Coolant Expansion Tank Replacment SI Disco 3.9 V8

**PhilipA** · 13th May 2007, 08:33 AM

Most of the time, all you want to do is get the water level below the level of the water pump or thermostat so that you can change either.
The Radiator method gets the level low enough even to remove the heads without more than a couple of teaspoons loss.
Another benefit by the way, is that the hose will suck up some of the crop in the bottom of the header. You can see how clean your coolant is.
I think Land Rover carefully placed the block drains on a V8 so that nobody would ever use them without being a one armed small stature Japanese model maker, inside the engine mount for goodness sakes.
Regards Philip A

**waynep** · 13th May 2007, 08:49 AM

Originally Posted by rick130

actually, the cap is a pressure cap, although I can't remember what the release pressure is off the top of my head.

Expansion tank/header tank. Bit like shock absorber/damper. Everyone calls them shock absorbers but they aren't, they are dampers but so what ? Everyone knows what you are talking about.

yes - There was another thread about making sure that the bits inside the black plastic cap are lubricated so it works properly as a pressure relief. I use silicone spray.

**4bee** · 13th May 2007, 09:36 AM

THE TANK is NOT an EXPANSION TANK nor is it a recovery bottle.

Shirley it is both?

Gets hot, the coolant expands into the bottle. Cools down, it recovers it. Same as the S3 bottle.

The cap has ' 5 ' moulded into the vacuum break valve, so that may be the system operating pressure in Metric that Rick mentioned & yes, the tank has 2 valves. 1 x pressure relief & 1 x vacuum break.

Graham, could your "flakiness" have been the spray that LR sprayed everything in the engine bay with prior to it's sea voyage?
My plastic bits, clutch & brake master cylinders inc. the tank, still have this crap flaking off after 11 years.

Rovernaut · 13th May 2007, 10:18 AM

Originally Posted by 4bee

Graham, could your "flakiness" have been the spray that LR sprayed everything in the engine bay with prior to it's sea voyage?
.

I was lead to believe that LR did spray Waxoyl all over the engine bay for corrosion prevention.

**Pavo** · 13th May 2007, 10:23 AM

Just to clear it up - the workshop manual uses both terms:

"1. Remove expansion tank filler cap". This quote is from draining the coolant section.

BUT, in the description of the cooling system it says "supplied from a seperate header tank".

I know, it's not important now, but thought I'd throw it in.

Pete

**jimbo110** · 13th May 2007, 11:25 AM

Originally Posted by Pavo

Just to clear it up - the workshop manual uses both terms:

"1. Remove expansion tank filler cap". This quote is from draining the coolant section.

BUT, in the description of the cooling system it says "supplied from a seperate header tank".

I know, it's not important now, but thought I'd throw it in.

Pete

I would also have thought that both terms were correct.

Originally Posted by Rovernaut

I was lead to believe that LR did spray Waxoyl all over the engine bay for corrosion prevention.

both my disco and 110 had that crap slowly peeling off, the disco was a jap import one too.

I thought the new white ones were supposed to be blow moulded in one piece so that there is no join like the black ones to split? I haven't seen one yet so I cant be sure.

**GrahamH** · 13th May 2007, 01:57 PM

People, I was wrong. I apologise for leading you astray. I had a close look at the tank cap this morning and it has two check valves in the inner part (anyone want to correct me on the terminology there?) oriented in opposition. Presumably they're arranged so that one will admit air when the coolant is sucked into the radiator and one which must be pressure-activated to allow air and, potentially, coolant to escape if the system forces coolant back into the tank at excessive pressure. The cap has an inner cap with four vents formed around it in the outer cap (which also function as the four hand grips on the outer surface). See photo below for an internal view of the cap.

The new tank shows every sign of being moulded in two pieces and glued together to me -I think it would be very hard to create the level indicating post below the filler hole in any other way but I'm no expert in these matters. There's a photo of the new tank front on (same as the old one in my first post) below.

The white powdery stuff around the seam of the old tank looks a lot like the white powdery residue on the inside of the cap so I really think it's dried coolant residue and not any kind of shipping protection, but, without the aid of a chemist, I couldn't be sure.

Thanks for all the comments - wow I never thought this would be so controversial!

(Photos added OK Mon morning)

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