Proactively replace AOS?
Discussion
I'd say replace it now. Under £100 if done DIY or perhaps £200 to have it done by someone in the UK?
Just DIY replaced the original AOS on my '02 2.7L with 180,000kms by which time, it had properly failed with the classic smoke bombs from a cold start.
A couple of years earlier, I began to notice rather unpleasant burnt hydrocarbon smells from a cold start (but little if anything the way of smoke). On reflection, that was probably an early sign but there was no increased vacuum at the oil filler cap as far as I was concerned.
Then I started getting P1128/P1130 error codes and went on a wild goose chase cleaning the MAF and replacing the oil filler cap. Then the cold start smoke bombs started by which time, I had the definitive failure symptom of considerable vacuum at the oil filler cap (when the engine was running, of course).
Perhaps your tech could slap a "slack tube manometer" on your car and test the crank case vacuum?
If all OK, you could leave it for another year or so and check again but, but you might end up spending more in diagnosis than the cost of preemptive replacement!
The downsides to letting it fail are that in extreme circumstances, it may be theoretically possible for a big slug of oil to be ingested leading to hydrolock. In more normal circumstances, any amount of oil that passes through to the intake will clart the intake with oil and it would clearly cost more time/money to clean it all out but it can be left dirty and then for a period of time thereafter, the residual oil will continue to pass through and you may get some more smoke for a while.
Also, when it properly fails and the crank case pressure is too high, it could lead to other vacuum problems and you don't really want a collapsed oil filler tube. I think I may have incorrectly refitted my oil filler tube (rear section) when I did my expansion tank and that may have been why I got some oil pooling on the right hand side of the block (under the oil filler tube, between the AOS and the alternator) an area that is tricky to clean up.
Just DIY replaced the original AOS on my '02 2.7L with 180,000kms by which time, it had properly failed with the classic smoke bombs from a cold start.
A couple of years earlier, I began to notice rather unpleasant burnt hydrocarbon smells from a cold start (but little if anything the way of smoke). On reflection, that was probably an early sign but there was no increased vacuum at the oil filler cap as far as I was concerned.
Then I started getting P1128/P1130 error codes and went on a wild goose chase cleaning the MAF and replacing the oil filler cap. Then the cold start smoke bombs started by which time, I had the definitive failure symptom of considerable vacuum at the oil filler cap (when the engine was running, of course).
Perhaps your tech could slap a "slack tube manometer" on your car and test the crank case vacuum?
If all OK, you could leave it for another year or so and check again but, but you might end up spending more in diagnosis than the cost of preemptive replacement!
The downsides to letting it fail are that in extreme circumstances, it may be theoretically possible for a big slug of oil to be ingested leading to hydrolock. In more normal circumstances, any amount of oil that passes through to the intake will clart the intake with oil and it would clearly cost more time/money to clean it all out but it can be left dirty and then for a period of time thereafter, the residual oil will continue to pass through and you may get some more smoke for a while.
Also, when it properly fails and the crank case pressure is too high, it could lead to other vacuum problems and you don't really want a collapsed oil filler tube. I think I may have incorrectly refitted my oil filler tube (rear section) when I did my expansion tank and that may have been why I got some oil pooling on the right hand side of the block (under the oil filler tube, between the AOS and the alternator) an area that is tricky to clean up.
Trev450 said:
What are people's thoughts on replacing this ahead of it's eventual failure? Car is a 2007 CS with 51K miles.
Absent any signs of trouble from the AOS I'd leave it alone. As an aside, my 2002 Boxster averages 80K to 120K miles per AOS. At over 300K miles the engine is on its 3rd replacement AOS.If you opt to replace the AOS before its eventual failure then why not the fuel pump? Water pump? Coolant tank? Wheel bearings? CV joints? Clutch? Radiators? Radiator fans? VarioCam solenoid/actuators? Window regulators? Door locks/latches? The list is endless.
Even if you replace the AOS you stil have to pay attention for even a new one can fail, either out of the box, or at any time.
Preemptive replacement is perhaps overkill, but in this case, it is a relatively inexpensive job/part (and quite satisfying to swap on a DIY basis).
In your experience, AOS failure has led you to have your car towed three times. That sounds rather inconvenient and preemptive replacement might have served you better?
"Three AOS's have come and gone. All 3 required I have the car towed to the nearest dealer for replacement. First failure tow was around 45 miles, the 2nd failure 90 miles, and the 3rd was just 10 miles."
In your experience, AOS failure has led you to have your car towed three times. That sounds rather inconvenient and preemptive replacement might have served you better?
"Three AOS's have come and gone. All 3 required I have the car towed to the nearest dealer for replacement. First failure tow was around 45 miles, the 2nd failure 90 miles, and the 3rd was just 10 miles."
Mogul said:
Preemptive replacement is perhaps overkill, but in this case, it is a relatively inexpensive job/part (and quite satisfying to swap on a DIY basis).
In your experience, AOS failure has led you to have your car towed three times. That sounds rather inconvenient and preemptive replacement might have served you better?
"Three AOS's have come and gone. All 3 required I have the car towed to the nearest dealer for replacement. First failure tow was around 45 miles, the 2nd failure 90 miles, and the 3rd was just 10 miles."
I also had the car towed for a fuel pump and a water pump. I managed to drive the car home when a VarioCam solenoid/actuator failed. Had a couple of batteries go bad over the years, too. One -- in my Turbo though not the Boxster -- failed after just 7 months.In your experience, AOS failure has led you to have your car towed three times. That sounds rather inconvenient and preemptive replacement might have served you better?
"Three AOS's have come and gone. All 3 required I have the car towed to the nearest dealer for replacement. First failure tow was around 45 miles, the 2nd failure 90 miles, and the 3rd was just 10 miles."
So, preemptive replacement of what items and at what mileage/time?
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