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Hey guys, need your help diagnosing an issue before I take it in to a tech. At a stop light I heard a hissing sound and the inside of the car filled up immediately with white smoke. I pulled over quickly and determined it had to be some A/C line that blew. My engine ran fine so just turned off the air condition and fan. Got home and opened the front hood. On the passenger side where you lift the black shroud by the battery you can see where something blew. There's oil all in that spot. Any thoughts on what happened or how costly this is going to be to fix?
My experience has been leaks at the compressor (in other vehicles), but according to some searching, the oil leak should show under UV light, and again, based on some searching, I would have expected it to be at a connection with an O-ring not in the middle of a hose.
Adding to my post. Here's a picture of the front passenger side where you can see the oil residue where something released or blew. I can't visually see a broken line. I cleaned some of it up as some sprayed over where the battery was.
sometimes its the high pressure sensor switch. The one with the green marking on it. the leak can happen where the wire connects to it.
That might make sense given the wires at the end of that were wet with the spray. Anyway I can diagnose it before taking to tech shop. I'm hoping that's it as I believe that's an easier fix.
only way would be to purge/vacuum and fill the system with some dye and freon, then operate the AC and track down the leak. the switch is relatively inexpensive and not difficult to replace. in other words, no engine drop needed. good luck..
What you have in this area, AC wise, is the expansion valve attached to the evaporator.
The small diameter metal tube on the right front side of the expansion valve (TEV) is high side pressure coming from
the condenser, and attached to it is a pressure switch. The larger diameter metal tube on the left side of the TEV
is the low side pressure going back to the compressor.
Places where a leak can occur are:
The Evaporator coil inside the evaporator box.
The TEV.
The o-rings on front and back of the the TEV.
The Pressure switch.
The metal AC lines do not normally leak, if they do : first you'd consider a braze joint and second something that crushed the line .
You can:
Charge the system and take an electronic leak detector and sniff those areas to pinpoint the leak.
Inject refrigerant dye tracer, charge the system, use a black light to possibly see the leak.
Or, look around, starting at the high side (small metal line with the pressure switch attached to the block fitting
which also has the larger metal line) and look south in the picture for the liquid spread.
When there is a major blow off like you initially described the splatter could be all over.
Thank for the diagram and additional information I have visually inspected the metal lines and don't really see a place where the release occurred. It seems to have blew/leaked out of the pressure switch end where the wires are as most of the oily liquid is sprayed on the black tubes you see in the pictures. Not sure why the pressure sensor blew, either a bad sensor or something else was the root cause. I'm hoping it's not an evaporator issue as I've heard that can be a big pain replacing. Another thing I noticed is that while I had turned the air condition and fan completely off, I noticed the air compressor fans up where the front radiators are were running nonstop on high. Not sure why that is.
The Pressure switch might be a 995 613 137 03 (there were a few super cessions, and there is an o-ring listed under the PN but not shown in the diagram, 999 707 555 41
All of the seals (o-rings) in the AC system refrigerant system are "static" seals with the exception of the compressor shaft seal.
Static means they do not move and nothing rotates around them, they are compressed in between two non moving component surfaces.
Once they are compressed between the surfaces any oil that was on the o-ring surface either remains or is squeezed away from the surface
leaving a nearly immeasurable thickness. When the ac system was being installed in your vehicles build the refrigerant oil
applied on the o-ring surface was simply to prevent extrusion and shearing of the o-ring surface when it is compressed in the joint.
On your year vehicle the oil does not have any impact on the flexibility of the o-ring (elastomer), the oil
cannot significantly change the physical characteristics (durometer, tensile strength, shear strength, etc. ) of the elastomer.
The compressor shaft seal makes contact with a limited area on the compressor shaft and this area seldom develops oxidation
after long periods of non movement.
The seal material in your model year is likely to be an HNBR (Highly Saturated Nitrile Hydrogenated Acryonitrile Butadiene) or
a Polyacrylate. Most common you will find is HNBR.
Years back (the years of R12 refrigerants) the o-ring material was a simple Nitrile or Buna (what was used with R12 refrigerants; your model year uses R134a).
Overtime Nitrile an Buna would harden and become brittle (regardless of oil). This seldom ever happens with HNBR elastomers.
When the internal surfaces (refrigerant metal lines, rubber hose lines, o-ring surfaces, evaporator tube surfaces, condenser tube
surfaces, drier, and compressor internal parts) sit for a long period of time the refrigerant oil does not fall off the surface completely,
the surfaces typically retain a very thin layer of oil.
Running the AC system after the system has sat for a long period of time does not significantly improve the life of the components
involved with the refrigerant aspect of the system. Things like electrical motors, components such brush contact surfaces or bearings,
or actuators and joints, might see a benefit from occasional use where surfaces are exposed to the elements.
The compressor pistons typically have a molybdenum coating so that on initial startup there is some anti-friction
until the refrigerant flow moves the oil through the compressors internals; if the moly coating is shot then things are pretty worn
piston wise.
Most modern vehicles (your model as compared to the older 911/930; pre 964) have a defrost function that utilizes the AC system. So in the cooler
months if your turn on the defrost the compressor will engage and refrigerant will circulate.
The biggest benefit of operating the AC system in the cooler months is that if something ain't working you'll know ahead of time so you can fix
it before the hotter months roll in.
Griffith, any thoughts on why I could hear the AC radiator compressor fans running on high even though I had the AC and fan turned completely off? Not sure if and when the pressure sensor blew there's some setting that triggered the fans in the front.
04-13-2018, 07:30 PM
997 AC line blew I think: Need Advice
