The aux fan has two modes - full tilt as directed by an engine coolant temp sensor and... uhh... less tilt as directed by the high pressure switch on the dryer (the one with pigtails). The fan should come on at low speed when you bridge the pigtail connectors. I'm not sure if the compressor has to be engaged for testing. If the fan doesn't come on, check for continuity across the step down resistor under the ABS pump. I can't imagine how to get to it without pulling the left headlight.

I used a 606 fan and clutch in my 93 SD with a similar engine. It worked. I refilled the SDL and 300D clutches with Toyota fluid. I can't say one is a more effective fix but I don't have a lot of hours on the Toyota fluid.

We are worlds apart in motivation if replacing lifters "looks easy." The catch is that noisy lifters is usually caused by poor oiling from sludge in the head passages. New lifters might help for a while, but... Given my perception of the amount of work, I'd replace all the lifters (I think they're about $30 each). P E H has a different opinion on that I can't comment on the performance benefits of new lifters.

I'd buy whatever 3-way connector looks like it'll work among the HELP! doodads at the auto parts store. I'm not a big fan of disabling vacuum devices as a complete solution since I found a leaky ARV plunger in my SDL. Instead my preferred solution is to physically block the EGR and ARV devices. I don't want to have to restore the amplifiers and vacuum lines and such so I leave them in place for when I complete the diagnostics that force me to temporarily disable those devices Check with Brian Carlton for a neat EGR kit. Also check that your ARV plunger sits squarely over the compressor housing port and that the spring is pressing squarely on the plunger.

Sixto
87 300D