Here's what's happening. After approximately an hour of cruising on the freeway, the temp gauge shows sign of air in the system. Needle creeps up to the hot line, give her some gas, it creeps down. Let of the throttle, it starts to creep back up. More throttle, creeps up even more, let off the throttle, it creeps down. Turn the heater on high 90 high fan, it creeps down and stays down for a while.

I'm trying to perform the black test now. However it seems that while I'm running the system with the radiator cap off, the coolant level keeps coming up to high and fills the test device with coolant, contaminating the test fluid. I'v ran the system before with the radiator cap off, and you could watch the fluid rushing past the filler neck. What would make it push up to the top of the filler and spill over, even while the engine is still relatively cool?

Should I try swapping out the thermostat? Would an AutoZone thermostat help, or should I try one from Infiniti parts online?

Here are some details about the car:

• swapped diff from a 350z now revs are always higher / cruises down the freeway at 80MPH right in the torque band at around 3,000 RPM
• 207k miles on odometer

Any ideas?

All the best,
~HollywoodJackson~

Check to see if the air flow to the radiator is obstructed. Also check if there are air bubbles inside the overflow tank while running (if so skip the T-stat and carbon test the coolant). I would also check the flow of your radiator internally (a quick test can be done with the car at operating temperature. Feel the temperature of the hoses. Top should be hot while the lower should be warm. If the lower is cold you have a flow issue). Drain the radiator, pull the hoses and put a water hose to the top and see how well water comes out of the bottom. Moving on from that, you could remove the T-stat and see if anything changes, if not the T-stat is fine, but at that point you might as well have just replaced it for $15. After that you need to start looking at more serious items, like I mentioned before, carbon testing the coolant to see if exhaust gasses are present. If so you are looking at head gasket issues and a compression/leak down test would need to be completed to isolate which cylinder has the issue. Start simple and work your way up.

Does it also overheat in city traffic (stop and go driving), or just out on the freeway?

MowgliCSM wrote: ↑

Sun Aug 26, 2018 4:52 pm

Check to see if the air flow to the radiator is obstructed...

Thanks. I'm going to check all the items you mentioned.

Skibane wrote: ↑

Sun Aug 26, 2018 7:30 pm

Does it also overheat in city traffic (stop and go driving), or just out on the freeway?

It only happens on the freeway.

Good points above.
Is your hydraulic cooling fan still functional?

EdBwoy wrote: ↑

Mon Aug 27, 2018 7:43 am

Good points above.
Is your hydraulic cooling fan still functional?

Hey EdBwoy! Yeah, the cooling fan seems to be blowing hard. I'm going to disconnect upper and lower radiator hoses and see how water flows thru it from a garden hose. But I was thinking, just if water flows thru it from a garden hose, that doesn't mean that parts of the radiator couldn't be clogged.

I'm really starting to think this is a thermostat problem to be honest (could be wishful thinking). I needed that block tester to work.

All the best,
~HollywoodJackson~

I just removed the thermostat, and snapped a few pics of it. It definitely has SOME damage...




SO the inner rubber ring, is torn and deformed. There are about 4 of the little holes fully exposed. It has me thinking, maybe these 4 tiny holes allow just enough coolant to pass, that I can drive around the city, stop and go, and the car cools off enough. However, on the freeway, when its hot outside, these 4 holes DON'T allow enough coolant to pass. And of course, at the same time, the thermostat must not ever be opening.

On my way to the part store to purchase a AutoZone - O-Reilly's replacement thermostat right now. I'll see if this helps. I could actually blow thru the lower radiator hose, and coolant came up out the radiator fill and out of the hole where the thermostat sits. So, hopefully this t-stat is my flow problem!

All the best,
~HollywoodJackson~

PS. I'm learning my lesson. When you make any repair to the cooling system, you SHOULD replace the hoses, t-stat, air relief valve, maybe even the water valve on the back. SMH!

