Fluid Leak Diagnosis
Leakage InspectionThe transmission has the following parts to prevent external fluid leakage:
- Gaskets
- Lip-type seals
- O-ring seals
- Seal rings
- Seal grommets
- Thread sealant
- Cooler Bypass Valve (CBV) sealing washers
External Sealing-4R100
Leakage at the transmission pan-to-case gasket often can be stopped by tightening the retaining bolts to specification. Refer to Torque Specifications. If necessary, install a new pan-to-case gasket only if gasket is damaged.
If leakage is found by the solenoid body connector, refer to Main Control Valve Body-Accumulator Body Check.
Check the transmission sealing washers on the Cooler Bypass Valve (CBV), fluid filler tube connection at the transmission case. If leakage is found, install a new short fluid inlet tube.
Check the transmission sealing washers on the Cooler Bypass Valve (CBV), fluid lines and fittings between the transmission and the fluid inlet short tube in the radiator tank for looseness, wear or damage. If leakage cannot be stopped by tightening a fluid line tube nut, install new cooler lines. When fluid is found to be leaking between the case and the cooler line fitting, tighten the fitting to maximum specification.
CAUTION: Do not try to stop the fluid leak by increasing the torque beyond specification. This can cause damage to the case threads and/or case fittings.
If the leak continues, install a new cooler line fitting and/or sealing washers on cooler bypass valve and tighten to specification. The same procedure should be followed for fluid leaks between the radiator cooler and cooler line fittings.
Check the engine coolant in the radiator. If transmission fluid is present in the coolant, the transmission fluid cooler in the radiator is leaking.
The transmission fluid cooler can be further checked for leaks by disconnecting the lines from the cooler fittings and applying no more than 345 kPa (50 psi) air pressure to the fittings. Remove the radiator cap to relieve the pressure buildup at the exterior of the fluid cooler tank. If the transmission fluid cooler is leaking, will not hold pressure, or both, install a new transmission fluid cooler in the radiator.
If leakage is found at the manual control lever shaft, install a new seal.
When a converter drain plug leaks, remove the drain plug. Install and tighten a new drain plug to specification. Refer to Torque Specifications.
Check for fluid leaking from the end of the extension housing. Leakage can result from a damaged seal, missing garter spring or worn extension bushing, or damaged speed sensor plug. Install a new seal assembly, bushing, or both, as necessary.
Inspect the line pressure plug for leakage. Make sure it is tightened to specification. Refer to Torque Specifications. If tightening the plug does not stop the leak the case threads and/or plug could be damaged. Remove the plug and inspect the plug and case thread for damage. Repair as necessary.
Check for leakage on or around the Cooler Bypass Valve (CBV). Repair as required.
Fluid Leakage in Torque Converter Area
In diagnosing and correcting fluid leaks in the front pump assembly and torque converter area, use the following procedures to locate the exact cause of the leakage. Leakage at the front of transmission, as evidenced by fluid around the torque converter housing, may have several sources. By careful observation it is possible, in many instances, to pinpoint the source of leak before removing the transmission from the vehicle. The paths which the fluid takes to reach the bottom of the torque converter housing are shown in the illustration. The five steps following correspond with the numbers in the illustration.
1. Fluid leaking by the front pump seal lip will tend to move along the impeller hub and onto the back of the impeller housing. Except in the case of a total seal failure, fluid leakage by the lip of the seal will be deposited on the inside of the torque converter housing only, near the outside diameter of the housing.
2. Fluid leakage by the outside diameter of the front pump seal and front pump body will follow the same path that leaks by the inside diameter of the front pump seal follow.
3. Fluid that leaks by a front pump to case bolt or pump gasket will be deposited on the inside of the torque converter housing only. Fluid will not be deposited on the back of the torque converter.
4. Fluid leakage from the converter drain plug, converter seal weld or converter to flexplate stud weld will appear at the outside diameter of the torque converter, on the back face of the flexplate, and in the converter housing only near the flexplate. Fluid leaks from the torque converter will leave a ring of fluid around the inside of the torque converter housing.
5. NOTE: White facial tissue may aid in determining the color (red is transmission fluid) and source of the leaking fluid.
Engine oil leaks are sometimes incorrectly diagnosed as transmission pump gasket leaks. The following areas of possible leakage should also be checked to determine if engine oil leakage is causing the concern.
- Leakage at the valve cover gasket may allow oil to flow over the torque converter housing or seep down between the torque converter housing and cylinder block causing oil to be present in or at the bottom of the torque converter housing.
- Oil galley plug leaks will allow oil to flow down the rear face of the cylinder block to the bottom of the torque converter housing.
- Leakage at the crankshaft rear oil seal will work back to the flexplate, and then into the torque converter housing.
- Leakage at oil pressure sensor.
Leak Check Test
Determine the cause of the leakage before repair.
