So my 300tdi Discovery kept overheating and ejecting coolant from the expansion tank. Curiously the coolant was only tepid. I suspected but ruled out head gasket,thermostat and water pump impeller failure.

I think I may have found the source of my problem.

When going through each of the hoses to check for sediment etc I removed the expansion tank to flush it out too. Once removed I heard a rattle from inside. It was a pebble!!!!!

So I think it had been blocking the return side of the cooling circuit when it sat like a bath plug partially covering the outlet. Hot water from the thermostat housing overflow would have been coming in at a quicker rate than the return side, filling up the tank to overflowing.

I need to get a new water pump gasket and rebuild everything tomorrow to check out my theory.

good luck I’ve got a cylinder head and injectors to replace on one of mine tomorrow 😉

good luck I’ve got a cylinder head and injectors to replace on one of mine tomorrow

Do you know the elastic band trick with rearmost two ‘head bolts?

Well, I think I found the source of problem, but not before the head gasket blew. At least I now know how everything bolts together this time and without the pebble the repair should last a little longer.

Weren’t you asking about purchasing/transporting a new engine a few days ago? Sound’s like you dodged a bullet, ‘cos presumably the new one would have suffered the same failure without removing the offending stone.

Yep, I had to get to the bottom of the problem. I’ll get the head off, if its toast I might just get a new one, they are only a couple of hundred quid on ebay rather than skimming the old one.

how did a pebble get in there?

how did a pebble get in there?

Nae idea. When I last changed the gasket I filled it from antifreeze containers from the sink.

I’ve only had the Land Rover a few months and I think the gasket had just been changed just before I bought it. Perhaps someone filled it with a watering can that kids had put pebbles in?

LOL – I’m currently wrestling with constant gurgling from my TD5, had a new head on last year according to service history, it’s driving me nuts – I can now bleed these things with my eyes shut!

So I got the head skimmed in town for a very reasonable £40. New gasket £15 – a couple of hours in the shed and I now have a fully functioning cooling system with a furnace for a heater.