Overheating! So Frustrated...Please Help!

[JohnCampbell08]

Seems like nothing but problems with my Q45. It is a 00 Q45 with a brand new thermostat, and completely bled coolant system. I purged air out of the upper radiator hose and the radiator itself to cover bases. All the fans are in working order....no visible leaks, and no weird stuff in the coolant itself. When the heater is turned on, the temp goes down like it should. Even after an hour or two of idle/driving, it doesn't seem abnormally warm under the hood or around the coolant lines etc.

I let the car idle for almost an hour bleeding the system with my funnel type bleeder. No problems. The car heats up to the halfway mark, and doesn't barely move more than that. But after a long while, the gauge creeps up to maybe 12:30-1 oclock position. As soon as the motor is revved, the temp goes down to maybe 11 oclock position, but will eventually creep back up. During the idle period...

As I drive around, the temp stays decent, until I come to a stop for a while (think red light). The temp will shoot up to the 1:30-2 oclock or so, not quite to that line before overheating (75%)....but again, if the motor is revved slightly, the temp usually goes down. It NEVER goes past the line before the overheating warning, but this still is way too hot for normal use. I have to fix this so that I know if the car is actually overheating or not.

I have also seen the temp gauge shoot up as soon as the headlights kick on. Not sure how these could be connected, unless the sensor is bad and the extra electrical drain is taking a toll.



So I have a few guesses :

Perhaps my coolant sensor is buggy, and is getting all worked up and going back and forth. I think this is a strong possibility since the temp gauge fluctuates quickly when the motor is revved and as it accelerates and slows, same with the headlights coming on. But since it still "works", my guess is that I am not this lucky

Some sort of blockage in the radiator? Perhaps the accelerating is forcing the water to get past a blockage in the radiator, and so there is a bottleneck in the system? I couldn't really get under there to touch the bottom of the radiator, to see if there was a temp difference, but at least side to side on the top, it is the same temp.

Water pump going out? I have no sounds from the bay, and I have no leaks from a weaping pump, but perhaps the revving is helping the pump cycle the water? I really hope it isn't this serious, but I have no idea when the last time it has been changed.


I am going CRAZY here. I can't even enjoy my car anymore...seems like a problem around every corner, and since this one COULD be serious, I can't risk driving it around town and something serious happening...

Any advice is appreciated. Sorry for the long post

[Towncivilian]

Have you tried replacing the radiator cap with a new OEM one?

[JohnCampbell08]

No, the radiator cap on the radiator itself looked to be in good shape. The one of the upper radiator hose does look old and a little "crunchy" on the spring, but could that seriously be the only issue?

I hate to throw money at the car and hope for the best. I did that with the thermostat and the funnel bleeder already....and neither helped in the slightest. At least those were cheap though, just like the rad cap I am sure

[Towncivilian]

Inspect your radiator cap again, following this TSB. Ideally you would pressure test it to verify that it's good too.

I don't know about the upper radiator hose's "crunchiness" - could you post a picture?

[JohnCampbell08]

I mean that the spring on the cap makes a slight crunch noise because there is debris there....I can tell it needs to be replaced, esp after reading the TSB. But I have never had a car overheat on me strickly due to a bad rad cap?

The one on the radiator itself looks fine. But the cap on the top radiator hose needs replacing.

Never thought about it! My guess is since the radiator cap on top of the hose is bad, it is probably stuck shut. It is probably acting as my bottleneck in my system, and giving me the same symptoms as a clogged radiator or weak pump!

I can only hope I catch a little break of luck, and it be the radiator cap instead of something very expensive!

[JohnCampbell08]

And what would be the difference between an OEM rad cap and let's say an autozone one?

I might as well replace both caps while I am at it, and although money is not an issue, time is not either. I am sure I will sell the car before I have issues with a cheap cap 30-40k miles later.

I only say that due to convenience. Autozone is next door...closest Inifiniti dealer is almost an hour away

[Towncivilian]

I've read anecdotal reports of aftermarket caps starting to leak after a few months or have the incorrect bypass PSI setting.

[JohnCampbell08]

Ok, so I changed out both caps, and it seemed like it did the trick...at first.

It took considerably longer to heat up to the halfway point....it was actually at the 1130 position (perfect!) for the whole idle, and the 15 min drive around the neighborhood. But it did start creeping up again, to the 1-130 position again.

There HAS to be an electrical gremlin there on the switch or something. If I turn on the headlights, the temp gauge jumps maybe 1 1/2 - 2hrs almost on the gauge! If I turn off the headlights, it is an immediate jump DOWN...same amount. And back and forth, back and forth...everytime I mess with the headlights.

So my next guess has to be the fact that the car is at good temps, but the gauge is reading wrong! Hopefully, it is as simple and messing with the temp switch....seems like a lot of these wiring clips and stuff get dirty/brittle/broken over time with the heat in the engine bays

Perhaps it could be an engine ground? Maybe someone can point me in the right direction, towards the locations of the temp gauge senders and the grounds that could be the culprits?

