Unfortunately, it would be hard to pin down the problem based on the information you've given. When a car is overheating, the cause can be any number of things. Off the top of my head, and this is by no means an exhaustive list:

- Faulty radiator cap (not allowing cooling system to operate at the optimal pressure)
- Faulty cooling fan(s) or in the circuit that operates the cooling fans
- Faulty coolant temperature sensor (this is used by the car's computer to control the cooling fans)
- Faulty thermostat
- Faulty water pump
- Air in the cooling system caused by a leak or by not properly bleeding the air out of the cooling system after it is opened for service/maintenance (e.g. after replacing a thermostat).

How long and how many miles was the car driven before it started overheating again? Have you checked the radiator coolant levels with the engine cold to see if it's full? Do you notice any coolant leaking under the car? Do you smell antifreeze after driving the car?

It's not clear what the dealership meant by "malfunction of the gaskets." Did they say head gaskets? If so, that's an enormous job and will probably cost a couple of thousand dollars to fix in a 2nd generation Murano (...presumably this is what you have since you're posting in this forum). I would be skeptical of what the dealership told you and get a second opinion from a reputable independent shop, particularly if there were no performance issues or noticeable problems before this happened (e.g. loss of power, misfires, white smoke coming from your exhaust etc). There's a kit you can buy from your local auto parts store that can test the coolant by chemically reacting to combustion byproducts that may be present due to a blown head gasket allowing coolant to leak into the cylinders. This could give you an idea of whether or not the dealership is trying to soak you for an expensive repair, but still, if you continue to have overheating problems then you should have it diagnosed by a mechanic. Hopefully, it's something other than a blown head gasket.

BTW...you inquired in another post that you were looking for online parts suppliers because you needed a new front axle and steering rack. Does your car really need all these repairs?

 

First, thanks to take your time for responding. The car was driven for exactly 236 kilometers before it started to overheat again (after thermostat change). About the coolant level, I checked every morning before starting the vehicle if the coolant level in the reservoir tank was at the mark of MAX, and it was at the correct level. So, no worries so far till the day that started to overheat again and the coolant in the reservoir was over the level of MAX. Also, I made sure that there was not any source of leaks under the car. By the way, the radiator was replaced about 6 months ago. Another information to take into account is that the radiator cap was also changed along with the thermostat.


Exactly, they said that the head gaskets might be the problem, but they want to change all the gaskets as well as the oil and water pumps. That's why I feel the same way as you said, skeptical. By the way, it is a Murano 2012. That is what I think too, among those 236 kilometers, the car was totally normal. About that, can a code scanner give information whether the head gasket or other parts (such as you mentioned) are the cause of the overheating.

About that kit, can you provide more detailed information because I already search and not sure if the want that I found are the correct ones.

Also, I attached a photo taken the first time I noticed overheating in the dashboard. It didn't reach the top of the gauge, but, the photo was taken a minute after the other person handle me the car.
Doing an analysis of what could happen, I suspect that if the gauge "did" reach the top (then we can assume a blown head gaskets), but in that minute that passed between the turn off and the turn on again, the needle couldn't decrease if it was at the top of the gauge. So I assume that the needle never reached the top.
All this facts makes me doubt.

Yes, it was me asking for possible site to shop online. As for the steering rack, it needs to be changed cause we replaced the inner tied rods because of a play handling the steering wheel. After a couple of months the play became much notorious so, also the nissan mechanics assume that the steering rack need to be changed. As for the front axle, there is a leak of the outer boot (righ side), so we wanted to do maintenance to all the parts and if we happen to find anyone that are wear out we would need to change it, so that's why I post that thread. But those repairs are off the table for now.

 

Assuming the car ran fine after the thermostat was replaced, under normal conditions, prior to seeing it running high again, I’m going with a coolant sensor or other electrical issue.

Did the dealer scan for codes?

 

About scanning, nissan mechanics did say that the scan showed high temperatures, but just that. Yeah, it's my first time that I am passing through this kind of trouble with vehicles, so I did not ask about a full report of code errors. But, can I still run that scanner?

 

The additional information that the radiator (and cap) were also recently replaced is important. 236 km is not that far to drive before noticing the overheating problem again. You said you checked the coolant reservoir, but have you checked the coolant levels in the radiator when the engine is cold (i.e. remove the radiator cap and inspect the levels)?

Presumably, the dealer tested the other aspects of the cooling system (e.g. cooling fans, temperature sensor etc) before determining the thermostat was the problem, but it could be that the technician didn't spend the time to properly bleed all the air out of the cooling system when they replaced the thermostat. Did you ever try to turn the heat on when the car is at operating temperature? If you notice that the air coming from the vents isn't getting hot or feels cooler than it should be then that's a tell-tale sign of air in the cooling system (trapped in the heater core).

Below is a link to one example of a test kit. Keep in mind that this kit can only determine if a blown head gasket is causing coolant to leak into the combustion chambers (and exhaust gases also leaking into the cooling system).

[ame]https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF/ref=sr_1_1_sspa?ie=UTF8&qid=1541374681&sr=8-1-spons&keywords=head+gasket+tester+kit&psc=1[/ame]

 

If your coolant level is at max when cold its normal for the level to go above the max after driving for a while (heat expansion), that is the purpose of the overflow tank. I would drain the coolant and remove the new thermostat and check it. Put it in boiling water and see if it opens. If its functioning properly, your possibles could be a clogged radiator or failed water pump. With your mileage, unless the car has been abused or misused or driven when its overheating, head gasket leak should not be a concern. If you see bubbling water going into the coolant overflow, you have white smoke coming out of the tailpipe, then that could be it. If not, I would first check the other 2 I mentioned. How quickly does the temp go up now?

 

I think it's important to mention that I live in a country in South america, and here we barely have cold temperatures. Why I mention this? Just for the reason that, along this 6 years of use I never observed that the coolant reservoir was overflown. Just in the two times that I detected the overheating, that happened and the radiator was with less water so I had to fill it with aproximatelly 700-1500 ml of water.
After the last episode of overheating, I didn't use anymore the car, not even tried to turn on.

Is it recomendable to turn on the engine again and try all the advices you guys said? (check the temperatures of the air conditioner and heater, how quickly does the temp go up, see if there is white smoke coming from tailpipe)

 

Just to be clear...you said the car has overheated twice. Is that once before the thermostat was replaced and once after?

 

Exactly.

 

O.K. Given that a few of the cooling system components have already been replaced (i.e. radiator, radiator cap, thermostat), what I would suggest doing is checking the following:

1. That the thermostat is opening and coolant is circulating through the system;
2. That the cooling fans are working;
3. That there is no air still in the cooling system from when the dealership changed the thermostat.

This can all be done at the same time by bleeding the cooling system. Given your location, I'm going to assume you don't have ready access to any specialized automotive equipment so see the links below to some YouTube videos that show how to bleed air out of the cooling system using a simple funnel (...different cars, but the principles are the same). Just be sure that when you start the engine that the heat is on with the temperature at the hottest setting (fan speed at low setting). It may be best to have another person help you--one in the driver's seat to monitor the temperature gauge to make sure the car doesn't overheat and that hot air is coming from the vents on the dashboard when the engine warms up and another person at the engine compartment to add coolant in the radiator as necessary and check that the cooling fans eventually turn on.

The needle on the temperature gauge should go no higher than right in the middle of the low and high readings. I'm sure you're familiar given that you've owned the car for years. If it starts to climb higher than this level like you experienced before then turn the engine off immediately.

If the car doesn't start overheating and the cooling fans cycle on and off a few times during this process (as described in the videos) then turn the engine off and replace the radiator cap and let the engine cool completely (...I suggest overnight). Then remove the radiator cap and check if the fluid level is full--if not, add more coolant and replace the cap. Take the car for a test drive with the heat on low and watch the temperature gauge. If the car doesn't overheat, turn the heat off and continue to drive. If there are no overheating issues then park the car, let the engine cool again and check the radiator levels. Repeat this process until the radiator coolant levels remain full after letting the engine cool down.

If during any of your test drives the car starts to overheat, turn the heat on with the fan on high and find a safe place to park and turn the engine off immediately. The risk with a badly overheated engine is that the head gaskets can get damaged.

On a side note, you should try to use a 50% distilled water/50% antifreeze mixture when filling your radiator.

Hope this helps. Good luck!

 

Greetings to all, I think it would be nice to give some information about what happened between these years. Well, we had to repair the cylinder heads cause apparently high temperatures affected them. The repair went good till now; the car has now 110.000 kilometers and it is starting to burn oil according to my mechanic. Also, he says that he hears some noises that aren't normal coming from the engine suggesting that the engine will fail in a future not that far. Resuming, he advices that I need to make a decision: repair engine, change engine or sell the car. Well, if any of you guys know or have heard a similar situation that have gone in some way good, it would be nice to read and have another point of view.
Thanks