breaker bar to open up the AC lines near the compressor. (covered when I rechange the system)

9) Screw driver magnetizer to help hold screws during reassembly.

ps - There is a picture of PAG46 oil which is supposed to be compatible with ND8 oil. Not 100% sure, but should work. A fellow rennlister found ND8 oil at a MB dealer. Also, there is a quart of DURA flush used to clean the system prior to recharging my AC lines. I bought the flush at NAPA.

tj90

First thing to do is remove the carpet liner from the trunck.

Disconnect the battery.

As seen below, the first thing that needs to come out is the gas tank. To do this, fuel must be removed. I found that by removing the fuel level sending unit, I could siphon fuel out of the tank directly into another vehicle. I used my strap wrench to remove the sending unit.

tj90

Try to get as much fuel out as possible, any remaining fuel will end up in your catch pan under the car. I ended up with 2 quarts of gas when I drained the tank after siphoning.

After siphoning, put back the sending unit to keep the fumes down. Leave the wires to the sending unit off.

In the trunk near the external gas cap, you will find 2 hoses leading to the fuel tank. Remove the 2 hose clamps on the lines. Remove the ones closest to the fender.

Dont worry about removing the mini-tank on top of the gas tank. I dont know exactly what this is - maybe an auxillary tank for fumes? DO NOT remove the hose that is running between the tanks - I did by mistake. The entire gas tank will come out as a unit!

Loosen the metal strap off the tank. I could not completely remove the strap (it will come out later) but you can bend it out of the way. Now you can remove the plastic cover that is between the strap and the tank.

Back under the car, remove the under-car access cover between the front wheels. Toward the back of this cover, there is a smaller plate that must come off as well. Above this plate is the fuel pump.

tj90

The fuel pump is held in place by 3 bolts. Disconnect the 3 bolts and let the pump hang. This gives you more room to disconnect the fuel lines.

I found that the best way to disconnect the tank is to disconnect the fuel line near the pump as well as the metal line. You will need a 17 and 19 mm wrench for the steel line and 8 mm socket for the hose clamp near the pump. I initially tried to disconnect the hoses near the tank. DO NOT try this. As I was prying the hose lines, I was putting stress on the tank - I did not want to break this!

Wear glasses and have the drain pan ready. Make sure your trouble light is well out of the way. Fuel will come out of the line. We dont want BBQed P-car owner do we?

I also want to mention that in this picture you can see the airbox drain (black rectangular outlet to the right of fuel pump). If, after a recharge with oil, you see any leaks from this area, thats a tip off that the evaporator is dead or there is a leak from deep inside your airbox.

tj90

It might be helpful to remove rubber/foam fuel line spacer that is wedged between the car and fuel lines aft the pump access plate to articulate the fuel lines during removal. I did this but probably not necessary.

NOTE: leave pump covers off until you are completely satisfied that you dont have any fuel links when you are done with this DIY. Correct any leaking fuel!

tj90

Go back to the top of the vehicle and get ready to remove the tank!

Make sure you take the tethered hose clamp off and stuff somewhere out of the way.

There is a rubber stopper thing that just pops out of its receptical on the upper tank. Hidden under is a 6 mm hose clamp. Remove it and take the tank out.

Notice in the pic that I have the fender cover on the passenger fender in place? This is where the fuse box is going to sit. Also to the right you can now see the firewall. Once the firewall is out, you will have access to the airbox.

I will post the remainder of the job later - time for bed!

jnor10

Great Post TJ,

its fantastic that so many bases are being covered by fellow rennlisters, taking on projects that the majority of people would pass on to a professional. Its always a process doing DIY projects for the first time, great to see such initiative!

Well done!

Jeff N.

Luis A.

TJ,

Nice job.

I must've missed it; how did you know you needed a new evaporator?

tj90

Check out "fuel pump removed" post above. I was leaking refrigerant oil out the drain after fresh oil freon recharge. My leak is so bad that I could smell freon as well with the blowers on high. A charge would only last me a few days.

I will get to it later, but after I had everything apart, I believe that my actual leak was coming from the expansion valve or just behind it (bad o-ring?) and not the evaporator. I will show pics of the evaporator and fresh oil was coating it from the top near expansion valve.

I replaced the evaporator anyway since so many p-car owners have experienced failures with them.

Any leak in the airbox will leak out the drain under the car.

Jastx

TJ, great DIY post!

I just went through a complete DIY A/C component upgrade on my 930 so am looking forward to seeing the rest of your pics.

leeham

My 993 went into the shop today after an unexplained Freon leak. It appears that it's almost all gone. The system last worked in December. If they say it's the evap, then I'm going to do it myself with your instructions. I can't afford 15 hours labor. Hopefully, the leak is somewhere else. A couple of questions, if you don't mind.

Where did you buy your new evap, and how much?

Have you heard of a fix for freezing evaps that relocates the temp sensor? Mine seems to freeze up after about an hour of driving. I then have to turn off the system until it thaws out.

Regards,

LeeH

tj90

My 15 hours is probably really 8 following the instructions. I learned as I went, hopefully my instructions cut your time in half.

I got my evaporator from Vertex (no affilation - $370). You can also go with Griffiths.com as well. Keep in mind that their evap is supposed to better than OEM and the price includes the expansion valve for around $560 - again no affilation..

I have heard of the temp sensor relocation fix. I have not done it, but I recall some threads on this in either the 993 or 964 board. Essentially, you move the temp sensor closer to the top of the evaporator to shut off the flow of freon before it freezes itself up. Your symptoms of AC stop running definitely sounds like maybe temp sensor.

Unless they took the car apart, I dont know how the shop can immediately claim evap. As I learned in my DIY, the problem was probably the expansion valve ($50) that sits on top of the evaporator.

I will post part 3 of my DIY that shows you how to get to the expansion valve. Once the firewall is out, you have easy access to it. Probably 2 hours of work. Of course, if you dont have UV in the system, it may be hard to determine exactly where the leak is coming from. You can buy a can of UV dye to inject in the low side port of the compressor, Inject with another can of freon and run the car to diagnose problem.

leeham

Thanks very much. They haven't gotten back with me to give a diagnosis of the problem.

I'll be looking for part three. Hopefully my repair will be something simple, like a leaking valve at the compressor. Your experience is enough to make me seriously consider selling the car.