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Let's play guess the overheating issue!

5K views 39 replies 11 participants last post by  JayAre 
#1 ·
Ok so, I've been having this issue the last two summers of the truck running hot in certain situations. I have tried a few things, and have a few ideas, but I wanted to get the opinions of the masses before I start doing some serious things, or throwing money at it. Here are the details:

2012 P4x w 72K miles.

When it runs hot:
When I'm pulling my boat with the A/C on, hot days (90º+) with the A/C on and under load or acceleration. Stop and go it doesn't get too hot, but if I've been sitting for a while, and then accelerate moderately (get into it), I can watch the temps climb on my BullyDog. Once I get to a decent cruise speed it cools back off (so maybe just when the trans is in lower gears?).

I have a friend who seems to think that my front bumper is blocking too much air (see pic below) but I'm not sold on the idea, since there are a lot of other trucks that have front bumpers that block a lot of air and they aren't reporting overheating issues. I plan to take it off and drive around for a few days when the temps are up in the 90s to see if that helps, and to rule out that as a possibility.

I had the dealership drain and fill the coolant recently, and I even topped it off again and burped the air out, but it still does it.

I have checked the clutch fan, and it seems to behave the way it should (spins but with a bit of resistance) I've even tried pressing a piece of cardboard into the fan to see if I can get it to stop when it's running, and it wouldn't. So it seems like it normal behavior (I think?)

The OEM electric fan on the back of the radiator is functioning (although really loud when it does) so I don't think it's that. I've even installed an efan on the trans cooler, and that doesn't seem to help much. Trans temps usually run 175-185º or so.

I have sprayed out the radiator numerous times, and even removed the trans cooler so I could clean out behind that.

I checked the trans fluid in the fall, and it looked good.

I'm running out of ideas of what else to try without just throwing money at it.
Anybody have any ideas of what might be causing this? I don't think it's the tstat because if it was I think it would be overheating all the time.

Here's the bumper that DRB thinks has something to do with it. I guess I'll find out when I take it off this weekend.





Whoever has the winning suggestion gets a sweet high five, and an awesome bro-hug.
 
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#2 · (Edited)
I have checked the clutch fan, and it seems to behave the way it should (spins but with a bit of resistance) I've even tried pressing a piece of cardboard into the fan to see if I can get it to stop when it's running, and it wouldn't.
If the clutch is fully locked up, you should be feeling a LOT of resistance (i.e., can rotate it by hand, but can't spin it at all).

If it's locked up, you should also be hearing some major fan roar at just about any engine speed above idle.

The "cardboard test" is kind of iffy. If you try it on a cold engine (just a few seconds after start-up, when the clutch should be fully disengaged), you might discover that cardboard doesn't stop the fan from spinning even then.

VERY sharp-looking truck, BTW.
 
#5 ·
It spins about a half to three quarters of a rotation when I try and spin it. I do hear a lot of roar, but not all the time. It does it when I first start it up, and then it stops, but then it starts up again once it gets up to temp. And thanks!

How hot is hot? Is it still in the normal range?
Normally it climbs to the low 220's, but if I push it a little harder I can hit the 230's, with the boat it's even hotter.

First off, your bumper is blocking the lower half of the radiator in comparison to the OEM bumper, so, it may have some affect on low speed cooling.

And just to clarify, you are talking when sitting at a stop for a while, traffic moves and you are then able to accelerate up to speed is when the temp climbs for a bit? What kind of temps are we talking?

Yes, it does it then, but it can also do it when I just set at a red light for a moment, then take off with a little spirit.


Fan clutch aside, I'm thinking what you are seeing is the fact that the truck itself is building up a mass of heat while sitting still. No large flow of air through the radiator and under the truck. Now add the stress of the boat when you are accelerating.

Can I assume this is a non issue without the boat attached? How heavy is the boat?
It's more of an issue with the boat attached, but it still does it without it, just doesn't get as hot. It's a 20' pontoon that's about 3,500lbs with trailer. I think once I take the bumper off it will tell me if that is the issue. It's just a PITA to unhook the winch, lights and all. I plan on doing it this weekend though.


Thanks for the responses gents.
 
#4 ·
First off, your bumper is blocking the lower half of the radiator in comparison to the OEM bumper, so, it may have some affect on low speed cooling.

And just to clarify, you are talking when sitting at a stop for a while, traffic moves and you are then able to accelerate up to speed is when the temp climbs for a bit? What kind of temps are we talking?

Fan clutch aside, I'm thinking what you are seeing is the fact that the truck itself is building up a mass of heat while sitting still. No large flow of air through the radiator and under the truck. Now add the stress of the boat when you are accelerating.

Can I assume this is a non issue without the boat attached? How heavy is the boat?
 
#8 ·
Sticky thermostat. Swap it out.
But would it not overheat all the time and not in only specific circumstances if it were the tstat? I may still explore this option since it's a part bound to go out eventually anyway.

Why not replace with a good-quality new fan clutch?

In the Arizona heat, I figure about 6 years for a fan clutch.
Is there a good-quality brand you would recommend? Price ranges all over the place on Amazon.
 
#7 ·
Why not replace with a good-quality new fan clutch?

In the Arizona heat, I figure about 6 years for a fan clutch.
 
#13 ·
Is your transmission still plumbed through the in-tank ATF cooler in the radiator, as well as the external cooler?

I've seen members report overheating when towing with the in-tank cooler bypassed.
 