That definitely doesn't look healthy in any way. Glad you were able to get to it.

I dont mean to scare you, but if you have the means, change course and go to a Nissan/Infiniti dealership and buy an OEM thermostat. It might cost even double, but would save you time in the long run if you had to do the job again.
I don't have enough data on the VK45DE, but have some evidence from the V6 side, that aftermarket thermostats dont jive well with Nissan's. I use OEM and have never had to redo a job.


*Also, make sure the jiggle valve is clocked properly when installing the T-stat.
Upright with a 10 degree allowance on either side.
In clock language, that's12 o'clock, but can range from 11:59 to 12:01. Not much allowance, lol.

Yeh, other Q45 owners have had trouble with non-OEM thermostats.

EdBwoy wrote: ↑

Tue Aug 28, 2018 1:42 pm

... change course and go to a Nissan/Infiniti dealership and buy an OEM thermostat.

I went with the O'Reilly's thermostat for now. Upon inspection, I can see why these aftermarket parts won't be up to snuff. The jiggle valve on the OEM part is right at the top near the outer edge of the thermostat, where the air pocket would be. As opposed to the jiggle valve on the aftermarket part, which is located halfway from the center to the outer edge.

I will be following your advice and getting a thermostat from Infiniti Online. For now, I've refilled the system. From the first refill, then running the motor to normal operating temp, revving 3,000 RPM for ten seconds a few times, then letting it cool to see if the coolant level drops... During the first run, I noticed a bubble like every 2 seconds. Fearing the worse, I was thinking na 2JZ with aftermarket turbos time! After I filled it the second time and drove around town jamming, there were no bubbles. Just checked the coolant level this morning, seems to be right where it should be.

This overheating problem COULD HAVE BEEN the thermostat! Damn lol. I'll keep you guys posted of course if there is another issue with the coolant system/heads gasket.

Thanks for all of the replies. Very helpful!

All the best,
~HollywoodJackson~

So, still overheating on the freeway. And I REALLY want to go to Pick-A-Part and grab a NA 2JZ, turbo charge it with a huge turbo, and swap it into the Q! 700-800HP is sounding great right about now...

All the best,
~HollywoodJackson~

Still overheating on the freeway, after about an hour. Yet seems to be able to handle hours of stop and go city traffic. Leads me to believe, still, it's not a head gasket issue. Overheated yesterday, and when I inspected around under the hood, I could see what looked to be wet coolant around where the metal AC lines that go into the firewall. This leads me to believe the two heater core hoses may be leaking, but only when the system is under enough pressure to push the coolant out. Could this be the case?

Further, inspecting the heater core hoses, I find something that may not be just right. See the picture below. Should parts of the heater core hose, with the T (air release valve) be reinforced with larger hose? That doesn't seem right.



I'm going to replace these two hoses and also the water control valve. However, looking at the FSM, no overheating issue has water control valve as a possible cause.

The problem is very frustrating, haha.

All the best,
~HollywoodJackson~

That is a very impressive sketch. But can you take an actual photo so we can compare with what we have?

However, I believe the OEM rubber hoses do have some sort of extra sleeve near the bleeder Tee.

*be very careful manipulating the bleeder. When you turn the screw, have one hand on the Tee so that all the twisting force isn't acting against the hoses. The plastic Tee might snap at the leg going into the hose. Ask me how I know.

I wasn't clear if you got and installed an OEM thermostat.
...or whether you have hosed down the radiator of leaves, mud and other junk that obstruct airflow.
What is the state of your main accessory drive belt system - is the belt still taut as indicated by the tensioner? Is it dry and/or glazed to sometimes squeal on startup?

The water control valve could in fact cause overheating, but that's not a very common failure on the VK45DE.

EdBwoy wrote: ↑

Fri Sep 07, 2018 10:05 pm

I wasn't clear if you got and installed an OEM thermostat.

