Coolant Temperature Dash Gauge Showing Hot

[GoadQ45T95]

Fairly sure the t stats fail open (by design) so I don't think that would be it. Its a 20$ part though, wouldn't hurt to change it to be safe. The only tell tale way I know of for diagnosing the water pump is if its leaking out the "weep" hole on the bottom. This would be fairly obvious though, you'd see coolant or wet spots below the pump. I don't suppose a flush would hurt if your completely out of options with it.

[my12by60]

No leaking from the weep hole on the water pump. So I think that is ok. I read that increasing the % of water in the water/coolant mix will help the coolant system to stay a bit cooler. So I removed the radiator petcock and let the gallon or so of fluid drain. Then I refilled with just distilled water. The fluid that came out looked pretty good to my untrained eye--nice and green with no signs of sediment or gunk. Based on that, I am not sure I am going to do a full flush. My wife will be out for a long drive tomorrow in the heat. So that will another good test to see if I am making any progress. Still have not received my scan tool. Amazon package tracker says it will be coming late.

[GoadQ45T95]

If the coolant mixture is anything like the first gen its 70/30 mixture for summer and if you deal with harsh winters they reccomend 50/50. Id recommend trying a product called water wetter as well. It has some good reviews including that from Q owners. Its about 20$.

[3Q Jay]

Fairly sure the t stats fail open (by design) so I don't think that would be it. Its a 20$ part though, wouldn't hurt to change it to be safe. The only tell tale way I know of for diagnosing the water pump is if its leaking out the "weep" hole on the bottom. This would be fairly obvious though, you'd see coolant or wet spots below the pump. I don't suppose a flush would hurt if your completely out of options with it.

Tstat can fail open or closed. fail open is a nuisance. fail closed and you only have the jiggle valve---could be catastrophic. I know he's got the app coming to read the no kidding deg F that the ECU is seeing. at this point if it rises monotonically and reads over 210F, i'd put money on bad thermostat. if the thermostat is good, you can tell that too because you will see the temp plateau in the low 190s and stay there until the capacity of the cool slug from the radiator fully mixes and saturates.
correct call on the 30/70 glycol to distilled mix. I put that in the very first reply.

[my12by60]

I don't think the thermostat is going to be the culprit based on what Jay is saying. The dash gauge (assuming it is working as best as it can) rises as expected from a cold start and holds steady at just left of noon on the gauge. The gauge will only rise beyond that point after 30 minutes of so of driving in high ambient temps. Once the engine has been running a while at full normal operating temp (low 190s per Jay), climbing a grade will make the dash gauge move to the right. Sustained climbing will start pushing the gauge closer and closer toward the hash mark on the right. Flatten out and slow down, and the dash gauge will settle back to around noon. Also, once the engine has been at full normal operating temp for a while, sustained freeway driving at say 70 mph can make the gauge flare up if the ambient temp is hot enough.

I thought these symptoms sounded like a fan clutch that had lost its full effectiveness. And the new fan clutch does not have any of the wobble/play that I felt in the original fan clutch. Yet my wife said the first drive after the fan clutch change still showed the dash gauge moving above normal. I need to do another drive to confirm.

When I changed the water pump and flushed the coolant in my wife's Durango, the first drive after the repair had the dash coolant temp gauge flaring up. Without doing anything else, all subsequent drives have had the dash gauge as normal. I guess one hot/cold cycle into the expansion tank relieved whatever bit of air was in the system from the drain and flush and returned things to normal.

I saw your mention to change the coolant/water mix in your first reply. I have been trying to do things one step at a time to see if I can pin down which step solved the problem.

Amazon says my scan tool will not be here until mid-week. My wife left me the Q today. So I may take it out for some errands to see if the higher water content in the cooling system has improved things.

[3Q Jay]

methodical troubleshooting is the best
I don't want to speculate too much without the hard data from the readout tool. i put very little faith in the dashboard gauge (although it IS there for a reason, and you are wise to heed it's warning cry).

[GoadQ45T95]

Inclined to agree with Jay. Everything we are saying is speculative at best until we get the hard data. It would be unfortunate if everything was operating as intended and the gauge is just acting funny. Since your in AZ id expect to see slightly higher temps than normal anyway. Has normal operating temp changed from gen 1 to gen 2? Gen 1's ideal operating temp is 180 not 190.

[3Q Jay]

yep, fgy33 has different thermostat--to run hotter by design. but I'm not ready to suggest that the 180F stat is the right answer here.

[GoadQ45T95]

I wasnt suggesting using a lower temp t stat. I just didnt know if with the new design they changed operating temp. Good to know.

