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Greyman110



Member Since: 29 Sep 2017
Location: London
Posts: 323

United Kingdom 
Coolant level when hot
I’m trying to work out what’s normal and what isn’t.

What level should the coolant be at in the tank when the car is hot?

On mine it’s sitting above the where it say ‘cold level’ on the tank .

Normal or not?

Thanks.
Post #852174 26th Aug 2020 6:09pm
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Pacha



Member Since: 23 Feb 2020
Location: North Yorkshire
Posts: 772

United Kingdom 2008 Defender 90 Puma 2.4 HT Stornoway Grey
You only need to check the level when cold - as long as it is on or a couple of mm above the 'cold level' then all is good. Rgds.

Chris
Post #852182 26th Aug 2020 6:59pm
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Ianh



Member Since: 17 Sep 2018
Location: Essex
Posts: 1778

United Kingdom 
As pacha said. Coolant level is checked when cold and vehicle on level surface.

The rest is fluid dynamics. Water, and coolant is mostly water, expands when hot, so will be at a higher level when hot as compared to when cold. And that is what you are observing when you see it above the cold level on the tank.

Ps. Water is one of the few things that expands when hot, yet also expands when very cold (ice). Metails etc don’t behave that way, they expand when hot but shrink when cold. That H2O is cleaver stuff Very Happy
Post #852201 26th Aug 2020 7:47pm
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Greyman110



Member Since: 29 Sep 2017
Location: London
Posts: 323

United Kingdom 
Thanks.

I've never paid any attention to this in the past because as long as its at the cold level then its fine. I'm trying to troubleshoot an issue with the car getting hot and the cap hissing so just wanted to make sure that its normal for the tank to get that full and that its not cause by some kind of airlock or dodgy pressure.
Post #852206 26th Aug 2020 7:56pm
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Pacha



Member Since: 23 Feb 2020
Location: North Yorkshire
Posts: 772

United Kingdom 2008 Defender 90 Puma 2.4 HT Stornoway Grey
Sounds like the cap needs replacing. Rgds.

Chris
Post #852222 26th Aug 2020 8:53pm
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Greyman110



Member Since: 29 Sep 2017
Location: London
Posts: 323

United Kingdom 
It was new on today! Rolling Eyes
Post #852225 26th Aug 2020 8:56pm
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Pacha



Member Since: 23 Feb 2020
Location: North Yorkshire
Posts: 772

United Kingdom 2008 Defender 90 Puma 2.4 HT Stornoway Grey
Ah. Rgds.

Chris
Post #852233 26th Aug 2020 9:08pm
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ozzie1989



Member Since: 25 Feb 2009
Location: Wales
Posts: 282

Wales 2010 Defender 110 Puma 2.4 USW Bonatti Grey
The cap has a pressure relief valve in it, so if the system is over pressure it releases it in a fairly controlled fashion rather than blowing holes in the tank or hoses etc. where possible.

If you bought a cheap cap I'd replace it, tried that myself and it's pot luck if they actually do the job properly. Yours could be faulty.

The alternative is that something is pressurising the system over normal levels, e.g. exhaust gases getting into coolant via say a head gasket leak.

May be worth trying:

- A new(er) cap
- Checking you have the right amount of antifreeze to water ratio*
- Having your coolant system pressure tested

* Antifreeze also raises the boiling point of the water and as such little or no antifreeze can cause issues when the engine gets hot. Now: 2010 2.4 TDCi 110 Utility Wagon
Then: 2004 2.5 TD5 90 Hard Top (X-Tech Edition)
Post #852281 26th Aug 2020 10:55pm
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andydef90



Member Since: 09 Feb 2015
Location: yorkshire
Posts: 617

United Kingdom 2014 Defender 90 Puma 2.2 HT Corris Grey
its a puma thing mine is on its third cap as said the cap as a relief valve on it so the hissing is ok . I'm thinking about changing the expansion tank tor a aluminium one . is your new cap a original one only asking as the cheap ones on are going to be poor copies and tent not to have the valve . also are you losing any coolant at all
Post #852297 27th Aug 2020 8:37am
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 16892

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
Make sure that you don't have air in the system at the high point, there is a bleed valve on the heater valve for this purpose.
Post #852302 27th Aug 2020 9:20am
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Naks



Member Since: 27 Jan 2009
Location: Stellenbosch, ZA
Posts: 2596

South Africa 2010 Defender 90 Puma 2.4 SW Alpine White
Treat the coolant cap as a service item, I replace mine every year, as it will inevitably leak Thumbs Up --
2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear
2015 Range Rover Sport V8 Supercharged



Defender Puma Workshop Manual: https://bit.ly/2zZ1en9
Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO
Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ
Post #852322 27th Aug 2020 10:48am
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Ianh



Member Since: 17 Sep 2018
Location: Essex
Posts: 1778

United Kingdom 
blackwolf wrote:
Make sure that you don't have air in the system at the high point, there is a bleed valve on the heater valve for this purpose.
.

If the engine is getting over hot, and the cap has been venting a little coolant I read in another thread that this can generate air in the system, so another good tip from Blackwolf .

Also here is a potential alternative to a standard landrover cap. https://www.defender2.net/forum/post710243.html#710243
and here in more detail
https://www.defender2.net/forum/topic44373...=iveco+cap
Post #852376 27th Aug 2020 2:31pm
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