So I bought another 05 G35 Rev 6 Speed earlier this week.

I test drive it and it ran great but didn't drive it a long ways. So here is the Issue. I can drive the car 20 or 30 miles and the temps will stay at normal range then all of a sudden it will slowly start to climb and once it gets close to the Hot line (2 or 3 lines before) the temp gauge will just drop back to normal and then start the process all back over again.

At Idle sitting in the driveway it will eventually start to overheat.

Ive replaced the Coolant temp sensor behind the engine and Ive flushed the radiator out. I did notice the passenger side cooling fan kick in once it got up to operating temp but the drivers side didn't come on, I flicked it and it started moving but not very fast. Not for sure if there is a delay or anyway to check this. Car has 157,000 miles and I haven't found the thermostat as I was going to go ahead and replace that also. Does anyone have any Insight on this, your help would be greatly appreciated.

Robert

 

Both fans should run, there is a low and high speed for them. I think fans turn on at 140F and switch to high speed at 205F. EDIT: They will either BOTH be off, BOTH be low speed, or BOTH be high speed. They are not independent of one another.

You can also force the fans to high speed at anytime by turning on the air conditioner, that's where I would start, turn on the AC and see if BOTH FANS are running on high. There are a different number of fan blades on each side so if you look at them one might APPEAR to be spinning faster but it might not actually be.

There are 3 relays in the IPDM for the cooling fans, swap them around and see if anything changes, they're all the same relay.

It's not uncommon for the cooling fans to wear out after 100k miles, fortunately they're pretty cheap, even cheaper if you just replace the motor and keep the rest, and it's really easy to remove.

 

I was wrong about the temps for turning on low/high, here's a snip from the FSM, it's in section EC under "overheat conditions" also is a snip of the IPDM layout, section PG and somewhere in the middle.

 

I just went outside and did the IPDM manual test so I can watch the fans, After all 3 runs the Drivers fan didn't even come on but the passenger fan came on low and high speed. I took my hand while the 3rd run was going and flicked the drivers fan and it started turning but really slow and it had a clicking sound to it once it got going.

When I flushed the radiator out yesterday with the heat on high I noticed the same thing, Passenger fan kicked in and spun as should, drivers fan did nothing. Im assuming that whats happening is the passenger fan is working overtime to keep the temps down but cant hold the temps because it has no assistance from the drivers fan.

 

Did you put a big funnel in the radiator cap and let the engine idle to get all the air out?

 

Did as you suggested and went out, filled the car back up with coolant, Turned the car on and turned on the AC just to see what they would do. Passenger side fan runs on high as u stated it should but drivers side barely turns now and still has the clicking sound. Going to just replace that motor and see what happens,

FYI... I decided to check the wives car and what do you know, its the exact opposite. Turn car on, turn on AC and the drivers fan blows on high and the passenger fan does nothing at all. Guess its time to check some relays or a motor for her car also.

 

Usually it's the fan motor itself that failed but you should swap relays to make sure, label them 1,2,3. First swap 1 and 3, the swap 1 and 2. If it's still doing the same thing you need a new fan motor.

EDIT: Just read that the motor is clicking, definitely a bad motor.

 

So what I found out is that after swapping out the relays on the wives car that passenger fan motor even with the AC on wont do a thing, its like there isn't a bit of power going to it.
On my car I noticed that when I turn on the AC the Drivers fan wont even begin to spin but if you flick it as I said before it will begin to spin but a lot slower than the passenger fan. I can even stop it with my hand but once I let it go it will start spinning very slowly again. Looks like its time for 2 fan motors, 1 for each car.