[my12by60]

I would be surprised to find out that the gauge is just acting funny. I bought the car last winter and the gauge never moved from noon. It has only been since our high summer ambient temps arrived along with, of course, use of the ac system, that that the gauge has moved right of center. Amazon package tracker says I will have the scan tool delivered tomorrow. So I will be able to eliminate a faulty gauge in the next few days of driving.

I am also going to try a bottle of the Redline Water Wetter that many here recommend. I read the reviews on Amazon and a lot of users have done before and after tests and confirmed lower coolant operating temperatures. Between changing the coolant to water mix, the new fan clutch and now the Water Wetter, I think the problem may be licked.

I had the car out yesterday afternoon and the gauge movement was reduced. Maybe the Water Wetter will be the final piece to keep things cool?

I will pick up the Water Wetter today then report back with scan results on Tuesday or Wednesday after I have gotten some driving in and have some solid coolant temp data.

[EdBwoy]

While just as speculative as the other posts, I wonder about the health of your water pump. It might not be leaking out, but how well is it pumping exactly? I am inclined to believe it's pumping well enough to get you to normal operating temp and mostly keep you there, bit bad blades will affect it's effectiveness. One way to check for an absolutely non-pumping one is to open the rad cap at startup and just watch to see if the coolant is moving either left or right.
2nd concern would be how well the aluminum engine withstood the initial overheating in 2013. After tightening the clamp, do you still experience any noticeable loss of coolant?
3rd, going on the simple solution angle, how clean is your radiator and its fins?

[my12by60]

Tomorrow morning I will add the Water Wetter that I just picked up. I will do the water pump check that you suggest.

The coolant level seems to be holding steady since I tightened a few of the hose clamps that were found to have drips.

Can't hurt to give the radiator a bit of a spray down to make sure it is clean. So I will do that in the morning also. I have looked at the fins and only see very few that have been bent.

[my12by60]

My OBDII scanner arrived yesterday but my daughter was unable to get it talking to an older LG Optimus android phone that we had lying around. I sent back that scanner back and ordered another one that will work with the ios system on her newer iPhone. The new scanner will be in tomorrow.

I added the Water Wetter the other day and cleaned the radiator as best I could without taking things apart. Not sure what to look for as far as fluid movement in the cooling system in order to check the water pump. With the engine cold the other day, I opened the upper radiator cap and started the car. Don't see much fluid movement at all there, but is that because the thermostat is still closed? Do I need to let it until the thermostat opens in order to do this fluid movement check?

Drove about 50 miles yesterday evening and only had a minor gauge movement when coming upgrade back into my town. Ambient temp was a bit cooler, however, as it was evening and we have some cooler weather at the moment.

[3Q Jay]

at the upper neck you won't see any movement until the t-stat opens. easier to see the stream if the level is not 100% full (but you want at least 50%, then use the lisle funnel to top off) at the upper neck.

[my12by60]

Received the OBDII scanner a few days ago but have not had the car out for any drives of enough length + hills to get the dash gauge moving off of noon. Coolant temp readings around town this evening were 95C to 98C (while climbing a hill). These convert to about 203F to 208F, which sounds about normal based on what I have read using a search. Ambient temp this evening was 92F. I will report back once I get some scanner readings from a long drive during the heat of the day.

[3Q Jay]

glad to hear the data gathering is in progress! Please also take not of how the temp rises. we are looking for a plateau soon after warmup--possibly followed by another rise (t-stat opens, releasing the cool mixture from the radiator into the rest of the system----until it saturates with t-stat wide open. but the (temporary) plateau is an important indicator.

[my12by60]

I will watch for that plateau pattern from a completely cold start.

[Q451990]

You should be able to change the temperature display from C to F in the setup menu if you want... it would save you a conversion step.

[my12by60]

Daughter changed the settings and we have readouts in F. I have not had the car out in the heat of the day for a long enough drive to get any dash temp gauge flare ups. I picked my wife and daughter up at the airport two nights ago (50 mile round trip) and the dash gauge was steady. My daughter had her ipod for the drive home from the airport and the data from the scanner showed the coolant temp never exceeded 206. Ambient temp was only in the 80s, however, as it was late at night.

I have not had my daughter and her ipod with me yet for a cold engine start to check for a thermostat driven plateau in coolant temp.

[my12by60]

Our weather here cooled off last year before I could get any definitive data on the coolant temp using the OBDII scanner. The dash temp gauge has not moved past its usual noon position all winter. In the meantime in preparation for summer, I am looking at other aspects of the cooling system.