I actually did not get an OEM thermostat yet. Still rolling with the one from O'Reilly's. However, I'm starting to learn my lesson. I will be ordering an OEM thermostat this week.

So with that said, here is another update (normally, this would be embarrassing, but I'm too optimistic to be worried about that, right now!).

I had my fan fluid in the reservoir filled to the brim, due to that leak I had at one time. I just corrected the fluid level, refilled the system with coolant, and ran the engine per the refill instructions. Revving to 3,000 for 10 seconds, 3 times. With the AC on. One thing I noticed right away, the air coming out of the ducts was ICE COLD.

I think this whole issue has been the fan speed not fast enough due to the reservoir being way too full of fluid! I'll be watching the coolant levels and the coolant overflow like a hawk for the next few days. Friday, I have to drive south again, approximately an hour drive into Orange County. That will be the ultimate test.

Hoping this will be resolved.

All the best,
~HollywoodJackson~

Drove the Q yesterday on the freeway, went down to San Pedro. Ran the AC some, ran a bit with the RPM's high in Manual Shift mode. The car didn't overheat. However I can see the limitations of the aftermarket radiator cap. The coolant overflow got full. And I had parked the car for a while in San Pedro. I initially thought it would suck the coolant back into the system. Then I thought maybe it didn't cool off enough. I'd also worried that when the overflow reservoir got full, maybe some of the coolant was blown out of the escape hole at the top.

This morning, I went to check the coolant levels. The overflow was still pretty high near the top. I siphoned that off into a water bottle. Removed the air release off the heater core line, and filled until the T overflowed. Recapped the T, then filled the radiator fill to the neck. To my surprise, it basically only took the amount that was in the overflow reservoir!

So my conclusion, while the aftermarket radiator cap works under pressure to relieve the system, it DOES NOT WORK well at allowing the system to pull coolant back in from the overflow reservoir.

OEM thermostat and OEM radiator cap will be on order this week! I wish there was a way to setup the system so the coolant temp is displayed on the dash monitor. I'm going to look into getting one of the Bluetooth devices you can plug into the ODBii port and have the info come to an app on the phone. Anyone know of a good one on eBay?

All the best,
~HollywoodJackson~

I think I paid 8 bucks for my BT OBD adapter. Can't tell you the brand.

The app I got for it is called Torque and it's great. It does everything from OBD codes to track day apps. Engine characteristics like temperature, throttle position, RPMs, etc. It also does acceleration in G forces, 0 to 60 times, quarter mile times. I highly recommend it.

I think it was six bucks for the full version, a bargain.

I have seen the same as referenced by Zipr. A Bluetooth dongle that works with the Torque App.

And I can't remember which subforum I saw this in, but someone said in his experience Nissan coolant filler necks don't take very well to aftermarket caps or pressure testers because of a depth issue. The depth is off and doesn't allow proper sealing...or something to that effect. But I have never looked into it myself, so please verify that info.

Glad to see you're getting this sorted out! If you want to continue diagnosing the leak you saw near the firewall, Advance Auto (and probably other parts places) have loaner tools available to pressurize the coolant system.


The ELM adapters on eBay with the Torque Lite have worked fine for me.

Thanks Q451990!

Here's the latest update. I went and purchased the OEM thermostat AND radiator cap. Also 2 gallons of AutoZone universal green coolant. I installed the new parts and cut the concentrated coolant with 30% of distilled h2o. I also corrected the fan fluid level, it was over-filled and fan not running fast enough.

Before these steps, a fresh coolant fill would get me to Irvine, about an hour of stop and go freeway driving. The coolant temp would shoot up after I got off the freeway. Closer to Irvine, traffic would let the carrun fast enough where wind could cool the coolant.

With these repairs done... Now I can make it from LA to Irvine, and back, before over-heating. The reservoir starts filling 20 minutes into the trip though.

