Is This Sort Of Overheat?

[jbjb]

I wrote a proper bleed procedure somewhere on G35, just search my name.

Also get a radiator cap with temp control gauge on it, you can go check yourself.

Thanks, Nate. Radiator cap with thermo gauge like this with 16psi?

[jbjb]

I am leaving mine as is as I am pretty certain its normal. I think I saw a similar thread on here that said the same thing. I had mine serviced and no problems were found. Also my needle is just below the middle, yours is above middle.

Ok, at least you are innocent now

[zei20l]

Also get a radiator cap with temp control gauge on it, you can go check yourself.

except that water temp at the radiator isnt water temp in the engine which is where you really need it

[jbjb]

except that water temp at the radiator isnt water temp in the engine which is where you really need it

Oh..right..nearly de-focus now. Should check air first. Step by step. Will feedback to you guys all then.

Found this link has more detail of how to bleed your coolling system though it is for BMW

I also found Nate's recommended linkI also found Nate's recommended link (http://infinitihelp.com/diy/gcoupe/projects/infiniti_g35_coolant_service_procedure.htm)

which is really helpful to locate the air release screw, thanks!

Edited November 30, 2011 by jbjb

[sonicii]

except that water temp at the radiator isnt water temp in the engine which is where you really need it

True.. and if you are low on water, this gauge will probably read low too.

[zei20l]

True.. and if you are low on water, this gauge will probably read low too.

nope, it will probably read too high as the fluid can boil with air in the system.......

[sonicii]

Yes, but when you lose coolant, the first place you will get air is in the top of the radiator as most cars are designed for this to the be the highest point. If the boiling coolant doesn't contact the radiator cap, the gauge in the cap will read low. Just like the normal coolant temp sensor will read low when you lose enough coolant for it to be surrounded with air instead of cooant.

[zei20l]

no, it will read high if there is no water. water wont boil under pressure in a sealed environment. like a cooling system in a car!

put some air in there and the water WILL boil and show a higher temp due to the steam being hotter than the water.........

[sonicii]

Um.. nope.. water under pressure boils at a higher temperature, the pressure doesn't keep the water cooler, it increses it's boiling temperature, so you could have steam at 101deg C in an open system, and it will be cooler than water at 110 deg C in a pressurised system.

Add to that.. steam is not necessilary hotter than the water it just boiled off, unless there is an additional energy source to heat the steam directly.

Also, steam doesn't conduct heat anywhere near as well as water, so even if there is steam at 101degC surrounding the temp gauge, it is still likely to read below that temp. if you have ever had a cooling system leak on a car, you will find the temp gauge drops once the coolant falls below the temp sensor, even though the engine is overheating and boiling the remaining coolant.

[zei20l]

so when there is no water in the cooling system, what happens to the temperature gauge??

it goes up, not down.

[sonicii]

Nope. A coolant temp gauge goes down.. if you have a head temp sensor, that will go up as the engine overheats.

[zei20l]

lol ok then good luck driving your car

[Daleo]

Um.. nope.. water under pressure boils at a higher temperature, the pressure doesn't keep the water cooler, it increses it's boiling temperature, so you could have steam at 101deg C in an open system, and it will be cooler than water at 110 deg C in a pressurised system.

Add to that.. steam is not necessilary hotter than the water it just boiled off, unless there is an additional energy source to heat the steam directly.

Also, steam doesn't conduct heat anywhere near as well as water, so even if there is steam at 101degC surrounding the temp gauge, it is still likely to read below that temp. if you have ever had a cooling system leak on a car, you will find the temp gauge drops once the coolant falls below the temp sensor, even though the engine is overheating and boiling the remaining coolant.

What you said about the water temp reading lower once there's no water in the system is correct; it's a water temp gauge, not an air temp gauge.

This is semantics.

The thing is; the object of pressurising the cooling system is to avoid boiling the water. But there cannot be any air trapped in the system for this to occur.

Running your car at 100deg with a cooling system full of boiling water is an undesirable condition, as the expanding air (steam) forces water out of the cooling system when it boils.

Water turning to steam can expand to 1000 times its original volume.

Eventually the expanding steam will force virtually all of the water out of the system. The water pump cannot pump air. Once there is no water in the system you have no ability to transfer heat out of the engine in any measurably useful amount.

This is BAD.

Having water at 110deg with no expanding air bubbles (also forcing the water pump to cavitate) ensures all the water stays in the cooling system. This is where you want it. In addition, the coolant in the cooling system pushes the boiling point of the pressurised water up to around 120 deg.

Pressurising the system and adding coolant are just ways of providing extra headroom to the system. It works.

Edited December 2, 2011 by Daleo

[sonicii]

Nope. A coolant temp gauge goes down.. if you have a head temp sensor, that will go up as the engine overheats.

I probably should qualify that by adding - if the engine is running at normal temperature, and the coolant gauge is in the normal position - then you lose all the coolant while driving (eg blown lower radiator hose), the coolant gauge will drop,not go up. Have had this happen once to myself, and has been confirmed by others who have had the same occur.

Just in case someone though I meant starting a cold engine without coolant.

[jbjb]

Your thermo fan should come on even when the a/c is off, once the car gets hot enough.

I would be checking for air in your system (which I bet is the cause). Or get a mechanic to install a water temp probe and actually check your water temp to see if your stock gauge is lying/broken.

My mechanic probed in the radiator and it showed 93degree, but when fan started working, it came back to 86......my mech recommended to change the thermostat. Will see how it goes tomorrow. If not, we may check toward blockage.

Edited December 22, 2011 by jbjb

[Deep Dish V35]

i wouldnt be too worried. my gauge runs at the 4th mark from the top, all day every day, regardless of outside temp.

[sonicii]

My mechanic probed in the radiator and it showed 93degree, but when fan started working, it came back to 86......my mech recommended to change the thermostat. Will see how it goes tomorrow. If not, we may check toward blockage.

Nothing wrong with those temperatures, was the gauge sitting in the normal position when the probe was reading between 86-93? (normal for you which is above half?)

[jbjb]

Thanks for your comment, Greg. It's like Deep Fish's stay above middle line all day every day even the temperature you reckon is normal.....weird~

[Deep Dish V35]

yep ive replaced anything and everything except for the gauge itself and the temp still sits on the 4th mark.

[Chris Rogers]

go see someone about it - carmen is probably the best one to do it. I have a scan tool but given its being a pain in the arse at the moment I can't plug into the car anyway.

go see someone about it and start there. most of the cars I have been privy to seem to dispaly what you have shown.