Please forgive me for how long this is going to be.

Okay so I have a 05 G35x 103k

So I figured I had a problem when my fans would kick on high after driving for a little while and staying on high for a long period of time.

I started to monitor my temps with a scanner and my car was reaching around 215 with fans on high on relatively cool days. So I would let the car idle after a drive (fans still on high) and temps barely move at all if they do it cools very slowly.

This issue was happening before any work was done.
I replaced the thermostat (motorad), coolant temp sensor, coolant was flushed, and new radiator cap and I bled the system multiple times with a spill free funnel. I’ve bleed it to the point on me revving it to 3k I didn’t see no activity in the funnel. So I’m about 98% sure it’s bled.

HERE IS THE KICKER!
So when I was bleeding the system it’s like just about everything was going great. Coolant reached 208 fans kicked on low and temp dropped almost instantly to 195. I can confirm both top and bottom radiator hose was hot. Everything seems to be flowing just fine. Only 1 issue I noticed was when both fans were on (low I think) the passenger fans seem to be moving a little slower then the other one.


So i decide to take it on a drive when I’m done bleeding. So after a drive temp reaches around 215 AGAIN. I opened the hood both fans running on high both seem to be going the exact same speed but I felt the bottom radiator hose and it was cool.

I’m so confused everything seems to be flowing fine when bleeding but coolant temps stay high after some driving?

This has been driving me INSANE. Please any advice or tips will be greatly appreciated thanks!!!

 

Did you open the bleeder at the firewall?

Did you bleed with the front of the car jacked up?

Did you check the heater hoses for temperature?

You absolutely should see coolant swirling in the lisle spill free funnel when bleeding, if you do not then the thermostat is not open and you aren't actually bleeding anything.

Did you try to search for the method of bleeding these cars? or do I need to grab a spoon.




https://my350z.com/forum/2003-2009-n...l#post11089725

 

What mix of coolant/water are you using? Don't use 50/50 unless you're driving in freezing temps. Use 70/30 water/coolant.

 

That is far beyond the problems this guy is having. 70/30 gains like 9% heat transfer coeff which only improves the cooling total performance by ~5%. If you are in any situation where you are within 5% of the capacity of the radiator and this is what makes the difference you need a better radiator and better airflow.

 

Yes I had the front in the air, spill free funnel in place, heat on max. I did crack the bleeder a few times as I was bleeding the system. I know for sure I was doing something right because I had someone doing the revs for me (3k for 10sec) I seen bubbles here and there. I continue doing the process while allow cooldowns between cycles. I’ve prolly done atleast 4-5 hours of bleeding this last weekend. When I finished up yesterday on my last cycle I could not get anymore bubbles to come out during my last cycle so I figured to call it a day.

here is the kicker!

During the bleeding process everything was going GREAT. Coolant temp eventually gets up to 208, fans kick on low and temp almost instantly drops to 195. Top and bottom radiator hoses were both hot so that’s how I would figure everything seems to be flowing just fine.

BUT

During my test drive afterwards I monitor coolant temps and there back up again to 215 and when I check the bottom radiator hose after driving it’s cool. Again my gauge needle never overheats and is always where it’s supposed to be. Why was everything going just fine during the bleeding process but after driving coolant temp stays high and fans stay on high for a long period of time….

Is it possible for me to have some kind of blockage/clog with the car lifted it has no affect but with the car on the ground it causes a problem?

I’m just confused. Maybe I should pressure test for leaks? Maybe it’s time for a radiator replacement?… thanks for the help

btw when I said no activity I was meaning bubbles I did see small waves of coolant being pushed up into the funnel as the car was being revved.

 

Good. I would probably try one more time. It should not take a super long time. It sounds like you have other issues though. My first thought goes to the radiator cap. A leaking radiator cap (that leaks back into the overflow tank) will cause the car to run hot and will cause the radiator to not get hot due to bubbles getting into the pump and cavitating. It may be a good time to check the thermostat also, but I would check the rad cap first.

Will the car overheat idleing just sitting and running for an extended period of time without any driving? (with the rad cap installed)

 

Ive had the thermostat changed already and I replaced the radiator as well in hopes to fix the issue but it’s still going on. N no the car doesn’t overheat at all technically just coolant runs a little hot.

like I said bleeding car was great but after driving my problem comes back.

 

Yeah, I'm not new. There's a reason why I'm asking.

 

Every time I take the car for a drive when the fans kick on high I stop and check the bottom radiator hose and it’s cold. But during the bleeding it’s hot so I know the thermostat is working. I believe I still have air in the system most likely near or behind the thermostat causing it not to open when driving. What do you guys think?

 

If you have air, but do not have an actual problem, you aren't following the process I listed.

If you are following that procedure and still have air, then you have a leak or failure in the system.

 

UPDATE!

So I’ve spent the last 3 hours bleeding again. It looks like we are actually making progress! It seems that the only problem was air in the system. Took the car for a test drive afterwards and bottom radiator hose DID get hot with the cap ON. Car was basically pretty warm when I began the test drive and I drove it for maybe 15-20min (was mainly stop and go traffic with some coasting), fans did NOT kick on the whole drive and coolant temp was ranging between 188-201 average temp was around 195-197ish. While I was coasting temps went down to 188, and it only reached 201 after I took off at a light a little hard. Fans finally turned on low after I got home and parked it and let it run but temp dropped back down to 195 and kicked off. I would say I’m definitely making progress. Things are looking a lot better. I do believe there is a chance there may still be air in the system so to be safe I might bleed it one last final time and I should be good to go! Man what I relief lol. Thanks everyone I really appreciate everyone who tried to help!

 

Did you do step 9 about 10 minutes after you turned it off? That is the step to really get the last little bit of air out of the system.