When a converter is considered to be reusable, the converter and cooler lines must be serviced by flushing out the old fluid. This will ensure that a freshly overhauled transmission will not be contaminated by the original fluid.
If flushing equipment is not available, use a suction gun or electric motor pump equipment used with the lockup bench tester to evacuate the converter fluid (for converters without drain plugs).
Converters without drain plugs can be drilled with a 1/8-in (3.57-mm) hole between the top end of the impeller fin dimples.
Tip the converter when drilling, and drill from the bottom. This will allow the metal chips to wash away as the hole is made and fluid leaks out.
For converters without fin dimples, never drill an air bleed hole anywhere into the converter.
Once the converter is completely drained, it is ready for mounting in a converter flusher. This piece of equipment slowly rotates the converter while a cleaning solvent is cycled in and out of the converter to purge the old oil and contaminants. The machine automatically adds timed blasts of compressed air to the solvent for agitation as it enters the converter.
- Ideally, the flushing machine screens the debris flushed from the converter so the technician can determine the origin and extent of contamination.
- For thorough cleaning, the machine flushing operation should continue for a minimum of twenty minutes.
- After flushing, drain the cleaning solvent, fill the converter with automatic transmission fluid (ATF), and drain again. This removes the residual solvent and avoids possible internal seal damage in the converter-transmission.
Don't attempt to clean converters with solvent and hand agitation. This method never adequately flushes the trapped converter materials and usually makes the situation worse.
Where the drain hole was drilled, coat a 1/8-in (3.57-mm) closed-end pop rivet with loctite and install. this is a special rivet that can be purchased at jobber outlets.
A 1/4-in pipe plug coated with Loctite can also be used to close a drain hole. The pipe plug can be removed and replaced when performing future draining procedures. A drawback must be noted before drilling a larger-sized hole. In doing so, the possibility of nicking an impeller fin and introducing metal chips into the converter is increased.
A mig welder also can be used to close a drain hole and produces excellent results.
As a final reliability check, the converter should be tested for leakage.