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Coolant loss through overflow tube?

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My coolant is dripping through overflow pipe, to prevent a complete loss of coolant, at the moment I bloked the overflow pipe. So I don't lose the coolant. I've also changed the coolant radiator cap, but that did not help... Any other Ideas, suggestion to find, where could be the problem?


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Hi Peter, nice to hear from you. It's been a long time. Hope you're well.

Looks like you're losing quite a bit of fluid when the system pressurizes. 

Did you replace the radiator cap with the correct pressure rating for the V6, which is 108 KPA ? (TRD version is slightly higher @ 127 KPA)

If you have, then the new cap could be faulty.

Best case scenario, it could be either the radiator cap, thermostat or a slight blockage in the radiator.

Worst case, head gasket issue. But, that can be confirmed with a pressure test of the cooling system.

Also, is the overflow bottle filled to the "Cold" fill line when cold and to the "Hot" fill line when hot ?
I'm suspecting you're not having any over heating issues. How long has it been since doing the coolant change ? I do recall you doing a write up about it here but I've lost track.

If I was doing the coolant flush, I'd definitely replace the thermostat. Use Genuine parts too. Don't be tempted by the slightly cheaper options. It's not worth the headache. Pay a bit extra for peace of mind, especially these engines.

Edited by Tony Prodigy
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Hi Tony, yeah it is been sometime since I've been here....  It was crazy times in last few years, getting better now. I had covid two times and been dignosed with acid reflux lately, now trying to find what I can eat😥and what foods causing my heartburn... Getting better now. Thank you for asking.

The fluid comes out quite fast, at the moment I just put a plug on the overflow pipe, in that way all liquid stays in the container. If not, then it takes about 15 min for overflow bottle to get empty.

I've replaced it with a new one with 108 kPa, but nothing changed. The next thing would be to try and changed thermostat. 

I did not change coolant, usually I just top it up when it was getting low.

 Overflow bottle filled to the "Full" line. When it is hot, it could be just a bit more over the line, but not by too much. 

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The supplied video is very helpful. What appears to be happening is that the overflow bottle is being pressurised resulting in the coolant coming out of the overflow pipe. I particularly noticed is that when you removed the radiator cap, there was no out pouring of coolant.

Therefore, I am thinking the worst case scenario of a head gasket issue.

However, I would remove the cap on the overflow bottle and check for any blockages in the cap and pipes connected on the inside of the cap. Next, I would also remove the radiator cap [engine not running] and top up with coolant. Idle engine for a few minutes and observe. I would expect the coolant to rise and overflow without any bubbles.

Hopefully this will confirm the need for a pressure test of the cooling system, or not.

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What is your water temperature gauge indicating ?

Have you verified the cooling fan works ?

The engine is over heating slightly raising the water pressure higher than its threshold. Radiator cap is new so then it's going above 108kpa pushing the spring back for the coolant to escape.

I was also wondering if the water pump impeller could be compromised too. If the water cannot circulate fast enough the Radiator cannot reject the heat and hot water gets recycled. 

Not sure how many kays yours has done, but a head gasket issue is not a common problem in our neck of the woods, and I know you take good care of your car.

If and when you can get the pressure test done and confirm no head gasket issue, I'd do a full service of the cooling system.

Replace the water pump as a preventative measure including the thermostat. 

Fully drain engine block and fill with fresh SSL pink.

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Ok, sure I will ask a local mechanic to do pressure test, as I don't have those tools myself. Also will do coolant drain from the radiator. And then will start getting into water pump and thermostat. Looks like a few things need to be done....

 The temperature gauge  is right in the middle.

 Radiator coolng fan works.

Can try another radiator cap. just not sure if that is going to help, can try to put this one

To replace the water pump, looks like I would need to move engine slightly from the bottom... that would be a tricky part for me...

To take thermostat  out, I would  need to take belt pulley out. Has anyone done a change of thermostat here on the forum?

Edited by krigeroz
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