Interior heating

This is quite a 'normal' problem that is caused by the failure of one of the water valves. These are located on the firewall, under a cover (some of the clips will probably break when this is removed). This is located between the E-box and the engine. The valves look like this (also shown is the auxiliary pump):



These can be found 2nd-hand (same unit used on the E32 and E34), but it is usually better to get a replacement from BMW. There are only three hoses and fixings to remove, pretty straight-forward but not much room to work in!

What are those valve/pump units like to remove on an 850?
Last week mine turned into captain steamo on the way back around the M25
All I could see was lots of steam from the n/s so assume the pump or valve is at fault?
Doesn't look like theres a lot of room to get at it ?

It's reasonably easy. You will leave some layers of skin behind as a memento but it's not difficult. Mine did the Captain Steamo thing on the M1 a while back, it was really exciting as I was going quite fast and all of the steam was coming out of the back of the car. In my case the "nipple" on the water pump (bottom right hand side of Tim's pic) had snapped off, I think this is a pretty common failure point. As Tim suggests, I'd avoid eBay on this one as they are all going to be old and probably let go some time soon.

Cheers
Had time to give it a go today
I shoulda removed the heater duct 1st, as with that out the way the pipes was easy to get at
Easier job then expected to remove
All I need now is to find a good one and refit lol

Good work!