I've faced the music, the writing is on the wall! I have an exhaust gas leak into the coolant. The oily sheen is slightly evident. When the system is under pressure, and hot, even when I turn the car off, you can see an occasional bubble come to the re esrvoir every 1 or 2 seconds. The system holds pressure fine. When hot, out will hold the pressure with the car off for an hour or more. So I'm ruling out the leak for now.

As EdBwoy said, the cooling system is pretty beefy. I had a 98 DeVille with the NorthStar, and the famous 'soft' headbolt metal that would fail and cause the same problem. That car would run hot and go to limp mode in 10 minutes. The Q, with the fan blowing high, pours up a great fight!

Any of you guys have more suggestions? I'm going to buy an engine out of a Q from the junkyard, give it a hasty lookover, swap my existing motor, then have it rebuilt. Then swap them again eventually. And have the junkyard motor rebuilt.

Is repairing the head gasket simple with the engine still mounted in the car? Is it a doable repair for someone that's been messing with wrenches all his life but not a 'real' mechanic? I've replaced the water pump, replaced the radiator, power steering lines, replaced the maf sensor and boot and performed the throttle reset, swapped in a 350Z diff, installed BC Racing coil overs, all on this car myself. Based on that ability, could I pull off the head gasket repair?

All the best,
~HollywoodJackson~

I actually thought I would be done with this thread, but I was wrong.

I unplugged the fan sensor yesterday. Now the fan is running at high speed all the time. And the coolant seems to not get pushed to the reservoir any more. So now I'm thinking maybe I have a fan speed/fan sensor issue, instead of a head gasket issue...



All the best,
~HollywoodJackson~

i wish I could help you more, but you have a 2002 and I'm only experienced with 97-98 maxima/infiniti engines lol.

But...from experience, OEM thermostat and radiator cap don't mean anything. Sorry to burst any bubbles (no pun intended) here. I had installed an O'reliey thermostat (seems only place that sells certain import parts), and 2 Advanced auto radiator caps. I never have overheating issues in the Q. The only difference is the OEM and beck Arnley stats have a seal around the flange...which I think makes a difference because I had a hard time stopping the leak between the stat housing and engine block.

Now on the 97 Max, I have had to replace motorad therms twice because when they get old, they tend to stop opening far enough. And I've been to California where they have those gradual and LONG inclining grades on i-15 out of Vegas and i-5 going to Bakersfield. If a thermostat is not fully opening in those conditions, an engine will start to run hot. However, just out of the box, an OEM therm won't do that, and the cases they did, I had them for like 2 years already and put a good few thousand miles on them.

What does matter though...is the coolant. Use the OEM or the Vavoline/Xerex for Asian vehicles. I had a 96 Camry that ate 2 waterpumps years ago. I believe it was due to the use of Green silicate coolant. I've had my Maxima on the (what I believe to be) original waterpump going into 370,000 miles. I even thought it was leaking at one point, but that was just loose hose clamps around the thermostat. It's still holding up.

Thanks for the reply @ 98_Q45.

I'm fairly certain now, that my problem was that the fan wasn't blowing at full speed. I've unplugged the Cooling Fan Speed Control Solenoid. It's a part of the water pump. The water pump is also responsible for pumping the cooling fan fluid. It seems my fan has not been blowing at full speed, when it needs to be. It looks like I need a new water pump, since the solenoid is a part of the pump.

When the solenoid is disconnected, the fan speed defaults to "balls to the walls" full speed operation at all times. Since disconnecting it, I haven't seen any of the symptoms of overheating.

1. Coolant level inside the filler neck, has remained constant.
2. Overflow reservoir isn't full of bubbly hot coolant after driving.
3. No longer smelling coolant.

When the reservoir fills with hot coolant, in the FSM, it says this is evident of 1 thing... Exhaust gasses getting into the coolant. It should have a second possible cause listed... Fan not operating at proper speeds/fan speed solenoid failure.

