Jscaramella

After a 20min ride yesterday I decided to try and pull the oil fill cap and noticed an abnormal amount of vacum when trying to pull the cap.
Im an avid reader of the 996 forum and have seen many threads stating this as a sign of AOS failure.

I have no oil leaks or coolant leaks that are visible at common areas.
Fill level has been consistsnt.

seems like after I replaced the coolant cap with the new unit i get more of a coolant smell after a long drive. I plan to pull the bumper to check behind the radiators.

Should I take preventive measures and do the aos now just based on that one test?

dporto

The coolant smell after replacing the reservoir cap is probably just the pressure relief valve blowing off a little steam (like it's supposed to do) when the engine heats up.

Macster

Define "abnormal".

Out of 3 AOS failures with my Boxster only the 1st one manifested the hard (make that impossible) to remove oil tube filler cap symptom due to excessive vacuum. Now it could be the other two failures would have also manifested this symptom but I never bothered to try as it was clear from the obvious symptoms what the problem was.

Absent a rough idle, CEL, varying idle, smoking , or because this is a 996 any signs of a coolant leak around the AOS I'm not willing to believe the AOS is a problem.

Yet.

Coolant smell after replacing the coolant cap could be due to the cap not being installed properly. You have to be sure the cap is not cross threaded and the threads and face where the cap seals are all clean.

Also, the smell could be from a leak in the coolant tank. The cap holds the pressure better and the tank is now manifesting the signs of a coolant leak. It was not very long after I replaced the cap on my 2002 Boxster the coolant tank went.

You can do the old driveway cooling system pressure test. Be sure the cap is installed correctly. Be sure the system has the proper amount of coolant in it. Do not overfill! But don't have the level too low either.

Drive the car around -- with the A/C off! -- until the engine is fully up to operating temperature. Know this by the fact the radiator fans are coming on.

Back home in the driveway raise RPMs to 1K and hold until you or a helper confirms the radiator fans are on. Check they are both blowing the same amount of hot air.

Shut off the engine.

Wait. The heat load of the engine will raise the coolant temperature and pressure and if the tank is the source of the smell I think you'll have clear proof of this shortly.

Sniff around the front of the car for a radiator leak and at the engine compartment for a leak at the tank (or cap) or some other place.

Be careful. When I did the above the coolant tank gushed hot coolant out to the ground.

kromdom

https://m.youtube.com/watch?v=FKmjatZmUo0

ejs1

Macster, not the the OP of this thread but just wanted to say that I appreciate all your knowledge and help in this community. Always valuable feedback. Thanks

Ahsai

You can use a manometer to measure the crankcase vacuum via the oil filler cap. It should be 4-5" of water. If it's much higher, yoir AOS has failed.

http://www.amazon.com/Meters-PDMM01-Digital-Manometer-Measure/dp/B005FU5HFI

If you smell coolant and you are sure your coolant cap is good, you have a leak somewhere else.