[Towncivilian]

Have your battery and alternator tested (most auto parts stores do testing free), and test the engine coolant temperature sensor's resistance values. See page EC-161 of the factory service manual for reference values. If it fails, replace it with an OEM one (I wouldn't go aftermarket for this part).

[JohnCampbell08]

Battery is new...the car sat for months so one of the cells went dead. Good thing it was under warranty so I got a free exchange. Car has been driven quite a bit and I haven't noticed any light dimming or other tells that the alternator is going bad. I think the new battery would have been drained by now.

I will check into testing the engine coolant temp sensor...thanks for the link and all the help so far!

I just noticed that they are saying the coolant temp sensor usually throws a code if it is bad? No code here

[JohnCampbell08]

My friend also brought up an idea...there might be a drain on the cluster or on the circuit board...when the lights dim and turn on, it drains the voltage and messes with the gauge reading.

He told me to try to mess with the dimmer switch and see if it affects the read out...so I will try that tomorrow and let you guys know what happeneds

[Towncivilian]

Generally it would throw a code, but since it's fairly easy to access the ECTS harness there's no harm in ruling the sensor out.

It could possibly be a faulty voltage regulator or loose ground on the instrument cluster, though in that case I would think that some other gauges would be acting up as well. I would tighten any brass screws on the backside of the instrument cluster - usually those are the grounds for the cluster.

What kind of thermostat did you use? Was it the same temperature as the OEM rated one (180F)?

[willko1]

Battery is new...the car sat for months so one of the cells went dead. Good thing it was under warranty so I got a free exchange. Car has been driven quite a bit and I haven't noticed any light dimming or other tells that the alternator is going bad. I think the new battery would have been drained by now.

I will check into testing the engine coolant temp sensor...thanks for the link and all the help so far!

I just noticed that they are saying the coolant temp sensor usually throws a code if it is bad? No code here

If you can find out what the actual water temp is compared to the corresponding value on the gauge maybe using an infrared thermometer just to ascertain with certainty you are maintaining a specific temp range. http://www.ebay.com/itm/GM300-Non-Conta ... 1e6e2f67dc

[Skibane]

There HAS to be an electrical gremlin there on the switch or something. If I turn on the headlights, the temp gauge jumps maybe 1 1/2 - 2hrs almost on the gauge! If I turn off the headlights, it is an immediate jump DOWN...same amount. And back and forth, back and forth...everytime I mess with the headlights.

Can you get the gauge to do the same thing with any other large electrical loads, or is it just the headlamps that do it? For example, what happens when you roll down a couple of power windows at the same time or turn the A/C blower on max speed?

[Q451990]

I think it would be a good idea to get some kind of scan tool that can read the ECU temperature sensor. It's a different (more accurate) sensor than the one that feeds the dash. I bought a cheap OBDII bluetooth adapter like this on ebay and downloaded a free app called "Torqueon my android based phone. It actually works pretty well!

http://www.ebay.com/itm/ELM327-Bluetoot ... 31&vxp=mtr

If I were buying again, I might get this one since it's shorter, and Nissan the OBDII port on my truck and G both point down right by the pedals - so I have to be careful not to kick it when it's plugged in.

http://www.ebay.com/itm/ELM327-V1-5-Blu ... 4ab8c549b3

Heath

[JohnCampbell08]

I didn't get a chance to mess with the car today before work, so I will try for tomorrow morning.

I will see if any other loads mess with the temp gauge, but the headlights definitely do the trick.

I thought about changing the sensor since it was a cheap replacement non OEM wise. No code for the sensor though. I know OEM is the go to route, but I am not sure how long I want to drive the Q after running into so many issues back to back. Maybe my thoughts will change after I get it running right again.

Every once in a while I throw a 1320 and 0325 code, for a random misfire and a knock, but it isn't consistant and doesn't seem to work in conjuntion with the temp gauge reading.

I'll update more as I know more. Thanks again for everyone's help

The thermostat was an aftermarket 180 degree.

[JohnCampbell08]

The dimmer switch does nothing....but again, the headlights adjust the gauge every single time, but only after it is fully warmed up.

If the engine is cold or still warming up, the headlights do nothing. Only until the full warm temp, and then it makes the gauge go crazy. Literally the second I flick the switch....so I don't think it is actual temp changes

I have no idea what it could be, and again, I don't believe the engine is actually hot. Maybe I do need to find a way to read the true temps, but not ruling out the possibility it could be running warm

[JohnCampbell08]

I bought one of those controllers you linked...hopefully it allows me to read the coolant temp sensor and tell me if it is actually adjusting with the gauge

[willko1]

I bought one of those controllers you linked...hopefully it allows me to read the coolant temp sensor and tell me if it is actually adjusting with the gauge

Ok so what happened, Did you fix? Explain, thanks for the sharing of knowledge

[maxnix]

And what would be the difference between an OEM rad cap and let's say an autozone one?

Correct spring pressure and seal. 3rd party ones have been notorious for not meeting OEM specifications.