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Discussion Starter · #1 ·
Hello everyone I have a quick question to ask about my Cruze so long story short the car will run at normal temp but when I driving down the highway faster than 65mph the temp gauge will show it's dropping in temp it will stay there for a couple minutes some time and then slowly go back to normal temp I changed the thermostat after it showed a code for it but it continues together cold and warm back up has anyone else found the same problem
 

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Latest problem with an electrically heated thermostat, main function in more expensive vehicles is to optimize the engine temperature based different driving conditions.

Not easy to really learn the reasons why this feature has been added, but I feel the key reason is to use that heater to open the thermostat quicker in production, you cannot fill it with coolant properly if that thermostat is closed, it has to be opened first. Some open at 100*F and is controlled by the engine computer and that may well be the problem.

If that heater is not there, engine temperature would have to be over 200*F before that thermostat opens, this adds to both production and maintenance time.


In one of my vehicles, was a recall on the thermostat, has a 26 watt heater in that very tiny wax cylinder, was erratic, those that had it replaced saw no improvements. Still a conventional wax bellows thermostat and in my long history, never saw a thermostat act like this before, with a failsafe stays wide open and engine never reaches normal operating temperature, without, stays closed, very bad, engine will overheat and crack the aluminum head.

Hooked up my storage scope to the battery, learned when hitting the starter, voltage was dropping below 8.5 V, ECU was not getting a proper power on reset voltage. Found a small connectivity problem, repaired this and never had this problem again.

Any electronic engineer or a tech would be dead meat without a scope, so why aren't dealers using these? Instead, get stupid comments like solid state do not test. Automotive electronics is one of the dumbest things every created, and they are all this way.
 

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Electric heater will NOT show the dummy gauge dropping. It may drop it in temp, but it will run at the 1/2 way mark @ 185-230F, which is a normal operating range for the Cruze.

OP, are there any CEL codes still stored in the computer? Something like a temp sensor for instance? Has coolant level in the overflow tank remained steady? It is possible there's an air bubble in the system somewhere and it just needs to be bled.
 

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Discussion Starter · #5 ·
The coolant reserve stays at the same level as far as the computer goes would disconnecting my battery overnight and see if that resets anything. Would a bad water pump let air in at the pump and it just keeps sending air into the system which keeps it from belding out fully?
 

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Would a bad water pump let air in at the pump and it just keeps sending air into the system which keeps it from belding out fully?
Yes, but you'd likely see the level drop, and it's nowhere near as common on the 1.8 as it is on the 1.4 for the WP to go bad.

Computer - if there are currently no codes, I don't think it's a computer issue. What you can test is that the thermostat remains closed as the car is warming up. When the car shows about 1/4 on the temp gauge, squeeze top and lower radiator hoses. They should not be warm/hot at all - this means that the thermostat is staying closed as it should be.
 

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Discussion Starter · #7 ·
Well update everyone the temp gauge is still dropping at 70mph I have been bleeding the system with te small white screw on the radiator I keep getting little bits of air should I countine to do that and hope it goes way I'm at a lose here guys
 
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