View Full Version : water pump woes

05-21-2002, 02:17 AM
Okay mazda guru's...a buddy found a "good deal" on a 12A to replace another burned up motor in his Rx7. Long story short...motor runs great...needs a water pump. We can not find the correct pump. He knows this is not a legal 12A motor and will be running it with the AROSC which only cares about displacement not year/model.

This 12A is rather unique to us, but it's in and runs good:. Here are the obvious differences to a 79-85 12A

5sp trans too large in diameter, (came with a 4sp) The OAL lenth of the 4sp and 5sp is the same +/- 1". Shifter location 4-5" farther forward in 4sp.

Separate distributors for L and T

Starter centered on top of motor

Header bolt pattern closer top to bottom, same side to side.

Water pump housing and front (not rotor) housing different.

We thought this was a '73 12A from an Rx3 but those water pumps form 2 different auto part chains were not correct.

Ideas? Other than the obvious rebuild the correct 12A.

lee graser
05-21-2002, 11:06 AM
Sounds like you do, have the early version of the 12A engine-----early RX-2 and RX-3----the simplest fix may be to, change out the early water pumphousing (what the water pump mounts to)for the later (rx-7 type housing---I think the steel housing (front combustion chamber) will,accept the later type water pump housing-----the later model water pump will of couse bolt to this----Please Post what you find on this----to confirm of refute this interchange theory.

05-21-2002, 12:26 PM
I take it that the waterpump is leaking from the "weep hole"? When you replace the unit, use a product called The Right Stuff. It works wonders in place of a gasket. I've used it on waterpumps, thermostats, and even diff housings. It is black in color and I think it works.

The starter on top verifies that it is an early '72 engine.

Corey L. Clough
ITS RX7 Soon-To-Be
[email protected]

05-21-2002, 08:18 PM

Thanks for the input, unfortunately, we've been down that road. The water pump housings are not interchangeable. The front steel housings are different. About the only thing that's exactly the same is the principle of how the motor works http://Forums.ImprovedTouring.com/it/wink.gif


The weep hole doesn't weep. The friggin shaft barely turns by hand! We noticed this while swapping the pulley setup with the aluminum oversize/undersize RB ones off the wounded motor.

We have tried several auto parts chains, many of which listed the same part number for all 12A's 1972, 1974-1985. We ordered a 73 and found out it's incorrect. A small MA & PA autopart store out in the sticks (traveling through on business) had a picture book (no computer yet) showing a 3rd part number for 12A's, no match there either.

Any idea if non-US spec rotaries had a unique setup?

Speed Raycer
05-21-2002, 09:08 PM
Weren't there rotary powered trucks as well? Maybe they used a different water pump????

Just a thought....

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it's how you build it
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05-21-2002, 11:59 PM
Ok...looking at an old mazda parts guide, it looks like 71-72 rx2 & 72 rx3 has this part number 2329-99-153, 73 rx2 & 73 rx3 had a 1620-99-153, and 74 rx2, 74-78 rx3, rx4, 76-88 cosmo, and 74-77 repu had a N232-99-153A. Which is same as a 79-85 rx7 it looks like.
Oh you might need the gaskets, 2329-15-132a for 1st one, 1620-15-132a for 2nd, and 1757-99-153 for last one.
I dunno if mazda still has these parts available but at least it gives you a year/model breakdown to chase. Good luck!

05-22-2002, 12:03 AM
We have found a store that listed different water pumps for a 72 vs. 73 vs 74-on. We'll see what happens. According to the racing beat catalog/tech manual "all pre 73 motors should use a 73 water pump due to its' higher flow rate....the easiest way to tell the difference is the 72 has a cast iron pulley, the 73 is stamped steel"

Well our mystery motor has a cast iron w/p pulley. I don't know how they expect you to use a 73 w/p on a 72 since the bolt pattern is not the same. Maybe you need to use a 73 w/p with a 73 w/p housing on a 72 motor?

Scott(speed racer) the rotary truck used a 13B...thanks for the thought!

Daryl DeArman
I Love RX7's...they taste like chicken :P

05-22-2002, 04:20 AM
Well, we tried, and we all learned.

Corey L. Clough
ITS RX7 Soon-To-Be
[email protected]

05-23-2002, 02:41 AM
All, I have a new WP in hand. I just need to make all the gaskets, "yes all", the new one came with a WP gasket but that was even different from the new pump, and the newest 12A pump.

Thanks for all the tips and input.

05-23-2002, 05:07 AM
Thanks for the final report. Now we all can sleep better at night knowing that you have solved your problem.

05-24-2002, 07:30 PM

I hope only one of us (DIR) was losing any sleep over this whole deal. I know it is not one of those exciting threads about RR shocks or air bushings. But when you have a problem that you can't solve there is just as much knowledge on this board as opinion..this is a great place to solicit both.

JRX13, thanks for the additional info.