1. Remove the fluid level indicator and note the color of the fluid. Original factory fill fluid is dyed red to aid in determining if leakage is from the engine or transmission. The red color should assist in pinpointing the leak.
2. Remove the torque converter housing cover. Clean off any fluid from the top and bottom of the torque converter housing, front of the case, and rear face of the engine and oil pan. Clean the torque converter area by washing with a suitable non-flammable solvent, and blow dry with compressed air.
3. Wash out the torque converter housing, the front of the flexplate and the converter drain plug. The torque converter housing may be washed out using clean solvent and a squirt-type oil can. Blow-dry all washed areas with compressed air.
4. Start and run the engine until the transmission reaches its normal operating temperature. Observe the back of the cylinder block and top of the torque converter housing for evidence of fluid leakage. Raise the vehicle on a hoist and run the engine at fast idle, then at engine idle, occasionally shifting to the OVERDRIVE and REVERSE ranges to increase pressure within the transmission. Observe the front of the flexplate, back of the cylinder block (in as far as possible), and inside the torque converter housing and front of the case. Run the engine until fluid leakage is evident and the probable source of leakage can be determined. When a converter drain plug leaks, remove drain plug and discard. Install a new drain plug and tighten plug to 26 Nm (19 ft. lbs.).
Leak Check Test with Black Light
Oil soluble amine or fluorescent dyes premixed at the rate of 2.5 ml. (1/2 teaspoon) of dye powder to 0.24 L (0.5 pint) of automatic transmission fluid have proven helpful in locating the source of fluid leakage. Such dyes can be used to determine whether an engine fluid or transmission fluid leak is present, or if the fluid in the transmission fluid cooler hose leaks into the engine coolant system. An ultraviolet light must be used to detect the fluorescent dye solution.
Transmission Fluid Cooler
CAUTION: Prior to this test, the in-line service filter (if equipped) will need to be removed. Failure to remove the in-line filter may result in a incorrect reading/diagnosis during this test.
CAUTION: Whenever a transmission has been disassembled to install new parts, the Cooler Bypass Valve (CBV), all transmission fluid coolers (in tank and auxiliary) and transmission fluid cooler lines must be cleaned and backflushed. Use a torque converter/oil cooler clearer.
NOTE: Cleaning and backflushing the transmission fluid cooling system along with following all the normal cleaning and inspection procedures during disassembly and reassembly will keep contaminants from entering the transmission, causing a repeat repair.
When internal wear or damage has occurred in the transmission, metal particles, clutch plate material, or band material may have been carried into the torque converter and transmission fluid cooler. These contaminants are a major cause of recurring transmission troubles and must be removed from the system before the transmission is put back into use.
Transmission Fluid Cooler Flow Test
NOTE: The transmission linkage/cable adjustment, fluid level and line pressure must be within specification before carrying out this test. Refer to Fluid Level Check under Verification of Condition. Refer to Line Pressure Test under Special Testing Procedures.
1. Before carrying out the Transmission Fluid Cooler Flow Test, examine the cooler lines for installation of an in-line transmission fluid filter. If equipped with an in-line fluid filter, remove and discard the in-line fluid filter prior to carrying out the Transmission Fluid Cooler Flow Test and system flushing.
2. Remove the fluid level indicator from the fluid filler tube.
3. Place a funnel in the fluid filler tube.
4. Raise and support the vehicle.
5. Disconnect the cooler return tube (rear fitting) from the transmission Cooler Bypass Valve (CBV).
6. Connect one end of a hose to the cooler return tube and route the other end of the hose up to a point where it can be inserted into the funnel at the fluid filler tube.
7. Remove the supports and lower the vehicle.
8. Insert the end of a hose into the funnel.
9. Start the engine and run at idle with the transmission in the NEUTRAL range.
10. Once a steady flow of fluid (without air bubbles) is observed, remove the hose from the funnel and place the hose in a measuring container for 15 seconds. After 15 seconds place the hose back into the funnel and turn the engine off. Measure the amount of fluid in the container. If adequate flow was observed, approximately 946.24 ml. (32 oz.) will be in the measuring container; the test is now complete.
11. NOTE: If the vehicle was not equipped with a fluid filter, install a fluid filter service kit (XC3Z-7B155-AA) follow the instructions supplied in the kit. If the vehicle was equipped with a fluid filter install a new filter (XC3Z-7B155-AB).
Once an adequate flow has been established, install a new in-line transmission fluid filter or filter kit assembly.
12. Once the fluid filter has been installed check that fluid will flow out of the filter.
13. If adequate flow is not observed, turn off the engine. Disconnect the hose from the cooler return line (transmission inlet).
14. Disconnect the fluid cooler line from the front case fitting and connect the hose to the case fitting (converter out) and repeat Steps 7, 8 and 9.
15. If adequate flow is observed from the transmission, look for a plugged cooler line and/or fluid cooler.
16. If adequate flow is still not observed, repair and/or installation of a new pump and/or torque converter may be required.