I have a 2003 g35 with about 185k miles on it. It is burning through coolant like mad, I have to completely fill the reservoir every two weeks. It's obviously burning the antifreeze since the exhaust has some white smoke coming out of it that smells of antifreeze. There are no signs of any leaks however, everything seems quite dry. I've done some research and can't quite figure it out. At first I felt for sure the head gaskets were blown but I've asked around and looked through some forums and from what I've heard, blown head gaskets on the vq35 engine are very rare and almost unheard of (the Japanese know how to make a good engine). I've read that it is possible the water pump O rings are to blame. Now, I'm no expert by any means, I just have a strong interest in cars so bare with me. I know water pumps should be replaced every 100k miles or so. I'm the second owner of the car and now that I've owned the car a while, it is plainly obvious the previous owner did not take care of the car as he should have. Is it possible the original water pump has lasted this long? My theory is the O rings are severely deteriorated and causing the engine to burn through the antifreeze, but like it said, I'm no expert. But maybe it's true, maybe the head gaskets are blown. If they are, I'm screwed since I've been told it would be better to just replace the engine, but I can't afford that. I'm hoping that something else is to blame so if anyone has any other ideas as to what might be wrong, feel free to share.

 

Inspect your oil. If it looks like a milkshake, you have a head gasket leak. But I already know you have a HG leak if the exhaust smells like coolant

 

I've checked the oil and it looks fine. It's a nice smooth dark brown color.

 

I would check all your lines... Upper and lower... But I am suspecting a head gasket, or a valve cover gasket leak....

 

Goto Autozone and ask for the engine block test. You pull out some coolant from the radiator and the liquid tester will change colors if it detects exhaust fumes in your cooling system. It's about 30 bucks from the store.

Safely jack the car up and look above the lower oil pan on the driver side. There is a weephole and see if there is any dried coolant on there. Water pumps are driven by the timing chain, so you don't have to worry about a belt breaking. However, the bearings can seize up, but you'd hear that happening (at least I did).

How does the coolant in the radiator look? Inspect your oil during the next change, but white smoke...I don't know doesn't sound too good.

 

I'll probably try a pressure test on the coolant system so I know for sure there are no leaks. The coolant in the radiator and the reservoir looks healthy but then again, I do have to put more in every couple of weeks so it would be hard to tell. Also, the white smoke is minimal and it only appears when my car is warmed up and has been idling for about 30 seconds. I also only smell antifreeze when there's smoke. I have to really look for the smoke or else I won't see it. That's why I've never noticed it until just this past week.

 

Did you solve the issue because I have the same is with my 2003 G coupe 133k miles ppl say it's my HG

 

I'd replace the water pump and the thermostat to see how things turn out, plus it can't hurt. If you do have a HG issue, I wouldn't drive the car much. If the heads get warped, you'll be in more trouble than you are now. Also, price a rebuild on your existing engine. Piston rings, gaskets, the sha-bangy-bang. The last thing you want to do is replace an engine you could have saved and built better. Just my two pennies.