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Hello, My truck is been acting up this last few weeks. Not too long ago I change the oil on the transmission. I have a 07 xterra auto tranny. After that everything felt normal until I took a 2 hour highway trip. I noticed that after a few minutes of driving over 75-80mph the temp starts to raised and wont stop unless i slow down, but under 70 the temp stays normal. After I got to my destination i checked the coolant level and it was low so I added more coolant. On my way back I tested it and it still got hotter as it drove over the 75mph. The coolant level stayed full and the truck still gets hot when i drive over the speed.

This happened in Florida pretty much flat roads and maybe a little hill, nothing noticeable. And i drove 75-80 and locked the speed control. I did notice the transmission shifting to keep the speed constant. Any Ideas what could be causing this ?
 

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couple ideas:

1) air in coolant system- check the coolant level in the plastic clear res with motor just started after sitting more than a few hours, like overnight. Level should be above min line.

do not just check with engine off and cold engine. engine needs to be running BUT cold to get accurate reading, it matters!

2) SMOD- hope not and if so I hope you have warranty. check for coolant in transmission fluid.

3) thermostat sticking maybe?
 

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I checked the coolant level and it looks where it is supposed to be. now is there and easy way to check for the water on the transmission ? The transmission shifts good and it doesn't slip so I will supposed it doesn't have water in it. but I will still like to check. Is there a post on the SMOD? I remember i read about it a long time ago.
 

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check at the stick, just use a 10mm socket with extension and unbolt the stick and check. See what color it is and that it is clear. if it is frothy/not clear and milk shake colored bad news.

Some say you have to drain a little to check. but i say check the stick at tranny, the coolant for clear green anti-freeze only in the res, and check the radiator and cap and if no milky pink anywhere but trans (clear pink is good or red) then you are good for now.

remember, this is a "common" issue among our x's from 2005-200x? and it tends to sneak up on people.
 

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Make sure there is no air in the coolant.

Take the caps off the tank and radiator before starting up in the morning, start up and let it run until coolant starts pumping out of the radiator(if it even does) and drops level in the tank, this will release air trapped in the system, fill the tank to the fill line while it is running, watch the level and see if it continues to drop, keep adding fluid until it stops. Don't let the engine run too long and heat up too much during this process, do it quickly. Very effective.

IF that is not it, maybe a bad fan clutch? Maybe your fan clutch isn't holding beyond 3000+rpm's very well. I don't have much knowledge in how a fan clutch works.
 

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I had many issues with the fan clutch. The bearing of the original one got some play and I change it with one that wasn't from nissan. The new one was a bit stronger and you could hear it at lower speeds pulling the air nicely, but It damage the bearing of fan clutch bracket. After that, I ended up buying a new bracket and a new fan clutch from nissan just to be on the safe side. I am going to do the AIR IN THE COOLANT TEST and see what happens. the funny thing is that the truck doesn't over heats in the florida sun. it gets pretty hot down here around 95 -100 and the truck runs fine even in heavy traffic.
 

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you sure it's not just the gauge giving false readings?

typically (from my experience), if you have air in the coolant, or a stuck thermostat etc. overheating will usually occur at idle or in city driving since the engine is not getting much airflow.

it's usually on the highway where the engine is getting airflow and it can stay in normal temperatures even if there is air in the coolant or a stuck thermostat. It just seems odd that it would only do it over 70mph.
 

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nickpapa, I agree with you on the air flow. But the weird thing is that once it starts to raise the temperature if you let your foot of the gas pedal and bring the speed down to about 70 the temperature gauge would go back to normal. now Is there any way to check if the gauge is working properly ?
 

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just curious, what if you brought the car over 70mph and dropped it in neutral to let it idle. i wonder if the temperature would keep going up or if it would drop.

maybe it's the coolant temperature sensor? i would think you'd throw a code if that was the case though
 

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Hello, My truck is been acting up this last few weeks. Not too long ago I change the oil on the transmission. I have a 07 xterra auto tranny. After that everything felt normal until I took a 2 hour highway trip. I noticed that after a few minutes of driving over 75-80mph the temp starts to raised and wont stop unless i slow down, but under 70 the temp stays normal. After I got to my destination i checked the coolant level and it was low so I added more coolant. On my way back I tested it and it still got hotter as it drove over the 75mph. The coolant level stayed full and the truck still gets hot when i drive over the speed.

This happened in Florida pretty much flat roads and maybe a little hill, nothing noticeable. And i drove 75-80 and locked the speed control. I did notice the transmission shifting to keep the speed constant. Any Ideas what could be causing this ?

Being an automatic trans if it is constantly shifting up and down to maintain that speed that could be part of the issue. Automatic transmissions have clutch packs that slip whenever they change gears creating heat that heat is then transferred to the cooling system via the radiator so excessive shifting of the trans can cause overheating.
 

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Being an automatic trans if it is constantly shifting up and down to maintain that speed that could be part of the issue. Automatic transmissions have clutch packs that slip whenever they change gears creating heat that heat is then transferred to the cooling system via the radiator so excessive shifting of the trans can cause overheating.
bro this thread is like 9-10 years old!

also the trans shifting up and down really shouldn't have any effect on the engine temp, trans temp sure, but not engine.
 

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bro this thread is like 9-10 years old!

also the trans shifting up and down really shouldn't have any effect on the engine temp, trans temp sure, but not engine.
Well the forum is being screwy then it showed me this thread under new posts and I haven't even been a member that long
 

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there is a stretch of highway in my neck of the woods where you can get away with going 80mph for a few minutes legally. She is nice and smooth at that speed BUT it's something i really don't want to do a long time with the heavy duratrac tires. Seems my Nessie prefers 67-69 mph for long distances.
 

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I just got back from a Minneapolis to Black Hills trip. I did a lot at 65, a little at 70 and a little more at 75. I could feel the truck getting lighter because the fuel consumption was outrageous. But, I didn't buy it for the mileage. Had to be one of the sexiest vehicles rolling across I90 in South Dakota.
 

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FWIW - here in SC the interstates are 70mph speed limit, and if you do anything less than 80 even in the right lane your going to get run over. Almost never see a trooper. If you do there usually passing you like your standing still. I pretty much always have my cruise control set at 80MPH - no issues whatsoever. Plenty of times I have been in a long line of traffic running 90. Its a little squirrelly at 90 I will admit, but temps are fine.
 

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Just got back from a 2,850 mile road trip of the South West and some of the interstate was 75 mph speed limit and a lot 70. The X handled the 80 fine but seemed most happy at 70. There wasn't a lot of traffic so I just set the CC at about 72 and motored on. With a roof box we averaged 19.75 mpg.
 
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