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Temp gauge reading high after thermostat replacement

18K views 17 replies 7 participants last post by  Carguy75 
#1 ·
My 2003 Murano (65,000 miles) overheated a few days ago (Temp gauge at Max reading.). Immediately pulled over and had murano towed to my mechanic. Mechanic changed thermostat and on my way home (uphill from sea level to 1500 feet) temperature gauge began rising to 80% mark. slowing down and turning off AC helped lower it but rose again as I proceeded uphill. Let car cool and checked radiator cap and it looks fine as well as fluid level.

Before the thermostat was replaced Temp. gauge never went above 50% even driving uphill to 10,000 feet with A/C on (live on BI of Hawaii). Only related? problem is that A/C would cycle on and off if Temp. outside was above 85F and driving in slow traffic or stopped on any terrain. Had previously discussed this with mechanic and he said sometimes if cooling system not functioning A/C will kick off if too hot. I had planned to have mechanic troubleshoot this further but had delayed doing this.

I have checked the fans and they function correctly. Let engine cool and fans are off unless A/C is on. As engine warms up fans come on even with A/C off. Plenty of fluid in reservoir. Will hose off area of cool engine compartment to remove radiator fluid residue from overheating and then check for leaks and small overflow hose near cap.

Other forum posts indicate that I should have mechanic check pressure since this can be a cause of the overheating. If the pressure is fine is there any reason to bleed the system? No other noises from engine or water pump.
 
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#4 ·
Could be a premature water pump failure, although not likely. Could be the thermostat wasn't the problem, i.e. radiator clogging. Could be the new thermostat and gasket were installed incorrectly (many will fit backwards and jam the flow, don't know if that's possible on the Murano) or simply that the thermostat is DOA defective. I once tore down an engine trying to find the reason for an overheat when nothing seemed to fix it. And found out it was a replacement thermostat DOA. Lots of work over a ten dollar part. So now, I test a new thermostat in a pot of water before it will be used.
 
#5 ·
So now, I test a new thermostat in a pot of water before it will be used.
Yes. :29: This is a very good step to always do whenever you are replacing your stat. Drop both old and new stat in the pot and compare its functionality right around boiling point. I have done this a couple of years ago on my 99 odyssey @ 192K. The oem stat was still working but much much slower on the opening and closing. Also avoid those stat that fails open. They have a higher rate of early failure than the regular stat like oem.
 
#6 ·
Mechanic replaced thermostat after I had car towed to shop after Temp. gauge went to highest possible reading and radiator fluid in engine compartment.

Today rechecked radiator cap and made sure completely closed. Drove vehicle with A/C on uphill for 10 miles and Temp. gauge never went above 50%. Outside Temp. today was 75F but outside Temp. for problem described was 90F, so keeping my fingers crossed if outside Temp. rises engine temp gauge will remain at 50% or below.
 
#7 ·
If everything is working properly, the temp needle should be lower than 50% more like 40-45% and stay there. I live in Vegas and this has always been my reading even on our hottest 115 + deg days. I don't remember an instance where the needle moved any higher than that since 2004.
 
#8 ·
" Also avoid those stat that fails open." Well, if it fails to open, it isn't "going to" fail, already DOA and a cheap paperweight.


Thermostats are really simple elegant engineering. There's a little cylinder full of wax opposite the spring. Special wax that expands like crazy when it heats up, moving the valve and pushing against the spring. But if that cylinder isn't machined correctly, or there isn't enough wax in it, or the spring is too strong...it also elegantly fails to open.


And when the engineers do their job, in theory it is impossible to put the thermostat or gasket in backwards, but some cars seem to have been built without the aid of engineers.<G>


Sounds like Robert's may have just not had the radiator cap seated down properly.
 
#9 ·
" Also avoid those stat that fails open." Well, if it fails to open, it isn't "going to" fail, already DOA and a cheap paperweight.



Sounds like Robert's may have just not had the radiator cap seated down properly.


No. When it fails its suppose to always fail on an open position allowing coolant to flow. This is the one folks should try to avoid....Fail-Safe Automotive Thermostat - MotoRad

Doubt it. Its hard to go wrong in screwing in the rad cap. It only goes in 180.
 
#10 ·
nitely-
That's NOT a conventional thermostat. As their web page says "Fail-Safe has a patented safeguard against overheating damage."


That's like saying a flat tire doesn't matter any more, because one company has developed run-flat tires. I don't know of any stock car that has fail-safe thermostats, but then again, they don't always send me the memo when something gets improved.(G)


Radiator caps are also still easy to screw up. Just a little anti-leak crud, or some corrosion, or dimpling the gasket as it seats, or catching a bit of rag under the cap, will prevent a seal. If all that Robert did was to reseat the radiator cap, then the simplest explanation is that it wasn't seated properly in the first place.


Occam's razor. Until proven otherwise.
 
#11 ·
Red,

Who is saying its a conventional stat? Where did that come from?
You seem to have missed the entire point I was trying to make regarding the fail open/fail safe stats. If you reread my prior post, I am giving a warning to folks that might be inclined to using those fail safe stats. I found out during my last stat replacement, that this fail safe stat has lots of report on early failures making it very unreliable and not worth using. That is all.
 
#13 ·
I went to motoRad site to see what is available for our MOs and I'm glad to say that there is no option for those fail safe stat for any year. They only make the standard stat fitted in the housing. But for other vehicles that you guys might need a new stat for, heads up and avoid the fail safe/fail open stat by motorad.
 
#14 ·
Follow Up

I am following up to this post -- My previous account "Roberthawaii" was deactivated due to some username issue and the Admin has been contacted.

The problem with the engine Temp. gauge reading high has continued. I have replaced the radiator cap and mechanic pressure tested the engine and pressure is consistent. His next step is to check and possibly replace cooling system and A/C system relays. However, the diagram/legend for the relays is not on or inside the fuse box/relay box cover. Does anyone have the relay fuse diagrams for a 2003 Nissan Murano SL?

Mahalo

Robert on Hawaii
 
#15 ·
Are you relying on the temp gauge to read the temp or using a hand held device? It is very possible that the sensor on your MO is faulty and showing more than it actually is. I would check the water temp using a hand held device before spending more money on parts or labor.
 
#16 ·
PROBLEM SOLVED: After additional troubleshooting, testing the engine Temp with a handheld infrared thermometer, which confirmed the engine was running hot, replacing the cooling system relays, checking coolant mix ratio, fan performance, or if the radiator was blocked in any way I decided to have my mechanic change the thermostat again.

When he removed the thermostat he discovered that the pin that is supposed to go in the hole at the 90 degree bend inside the assembly, was not in the hole. He replaced the thermostat assembly at my request and the engine is no longer overheating.

Since this was not the mechanic who replaced the thermostat originally I have no idea what he did. Either it was a defective part or something else? When I first returned he should have removed the thermostat and checked it, since it was the last part replaced. Instead he wanted to replace the radiator. My mistake for not demanding this first. In the end I'm glad I found a reliable and trustworthy mechanic.

Others on this forum have reported the same symptoms and based on my experience I would say make sure your thermostat is really working or just replace it, it's an inexpensive and easy repair compared to the damage that an overheating engine can cause. Thank again to all the responses
 

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#18 ·
Thanks for sharing this useful bit of information.

Your story is why I try to do all the work on my cars myself(or taking it to the dealership if all else fails) due to how hard it is to find a competent/honest independent mechanic that will correctly fix a problem instead of missing simple solutions and/ or creating problems to keep you coming back for more repairs.
 
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