Admins, please sticky this thread and edit/update with information and appropriate AN or NPT adapter part numbers as needed. I'll be taking pictures of each connection as I find them, to aid in identifying each thread pitch

Have you found yourself looking at your beloved FC with a leak in one of the many threaded connections? Or worse yet, stripped the threads on something costly like the A/C condenser lines? We've all been there and found that by searching, this information is oddly scarce from the Second Generation Section. Out of necessity on my 20B conversion, this is why I'm starting a thread specifically about fluid connection fitting thread pitches.

This is by no means a complete list as of yet and will require updating as new information becomes available regarding each fitting pair. And please, use flare wrenches. $10 at Harbor Freight is cheap to have the right tools.

Oil System:
On Shortblock:
Rear Oil Cooler Line port: M18x1.5 Female thread
Front Oil Cooler Line port: M16x1.5 Female thread
Turbo Oil Supply port: M14x1.5 Female thread
Oil Filter Pedestal: M18x1.5 Male thread
Oil Pressure Sender Port: 28-BPST Female thread (Approximately interchangeable with 1/8" NPT)

Not on Shortblock:
Oil Cooler (both ports): M18x1.5 female thread
Turbo Oil Supply:
Turbo Oil Return:


Coolant System:
On Shortblock:
Coolant Temperature Sender port (Back of Water Pump housing): M12x1.5 Female thread
Fan Switch port (Top of Water Pump Housing): M12x1.5 Female thread
Temperature Gauge Unit Sender (Rear Iron)- S4: M8x0.75 Female thread, S5: 1/8" NPT Female thread

Not On Shortblock:
Low Coolant Buzzer port (Top of Radiator): M12x1.5 Female thread
Cold Start Assist Switch port (S4 only, Bottom of Radiator): M12x1.5 female thread
Turbo Coolant Supply:
Turbo Coolant Return:

Power Steering System:
Pump to Rack Send Line:
Send Line to Steering Rack:
Rack to Return Line:
Return Line to Cooling Loop:
Cooling Loop to Pump:

A/C System (S4 SANDEN Compressor):
Compressor line to Condenser (Driver's Side): M18x1.5, Male on Condenser, Female on Compressor line
Drier line to Condenser (Passenger Side): M16x1.5, Male on Condenser, Female on Drier-to-Condenser Short Hardline
Drier to Short Hardline:
Drier to Passenger Side Hardline:
Passenger Side Hardline to Passenger Side Firewall Hardline:
Firewall to Passenger Side Firewall Hardline:
Driver's Side Firewall Hardline to Firewall:
Driver's Side Firewall Hardline to Compressor Line: