[yazanhd]

Dear my friends,
I have a problem in my car and I need your help.
I have a NISSAN Pathfinder car model 2003 Automatic Gear with Millage 98,000 KM
The problem in my car is overheating especially at high speeds.
I have changed the rear and front Thermostates and also I changed the Radiator by a brand new one.
But now after I did all these repairs the tempreature is very good at low and medium speeds (up to 100 km/hr) but at continuos high speeds (more than 120 km/hr for at least 10 minutes) the engine's tempreature is starting to increse to the middle and sometime to the high level, but when I decrease the speed the tempreture return to the normal level
The reason could be that the Cylinder Head Gasket has got failure and need replacing, but before I spend money to change the Gasket I must be sure that it is the main reason.
Kindly help me in this issue

 

[rogoman]

There may be air in the coolant system. Your best bet may be to drain down the coolant and start all over again with the filling of the coolant.
Here's how I do it:
1 - drain coolant
2 - open the bleeder screw
3 - optionally jacking up front of car helps to purge air pockets
4 - fill system until coolant starts coming out the bleeder hole
5 - close bleeder screw (not too tight; screw is easy to break off)
6 - continue filling until coolant is at the bottom of the filler neck
7 - do not put cap on the radiator
8 - start motor; as coolant starts to warm up, you may see a few air bubbles
9 - squeeze the hoses by hand to free up possible air pockets
10 - put cap on radiator

 

[yazanhd]

Thank you my friend for your help
In fact I installed the new Radiator before two days and the mechanic who installed it also filled it by coolant and I think he filled it proberly.
By the way, can you tell me what do you mean by the bleeder? There are two holes to fill the radiator, one is at the top of the radiator and the second one is for the reservoir with min and max marks.
I want to add another observation; when the tempretaure rise to maximum I directly park the car and turn off the motor and when I open the hood and open the reservoir screw I see the air bubbles in the coolant reservoir, it seems like it is boiling.
One more observation is that after the engine is getting overhating at high speeds, and after I reduce my speed, the tempreture return to normal, but again it start increasing when I driving at low speeds and making turns or stop the car.

 

[rogoman]

The bleeder should be located where the top hose connects to the head.