Automatic Transaxle - Air Check Procedures: Overview
BULLETIN NO.: 99-T-56ISSUE DATE: November, 1999
GROUP/SEQ. NO.: Transaxle-08
CORPORATION NO.: 99-07-30-026
SUBJECT:
Service Information Regarding Automatic Transaxle Air Checking
Procedures
MODELS AFFECTED:
1991 - 1997 Saturn S-Series vehicles equipped with MP6 or MP7 automatic transaxles
PURPOSE:
When diagnosing a shiftability concern that involves a possible hydraulic leak in a clutch circuit, it may be necessary to perform an air check. This bulletin provides detailed information for use when an air check is required to help in determining the source of any leakage that may exist. The information in this bulletin is contained in the 98-99 and 2000 Automatic Transaxle Service Manuals.
PROCEDURES:
CAUTION:
PROTECT YOURSELF BY WEARING SAFETY GLASSES WHEN PERFORMING THE PROCEDURES IN THIS BULLETIN.
IMPORTANT:
All electrical Diagnostic Trouble Codes (DTCs) should be diagnosed and repaired before diagnosing or verifying proper hydraulic operation with an air check. This is necessary since many electrical DTCs may in turn set DTCs related to hydraulic operation.
For example, DTC 0758 - Transaxle 2nd Gear Actuator Shorted to Voltage, may cause a DTC 0732-Transaxle 2nd Gear-No 2nd Gear to set even though there is nothing wrong with the 2nd clutch hydraulic circuit. Also, when numerous DTCs are set, consult the appropriate year automatic transaxle service manual to determine which DTC to diagnose first. For example, a DTC P0783 may cause a P0732, P0733, and P0741 to set.
Repairing the cause of DTC P0783 will also correct the cause of DTCs P0732, P0733, and P0741.
BEFORE YOU BEGIN:
^ Regulate the shop air to between 552-689 kPa (80-100 psi). Pressure less than 552 kPa (80 psi) or higher than 689 kPa (100 psi) may lead to mis-diagnosis.
^ Inspect rubber tipped nozzle on blow gun to verify that it is in good condition.
CLUTCH AIR CHECK PROCEDURE:
1. Remove the valve body according to procedures in the appropriate model year Automatic Transaxle service manual.
2. Place rubber tipped nozzle in the proper apply port according to illustration. Press firmly to create a good seal between the nozzle and the apply port.
IMPORTANT:
A small amount of air bubbles coming from the lube holes of the clutch housing that is being air checked is normal.
3. Apply air to the hydraulic circuit. Watch and listen for a quick apply of the clutch being checked.
4. After the clutch has been applied, continue to hold the air nozzle tightly against the port to form a seal, and release the trigger on the air nozzle. While the air nozzle is still held tightly against the port, the clutch should hold pressure for approximately 1-2 seconds before slowly releasing.
IMPORTANT:
If no air leak at the clutch can be found, the leak is most likely not a cut/torn clutch piston, but is more likely one of the other potential causes listed below in the section for the appropriate clutch in question.
5. Listen and look for leaks.
PRESSURE PORTS - AIR CHECK
To air check a clutch, apply compressed air to the corresponding pressure port with a rubber nozzle air gun.