As is traditional for me (don't start), a routine disassembly becomes more complicated as a result of a sheared bolt. Removing the water pump for inspection, it was the centre top bolt - with the thread exposed at the back, so likely corroded in. The good news, the bolt sheared just below the hex, so maximum bolt length to remove the stud. The bad news, the bolts are threaded for their entire length, so I can't get the pump off due to this one sheared bolt.

The bolt seems to be an M8 flanged 30mm. Lrcat talks about M8 but 25mm - I doubt it matters greatly, but I just wanted to be sure I had the right spec, anyone know?

I'm hoping that when I get the water pump off I find that the impeller is on its way out, which will make me feel better. There's definitely some play in the bearing, so that's good.

Actually, can anyone confirm that the bolt holes on the water pump housing are threaded? Perhaps they're not and I just need to pull it nice and straight. I think there's probably just crud holding it on

ok, a lot of wiggling and it came loose, so looking good.

The pump has a metal impeller (good) and is pretty solid, but with some surface pitting, as if someone has taken a hammer and punch to the surface, v odd. I'm in two minds about replacing it. The bearing runs "dry" i think would be the expression ie as it goes round i can hear metal on metal in the bearing, but no grease, there's a little play in the bearing but not much. How do the bearings of a new water pump get lubricated - are they pre-packed/ sealed with a marine grease?

If there's play in it, replace it. As soon as they get a bit of play the seal no longer holds so they leak when turning, the coolant evaporates on the hot metal and all you notice is that the coolant level keeps dropping. The bearing is a sealed for life ball bearing race, the sort with a seal pressed onto both sides.

Roger that...Airtex only, right?

Yup......

I'm thinking the short bolts are M8 x 1.25 and the long are 5/16" with 18 tpi, at any rate the thread pitch seems to be fractionally larger on the long bolts vs the short. The short bolts/ holes take dies/ taps of M8 x1.25, but the M8 die doesn't work on the long bolts, and nor does a 5/16-24. I know LR are good at mixing metric/ imperial, and I suppose the longer bolts go into the (imperial) block. I only really need to know for thread cleaning purposes

Quite possibly, never tried swapping them around. Do you have a 5/16" 18 tpi die to run down the bolts to check?

Nope, but I've ordered one on ebay. Lrcat doesn't list the long bolts, but the other front cover bolts are all listed as 5/16 UNC, so I think my hypothesis is correct

Patient closed up- new thermostat (old one opened a bit slower), water pump ( old bearing was on its way out) and new Ect sensor ( intermotor, not Lucas). Shd improve heat management, is the plan, and keep some heat off the fuel rail when the engine has been turned off.