Hey! I've got an '05 G35 sedan with a bad attitude. We bought this car last august from carmax (yeah..I know.) and we've had on and off issues ever since. I really don't want to, but I'm tempted to just bite the repossession and get back into an old truck. Here's what we've done so far:
* changed out radiator
*changed out water pump
*changed out thermostat THREE times (and eventually just left it out since nothing ever changed the situation, anyway)
*changed radiator cap four times
* burped cooling system more times than I would like to admit
*flushed the cooling system and a LOT of gunk came out..this was back in about February

So far, I've noticed that the overheating is completely at random. It doesn't necessarily get worse as the time goes by. It just plain overheats at random. I've been told the fans were out, but I hear them working. Kicks on and goes through three different speeds.. Cools off once they kick on, USUALLY.. But not always. It's been to three different mechanics who all said it's either fans or internal. Well, the car purrs like a kitten. I don't lose any get up and go, there's no odd noises, no smoke coming from the tailpipe, no water/oil mixed, nothing. It looks and functions completely perfect, other than this random overheating crap. You would really never know it had a problem until it happens. We did open the radiator cap and run the car to see if the water would shoot out at temp to see if it was the head gaskets, and in park, it was perfectly fine. We decided after about a half hour to throw it in neutral and the water shot over the top of the hood. My dad thinks it's head gaskets because of this, but I just can't see that being it with the car running SO well. I'm at the end of my freaking rope. My husband wants to call it quits. But I know this car has potential. Could it be head gaskets despite the perfect performance, or maybe something electrical? Or is it time to say goodbye? I can't deal with this anymore. It's been a year now, guys. What are we missing?? Thanks so much for the help in advance.

 

Have you changed coolant temp sending unit?

 

Ehh.. No. Where's that at? You're gonna have to bear with me. I'm an old gmc chick. I'm learning this one as I go lol.

 

Never mind. Just found it. I suppose I could change it out, but I've got to ask. Is the pressure pushing the water out of the radiator a sure fine way to tell the head gaskets are blown? I was taught that one a long time ago and I just wanna make sure this isn't actually engine related. Maybe I should do a compression check, anyway?

 

A compression test is for your rings. But I would definitely get a pressure test and leak down test if you're losing coolant.

Its, cool, I came from gm too. A motors a motor.

 

Yeah, I guess so. We did the pressure test and everything. The only place I ever lose coolant is out the top of the reservoir, though. No leaks at all. I'm fixing to get that sensor and see if that doesn't fix the problem.. Thanks so much. I'll be back if it doesn't work out, for sure. ^_^

 

Everything I know I learned from owning a couple 3rd gen camaros, so you know I've done it all. Haha jk

But yeah, if a sending unit is broken it can send you false readings.

 

Hah! I don't doubt you at all.. Got a friend into old school camaros and the work she lists that was done is unbelievable. Dang thing caught fire so many times lol! Anyway, yeah, this whole computer thing is not my jam. Give me something less complicated and I can do it myself. This car will be the death of me. Already finding out it's a dealer part. Woo.. Thankfully I've got a guy who can lower the price if it's too bad. I really think I'm just gonna let this car go. We're paying way too much a month for so much bs. But I'm gonna try this anyway. If I can fix it, I can at least try and sell it.

 

hey!! I've been having this problem as well. did EVERYTHING you did... except for the coolant sending unit (never thought of this.. and still not sure where to go about that) and I'm starting to replace the head gaskets myself.

Would you mind if I shared threads with you? I'm just a thread or 2 below you. same symptoms as well. and coolant *Does* shoot out of the radiator like a geyser when it gets hot.

do you mind showing me where the sensor for the coolant temp sending unit is?

thanks!!! here's a link to my thread.

edit~~ link

https://g35driver.com/forums/g35-sed...ine-apart.html


I should have named the thread something along the lines of "overheating"

 

Okay check this out. I called the dealership. I was told they've NEVER heard of a part like that before. They suggested I bring it in (how about NO...). Something smells fishy. These people all over these forums have changed this part, but Infiniti doesn't know what it is? UGH. Anyway, I googled "coolant temp sending unit" and looked at the pictures. For me to find it (if I'm on the right track), it's by the thermostat and I wouldn't be able to see that without removing that filter thing in the front to the right under the hood. (Sorry, my "girl" is showing. My bad. :P )
Anyway, if YOU can find that part, let ME know haha. Because so far, I feel like I'm being run around a tree. And thanks so much for the link. I'm going look, now. Sorry you're going through this, too. These cars are too beautiful and pricey to be dealing with all this bs.

 

Damn, that's so weird... Don't they offer a legit extended warranty? I hope you are able to get this cooling issue resolved...

 

On my car an 06' the coolant temp sensor is in the pipe, near the passenger side, and rear of the engine. If you unplug it the fans should kick on and temp sensor stays at bottom. Atleast that's what my car did.

 

Have you tried a leak down test? There is a tool that you can rent at Oreillys that test your coolant at the radiator cap that rest for exhaust gases. If it changes color you have a bad head gasket. I wouldn't recommend just replacing the gasket when that may not be the problem.