Ok here is the story, i have bought a spares and repairs project for my sins, i have fixed nearly everything except one issue i just cant get my head around, that bizare cooling system!

For the last three months its been sat in my yard with me working on it as and when i have a spare hour or two, as of yet it hasnt even been driven on the road yet atleast four times in the last few months i have had the "check coolant" warning on the dash, atleast i think thats what it says, lol, another issue right there.. Anyways, i have each time topped up about 1/2-1litre of water everything all fine. Now what my issues are as follows;

1) Where is the mysterious coolant vanishing too? there are no obvious leaks, engine runs fine, no steam, no missfiring when hot passed mot emissions test fine and have done a head gasket test which tested fine

2) It holds alot of pressure in my opinion, once it's been running ten mins or so the coolant pipes are rock solid, and whats more if left for say five days and remove the cap there is still pressure in the system, but this does kinda reinforce my thoughts of there being no leaks.

3) when it's been idling for a while (hour or so) theres all kind of gurgling noises from the header tank and top hose area.

4) i have tried bleeding it all with the bleed screw several times and there is always air in the system, whe the header tank bleed screw is loosened you can hear air bubbling in the top rad hose.

5) the heater is cold at idle, again leave idling for an hour heater is cold. soon as i drive it around my yard i have heat, park up it goes cold!!!

I kinda wish it failed the HG test so i could replace them and then have it fixed but right now i have no idea!

It has a reasonably new water pump on it that the previous owner fitted so i've ruled that out, my next step was google which brought up about different rad caps, i have just been down to my yard to check and would you know it, i have a 140 cap!

So my questions are those of you with cooling system issues and a 140 cap did you have experiences like mine above? & if so did the fitting of a 200 or indeed a 280 cap cure the problems?

Sounds like an airlock to me, think you'll have to take it for a few runs to work it out the system... could also be that the auxiliary pump doesn't work. Pete
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Under what conditions should the aux water pump work?

Ive checked voltage down there and have 12v with ignition on but no sound from pump. So ive just ordered one from ebay.. thanks for that i didnt realise there was a pump there...

Can't promise that will fix it, mine doesn't work either but I don't have your symptoms.... they do like air in the system though and it needs driving to get it out... well mine did.... Pete
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Mine was holding pressure turned out to head gasket how did you check it 1994 softail full stars n stripes custom harley davidson

I've checked it using an exhaust emissions tester with the probe over the expansion tank with the cap of and engine warm raising the revs to 2500 revs. The idea being if co or hc was present in vapour from coolant tank I would get a reading on the screen. Which I didn't it stayed at 0.00

I'm going to order the 200 rad cap aswell and hope the new pump, cap and driving it all come together and it works....

Hay lands, what cap you running?

Filling the system is best done very slowly. I think a long time ago I put my way of filling it on here and it worked well for me. The process of filling from dry is important to get right and having it overfilled at the tank does not equate to easily getting rid of air locks I found.

Another aspect is the thermostat setup makes the coolant run very hot by default, which in turn really pushes up the coolant pressure. I fitted a lower temp stat to mine which I felt greatly improved the engine both in its running, heat and all but stopped a slow coolant leak that I never managed to trace.

I put a thread on here about that too. V8 or else ...

Sorry, didn't see your question, actually haven't a clue what cap I have, I have taken the thermostat off and junked it's innards as they just set it to running too hot, It now runs cooler...

Do have to say my hoses aren't that tight when hot.... I still recon you need to take it for a run, a few hot and cold cycles will get any air out...

Having said that, mine has a newish rad as well.... maybe, if yours has been neglected, it has sludge in the bottom... try the drain cock (If you have one, as my new one doesn't!!) and see how fast the coolant comes out, there's a thread on here somewhere to check the coolant flow...

Do you have an IID tool or similar, how hot is the engine when it's up to temp?? Pete
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James4287 wrote:

Anyways, i have each time topped up about 1/2-1litre of water everything all fine.

There isn't any such device on our old Rangies, mine had neat water in it when I got it and I had no warnings up... Pete
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Mine is a 2003 BMW engined one and as far as I know it has this SG device fitted.

Yer they have an SG probe in the tank. That will give a false check coolant message. The heater controls shluld be set to max hot before draining the coolant system to aid refilling. Someone on.here mentioned using a 2l coke bottle upside down to keep it toppednup and a few good revs to push the air out using the water pump. [img]http://www.fuelly.com/driver/rob2529/range-rover[img/]
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If something can't be fixed with a hammer....... You have yourself an electrical fault!

To be fair BMW can't build an engine that can hold water for any length of time and they are also prone to air locks a lot of the straight 6 engines are a pig to get the air out. As much as I curse our Range Rover the only thing that has ever gone wrong on it are the BMW parts..... Says a lot really

Anyway from the way you describe it, it does sound like there is air in your system. Our Range Rover was doing the same in terms of the coolant light coming on and then having to top up with 1/2 - 1 litre of coolant/water. There is no obvious leak but after lots of poking around and looking between the inlet manifold from the offside towards the back of the engine there was pink orange staining around the valley pan. From underneathe the RR where the gearbox joins the engine there was also staining from coolant which runs down the back of the block and then drips on the floor although its in the same place where the air con drips too.

So this weekend the plan is to replace the Valley Pan cost £338 in parts so its not the end of the world to replace and is very common on the BMW M62 engine just google it you will see what I mean.

To be fair check every single hose etc over and over again like we did as there are a few annoying ones at the back of the block but from what you describe it does sound like an air lock. Good to see another Cornish FFRR on here  2011 4.4 TDV8 Autobiography