To be quite honest, pan removal might not be a bad idea, based on your limited description. In order for Auto-Rx to work, oil must be able to circulate throughout the oiling system in your Nissan V-6. There must be at least decent passage for oil to circulate to your crank journals and bearings. There must be free passages in the heads and block for oil that gets pumped up to the top end of the motor to gravity feed back to the sump. Auto-Rx added to oil can only clean where oil is free to travel its intended path.
With respect to your question regarding will Auto-Rx clog your screen and pick up tube to the oil pump that is fairly unlikely. Auto-Rx used in the cleaning and rinse procedure is a relatively slow cleaner and will cease to clean after the power of a 12 ounce bottle is exhausted. It will help maintain that what is dissolved will stay in the oil suspension and be either filtered out or suspended in the oil until the next drain. In any event you are looking at a couple treatments following the heavy sludge application.
Based on your description of the heavy sludge found at the top end of the motor I would proceed as follows if you choose to do so. First you should check out your PCV system, or more commonly known as the crankcase ventilation system on your motor. Change out the PCV valve and make sure that the attached hosing or plumbing is free from obstruction. This in itself may have been the cause of sludging in the first place. By not correcting this first, if needed, you will be forming new sludge at almost the same rate that you are trying to remove it.
Next take a measurement on your dip stick when the motor has sat idle for 15 to 20 minutes. Now start up the motor and run it for 5 minutes driving around the block up to operating temperature. Shut the motor down and check the dipstick level again within 45 seconds to 1 minute. If it is not at the same level then you may have blockage in the return ports. In which case you need either to remove the heads for manual cleaning or replacement heads.
If you have graduated beyond these two test parameters with positive results then you may well be a candidate for the heavy sludge application. I would start with a fresh change of oil and filter, with conventional oil. Add the entire contents of 1 twelve ounce bottle of Auto-Rx to the crankcase. Run approximately 750 miles and change out the oil filter. Run another 750 miles and dump the oil and auto-rx. Now run a fresh change of conventional oil, with no Auto_rx for 750 miles and change out your filter. Run another 750 miles and dump the oil again.
Repeat this process one more time. At this point if oil has been able to flow to all frictional areas of the motor you are on the way to recovery.
At this point you should be able to run a standard treatment of 1 -12 ounce bottle for 3000 miles for ultimate cleaning, followed by a 3000 mile rinse.
I hope this info is helpful to you, please fire back any questions you may have.
