Hi!I have a 2009 Nissan Navara D40 DCI ! I just finished doing head gasket on my car.The water pump is new,thermostat is new,radiator is clean but the engine coolant temperature raises when going in high rpm but lowers when going about 2000 rpm.The heater in the cabin doesn’t works when coolant temp is low and, when coolant temp is high,it is not as hot as it should be.I can’t understand the problem.Could it be the engine coolant temperature sensor? My car has 250k km.Please help!
Help!
- Thread starter Frensi
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There are two things I think need checking. First is the thermostat, which may not be opening at 85C like it's supposed to. This would reduce the flow through the radiator and prevent both effective cooling and a proper measurement of the coolant temperature.
The other thing I'd check is the viscous hub (after fixing the thermostat, there's little point beforehand). The viscous hub is supposed to fully engage at around 91C. You can test it in two ways. First is to remove it and put it in water and heat the water (using a thermometer to monitor temps). As the temp rises past 91C you should see the central "spring" turn, which engages the clutch inside. If it doesn't, the bimetal element is damaged and the unit should be replaced. If it does work, you need to try turning the two halves against each other. If they turn easily, the clutch is low on silicone oil and can be topped up (I've done this with success).
Testing on the car (if the thermostat is working) is probably easier. Get the engine to normal operating temperature, pull over and pop the bonnet. Watch the fan as someone turns off the engine - the fan should stop with the engine, it shouldn't spin much on its own (if it does, it's faulty). This is an easy check to perform at any time.
The other thing I'd check is the viscous hub (after fixing the thermostat, there's little point beforehand). The viscous hub is supposed to fully engage at around 91C. You can test it in two ways. First is to remove it and put it in water and heat the water (using a thermometer to monitor temps). As the temp rises past 91C you should see the central "spring" turn, which engages the clutch inside. If it doesn't, the bimetal element is damaged and the unit should be replaced. If it does work, you need to try turning the two halves against each other. If they turn easily, the clutch is low on silicone oil and can be topped up (I've done this with success).
Testing on the car (if the thermostat is working) is probably easier. Get the engine to normal operating temperature, pull over and pop the bonnet. Watch the fan as someone turns off the engine - the fan should stop with the engine, it shouldn't spin much on its own (if it does, it's faulty). This is an easy check to perform at any time.
What is viscious hub
Are you talking about the cooling coil?
The viscous hub is the device that attaches to the water pump and holds the fan.
Are you talking about fan clutch?
It goes by many names. In Australia, ours is a large device with fins for heat dissipation and is filled with silicone oil.
I think you are talking about fan clutch
"Fan clutch" is another name for it, yes. When I ordered a replacement, I had to use the term "viscous hub" to get the part that I wanted (both at Nissan and at the aftermarket shop that I bought mine from), so that's the term I prefer to use.
Yes,I understand you but fan clutch is new.I replaced it because i thought that it was the cause that my car gets overheated but the problem of overheating was the head gasket.I replaced the head gasket and then this problem showed up
That leaves the thermostat to check.
Ok thank you very much for your information.It was very thankful.Thanks
fuzzylogic
Member
Are you sure there isn't air trapped in the system?, these can do a similar thing to what you are describing when there is...make sure your heater control is on hot when you're refilling the system so the heater core and piping fill with water too...
Before replacing thermostat( new or tested) , drill one or two 3/4 mm holes in skirt. This will make sure the bimetal spring has water flow and opens thermo. Engines with horizontal thermostats as in early Subarus had this problem which would cause severe overheating. I do it to any thermostat , engine will take only a little longer to reach operating temp, hardly noticeable.
The other thing to do is fill radiator to very top with engine running and chech for bubbles of air coming out. Do it hot and cold. Replacing head gasket does not always cure air being forced into cooling system
The other thing to do is fill radiator to very top with engine running and chech for bubbles of air coming out. Do it hot and cold. Replacing head gasket does not always cure air being forced into cooling system
Sounds like there is no water circulation, either that or water flow is badly restricted. As others have said, an airlock could do this. When you fill it it's a good idea to have the front of car up higher, as high as you can get it so the top of the radiator is the highest point.
How do you know the radiator is clean? The only way you can tell this is via measuring the flow (as radiator places do). What you describe are classic symptoms of a restricted radiator. Not sure it's worth changing a head gasket and leaving the old radiator on, unless it has been cleaned professionally. Then it's usually as cheap to buy a new after market one.
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prob not same problem ,i have had trouble with my heater control valve coroding in other makes of cars, usualy would stay partially open all the time .would make the air con blow warmer air and heater stay on all the time
