Hey so, I’m having an overheating issue with the M35.

A few weeks ago, the car was sitting in the parking lot with the AC on full blast. I went into the store and came back out, the engine had quit. Electronics were still on. Tried to restart it but it seemed as though the battery had drained. I also noticed the temp gauge read a little hotter than normal. I let the engine cool, and got a jump. I drove the car for maybe 2 minutes and I heard a clingy type sound I’d never heard before from under the hood. Next, I heard a pop and then smoke from under the hood. Temp gauge shot up, and I immediately shut off the engine.

I called my friend and he came out and said that coolant had leaked out. Had the car towed to Pep Boys (big mistake) and paid $900+ for the two oil cooler hoses that they claimed burst, and new drive belts. Picked up the car, drive for maybe 3 minutes and it overheated again. I took it back told them, and they claimed I might have a blown head gasket or cracked head.

Now I looked up the symptoms, and I’m not experiencing any of them (milky oil, white exhaust, misfire). However, there is no heat in the cabin, and when I did drive it home, I checked the coolant in the overflow tank and it seemed as though it was boiling or bubbling quite a bit. As I watched, it did this for maybe 15 seconds after shutting off the car, I heard a click and the boiling/bubbles stopped right at the click. Then the coolant in the reservoir drained out completely. I see no leaks from under the car.

Now, both the radiator fans work but to me, they aren’t running at full speed. I’ve noticed them running a lot faster many times (I have the always on condition).


I’ve driven the car around the neighborhood since, and have added coolant to the reservoir. It takes about 5 minutes before the gauge begins to rise. But there is no boiling/bubbling in the reservoir.


What could possibly be my issue? I’m not entirely sure if they burped the system, or even replaced the existing coolant.

Any help would be highly appreciated.

06 M35 170,000(give or take) odo

I'm suspecting a water pump or a thermostat issue. I'm guessing it was NOT smoke you saw from under the hood. it was likely steam from overheating. Your reservoir tank has marking levels for cold and hot. Check the tank when the engine has sat overnight so it is completely cooled. The coolant should be at the cold level. That is the best way to confirm you have the proper amount of coolant in the system. I check mine every time I wash my car or have the hood raised for any reason.
There is a good chance that pep boys might be able to inflate a tire properly, but anything else is probably beyond their knowledge. If you have a road service, have it towed to the nearest Nissan or Infiniti dealer. They can test the entire cooling system and tell you what is going on. You don't have to have the work done there, but at least you will know what it needs and decide if you want to limp it home, buy the parts and DIY it, or have them fix it.
Hopefully, our residen Guru of M35 / M45 Ed will see this post and chime in. That might save you a trip to the dealer or at least give a good idea what to check.

Be prepared for head gasket or cracked head etc. @ 170k , with those bubbles yeah maybe. That oil & coolant cross mixing and EVEN one going into the other only, doesn't necessarilly happen - it can be very much under the radar - not seen. But those bubbles , I had them , was blown head gasket ,and oil escaped slightly and inconspicuously OUTSIDE the motor and not into coolant. Bubbles blew most of coolant out of the overflow and NOT into oil !
Look at how complex the oil drainback and water / steam holes are complex in these heads (as seen w/heads off block) - now imagine if there's just a crack somewhere , and you'll see why this can happen.3.1 L GM V6 '97 code M did exactly that.

Thanks for the responses. This morning, something told me to do a few additional checks to see what I came up with. I took off the radiator cap and started the engine. It took a minute for the coolant to begin moving but it began to overflow and come out of the radiator. I put the crap back on and let the car idle for 10 minutes. I then checked both hoses, noticing that the upper hose was hot and lower was cold. I’m assuming blockage? Thermostat/Water pump? I think this may be a good sign so far. Pertaining to not having a possibly cracked/warped head or blown gasket. At least I hope it’s a good sign.

Also to add, there were no bubbles in the coolant at the radiator cap. Just a slow rise. And she didn’t overheat while idle.

It did get to normal temp. One fan did come on but it was extremely low in speed. I noticed the AC compressor cycled on and off as well. Is that normal?

Yes. The compressor will cycle on and off. I'm told this happens even when you aren't using the air/con at all.

I just had this similar problem...I simply burped the coolant system and voila! No more fluctuating temperature and I have heat again!!!