I lost the alternator belt on my 70 xke last weekend (the car does not have air conditioner) . Appears the alternator froze up. I drove home without the belt nearly 10 miles with no problems ( no overheating and very little loss on the electrical gauge. The other belt did not break so I"m wondering if the other belt from the crank runs the water pump thus no overheating which allowed me to get home??? I’m hearing different opinions on which belt runs the water pump – the belt connected to the alternator or the other belt off the crankshaft???
There are 2 belts. The lower one runs the water pump and the water pump has another pulley and belt that runs the alternator.
Replace all the front belts.
Walter
Thank you! I assumed as much since I drove without the alternator belt and the car did not overheat; I’m assuming the water pump is run by both belts??? .
Ah, carbs. Ya wouldn’t have made it with EFI. It would have killed your battery halfway home.
I must be missing something Ted. Presumably you lifted the hood at some point to conclude a belt had broken? If so, wouldn’t an extra 1.98 seconds added to the same look have answered the question about belt ancillaries and what was still functioning?
OK, maybe 2.43 sec if it was dark, +/- 0.67s? 
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Ted, To answer your question for yourself, consider that belts transmit power. The power needs to come from somewhere. The power that drives the water pump (and anything else like AC; PS and alternator/generator) comes from the crankshaft. The crankshaft runs through the bottom of the engine, front to back, and has a large pulley on the lower front of the engine. The belt receives the power from that lowest pulley and transmits it to the water pump pulley, about half-way up the front of the engine. From the pulley on the front of the water pump, another belt goes upwards and/or side-wards to the alternator to take the power (mechanical) on to the alternator to drive it. I do not intend at all for this to sound patronizing, so my apologies if I am telling you what you already know.)
Ted
These guys should cut you some slack here. When I bought my car new 50 years ago I had no clue how it worked. 500 miles off the dealer lot the car broke down with a bad coil. I purchased the Bentley manual and started learning quick. Back then there was not a forum to refer to and I used the E to get to work.
If car broke down on the way home as it would I had to fix it that evening. I remember my slave cylinder failing on the way home, stopped at Jag dealer and picked up part and installed it in my aprt. garage.
I have friends male and female that have no clue how to fix their British cars, they depend on a mechanic to check out the car a few times a year. The Jag was the first car I ever worked on, take baby steps and/or find a good mechanic.
Glenn
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Tough room tonight.
The belts you need are readily available from O’Reilly’s, AutoZone and such. I can get the Gates numbers off of mine if you need them.
The alternator belt is driven by the waterpump and tensioned by moving the alternator in it bracket.
The waterpump is driven by the crank and that belt is trickier as it is tensioned by a spring loaded ‘idler’ or ‘jockey’ pulley. It needs to be pretty tight or it will squeal but still just big enough that you can get it on. I install it by pulling the springed idler back with a length of wire or rope then positioning the belt over the waterpump, idler and partway on the crank pulley (say from 3:00 to 7:00). The with fingers and tools well clear I bump the starter. If all goes well the belt pops on the pulley and Bob’s your mother’s brother.