How do you change water pump on a 1985 jaguar XJS V12?

Answer 1

What the Jag manual calls the "cross pipe" is the pipe that connects the two thermostat housings to the water pump inlet, and has the fill cap on top. It is variously called a crossover pipe, a bypass pipe, and several unprintable names. Note that the air balance pipe at the top rear of the engine connecting the two intake manifolds is also called a crossover pipe; try not to get confused. The repair manuals indicate that the crank pulley must be removed to remove the water pump, but the cross pipe can stay where it is. The water pump will come out and go back in without removing the crank pulley. But the pump will not go back on with the crossover pipe connected if the pulley is still on as you have to snake it in over the pulley and the crossover pipe would be a big impediment. So having said that and realizing that you are now going to replace the crossover pipe with the water pump already installed, there is only one way: Lubricate all three of the pipe connections (on the two thermostat housings and the water pump) liberally with 3M water hose sealer. Then lubricate the three matching pipe ends on the crossover pipe with the 3M stuff. Now slip the new, cut to the proper length, hoses onto the crossover pipe. Put two clamps onto each of the three hoses, not tight,

just enough so they don't slide off. The two clamps on the right side should be placed so the screw is on top when installed and slightly back. The clamp on the thermostat housing on the left side should be so that it is on the bottom and slightly back so there is enough room for a screwdriver angled down below the header tank. The two clamps on the water pump hose should be on the left side of the hose slightly back so the screwdriver is angled to the left side of the car. If you set the clamps up this way you will save a lot of grief later on. Now push the hoses up onto the crossover pipe as far as they will go. Next place the center (water pump), hose onto the water pump tilting it and the crossover into position. It will take a little pushing and prying with a screwdriver, but

it's not too bad and the hardest part is done. "Now, pull all the three hoses into approximately the correct position and lightly tighten the clamps. Now make sure the small pipe on the top of the crossover is clear of the big bolt on the block so that the hose to the overflow tank can be put on without being in a position to rub a hole in it. Tighten all six clamps and you are done."