JimEb

Had my car in for service last fall and have since been fighting the coolant fault warnings. Thus far on two separate instances I found two different vacuum tubes left unconnected. The shop did a sloppy job reassembling my car.

Second time I had to tear back in I made a better effort to check all the reasonably accessed tubes and valves for any other surprises.

I tried to find the vacuum pump itself. I know it’s somewhere on the right rear of the engine but is it even accessible without dropping the engine? Figured if I could just access the vacuum tube directly off that pump I could pull a vacuum with my hand pump there and check the whole system at once.

Would at least give confidence I found all the leaks before buttoning the car back up.

Anyone know how to access this?

SilverSFR

Maybe Plenum's documentations can help in your journey. Lots to good COV diagrams, COV locations.

Porsche COV info and documentation - Thanks Plenum

dannyk304

The vacuum pump is on the right rear of the engine on the head connected to the camshaft sprocket from where it gets its power - see picture, circled in yellow. It's a black round cap. However, I'm pretty sure it only powers the brake booster so unlikely that your test will yield the results you're looking for. As for the fault code, I had that recently and chased around, ultimately found that the helmholtz (resonator) in the airbox was blown and not holding vacuum. I plugged that COV and cleared the code, hasn't returned. You can just suck on the line leading to that and the symposer and you'll know quickly if it holds vacuum. Good luck.

Autobahnschreck

The vacuum pump not only supplies the vacuum for the brake booster, but also for all the COVs.

vanlieremead

I’ve often thought about those resonators. Seems to me that are what I would define as “foo-foo.” They aren’t necessary for the mission of the vehicle. Yet they have these issues and of course add cost.

JimEb

Lots of features on these cars can be classified as frivolous. Time will tell as these cars age and people keep them on the road what aftermarket workarounds will come up. I know that coolant shutoff to block coolant flow in the engine to heat it up faster makes me uncomfortable. That’s just needlessly flirting with the danger of having a roadside overheating problem. That makes my top list of features I may end up defeating.

Gearcruncher

Do you mean the one in the 991.2 that bypasses the pump itself? This fail safes to full cooling when it has no vacuum applied. The COV would have to fail open when no electrical power is applied to cause this issue. You can reach right under the car and pull the vacuum nipple off without jacking the car up as well, which will lead to full cooling.

The bigger failure here is when the whole mechanism fails and allows coolant to leak around and into the mechanism, but you'd need a whole new pump design to work around this, and the newer pumps seem much more robust to this failure.

JimEb

No, talking about the 991.1. Theres an engine coolant shutoff valve in there instead of in the pump like the .2 has. The COV is only half the equation. The COV’s are solenoid valves to switch on/off vacuum. The vacuum then operates a mechanical valve thats actually controls the air, exhaust or coolant flow.

Shutting the cooling off to the engine it should be fail save if the COV fails. It just wouldn’t actuate the mechanical valve and never shut off coolant.

The mechanical valves then must have spring returns on them to return them to normal position when vacuum is turned off. That’s my concern, an aging spring breaks or something and that mechanical valve fails to open back up. Then you are overheated on the side of the road.

Gearcruncher

Gotcha. FYI, The 991.2 has the shutoff valve as well as the switchable coolant pump.
Has anyone actually had the failure you are concerned about? Wouldn't it be easier to just proactively replace the valve at 100K miles than try to bypass it and all the error messages that will cause?