Callas Rennsport CR Tools Manometer instructions

CR Tools AOS Analysis Tool

Generally speaking, all Porsches 1978 and newer are equipped with a Positive Crankcase Ventilation (PCV) emissions device, meaning the engine crankcase has a vacuum source supplied to it from the intake manifold. This collects and burns residual combustion by-products known as “blow-by.”

On the Mezger-based flat‑6 air‑cooled engines built from 1964–1998, these dry‑sump oiling systems normally do not require an Air Oil Separator (AOS). However, all water‑cooled naturally aspirated 986, 997, and 991 sports cars equipped with the M96, M97, and MA1 engines (1997–2017) require this tool for AOS diagnostics (except GT2, GT3, and Turbo models). The AOS functions as a vacuum‑oil separator by applying a small vacuum to the crankcase. When the AOS fails, crankcase vacuum can rise excessively, drawing oil into the intake and causing exhaust smoke that can foul spark plugs, contaminate sensors and catalytic converters, and damage engine management components.

Misfire Faults

Early stages of AOS failure can produce very high vacuum values (up to –40.0″ H₂O) during cold startup—often without visible smoke—leading to a lean running condition that may trigger misfire faults and illuminate the check engine light without other symptoms.

Normal Sports-Car AOS Readings

The only way to definitively test the AOS is to measure crankcase vacuum with a slack-tube tester or manometer (an ultrasensitive vacuum gauge). On 9X6 and 9X7 Porsche engines, nominal vacuum is –4.0″ to –6.0″ H₂O; a failing AOS can push vacuum to –10.0″ to –15.0″ H₂O or worse.

Porsche Sports Car AOS Data – What Do the Readings Mean?

Low Vacuum Reading: Caused by leaks such as missing oil cap or O‑ring, cracked spark plug tubes, disconnected dipstick tube, or torn AOS boot/oil filler tube.
Nominal Vacuum Reading:
- M96 & M97 engines: –4.0″ to –6.0″ H₂O
- MA1 engines: –14.0″ to –16.0″ H₂O
High Vacuum Reading: Indicates faulty AOS or internal sludge; may cause vacuum leaks at seals, silent CEL, or engine honking from reverse flow.

Porsche AOS Data – All Models and Legend

Panamera

2010–2011: –6″ H₂O
2012: –6″ or –40″ H₂O
2013–2017 (Non‑Hybrid): –40″ H₂O

Macan

2014–2016: –40″ H₂O

Cayenne (Non‑Hybrid or Diesel)

2004–2011: –6″ H₂O
2012: –6″ or –40″ H₂O
2013–2017: –40″ H₂O

Legend for Sports Cars

M96: 1997–2004 Boxster, 1999–2004 911

M97: 2005–2008 Boxster, 2005–2008 911

MA1: 2009–2016 911, 2009–2016 Boxster

Please note: Try not to leave the oil cap off for too long with the engine running, and do not overtighten the cap. When running the car for extended periods, avoid parking over grass due to fire hazard.

Technical assistance: [email protected]

Phone calls not accepted.

Operation

Power: Press the ON/OFF button to turn the meter on or off. The meter performs a self-test on power-up and defaults to the last used setting.
Zero Adjust & Offset: With no pressure applied, press and hold the HOLD button for 2 seconds to zero the meter. Press the DIF button during measurement to display the difference from the last zero setting.
Data Hold: Press the HOLD button briefly to freeze the displayed value; press again to resume live readings.
Record: Press REC to cycle through MAX, MIN, and AVG modes, showing the highest, lowest, or average readings with relative timestamps.