Expansion Valve and Mirror Questions

[Chunkerz]

I have my HVAC box out so I decided to replace my expansion valve while I was at it. There was a thick tar like substance all over it and the pipes coming out of the evaporator. I had to remove it in order to replace the valve, so I was wondering if this tar stuff was required, or would it be alright to put it back in the car without it? If it is required, what can I use in its place? Will that hollow insulating foam they slide over pipes work, or does it have to be that black tar stuff?

Also, the bolt that holds the two halves of my mirror together backed out, so I took the mirror apart to fix it. The problem is I cannot get the bolt to thread in because of that overly strong spring. If I remove the plastic shims above/below the spring I can get it to thread in. My mirror seems nice and stiff without the shims, so I was wondering if they were necessary? Would there be any repercussions if I left them out?

[Sehrgut]

I had a similar problem with my mirror. I took a trick from old school suspension. I simply heated the spring over my stove until it just became red and compressed it with slip-joint pliers just a little. Worked for me and I've had no problems in over 5 years. Good luck....

[Chunkerz]

I'll give that a shot. Thanks!

[kuehl]

Chunk,

The black 'tar like' substance is an insulation. The ac trade calls it "prestite tape" (not be confused with a trade mark pres-tite; an adhesive).

Your expansion valve (aka TEV or THV) has a copper tube brazed to the top and its end is formed in a 'pigtail'. Inside the copper tube is refrigerant gas that expands and contracts based upon the temperature the pigtail sees when it is properly attached to the evaporator outlet pipe (there is a metal clip that secures the pigtail to the top of the pipe). As the gas inside the copper tube expands or contracts it moves a bellow and pin that meters the refrigerant coming from the receiver drier through the TEV. The prestite tape is wrapped around the evaporator pipe and the pigtail to help insure the temperature the pigtail sees is the that of the refrigerant gas existing the evaporator; hence prestite is an insulator.

Prestite is also used to seal off any openings in the evaporator box adjacent to the TEV and evaporator inlet and outlet tubes. Occasionally you might find a TEV completely wrapped in prestite. This is not necessary.

So, you can use what ever floats your boat to insulate the pigtail and evaporator box air gaps. However, the ac trade usually uses prestite because can remove it more easily than other products.

If you unclip the TEV's pigtail insure you position it at the "top" of the evaporator outlet, not on the side or bottom; the pigtail is suppose to measure evaporator gas outlet temperatures; occasionally, refrigerant oil tends to follow gravity and it exits the evaporator outlet pipe's lower circumference hence insulating the refrigerant gas inside which could give a false signal to the TEV.

Tip: don't forget to replace your drier, inspect the quality of the refrigerant oil that comes out of the evaporator, remember to replace the refrigerant oil that is removed from the evaporator as well that it is lost when replacing the drier; 2-3 ounces should be enough; and if your system is empty of refrigerant you might as well replace all the other o-rings in the system.

Griff
Porsche AC

[Chunkerz]

I bought some special A/C insulating tape at work. According to the catalog it's good for evaporators, A/C lines, expansion valves, etc so it should do the trick. I got a new receiver/drier with my A/C update kit from 944 Online, so don't worry I'm planning to replace it along with every single oring in the system. I'm just waiting for it to warm up so I can get the system flushed before installing my new components.

[Chunkerz]

Just in case someone does a search related to this topic in the future, here's how I solved my mirror problem: I placed the spring that goes over the hollow bolt in my vice and heated it up with a torch. Once it was nice and soft I tightened my vice and compressed the spring about 1/4 inch. I let it cool off then put it all back together, including both plastic shims. Some force was required to engage the threads, but it wasn't impossible like before. My mirror is nice and stiff but not impossible to fold in.

[Sehrgut]

Hey Chunkerz,
Glad it worked out for you. I don't have a vice, or a torch. I just did the best with what I had. Your solution is much more Porschesque.
~Chris