Hello guys I have a 2003 g35 sedan. It over heated a little bit today. I can't seem to find a leak . But they coolant was drained. And if I had a blown gasket I would of been blowing out smoke but I have no problems like that. I let the car cool down and filled it up the reservoir again with coolent and it's normal again ?

 

You might start by following the troubleshooting steps in the FSM?

http://www.nicoclub.com/service-manu.../Sedan/2003/co

Have you done a pressure test?

LEAK CHECK


To check for leaks, apply pressure to the cooling system with
radiator cap tester (commercial service tool) and radiator cap
tester adapter [SST].
WARNING:
Do not remove radiator cap when engine is hot. Serious
burns could occur from high-pressure engine coolant
escaping from radiator.
CAUTION:
Higher test pressure than specified may cause radiator
damage.
NOTE:
In a case engine coolant decreases, replenish radiator with engine coolant.


If anything is found, repair or replace damaged part

Start on page CO-7

OVERHEATING CAUSE ANALYSIS
CO-7

Revision; 2004 April
2003 G35 Sedan
OVERHEATING CAUSE ANALYSIS
PFP:00012
Troubleshooting Chart
ABS0001H
Symptom
Check items
Cooling system parts
malfunction
Poor heat transfer
Water pump malfunction
Worn or loose drive belt
Thermostat stuck closed
Damaged fins
Dust contamination or
paper clogging
Physical damage
Clogged radiator cooling
tube
Excess foreign material
(rust, dirt, sand, etc.)
Reduced air flow
Cooling fan does not operate
Fan assembly
High resistance to fan rotation
Damaged fan blades
Damaged radiator shroud
Improper engine coolant
mixture ratio
Poor engine coolant quality
Engine coolant viscosity
Insufficient engine coolant
Engine coolant leaks
Cooling hose
Loose clamp
Cracked hose
Water pump
Poor sealing
Radiator cap
Loose
Poor sealing
Radiator
O-ring for damage, deterioration or improper fitting
Cracked radiator tank
Cracked radiator core
Reservoir tank
Cracked reservoir tank
Overflowing reservoir tank
Exhaust gas leaks into
cooling system
Cylinder head deterioration
Cylinder head gasket deterioration
OVERHEATING CAUSE ANALYSIS
Revision; 2004 April
2003 G35 Sedan
Except cooling system
parts malfunction
Overload on engine
Abusive driving
High engine rpm under no
load
Driving in low gear for
extended time
Driving at extremely high
speed
Powertrain system malfunction
Installed improper size
wheels and tires
Dragging brakes
Improper ignition timing
Blocked or restricted air
flow
Blocked bumper
Blocked radiator grille
Installed car brassiere
Mud contamination or
paper clogging
Blocked radiator
Blocked condenser
Blocked air flow
Installed large fog lamp

Telcoman

 

Telcoman, you could have posted "Use our Search function" at the top and saved 30 minutes of posting!
Gary

 

True but I think the OP was not qualified to do the search otherwise he would have done that prior to his post.
Just trying to be helpful.

Telcoman

 

Thanka guys. It seems to have a leak but when I get under the car I don't see any visual leaks

 

I think he just copied and pasted, 3 minutes at most lol

 

My G35 has been overheating for months now. I have changed my thermostat, had a mechanic check if it was a head gasket, and flushed my heater core. Somehow, when ever I take trips longer then 30 minutes, the car overheats and I have to pull over and let it cool off before driving the rest of the way. I'm at a loss, I don't know what else it could be. Someone please help!!!!

 

Did you read post #2 above?

Telcoman

 

Typically a radiator flush will give you a good idea of the condition of the radiator and engine water passages, mystery overheats can be caused by people not using glycol coolant in the system and instead just adding a bunch of water. One of the primary reason for glycol is it's corrosion resistance, water will rust/corrode the entire system over time. If small chunks of crap come out in the flush the replace the radiator first, it's easy and is probably all clogged with bits of debris. The water pump impeller will eventually be damaged by the junk as well and may need replaced too but it's a considerably harder repair.

Read post 2, it has a lot of potential causes.

 

Rent a block tester and pressure tester from AutoZone. You can test the cap and system by pressuring the system and looking for leaks. The block tester is a chemical test that siphons air and looks for combustion gases in the radiator.

Does it overheat at idle, load, or anything like that? Need a little more information...my car starting overheating recently and it was due to the fans. The motors crapped out after 11 years....

 

It just starts overheating after a long drive, no particular at idle or at highway speeds, it's happened both places. I did the combustion test two days ago and nothing came up. So I don't believe it's a head gasket because from what I have heard, that's a fairly reliable test. I could replace the radiator and see if that's possibly the issue. I don't really know what else it could be.

 

I'd try the following:

make sure it's thoroughly bled
Rent a pressure tester and pressurize the system.
Take your thermostat out and put it in some boiling water. You'll have to drain some coolant though.
Last option could be the water pump. When mine went out it was the bearings (it was loud!) Sometimes the impellers can rust off.

 

So an update on my car. I took it to the shop and had them look at it just to get another idea of what could be wrong with it. They drove it for 35 miles, I checked because I recorded mileage before and after I took it in. They said it didn't overheat once, then I drove it home and nothing happened. The next day, It overheats just driving down the street. Same thing today. The hose coming from engine into radiator is boiling hot, the one leaving into the engine/thermostat, is cold as ice. Could that mean my water pump isn't pumping water at all? could the shaft in there be broken possibly? I've replaced my thermostat so I don't believe that would be it.

 

Read post #2

Telcoman

 

Motors on my fans also crapped out after 11 years. Coffey, are you me one year back?