Coolant Expansion Tank Replacment SI Disco 3.9 V8

**GrahamH** · 12th May 2007, 08:24 PM

Last weekend I fitted the Engine Saver alarm to my top hose (thanks Landy Andy and Dave for the discount arrangements) and whilst playing with the coolant system noticed that my coolant expansion tank looked quite sick. It's the original (and black). The photos are below. The front upper edge appears to be blistering - I assume this is due to heat - and there are a couple of chips out of the surface leaving the tank wall much thinner there than it should be. Also there are signs of dried coolant around the glued seam.

I got a new one last week (thanks Doug from Rovparts) and fitted it today. The new one is opaque - what has been described elsewhere on the forum as white. I discussed the longevity of these with a few people and the consensus is that there is no real evidence to suggest they should last any longer than the original black ones. They are plastic, they contain hot water and they're under pressure so it would be unrealistic to think that they won't fail eventually - but since my original has lasted 240,000Km there's no reason to panic replace them on spec. The glue in the new one might be new technology and last a bit longer but, white or black, they shouldn't be regarded as indestructible.

It would be sensible to keep an eye on the tank and if it shows the same signs as mine or anything else which might be suspicious, then replace it before it fails by all means.

A couple of tips which might help if you have to do this yourself and it's the first time you've worked on the cooling system....

As there's no drain tap on the radiator I have to loosen and slip off the bottom hose at the radiator to drop the coolant level for this job. It's a bit of a sod to get the hose wiggled free but it helps a lot if you take off the battery positive lead and put it out of the way (disconnect the earth lead first of course).

When you put hose clamps back on, if you fit them with the tank out of the vehicle, make sure you orient the worm drive screw head so you can get at it with the whole thing assembled (those flexible 1/4" square drive hand drivers with a few selected sockets are bloody marvellous!).

Has anyone fitted a drain tap to their radiator tank or, perhaps in the bottom hose? It would make life a heap easier and if you had to change a hose out in the bush, and it would be much easier to recover the coolant and reuse it if there was a tap with a spigot to put a small hose onto to lead into a bucket. If you have, how about some photos and a description of the device?

Of course while under the vehicle today I've now noticed that the drive-shaft doughnut is showing signs of tiredness, a rubber bush on a muffler hanger has failed and the engine mount rubbers are looking a little the worse for wear. That's what I love about LandRovers - once you own one, you need never have an idle weekend again.

**Stepho_62** · 12th May 2007, 08:40 PM

G'day All

I have to point something out WRT the cooling system on my Defender AND I'm assuming on the disco's and RR variants.

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

It is in fact a FULL PRESSURE Header Tank. Anal Retentave i know but the distinction is IMHO critical.

Make no mistake about it if this tank is leaking, then u have a problem.

If this tank is NOT under pressure then u have a problem.

If the coolant level in this tank is going down then you have a problem.

Unlike a recovery bottle, if this tank is anything except consistent in level, (e.g. in pressure, colour etc) then you potentially have an issue.

Sorry about being anal

Cheers

**PhilipA** · 12th May 2007, 08:49 PM

I got flamed a couple of years ago for saying that!
Agree completely.
An easy and clean way to empty the rad is to get abit of 13MM clear plastic hose and stick it in the filler on the RH of the radiator, and push down to the bottom of the tank.
A quick suck, avoiding getting it in the mouth and you can empty the coolant into a clean bucket and reuse it. With Longlife coolant , this saves the environment and money.. You also know if you have an airlock if it doesn't all fit back in.
This is way I always do it now.
Regards Philip A

**Stepho_62** · 12th May 2007, 09:03 PM

Originally Posted by PhilipA

I got flamed a couple of years ago for saying that!
Agree completely.
An easy and clean way to empty the rad is to get abit of 13MM clear plastic hose and stick it in the filler on the RH of the radiator, and push down to the bottom of the tank.
A quick suck, avoiding getting it in the mouth and you can empty the coolant into a clean bucket and reuse it. With Longlife coolant , this saves the environment and money.. You also know if you have an airlock if it doesn't all fit back in.
This is way I always do it now.
Regards Philip A

See PhillipA. After the flogging over the fueling issue I knew there would be something you and I agree on. WRT the methodology you describe I can neither confirm nor deny but it makes perfect sense. My only comment is BE VERY CAREFUL with Ethylene Glycol as it is a proven carcinogenic. Not to mention it tastes like crap.

Cheers

**97discotdi** · 12th May 2007, 09:12 PM

That is why the RR level switch in the tank is just as good as a probe in the hose. If there is any loss of water it will show up immediately as a drop in tank level.

**GrahamH** · 12th May 2007, 10:02 PM

Good point guys. Actually I was going to refer to it as a header tank but everyone-else on the forum seems to have referred to it as an expansion tank so I thought I was wrong. But I did realise this afternoon that there is no pressure cap and nowhere for the tank to vent. Thus it's a completely closed system and therefore it cannot lose fluid - unless there's a major malfunction. Thanks for clarifying - from a fellow anal-retentive.

I'll bear in mind about the syphoning option for next time, albeit very, very carefully. The longer the hose, the safer it is, I guess.

**chunk** · 12th May 2007, 10:20 PM

isn't there a drain plug on the side of the block for draining out the coolant.

**JohnE** · 12th May 2007, 10:24 PM

Instead of sucking why not get one of those $2 drill powered pumps, quiggers mentioned one on a post ages ago, the alstonville $2 shop sells them, ( not saying you should go there to get one)

saves getting a mouthful.

john

**GrahamH** · 12th May 2007, 10:40 PM

Yes Chunk, there's a drain on each side of the block, but one of them is even worse to get at than the bottom radiator hose - the other's manageable though. They have a 10mm square head so they're difficult to crack open - once they're cracked I can use my ratchet ring spanner. I think they're really there to drain the block after you've drained the radiator but it might work - I hadn't thought of using the accessible one for an overall drain - thanks for the tip.

JohnE, I'll check out one of the car accessory shops or Bunnings next time I'm in one for one of those pumps - Alstonville is a bit of a water bottle trip from Adelaide (but no doubt worth the effort!).

**rick130** · 13th May 2007, 08:08 AM

Originally Posted by GrahamH

But I did realise this afternoon that there is no pressure cap and nowhere for the tank to vent. Thus it's a completely closed system and therefore it cannot lose fluid - unless there's a major malfunction.

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.

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