Insulation for underhood AC line

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JHZR2

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Hello,

On w123 body mercedes diesels, there is a metal line that ultimately connects to the compressor, which routes right in front of the valve cover on the engine. The cover gets quite hot, and so likely imparts a lot of heat to the AC line.

The AC line was insulated from the factory, but since these cars are all nearing 30 years old, the insulation isnt great anymore. Often it is broken or fallen off.

IMG_2023.jpg


I was initially thinking pipe insulation from home depot... but wanted to get opinions if there was something better to consider.

Any thoughts?

Thanks!
 
No reason to cover it. The covering is just to make it purdy. Thats all. I can't tell in the pic but is it a high or low side hose? Whoever made it has the same crimper that I do.
 
That is the low side fill port for the R12 system.

I figured that given the heat transfer of metal (vs rubber), and its placement so close to hot stuff, it could pick up heat, harming the efficacy of the system...
 
Originally Posted By: JHZR2
That is the low side fill port for the R12 system.

I figured that given the heat transfer of metal (vs rubber), and its placement so close to hot stuff, it could pick up heat, harming the efficacy of the system...
Nope. Thats the low side and is returning to the compressor so it's already done it's job in the evaporator. The compressors job is to pump it back to the condensor and it's gonna be hot going there anyway. Much hotter than the 200* or so engine temp.
 
I have used heater hose (which is available in bulk from most auto parts stores). I use a razor to slice it down one side so I can cover the exposed hose and then ziptie it every 4-6" to keep it in place. I didn't do it so much for the insulation (temperature) value as to keep the metal line from vibrating against the body. On one of my vehicles that metal return line runs under the airbox along the frame until it gets to the expansion valve. I've used the same trick to protect rubber hoses that were rubbing against other objects or other hoses.
 
Originally Posted By: Chris142
Originally Posted By: JHZR2
That is the low side fill port for the R12 system.

I figured that given the heat transfer of metal (vs rubber), and its placement so close to hot stuff, it could pick up heat, harming the efficacy of the system...
Nope. Thats the low side and is returning to the compressor so it's already done it's job in the evaporator. The compressors job is to pump it back to the condensor and it's gonna be hot going there anyway. Much hotter than the 200* or so engine temp.


True,it's already picked up the heat from the cabin in the evaporator. While it's still cold and gaseous before it hits the compressor, once compressed it will heat up, so what you say makes sense (I think you're saying who cares if it picks up heat from the engine at that point, since it's going to get hot when it's compressed).

So why is the lo side in almost every car wrapped in insulation? Same for a home system...?
 
The low side is usually wrapped/insulated to prevent condensation from forming on the cold line. Condensation mixing with dust, salt etc. will sometimes result in something that may attack the alloy line causing pinhole leaks.
 
That does make sense, as the exposed metal indeed shows condensation. Protection against that requires a very tight intimate fit, perhaps glued on to displace moisture, Id guess.

If the low line is hotter than the temperature under the hood, then n big deal, however, the line does show condensation, so it cannot be. Adding heat from underhood undermines the operation of the system, IMO, because then after the rise due to compression, there is even a few more degrees which needs to be shed... and likely a few additional psi. This is my worry.
 
I'm planning on insulating our Escape AC lines before next spring. You have to use a certain kind pipe insulation that doesn't emit posionous vapors.. never remember the name of it. If your ac is working good now you could probably hang meat in there after.
 
It is R12, holds a charge, and blows nicely. If you find the name, Id appreciate knowing it... Ill do the same as I research.
 
The internet is all screwy today so I'm having a hard time looking at Home Depot etc. You want to find EPDM pipe insulation the common rubber insulation that the big box stores carry is the one that can give off a toxic gas when subjected to heat. Many do use it though I for one won't.

Found it:
Click me
 
Originally Posted By: Familyguy
I have used heater hose (which is available in bulk from most auto parts stores). I use a razor to slice it down one side so I can cover the exposed hose and then ziptie it every 4-6" to keep it in place. I didn't do it so much for the insulation (temperature) value as to keep the metal line from vibrating against the body. On one of my vehicles that metal return line runs under the airbox along the frame until it gets to the expansion valve. I've used the same trick to protect rubber hoses that were rubbing against other objects or other hoses.


I do the same thing, it has some insulation value, how much I don't know. I use it for protection of parts that could rub together, etc.
 
I may be able to come up with some of that for you. I think I saw some scrapped AC lines at work - if they have some of that wrap on them, I can send you some. Of course you'd have a GM part on your MB!!
 
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