Disco 2 No heaters, overheating and coolent backing up into the expansion tank

Well, this has been a fun day! Went on a trip out for a walk around Arnside (about 40 miles from our house and about 2/3'rs of the way there the heaters went cold and the engine temp began to shoot up and we began to lose engine power.
I pulled over into a layby and popped the bonnet to see that the expansion tank was full to overflowing. Once the excess coolant had drained away (seemed too be a lot of air in there too) the heaters kicked back in and the temp went back to normal. Also to note was the top hose was warm/hot yet the contents of the expansion tank were quite cool in comparison.
By the time we got back to Arnside we were back at the same problem. Thankfully we had some water in the car and could top up the missing coolant.
This happened twice on the way back too (we had to follow the A6 all the way home).
Two other weird 'symptoms' we noticed are a rapid 'pock-pock-pock' noise coming from somewhere in the front left of the engine and a rattling noise like a small stone rolling from left to right (pass to drv) in the top of the dash shortly before the heaters kick back in (when the temp is near the red).
Now, this could be caused by a replacement water pump I had fitted last month (QH part) which may have left an air lock in the system when the garage refilled the system and I doubt it is the cylinder head as I had a new gasket, skim and pressure test in last summer.
I'll get it in the garage next week as I'm pretty sure the pump they fitted is not behaving and will be be covered by them (and they can do some free fault finding whilst they diagnose the problem!).
Any other thoughts as to what this problem could be would be greatly received!

Your symptoms are very similar to those I had with a previous vehicle (completely different engine, VW1.9tdi). Mine was a cracked head letting combustion gas into the the coolant and pressurising it.

level in expansion tank dosent indicate the level in the engine you need to remove bleed screw on top hos with engine off to do that,youve had a serious lack of coolant hence cold heater and poor running etc,it wont be an airlock left over but a recent loss or pressurisation issue ie head gasket

I shall be very unhappy if it's a head gasket issue especially after having it done about 7 months back

Could even be the valve in the expansion tank cap, I've had that before now if it fails it allows the water to boil off and overheat.

Now it's light I went and had a good look around and refilled any missing coolant and did some panicked checking for coolant in the oil etc.
One of the very last things I checked was (and this was just an afterthought) the fuses.
Yup, I'd blown the cooling system fan fuse. The problems we had yesterday occurred once we'd left the M6 and went onto the A6 and slowed down.
Hopefully now it's replaced all will be well again so I'm just about to take it for a run out.

Bugger, blown the fuse again, still overheats and puts coolant into the expansion tank. I have noticed though that the tank cap does not vent (allows coolant to escape via the overflow pipe) until it's been turned quite a bit.

Are we talking td5 here?

I think you have a bigger issue than a fan tbh.

Yup 2001 Disco 2 TD5.

Cap should be vented on a td5
It's designed to open when pressure exceeds system design, I'd fit a new cap bleed system properly then try it, also td5 cooling fan is viscous not electric, I think the one your referring to could be the air con fan

The aircon fan should kick in when the temperature exceeds a set value (110 degrees IIRC). But they're usually seized hence the blown fuse.

It does look as though you may have a more serious problem, although my Td5 lost some coolant a year ago (due to an undetected leak) and the red light came on. Let it cool down, added coolant and it's been OK since - another 8,000 miles or so - so don't worry - yet........

I'll order a new cap as a 15 year old one will probably be a bit past it anyhow and see what the garage say next week.
TBH, it could be one of a dozen things both cheap and not so cheap to rectify.

Well, Got a new cap and had a new thermostat fitted as the cheapest diagnostic course of action.
No joy. It's still overheating and pressurising. Strangely only of fast journeys i.e. motorways 2500+rpm, on a\b roads it remains fine.
Looks like I'll have to dig deep with this one. May just cut my losses and get a refurb head.
Anyone recommend a company that delivers?

DosBox said:

Well, Got a new cap and had a new thermostat fitted as the cheapest diagnostic course of action.
No joy. It's still overheating and pressurising. Strangely only of fast journeys i.e. motorways 2500+rpm, on a\b roads it remains fine.
Looks like I'll have to dig deep with this one. May just cut my losses and get a refurb head.
Anyone recommend a company that delivers?

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i think id look at gasket before i bought a head

The same guy who is looking into this for me did the head gasket last year we also had the CH pressure tested and skimmed.
If it is the gasket it will be covered under warranty but if it's deeper than that then I'm going to have to brace myself!
I can afford it, I'd just rather not!

DosBox said:

The same guy who is looking into this for me dod the head gasket last year we also had the CH pressure tested and skimmed.
If it is the gasket it will be covered under warranty but if it's deeper than that then I'm going to have to brace myself!
I can afford it, I'd just rather not!

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an over heated head if it had previously been hot enough can very likely bend again, i would warranty that

Pm sent regarding head !

It look slike I may have found the problem. It's in next week to have the gasket checked.
I use Millers Diesel Power EcoMax additive occasionally (well, the bottle does fill up quite a few tanks!) and apparently (after looking around) there are issues with some fuels additives and some types of gasket sealent in that it effectivly eats it.
Whilst I don't rag my Disco I do use this stuff every other fill up and there is a possibility that this may cause what I'm seeing.
My gasket change last year at 125k was most likely time due but this time may be for reasons I had not forseen.
I shall keep you all posted.

DosBox said:

It look slike I may have found the problem. It's in next week to have the gasket checked....
I shall keep you all posted.

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How did you get on?