How to use a S4 (1986-1988) aluminum water pump housing on a first gen (1979-1985) 12A

Parts:
1. S4 1986-1988 Water Pump Housing
2. S4 Water Pump and Gasket
3. S4 Water Pump Pulley
4. S4 Air pump bracket – if an air pump is installed
5. 12A Water Pump Neck

Tools:
1. M18x.1.50 Tap
2. M8x1.25 Perma-Coils
3. M8x1.25 Plug
4. High temp sealer

1. Obtain 1986-1988 S4 aluminum water pump housing. This can be turbo or non-turbo. A S5 will NOT work.

2. I used stainless steel bolts/nuts but they are not required. They are expensive but are nice because they do not rust and will not cause issues with the aluminum.

3. Remove the large sensor from the rear.

4. Tapped the large sensor opening to M18x1.50. This will be used for the 12A factory water temp sensor used for the choke. You don’t need an expensive tap. Your only tapping soft aluminum.

5. The location of the rear nipple is where I tapped for a 1/8 NPT water temp sensor. I like electrical gauges for the ease.

Use a pair of pliers and turn the rear nipple to free it up. Do not bend it. It should turn but if it is stuck, don’t worry. The nipple can be cut and drilled out or a small screwdriver placed between the nipple and housing to deform the nipple. Don’t go crazy and take your time.

6. There is one less long water pump engine stud on the 12A vs the S4. To overcome this, I used a Perma-Coil (Heli-Coil) on both ends the water pump housing. The size is M8x.125 to be the same as the stub. The rear Perma-Coil gets a M8x1.25 plug.









I media blasted and powder coated all my parts. This is not required but sure looks nice.



NOTE: If doing this for a 1984-1985 GSL-SE 13B, do not remove the rear nipple.

 

came out nice

 

Looks Good!

 

Thx for the comments. Can't wait to get this thing back into the car. Just have the intake, carb and engine bay to cleanup before it goes back in.

 

any pics of the car that this engine is going on

 

 

This is an awesome thread! I vote for an archive with this one since it's well-written, thought out, has good pictures and will be easy for people to understand

 

What's the benefit of this change? Better flow rate? Parts unavailable for SALE? Just curious, as I know theres probably an extra 5-7lbs on the cast iron pump housinget vs. aluminum.

 

Primarily weight savings.

 

Weight saving is the main reason. I like the ability to more easily add a water temp sensor.

 

Bumping this thread to show a variation in my plugging since I'm not using any sensors at the pump.
I had this '86 13B pump housing from my first rebuild and it's going on a '79 12A iron on my next engine.

The water temp sensor on mine has M12x1.5 threads.
The hose nipple I tapped to M10x1.5.
I use these plugs from McMaster Carr: M10x1.5 , M12x1.5. These plugs have a rubber seal under the head, but still use thread sealant.
The M8x1.25 plug and helicoil are the same.