I am having a problem with my engine running hot. It runs fine when I have on the heat, but when I turn on the AC or ride without the AC, the temp hand moves from normal operating temp (half way mark) all the way over to the 3 quarters mark on the temp gauge. It has never passed that point. It will get there, then it will slowly fall back to normal operating temp, and then rise again. I am not losing any coolant and I am unsure of what could be causing this. I asked 2 repair shops and one person told me that it was normal for my car and engine to do that and the other repair shop told me that it was nothing to worry about altogether. I am unsure of what to think because I never had a car that runs hot like this.
If you feel it is raising to a point of concern and it hasn't done it before, there is a problem.
The fact that it lowers with the heater on isn't uncommon. The heater core acts as an additional (small) radiator where coolant has extra time to cool.
On the other hand, the AC places an extra load on the engine that can cause it to run hotter.
Now, if the car only heats up when you are at a stop, make sure the cooling fans are running (when the gauge shows hot). If they are not, they need to. When the car is sitting, there is no air flow through the radiator to cool the coolant. As a result, the fans draw the air through it to keep it cool. When you drive, air flows. Therefore, if it is heating up while you are moving, I would suggest replacing the thermostat. It is a cheap part to start with and if it is sticking, it could be causing the problem as well.
If you want, we have a "how to" for checking the thermostat on our homepage under the DIY section. The hardest part is removing it. However, I would just replace it if I remove it. They are like 5 bucks.
Let me know if this answers your question and helps. If you have other questions, let me know.
September, 15, 2011 AT 1:42 AM
My coolant fans are running and I have had them checked before. The radiator is also full to the top with coolant as well. I will try to replace the thermostat and see if that resolves anything. I have one more question though, would driving the car while it is hot affect anything? Like I stated before, the temp hand rises and falls but never overheats.
September, 15, 2011 AT 2:16 AM
You don't want the engine to overheat. If it does, it can cause other problems such as a blown head gasket, warped head. Because I'm not there, I truly don't know how hot it is getting which makes it hard for me. Regardless, chances are it will continue to get worse over time. I would first start with the thermostat. Also, since you have to drain the radiator regardless, go to the parts store and get yourself a good radiator flush and flush it. That way you can kill two birds with one stone and not have to re-drain the radiator if the t-stat doesn't fix the issue.
Hope this helps.
September, 16, 2011 AT 3:30 AM
I have had my thermostat changed and the radiator flushed out and added new coolant to the system. It still is doing the same thing. I took it to multiple shops and I continue to get mixed answers. I am unsure of what to do next. I don't have any leaks and everything seems to be working fine, but the temp hand still rises above normal operating temputure and ocassionally falls down back to normal operating temputure.
September, 16, 2011 AT 3:32 AM
I have also noticed a sharp drop in fuel economy, and the transmission starts shifting harder when its hotter than its supposed to be.
September, 16, 2011 AT 3:47 AM
Can you tell me what they have checked so far?
September, 16, 2011 AT 11:19 AM
So far I have gotten my spark plugs changed, my coolant system flushed, and a new thermostat. Everything else seems to be in working order says the people I took it to.
September, 16, 2011 AT 5:29 PM
My temp stays within this range. It doesn't go over that line, but its gets there and falls back and rises up again.
September, 16, 2011 AT 5:45 PM
When it goes to 3/4 the fans come on and it drops to 1/2. If you were overheating you would know.A restricked radiator can cause this or a faulty coolant temp. Sensor. Ty for using 2carpros
September, 17, 2011 AT 3:40 AM
If everything is good with the cooling system, the only thing I can think of is a bad temp sending unit. That is what sends the signal to the gauge. However, I can't understand why it would do what you described unless there is a resistance problem within the switch itself.