I unscrewed the temperature sensor gauge from the top of the thermostat housing and took a good look at the sensor and the wiring. The portion of the sensor that has contact with the coolant was a bit discolored, but did not look gunked up in any meaningful way. I used some light sandpaper to clean up the sensor.

The wire coming off of the top of the sensor and leading to the wire harness was in bad shape. The wire itself had a plastic insulating sleeve that was all cracked up and missing sections. I crumpled the remaining sections of the plastic wire cover with my fingers and removed it. The wire that was inside the plastic sleeve was also in bad shape, with a few sections that were just exposed copper strands without any wire jacket at all. I wrapped the whole wire from the sensor head to the wire harness with some electrical tape to cover the exposed copper strands. Maybe this poorly insulated sensor wire was contributing to the climbing of the dash gauge that I was experiencing with high ambient temps?

I am also thinking about doing a coolant flush to get to a confirmed 30% coolant/70% water mix. I am not sure what the current mix since I have only had the car for 18 months. I don't want to mess around with plugs in the block.

Should I just take off the lower radiator hose and refill with distilled water?
Then repeat this cycle a few times until I start to see very little green?
Is any flush chemical recommended or best to just keep it simple?

[Q451990]

I use the process you mention with a coolant flush in the first cycle. I think I usually go through about 6 gallons of distilled water.

[my12by60]

How many times did you take off the lower hose then refill with distilled before you got to fairly clear radiator contents?

Did you stay away from using any of the flushing chemicals (Prestone flush, etc.)?

I cut the heater hose on my wife's Durango and installed the plastic Prestone flush kit. I don't see anybody here mentioning going this route. Do these kits not work on the Q's heater hoses?

[my12by60]

I think I might have finally solved the problem with my climbing dash temp gauge. A week ago, I bypassed the heater core. This seemed to have little to no impact. Then a few days ago I changed the thermostat from a 180 degree version to a 170 degree version. At the same time, I read in another Nissan forum that the setting of the AC system has some bearing on how effective the cooling system operates. So when I was out today I made sure that the AC system was in Auto mode. In the past, I never used the Econ mode, but I did have a habit of adjusting the fan speed manually, which would make the word "Manual" show up on the AC display.

My wife was with me today with her iphone connected to my obd2 wifi device. The outside temp was 110, so a good test day. Normally, when making the climb back to our suburb, the temp gauge would flare well to the right of the water symbol located at high noon on the gauge. Today the gauge only moved very slightly to the right and never left the water symbol. My wife was watching the actual coolant temp on the iphone and the peak temp reached was 219 at the to top of the climb. The temp quickly came back to 203 once we stopped climbing.

I tested the old 180 degree thermostat in a pot of boiling water and its operation appeared normal. So I don't think the old thermostat was bad. So either the switch to a 170 degree thermostat or the change in how I had the AC set made a difference.

Has anybody else of the AC settings having an impact on cooling system performance?

Has anybody else noticed improved cooling system performance by switching to a lower temp thermostat?

[EdBwoy]

I might have missed this, but is either the original or replacement thermostat OEM?There was a thread recently on the m35 subforum about an overheating issue with autozone Tstats that seemed ok in a pot of boiling water. Nissan OEM cured it.
A lower temp one will allow coolant to get to the radiator at a lower temperature, but I can't quite picture how that would affect it's top end in the long run.
But hey, a fix is a fix, right?


On A/C function affecting the coolant temp? I see it possible for electric fan systems with dual fans whereby the A/C is one of the triggers that kicks on the secondary fan, thus helping cool the radiator as well.

I am not sure how the q45 in-cabin heat exchange box is set up, but in the 2006 M45, the refrigerant HX sits behind the coolant HX/ heater core and air would be cooled first then heated. For that system, since coolant is constantly circulating, I can see a minimal cooling effect on the coolant when the A/C compressor is asked to do its magic.
*The heater core is much smaller & also the amazing specific heat capacity of water tells me that it shouldn't be jumping degrees down.

[my12by60]

The thermostat that was replaced had the brand name Motorad on it. I saw this brand on Amazon as a possibility for the Q. Autozone does not appear to sell this brand. I went and read the thread on the M35 forum. I could not tell from the thread if the OP rechecked both of the Autozone thermostats in boiling water or not. Sounds like one of his t-stats was not opening at all.

By the way, when I tested my Motorad t-stat, it would only open once the water was at a full, bubbling boil. If water boils at 212 degrees, and the Motorad t-stat was a 180 degree t-stat, why does it need 212 degree water in order to open? Is a 180 degree t-stat supposed to open at 180?