I will continue to drive the car, and this weekend I will be putting it on the highway for an ultimate 2-3 hour continuos high speed test. I'm 99.9% sure it's going to be fine though.

All the best,
~HollywoodJackson~

Man, this has been quite the trip!

How much are you seeing new pumps for? How much are you hoping to spend?
Part # for search purposes - 21010-AR025

If you are willing to take a gamble, I have a bunch of pumps from the JDM engines I've been working on, and I have no urgent use for them. Urban legend is that those cars/engines usually get "relegated" at around 60,000 kilometers or so. Official proof is hard to find but I'll tell you I can attest most of the engines I've seen do look newer than what I'm working on (outside factors accounted for).

All this to say, if you want a free water pump with likely low usage, let me know.

EdBwoy wrote: ↑

Fri Sep 21, 2018 9:04 am

Man, this has been quite the trip!

Heck yeah this has been a trip! I'm SO GLAD the overheating has stopped. That ish was depressing!!

I just replaced this water pump with a new OEM from the dealership about 2 1/2 - 3 years ago. Now, not knowing that having the fluid level way too high would prevent it from pumping fluid, is probably what may have ruined the Fan Speed Control Solenoid (or at least is my guess). I'm going to pull one off a Q at the junkyard later today, for $15. It would probably cost around the same for shipping.

I definitely appreciate the offer bro!

All the best,
~HollywoodJackson~

Yep! You're, right. I forgot not everyone lives in an Infiniti desert like me for the costs to make sense.



Just thinking, we probably need to post pictures for people with no experience of early model VKs reading this thread and wondering what in the world a water pump has to do with radiator fans... Or why we are topping up fan fluid. Sounds like something you find in the AutoZone aisle that carries muffler bearings, left hand nuts and blinker fluid.

Lol no doubt!

My ability to post pics is compromised right now due to server issues. At any rate, in effort to save precious HP on the early VK (thankfully Infiniti was Hell bent on producing the highest in-class HP for '02, which they achieved), they opted to not havea belt operated cooling fan. The '02 Q45 design also already had alot of features and systems pulling from the alternator. So, they decided not to use an electric fan either.

That left a hydraulic fan operation as a choice. So the '02 atleast, has a beefed up water pump with an added channel for hydraulic fluid, and a solenoid to control how much fluid passes, to spin the fan.

I suspect when the fan is going at top speed, there is no reasonable sized electric motor that could compare. Its fast and torquey (the fan AND the Q haha).

Alas, it is a confusing setup. The first time I had a problem with it, for 2 day's I was wondering "how in the f*ck did my ex-girlfriend and her new dude get an opportunity to steal my cooling fan fuses???"

LMAO

All the best,
~HollywoodJackson~

Good Lord, that sounds like Cadillac's alternator fluid stuff. All that just sounds complex. I was always used to electrical fans, and the Q threw me off with the waterpump driven fan.

HollywoodJackson wrote: ↑

Fri Sep 21, 2018 3:33 pm

Lol no doubt!

My ability to post pics is compromised right now due to server issues. At any rate, in effort to save precious HP on the early VK (thankfully Infiniti was Hell bent on producing the highest in-class HP for '02, which they achieved), they opted to not havea belt operated cooling fan. The '02 Q45 design also already had alot of features and systems pulling from the alternator. So, they decided not to use an electric fan either.

That left a hydraulic fan operation as a choice. So the '02 atleast, has a beefed up water pump with an added channel for hydraulic fluid, and a solenoid to control how much fluid passes, to spin the fan.

I suspect when the fan is going at top speed, there is no reasonable sized electric motor that could compare. Its fast and torquey (the fan AND the Q haha).

Alas, it is a confusing setup. The first time I had a problem with it, for 2 day's I was wondering "how in the f*ck did my ex-girlfriend and her new dude get an opportunity to steal my cooling fan fuses???"

LMAO

All the best,
~HollywoodJackson~