Coolant overflowing 2003 Patrol GU3 3.0L Diesel

I recently purchased this car and had a mechanical inspection report undertaken by MTA. The mechanic was concerned when the coolant appeared to be under pressure when the motor was stone cold so he undertook a C02 test and found no evidence of C02 in the coolant. I contacted the previous owner and she said that sometimes she had to add coolant if she went for a drive up into the Adelaide Hills. The motor runs fine, starts easily and the oil is still a nice reddish colour but I noticed again today after a 20min drive that the coolant was full to the top and overflowing a little. Has anyone else experienced this?

Maybe you need a new OE thermosat?

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Originally Posted by threedogs

Maybe you need a new OE thermosat?

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Worth checking - also the radiator cap as it should allow any pressure buildup to push into the overflow tank. When required the motor should pull the fluid back into the coolong system. It would be unusial for the motor to pressurise the cooland, failed head gasket or cracked head, with no indication of hydrocarbons in the water and no issues with running.

Thanks, I think I will take it for a big drive on Sunday and see how it goes. I need to be sure as the first day my son gets it off the train he has to drive it 1000km from Darwin to Nhulunbuy

That should sort it out

the car is 12 years old . if the radiator cap is not holding enough pressure it might be releasing coolant but not enough to over heat unless pushed hard. radiator caps are cheap so maybe a good place to start . some people overfill the radiator and when the car warms up it spits out some coolant . when the car is cold fill the "overflow bottle" up to the maximum mark . after the next time the car is warmed up , it will suck in coolant if it needs it "when the engine cools down" . if it dosent need any more then the level will stay around the maximum mark "when the engine is cold" . ( the overflow bottle will appear over full when the engine is warm , this is normal ) . hope this helps .

And as I just found out the radiator cap is on the plastic overflow bottle
the cap itself on the radiator is about $18 on Ebay, or try Mudski for one.

I think now that the caryard may have simply over filled the coolant, it was around 5cm above the Max line when I checked it this morning. We took it down to Deep Creek Conservation park today, I wanted to test the 4WD low on the track down to blowhole beach. It was around a 150K round trip at 100kph most of the time, including a long climb out from the beach in 4WD low and when I got home the coolant was still sitting at the same level, a little had overflowed but as stated, it was overfilled in the first place.

Is the cap on the radiator just a 'blank' ie no pressure device underneath?

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Originally Posted by Hallett505

Is the cap on the radiator just a 'blank' ie no pressure device underneath?

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Thats correct but saying that it still needs to seal.

Thanks, and one last newbie question, when cold should the radiator have cooolant right to the top of the tank or does it get sucked in from the plastic reservoir as it warms up?

It goes the other way. Out to the surge tank when the coolant heats up. And back into the radiator when it cools down.

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I have now read some comments on forums suggesting a hair line crack in the overflow bottle that only allows coolant to escape virtually in a steam state can cause this issue, or even a small crack in one of the hoses, they suggested some bars leaks in the first instance and if that doesn't work, replacing the overflow tank and hoses, I will just take it a step at a time, doing the cheaper things first, so I will replace both caps and get some bars leaks on the weekend and try that

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Originally Posted by Hallett505

I have now read some comments on forums suggesting a hair line crack in the overflow bottle that only allows coolant to escape virtually in a steam state can cause this issue, or even a small crack in one of the hoses, they suggested some bars leaks in the first instance and if that doesn't work, replacing the overflow tank and hoses, I will just take it a step at a time, doing the cheaper things first, so I will replace both caps and get some bars leaks on the weekend and try that

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I wouldn't be using bars leaks in it yet. I dont think this will fix your issue. The surge tank on my zd had a hairline crack in it and coolant didn't steam out mate. It just dripped out all over the aux battery tray. You sure the over flow tank, the one with the screw cap on it, is not just over full?

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Replace the hose between radiator & surge tank first. Cheapest & easiest think to try.

They're a large, well largish 1/2 inch id hose cuppa. I doubt it would be this. I would empty the overflow on this, not the top tank with the pressure cap and then take it for a run.

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Thanks everyone, I got two new caps this morning (only cost $20 in total) Once I got the Patrol on level ground I found it had a full radiator of coolant and the overflow is still full so all good! Looks like I was worrying about nothing

A good 3ltr will do that to you ha ha ha
Good to here you got it sorted