When parked it leaks coolant

2007 NISSAN XTERRA
122,700 MILES • 4.0L • V6 • 2WD • AUTOMATIC
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KAROL JOHNSTON
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When I park the vehicle and turn off the engine the coolant dumps out. I'm not sure, but I think it's dumping from the reservoir tank because the leaked coolant is sort of under that area. Weird but I replaced the reservoir tank cap last week and with my research I found that having the wrong cap can cause overheating issues. I replaced the cap today with a looser fitting one and my vehicle didn't overheat according to my temperature gauge but when I park it still dumps the coolant; and I noticed that there is a faint odor of coolant in the cabin. I replaced both the upper and lower radiators hoses the other day. I did not replace the thermostat because, from what I could see of it anyway, it looked pretty new. (I just bought the SUV via private sale 3 weeks ago.) I also checked the two 'ports' where the transmission cooling hoses(?) go into the radiator and found no evidence of leaking. When filling the radiator and reservoir I have not noticed any leaks there either.
I'm not sure what else to do so any advice is more than welcome.
Thank you very much!
Jun 4, 2020 at 12:09 AM
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ASEMASTER6371
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Good morning,

I would change the thermostat. It looks new does not mean it is working and if it overheated then it needs to be replaced.

https://www.2carpros.com/articles/radiator-pressure-test

https://www.2carpros.com/articles/engine-overheating-or-running-hot

https://www.2carpros.com/articles/replace-thermostat

There is only one cap listed for the car. There is no loose or tight cap. If it does not hold pressure, then the valve in the cap may be bad and yes, it can cause it to overheat.

I attached a picture for you.

Is that the cap you replaced?

Roy
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Jun 4, 2020 at 4:04 AM
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KAROL JOHNSTON
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Thank you for your quick response.
Yes, that is the cap I referred to.
I am going to replace the thermostat in a little bit but I'd like to tell you what happened today. It has left me baffled. Before I read your response, I replaced the 'looser' reservoir tank cap with a tighter (sealing tighter) cap and the Nissan definitely overheated with the temperature gauge going nearly to the red zone before I was able to shut it down. I lost most of the fluid again. I want to be clear that it did not reach the red zone. Once the engine cooled down I refilled the radiator and switched the reservoir cap once again to the 'looser' one. I then drove about 10 minutes to the parts store. Once parked, I lost fluid but only about a quart, if that. I topped off the fluid and drove maybe 10 minutes more to the gas station. I should say I did not use the A/C to the parts store or gas station. Also, the temperature gauge didn't move out of its normal range to either location. After shutting the engine down at the gas station I checked for the usual coolant pool under the SUV - nothing, it was bone dry, no loss of fluid. I then drove back home, without A/C, about 30 minutes, mostly highway speeds, and shut it down at home, again, no coolant loss. I'm super baffled. Could something have been stuck and then freed up? If so, what could it have been - I suppose the most logical could be the thermostat?
Jun 4, 2020 at 6:49 PM
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ASEMASTER6371
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This could be the thermostat that is sticking. Replace it and see if that takes care of it.

https://www.2carpros.com/articles/replace-thermostat

As far as the cap, there is no loose or tight cap. There is only one cap only.

Keep me updated on the results.

Roy
Jun 5, 2020 at 4:46 AM
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ASEMASTER6371
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Did you respond? I got an email but nothing came through.

Roy
Jun 6, 2020 at 3:46 AM
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KAROL JOHNSTON
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I am so sorry I didn't get back you sooner, some things came up demanding my attention.
I replaced the thermostat and since I have had no overheating or any coolant loss..
Thank you very very much for your help!
Jun 8, 2020 at 5:24 PM
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ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
Jun 8, 2020 at 5:28 PM