PorscheAddict

Can anyone tell me what the right hose is here and what it carries? I changed spark plugs and headers today and noticed it has some oily build up on it. It is not leaking much, not enough to really see what the liquid looks like, but it is certainly damp/moist. Any ideas what it is?

In other news, a single plug had a drop or so of motor oil on its threads. The tips are dry, and the threads are dry except toward the back of the plug. It doesn't appear to be in the cylinder from my view. I first thought maybe someone applied oil to lubricate the threads, but if that was the case why 1/6 oily? Seems pretty soon for a tube guide to fail at 25k miles on a 2014 Cayman S, but I guess it's possible. Thanks all.

PorscheAddict

Here is the plug and chamber in question. This is cylinder #1 (passenger front).

jscott82

You are asking about the aluminum tubes? Those are the AC lines to the compressor.

PorscheAddict

Really the thick black tube on the right in the first pic - it looks fuzzy, kind of. I thought it feeds into the aluminum tube, but if not I need to remove the aluminum tube pic.

jscott82

I'm looking on m phone, so can't really see the first pic, but that does look like the ones that would feed the alum. I doubt it the AC thats the source. The black one snakes up and over the motor, so it just may be a conduit from another leak.

PorscheAddict

Thanks for the thoughts. Agree it is likely not AC leakage. It appears to be this circled hose (have not had the engine cover off yet, but the sizing and spacing seems right). Photo credit to Voyager6. Does anyone know what this carries? I can hopefully take the cover off tomorrow and see what's going on in there. A bit perturbed by this and the oil on the spark plug threads since the car is a 981 and has not been driven that much. It doesn't smoke, and drives well. I planned on just doing plugs as maintenance and came across this while I was down there.

okie981

That hose/line with the oily residue on it is the low pressure air conditioning line (return from evaporator in the cabin of the car under the dash). The compressor lubricant flows around in the system lines and is likely seeping where the hose is crimped into the metal tubing. This means you are also leaking some refrigerant also. Could also be a pin hole in the rubber itself. If it's not seeping compressor fluid from inside the lines, it may be oil/lubricant being thrown on the hose from something else, but I don't see any evidence of that on the areas surrounding the hose in your photo.

As far as the oil on the spark plug threads, I saw this on a couple of my spark plugs when I changed mine at 26,000 miles (2016 BS) last week. I'm doing a header install and decided to swap the plugs for ease of access when there are no exhaust headers in the way. This is a theory for where it came from...crankcase oil vapor is routed into the intake manifold by the crankcase ventilation system. Yes there is an oil separator but they are notorious for not catching all the oil vapor (zillions of posts about this on the internet for direct injected engines) and that oil vapor that makes its way to the intake manifold eventually makes its way towards your intake valves. Due to the design of the flat 6 engine, when you shut your engine off, at least 2 of the cylinders will be "parked" with the intake valves partially open. Oil vapor that has condensed to become oil fluid can slime its way down past the open intake valves, drool onto the spark plug threads and by capillary action, soak into the spark plug threads. With intake/exhaust valve overlap, it's possible both intake and exhaust valves could be cracked open slightly when the piston is near TDC. This will allow condensed oil to seep down into the exhaust ports. Why do I think this? Because when I took my headers off and looked up in the exhaust ports, 1 of the 2 cylinders that had open exhaust valves also had some light coat of oil residue that was wet to the touch in the exhaust port, more so in the valve that was aft-most in the engine of the two exhaust valves in that cylinder. Spark plugs look good in all cylinders, inside of OEM headers in all cylinders all look clean and no evidence of carbon buildup. I can imagine no other reason I saw damp oily residue in 1 valve's port of 1 cylinder, and that cylinder happened to be one that had exhaust valves parked in open position for several weeks as I worked on the car. I had last shut the engine off after running it up to full operating temperature while the car was on jack stands to bleed coolant after installing the 3rd radiator (center mount).

PorscheAddict

Thank you very much, both explanations make sense. The AC still blows cold for now, but I'll have to pressure check it and keep an eye on it. I thought it was very odd that only one plug seemed to have any oil, and that the oil present was a drop or two total, but I have seen many reports of the AOS not working great. Thanks for taking the time to write that out.