Hey Guys,

So I think my g is acting up with cooling. I was driving on freeway today and I noticed that the temp gauge would rise to halfway or slightly above and then would come back down to normal (slightly below halfway) and it got me real worried. It would fluctuate between these two. It was only 60F outside and rainy. I got home and parked it and let it idle, the temp gauge stayed at normal range and both fans ran at full speed for over 15 mins before I turned off the engine. The engine bay was very cool and the air blowing upwards was not hot at all. However, the fans didn't turn off until I switched off the car. I started it back up and the fans started running at slow speeds this time. And also my coolant reservoir is overfilled since I last visited the dealer. Is this something to be worried about? Can this be causing it or should I take out the excess coolant? And how can I do it?

And lately I have noticed that both fans run for very long time, like over 15mins before slowing down, after parking the car. And I could feel slight vibration in the car when fans are running at full speed. Before they use to only run for couple of mins and then slow down or shut off, even on really hot summer days. Does this mean that something is wrong with the temperature sensors or thermostat? It most likely doesn't matter but I did wash my car thoroughly today and sprayed the front grill with water, any connections?

But my main question is that considering all this, should I be worried about the slightly fluctuating gauge and long running fan times? If so, what steps can I take for diagnosis.

The car is 07 g35 coupe 6mt with 88k miles.

I would really appreciate any help regarding this! Thanks in advance!

 

What did you have done at the dealer?

The cooling system has to be bled properly or the air that's stuck in the system will cause problems.

Or it could just be that your thermostat is out, thought that's kind of early. I have 94K on my car and my cooling system has never hiccuped...

 

It was just an oil change and top off of fluids. Nothing was done to the cooling system. So I don't think it is air in the system. Its just that it was not overheating at all on idle for over 15 mins and I even rev the engine above 3k. So only overheating on freeway speeds, I am thinking it has to be thermostat.

Any other possibilities? Definitely not a blown head gasket or something, right?

 

So I checked the reservoir and radiator cap and I found whitish particles floating in it. I checked the oil and it was pure, nothing milky or white on it. Ran the car for 15 min idle and no overheating.

What are these white particles? Again they are only in coolant and nothing in oil. I have never flushed the coolant and the car has 88K miles, is this the reason?

Thanks!

 

Sounds like it's the material out of the thermostat. I'd have that checked out...

 

Thanks for all the tips guys! I really appreciate it all. Here are the pictures of the particles. They are not oily so it is a good news, more like crystalline solids or 'salt' deposits. The ones in the picture of the radiator with no cap are shiny because I was shining flashlight on em.
They feel like if you put little bit of water in washing powder and feel them in your fingers.

So, I guess it could be safe to say that my head gasket is good, right?

I am going to get coolant flushed and probably replace thermostat. Moreover, the top hose (the one coming from next to the radiator cap) feels hot and is somewhat squeezable, is that normal?

 

What you're seeing in the radiator fluid is hard water deposits. Your overheating issues may be caused by these deposits building up in your radiator and plugging it up, not allowing free flow of the fluids. You could try a flush with new coolant but use distilled water rather than what comes out of your hose. If that doesn't work you'll need to visit a radiator shop and have it cleaned out....rodded.
Gary

 

Thanks Gary and Revo.

I got the coolant flushed and refilled. There are still some of these particles floating around but much less. They were definitely just deposits of 'salts/hard water' or something.

I haven't been able to take it out for a long drive on freeway so I don't know whether or not it will heat up again like before but what I noticed is that after parking the car, the fan turned-off or slowed down after 5 mins. This is how it used to be until recently when they would never slow down or turn off. So I think it is a good sign.

 

My overheating woes continue. The car didn't seemed to overheat for a few weeks since coolant flush but today it did again on the interstate. Again, all similar conditions, outside temp like 70-75 F and 65+ mph speeds on interstate. As soon as I got to city, it was back to normal.

I am thinking of changing thermostat and radiator cap. I tried to squeezed the top hose with car running and warmed up and it not like a solid and I was able to compress it somewhat. Should the top hose be like rock solid? And also it seems that top hose is hotter than lower hose, is that how it is suppose to be?

Does anyone has any other suggestions? And I was also wondering if it could be the water pump? Any ideas on that?

Thanks in advance!

 

Yes. Change the thermostat. Those were my initial suggestions.

 

Got it Revo! I was going to but then it was okay after coolant flush so I didn't. Do you know any DIY links for replacing thermostat? Any tips and things to be careful about when doing that?

 

Have you got the aircon switched on? this will make the fans run full time!

 

i agree, change the thermostat, cap and rebleed the system.

 

I'm having very similar issues except my temps are skyrocketing towards H when the car is in motion. Same story, oil change - now the car is overheating. Changed the thermostat, STILL overheating.

Full story here:
https://g35driver.com/forums/engine-...ml#post6366195

(sorry to thread jack, but since I'm subscribing to this issue, I wanted to post a link to mine as well)