Barrier Hose Upgrade
Would you believe the typical Porsche 911 we are working on has nearly 40 feet of rubber air conditioning hose! And the air conditioning hose type or design dates back to the 1950's. Why so much hose? Well the air conditioning compressor is in the back. The evaporator is in the front along with the drier and front condenser. And the primary condenser in the back. So, if you run back and forth you cover a lot territory. The real problem with the stock a/c hoses is that they leak refrigerant on a constant basis. Meaning for every linear foot of ac hose you have so many parts per million of refrigerant that slowly leaks out. The leak rate per linear foot is so small that refrigerant dyes will not penetrate refrigerant hose because the dye is suspended in the refrigerant oil. And, an electronic refrigerant "sniffer" will not detect the leaks because the electronic detecors are not that sensitive: if the detector was sensitive enough for a leak that small the detector would most likely be set off by other things nearby. So what you have are thousands of very small "leaks" spread out across a lengthy piece of hose... and all the small leaks add up to a large one.
With these facts in mind, if we step back to 1982, when this car rolled out of the factory fully charged with refrigerant, it was only a matter of time, usually a year or two, before you had to "top off" or add more refrigerant. Every year. Back in 1982 that was not such a big problem as R12 only cost $1.75 per pound, we were not aware of "ozone depletion", and the EPA was... what was the EPA?
With the development of R134a the a/c industry came up with a new standard for refrigerant hose design, outlined in SAE (Society of Automotive Engineers) specifications, we call "barrier" hose. Barrier hose has an additional liner inside the hose ( a non plasticized nylon co-polymer) that reduces the permeation (leakage) rate of refrigerants. Less permeation is critical especially with R134a refrigerant since the molecule is smaller than R12, system pressures run at bit higher and so the refrigerant could leak out of old style hoses sooner than expected. In addition, this new type of ac hose construction tends to be more forgiving when flexed; the 911 ac hose lines have a few corners here and there to bend around. So barrier hose is a nice thing!
So we stripped out all 5 of the 22 year old a/c hoses and installed a brand new Griffiths barrier hose set. The job of removing the ac hoses is straight forward and you do not need a car lift. As a matter of fact the entire Mr. Ice Project was done with a simple roll around jack and a jack stand or support. Take one a/c hose out at a time and replace it with the new barrier hose. Though replacing the ac hose set is the most time consuming part of the project, figure 8 hours for the average 911 DIY or do it yourselfer on the ground, a few hours less up on a lift, it is an absolute necessity. It does not make much sense to achieve lower vent temperatures one day only to find out the reason your vent temperatures have risen the following week was because you did not replace the original leaking a/c hoses.
Replacing the a/c hoses is not difficult. You do not have to remove the engine or the car's interior. When we got done with the project we came up with a "how to" instruction set that walks you logicially through the procedure. Here is a brief summary: There are three a/c hoses in the engine compartment: compressor to evaporator and the rear condenser to front condenser. Two of the hoses exit down in slots adjacent to the rear shock towers and come out near the heater boxes underneath, traveling further under the tub to their component destinations. The compressor to rear deck lid condenser hose is one of the easiest to replace by the way. There are two hoses which are accessed behind the driver's side front tire, the drier to front condenser and the drier to evaporator, and the rear condenser to front condenser passes by here too. All the a/c hoses are held to the body with a clamp and screw. We simply removed them, dropped the hose, temporarily put them back in place so we could find the mounting points easily, and re-attached these orginal clamps while installing the new barrier hose set. Almost all the hose fittings (ends of the hose) have a nut on them of which are in inch increments, for example, 3/4", 7/8", so you can use standard non metric wrenches.
On this installation, with the Kuehl Fender Condenser we designed, we used 6 refrigerant hoses compared to the original 5 hoses the car came with. In reality we will have a little more total length of hose as compared to the original hose set, however we end up with less hose weight and less hose volume because of the size of the hose we are using and the type of hose. And, we will be using less refrigerant! We will talk about the "less refrigerant" idea later on.