Hello everyone, I have a 1985 12a RX7 and the previous owner before me did an ac and air pump delete. My belt that connect to the water pump to the crankshaft is very loose but it looks like he also took out the idler pulley. So my question is, is there anyway to tighten this pulley?

 

Dude, you need to get that fixed right away - it has the potential to lose tension on your water pump and result in overheating, killing your engine.

Proposed fix: get an alternator "Dual Sheave" pulley, along with two new belts for "Crank-WaterPump-Alternator" loop, and run BOTH belts over your two remaining pulleys. This is common for engines that remove air pumps, as the belt tension on the Water Pump is reduced. Doubling-up on that remains is a well-known reliability mod, and Toyota LandCruisers came with double Sheave pulleys and two belts from the factory.

Mazdatrix and RacingBeat both sell the Alternator pulley you need, in underdrive for high-RPM, or I've also heard an alternator pulley for a Dodge minivan will also fit.

 

Also see no fan shroud.

 

I ordered a pulley and a belt off atkins rotary, thanks for the help! I have an oem shroud but it doesn’t fit with my electric one.

 

When you get belts for the double pulley, you want to get two of the same type so they are close to the same length also the same brand. This way one isn't super tight.

 

Also, be aware that cranking up the tension on those belts via the Alternator can put excessive side-loads on your Alternator bearings, Front Eccentric Shaft bearings and Torrington bearings, so apply just enough tension so they don't slip. Having two belts there literally doubles the friction surface area for the driven pulleys from factory design, so you don't need much.

I like to buy both belts at the same time from the same retailer, and try to get the same lot numbers. Toyota makes this easy by zip-tying and selling two belts that were cut off of the roll right next to each other, and his guarantees they'll have the same tension when installed.

 

Thank you for all the knowledge, I thought the stock pulley that goes from crankshaft-water pump-alternator was fine and I just needed a belt for the alternator-water pump, but is this not the case?

 

Given the picture you posted above, this is what you're after. Note that on my setup, there are ONLY 2 belts, and no auxiliary belts in play (*Air Pump, A/C, and Power Steering are disabled). The 2 belts run from the Eccentric (crank) to Water Pump to Alternator, using the double-sheave Alternator pulley you bought. This is a common street and track setup, as it increases water pump belt tension to preserve coolant flow, and reduces drag from other accessories not in use.


Note that whoever monkeyed-up your car has removed the front 2 Eccentric drive pulleys, likely to make way for his plan to reduce cooling efficiency by removing the fan shroud and installing an inferior electric fan...

 

It already has 2 belts. That 3L220 aka "yoohoo" belt goes around just the main pulley and water pump.
Those were all the rage 10+ years ago with people claiming lower temperatures but some found that if they were slightly too small it caused that bearing wear that LongDuck describes.

I think the fan shroud is more important for cooling.