GU Patrol Coolant Reservoir level

Submitted: Sunday, Apr 15, 2012 at 13:37
ThreadID: 94908 Views:13112 Replies:3 FollowUps:3
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I have a 2009 GU with the ZD30. Apart from the radiator, there are 2 coolant reservoirs - upper and lower. The upper one has a pressure cap, the lower one just a plastic cap and marks for the Min and Max level. This is the one used to keep the fluid topped up - I assume. There are no such marks that I can see on the upper reservoir. The upper reservoir has been pretty much empty lately - even though there has been normal levels in the lower tank and the radiator itself is also full.

Should the upper tank be full?

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Reply By: Member - Troll 81 (QLD) - Sunday, Apr 15, 2012 at 17:26

Sunday, Apr 15, 2012 at 17:26
My understanding is that the empty one should be empty, it's used when you run hot and boil the coolant will flow into the overflow bottle.
AnswerID: 483200

Follow Up By: DaveA - Sunday, Apr 15, 2012 at 17:31

Sunday, Apr 15, 2012 at 17:31
Thanks for that. Since posting, I have also had another look and noticed that the lower reservoir (with min amd max marls) also has a little overflow outlet right at the top just under the filler cap. It is open. Is this normal or should it have some sort of "cap" on it?

Thanks again.
FollowupID: 758444

Reply By: Ross M - Sunday, Apr 15, 2012 at 22:06

Sunday, Apr 15, 2012 at 22:06
G'day DaveA

The reservoir with the pressure cap on it should be full at all times.

The one which is fed from the pipe just under the pressure cap, is the overflow bottle and is vented to atmosphere. It should be above low when cold and possibly not above high when hot.

When the engine is cold, so is the water, and the water volume is the smallest. If working properly, the system will expel some water from the pressurized tank to the overflow bottle as the volume of the water increases with heat.
Once warmed up it should run al like this. At this time the overflow bottle will be at its highest level.
As the engine cools, some water is drawn back from the overflow and into the sealed section of the cooling system.
It does all this normally everyitme you run it.
If the sealed bottle with the pressure cap is not full all the time then something is wrong with your cooling system or there is insufficient water/coolant in the sytem for it to operate normally.

The sealed bottle, the one with the pressure cap, will probably have no level indicator as it should always remain full while the system is hot or cold.

Ross M
AnswerID: 483228

Follow Up By: DaveA - Monday, Apr 16, 2012 at 18:26

Monday, Apr 16, 2012 at 18:26
Thanks - exactly the sort of detail I need. I'll sort it out next time it's cold.


FollowupID: 758544

Reply By: Grumpy old fart - Saturday, Apr 21, 2012 at 17:14

Saturday, Apr 21, 2012 at 17:14
If I was you DaveA I would get rid of the Nissan and get a trusty Rodeo !!!

AnswerID: 483763

Follow Up By: DaveA - Saturday, Apr 21, 2012 at 18:06

Saturday, Apr 21, 2012 at 18:06
Yes - might have to give that some thought. OK finished thinking. Back to a real 4WD :-)
FollowupID: 759038

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