2005, G35 Sedan.

Had this car for about a year and a half with little to no problems. For some reason, the engine has been running hot when I run the AC now. Refilled the coolant twice this week! Could this possibly stem from needing to change my oil? If I keep driving it and just turning off the AC when it starts getting hotter, am I damaging my engine? Thanks for your help!

 

Whoa.... Definetly need to take a look at the water pump and the thermostat. Something is clearly wrong.... Any proponged use can and will kill the engie. Fix it ASAP!

 

how much hotter is the question. and how long ago was your last oil change out of curiosity.

 

That's exactly what I was wondering. What are you using to judge how hot the engine is?... the gauge on the dash, an aftermarket coolant gauge/configurable digital readout gauge(such as a Scangauge-II), or are you just going by the heat that you can physically feel coming off of the motor when you get out of the car and stand over/near the engine bay?

Keep in mind, if you're using the Air Conditioning, it's probably hot out anyways... so the motor is going to run hotter than it would on a cool day. If you yourself are getting hot just sitting there in your car, just think of what the engine has to deal with considering it has to lug itself, you and all your cargo and passengers around.

Take a look at your radiator and make sure the fins are clean and not all bent or damaged, and also make sure that they aren't reddish in color. Also, once the car is hot, feel both radiator hoses and see if they both feel pretty hot. They should both feel warm if the radiator is doing its job on a hot day. Be careful not to burn yourself and watch out for moving parts in the motor if you do it with the car running, and also make sure you don't have any chains, or work-place ID badges, or loose clothes hanging off of you which could get caught in moving parts of the motor when you look in there.

 

Well it gets up to about 10 o'clock and I turn off the AC and turn the heater on just in case. I changed my oil at 67,000 and it's almost at 73,000, I change it myself with valvoline usually. Just been slacking on this change!

 

With your engine warmed up, take the cap off and look in the coolant reservoir and see if you have bubbles in there while the engine is warm and running.

 

No aftermarket anything. Just using the normal guage. Thanks for the suggestion, I will do that in a few minutes. I actually encountered this problem last summer, it over heated once. Then after, it would run hot SOMETIMES. Now that summer is coming up again, it seems as if it's started to do it again. I live in California, so it's not a huge temperature difference, but it runs fine all the rest of the year. Thanks for your help!

 

Hey man I work in Costa Mesa so if you want me to take a look at it, let me know...

 

I would recommend NOT taking the radiator cap after the car is already warm/hot. You could severely burn yourself by opening the radiator when the car is already pretty warmed up or hot. You can however take the radiator cap off while the car is cold and idling and let it warm up with the cap off and see if it starts to bubble up once it reaches operating temperature and your thermostat opens(assuming the thermostat is functioning properly to begin with).... that would be the safer approach, since there will be no pressure built-up in the radiator and the fluid will not be that overwhelmingly hot if it were to bubble up and spill on him.

 

he was talking about the coolant reservoir cap.

 

Do you work at a shop? I'm in Encinitas right now but maybe if I come up. Thanks for the offer!

 

The thermostat works, I can tell because I when the temperature starts to go up, it releases water to cool the engine and instantly goes down. Problem is, it seems like it stops affecting the engine after a while, especially when it is hot outside. Also, both hoses coming from the radiator are warm/hot while it runs so they are working properly. Also, no bubbles in the reservoir while running.

So something weird happened today, or maybe this is normal when it gets too hot. It seems like I have a leak, but there isn't any fluid under the car. I've checked several times. Last time it was running hot, I refilled the reservoir because it was nearly empty. I drove 9 miles home, still running a little hot. Then when I left home a couple hours later, I checked the reservoir again and it was empty. No fluid under the car, checked the radiator and it was full, just an empty reservoir. Refilled it, drove to my friends house and back and it is still full. Did it burn up the fluid because it was already running hot? Does this mean I need a new radiator or does this sound like my gaskets could be leaking?

 

Before looking more like a douche, why don't you re-read my statement...

 

A thermostat is a couple of bucks from autozone, to give you piece of mind its probably due for a change, but if you dont see any bubbles in the reservoir or white smoke out of the tail pipe, i would suspect a bad water pump followed with a complete coolant flush.

 

i would change the thermostat and reflush the coolant and rebleed the system. It shouldn't cost you too much money and its something you can do on a weekend.