NA Miatas with air conditioning but without power steering are a rare configuration. All trim levels offered air conditioning as an option (special edition and ‘M’ edition cars came with it standard), but only ‘base’ model and ‘R’ package trim came without power steering. It’s unlikely someone payed for the A/C option without just upgrading to the ‘A’ package trim which also included power mirrors. Package option information from the miata.net faq.
The power steering pump usually acts as the tensioner for the accessory belt that also powers the air conditioning condenser, except for these few configurations that use OEM Mazda part (BP01-15-930) which was discontinued long ago.
A possible alternative is the Kia Sephia part (0K201-15-930), also rare and difficult to acquire. Here’s a miataturbo forum post for reference.
For a few months I tried running without the tensioner, I followed Sixshooter’s forum recommendation to buy a smaller belt (4PK0775 or 5040305) and shim some washers behind the AC compressor mounting bolts. This never worked great for me, it was difficult to adjust, and the belt squeak was excessive.
I decided to follow in the footsteps of leakyfaucet and gut a power steering pump.
First order of business was to acquire a crusty old power steering pump off ebay.
This contraption weighs 7.3 lbs (3,340 grams!)
I immediately started with complete disassembly.
I’m not planning to attach power steering lines. The tricky part is to seal off all the openings so that oil can be added to the pump without it leaking everywhere. Disconnecting the lines and running it dry will probably make it overheat and die.
The port on the top is super easy, all that’s needed is a M20-1.5 (fine pitch) drain plug. The one I bought needed the end cut off to be short enough to thread all the way in.
The other threaded port has what appears to be a pressure sensor. I didn’t bother replacing it with a bolt.
The final hose fitting required some custom fabrication. I built a plate with washers and a O-ring to roughly match the fitting of the power steering tube, and used gasket maker to fill the gaps.
The next step is to remove the unnecessary guts of the pump and replace the old rubber seals.
Pay no mind to the increasing quantity of red transmission fluid through the next few photos, I may have launched preemptively with the old dried out seals.
There are two slightly different rubber seal kits for these Miata power steering pumps. I ordered the wrong seal kit the first time and tried to force the seal onto the main pulley shaft.
There is a difficult snap ring that needs to be pried out keeping the shaft of the pump/pulley in the housing. During reassembly the main rotating piece will need to go back in because it spaces the position of the shaft in the housing. The pump fins are removed though.
The gasket seal above failed, and I resorted to creating a thin paper gasket by tracing the mating surfaces.
ATF made sense to me as the right fluid, it’s meant to be spun around without frothing, and isn’t expected to constantly run through a filter like engine oil. On the first attempt, I overfilled the pump and the heat/pressure caused it to leak, I think it should only be filled about half way.
|90-97 Miata power steering pump and hardware (ebay)
|Gates 348422 seal kit
|Gates 348378 seal kit
|Power Steering and AC Belt
This project worked successfully and hasn’t leaked too much in the 1.5 years so far since it was installed. However, I don’t recommend it. The pump is too difficult to make leak-proof and the whole contraption is very heavy. Flyin’ Miata recently announced (2023) they are working on a new idler and auto-tensioner specific to NA and NB Miatas. I am very excited to see what they’ve come up with.
2024 update: Flyin’ Miata belt tensioner installed!