my coupe started to get hot on the way home from dinner one night. I have been monitoring it for about a week and a half. It takes about 15 minutes to go over half way and then I turn on the defog to 90 degrees and full on so it would take heat away from engine block. I replaced the thermostat with one from Auto Zone. Took it around the block and it shot up to almost all the way up to Hot on the gauge. The air blowing out is still cold, not blowing out hot air at all like it was before. All the coolant in the extra reservoir was still full. No leaks anywhere from thermostat replacement. What should I do next?

 

are both of your engine cooling fans working? They both should start spinning when you turn on the AC.

 

Sounds like you didn't bleed the system properly...tons of air left in the system and needs to be topped off properly after being bled.

 

Yep... what he said. Since the problem got worse after you replaced the Thermostat and your vents are blowing cold, that pretty much definitely indicates a coolant flow problem. You most likely have air pockets in the system. When refilling the cooling system after maintenance, you need to refill it very slowly in order to avoid getting air pockets in there. It also helps to bounce the car up and down a bit as you're refilling it, and then to start it up with the radiator cap off (when the motor is cool) and do a few light revs to work bubbles out of the system. Once it gets to the point where coolant is bubbling up near the top of the radiator, shut it off and put the cap back on, and take it for a drive to see how it runs.

 

Thanks for the info. What's the best way to bleed the system? I have seen posts about some type of funnel but don't know what to look for to purchase. Also, fans working fine. In fact they come on about 6-7 minutes into driving. I'm afraid there may be something wrong with radiator or water pump as well. The radiator looked full even after replacing the thermostat and not topping it off.

 

If the fans are working then the easiest (and cheapest) thing to do first is properly bleed the air from the cooling system.
You likely wouldn't be able to tell if there is still air in the system just by looking at the coolant level.

It is a pretty easy process. There are plenty of threads on here that will tell you how to do it properly.

If you don't feel confident doing it yourself, you could take it to Infiniti and have them do it. I am not positive but JiffyLube might also be able to do it.

 

You need to make sure the car is level, remove the bleeder screw on the rear passenger side of the engine and fill the engine through the radiator cap until coolant comes out of the bleeder screw.

 

Is the fluid in the radiator swooshing around pretty vigorously? That is a good indication of how well your water pump is working.

 

Ok. Not sure if I've done it properly. Fluid bubbled up from the bleeder screw but air blowing out of the vent is still as cold at 90 as at 60 degrees. I didn't have to put additional coolant into the radiator. It only went down maybe an inch from the top. The reservoir only went down a little bit from its original level. Not sure what to do now. Thanks for all the help.

 

You did install the thermostat in the correct direction right?

 

yes. There's only one correct way to install it.

 

take the cap off your radiator when its cold and let the car warm up and see if the coolant flows across the top of the radiator, if not your water pump has failed.

 

Needs to make sure there is coolant moving.

 

take your radiator cap off and jack the front end of the car up. Run it for a while. The air needs an easy route to the radiator to get out and the easiest way to do that is elevate the radiator above the engine. If you still have problems try lowering/lifting the front end of the car a couple times while its running to a agitate the coolant level and try get the air pockets moving. Also, if you have access to an air compressor you can buy a kit that will put a small amount of vacuum on the coolant system. makes filling/draining the coolant system very easy.

 

I have seen posts about some type of funnel but don't know what to look for to purchase.