#14 ·
I'm not sure if it is also ran through the radiator, but the trans cooler is the OEM kind that they started putting on these to help prevent the SMOD, so I didn't have to do any bypassing. I just put a fan on the trans cooler as a precautionary step. Going off of the trans temps reported on the BullyDog, I would say the trans isn't what seems to be overheating. I went an picked up a tstat during lunch, so I'll probably swap that out at some point over the weekend.
 
#15 ·
I'm not sure if it is also ran through the radiator, but the trans cooler is the OEM kind that they started putting on these to help prevent the SMOD, so I didn't have to do any bypassing.
All 2nd generator Frontiers with automatic transmissions are factory-equipped with an in-the-radiator ATF cooler. The external cooler is just a supplement to the in-the-radiator one - It's not intended to replace it, or to prevent anything other than overheated ATF.
 
#16 ·
It is my opinion, and it is hotly contested here, that the internal pass of the trans fluid through the radiator isn't so much to cool the trans fluid as it is to pre-warm it on startup.

My trans operating temp is 150 degrees + or - a few. My coolant operating temp is 180 (again, with fluctuations)

At operating temperature, in ideal conditions, the trans runs cooler than the engine. If anything the engine coolant is *heating* the trans fluid.

Now, the argument has been made that in extreme situations (towing, hauling, etc) the trans fluid will hit the 180° mark and beyond. At which point, theoretically, the coolant should bleed heat from the trans fluid.

I'll tell ya something, if my trans hits 200° + when towing (and I do, a lot, through CA mountains) then something is wrong with my setup or I'm pushing it too hard. I'm certainly not going to depend on a slow pass through a chamber that is only 20° cooler, It's just not practical.

/shadetree mechanic

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#19 ·
Perhaps "cooler" would be better if it were replaced with "fluid temperature maintainer?" It does both: it warms the fluid quicker to normal operating temperature and it offers cooling if the fluid gets too hot. Trans fluid's optimal operating temperature is 175-200 degrees F. in the pan and shouldn't drop below 150 degrees. Using only an air-to-liquid cooler could possibly over-cool the trans fluid, whereas a cooler inside a radiator tank will typically keep the fluid temperature in the proper range. Radiator integral coolers are practical because the are a liquid-to-liquid cooler and are far more efficient that air-to-liquid coolers and the reason they've been used in vehicles for over fifty years. Some GM trucks not only use them to cool the trans fluid, but also to cool the engine oil.
 
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#17 ·
Reading shows sketchy quality on cheap fan clutches. I use Hayden on my Mazda truck, but admit to O'Reilly on my 1998 Frontier with 209K miles. I think 1/2 to 3/4 spin when hot is getting excessive, guess it depends how hard of a push one puts on the fan blade.

So my preferences would be Hayden or Nissan.
 
#18 ·
Reading shows sketchy quality on cheap fan clutches.
Yep.

I had to return one I bought at Auto Zone. It didn't work much better than the old, dead one it replaced.

In the RV world, metal flex-blade fans are a pretty popular replacement for the original clutch and plastic fan. Typically, they're installed with a spacer kit that replaces the original fan clutch.

They're capable of moving a LOT of air, without having to worry about a fan clutch failing. However, they're noisy.

 
#21 ·
Hmmm, hot when you accelerate...all things being equal, I'd say your cooling components are working normal, never heard of this particular issue and I ran with the jeep crowd for years.. If you have cooling component issues, sitting idle in high heat with the AC on is when you find out. Are you absolutely sure your temp. sensor and gauge are working 100%
 
#22 ·
Well, when taking things apart to get to the tstat, I noticed the back of the radiator was still filthy with crud caked into it. So I decided to go ahead and pull the radiator out completely and give it a thorough cleaning as well as the condenser. Then changes the tstat and then put everything back in. Just need to refill the coolant and then I will see if it helped. Good thing is I now know how to resolve my fan clutch and radiator if I decide I need to. Just going off of the amount of crap I washed out of the radiator it has to have helped at least some. It was super dirty, especially behind where the stock efan was.
 
#23 ·
Got it all put back together, and filled the radiator, and reservoir up with coolant. I have one of those elevated funnels that attach to the radiator, and put fluid in that too. Then I started the truck up with the defrost on high heat and let it run for a few minutes. Within 10 minutes it was already hitting 226º and the heater is blowing cold air. I shut the truck off, let it cool for a bit, then topped it off again. Still doing the same thing. I felt the lower radiator hose and it didn't feel like it had any fluid in it and it was cold to the touch. Should this hose be hot when coolant temps are in the 220s? I feel like the new tstat is not opening at all now. If so, I'm going to be pissed!!

This is the thermostat I just put in: Murray Temperature Control Plus 39170 - Thermostat | O'Reilly Auto Parts

Possible that it's a junk thermostat?
 
#25 · (Edited)
I've never opened the tstat housing on a 4.0 can it only be installed one way? Some engines it's possible to install a tstat backwards...

Also, the lower hose is the return from the engine, so if the tstat never opened, the engine heads never got coolant, so there would be none in that hose until it does. Which is why it over heated almost immediately.

I think...

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#24 ·
Lots of modern vehicles are challenging to purge all the air out of the system. Some Nissan engines (1st Generation for sure) have air bleed screws. On some trucks I jack up the front end and run with cap off and keep adding coolant until it's really full.

I think crud on the radiator will definitely hurt cooling, need that air to pass through.
 
#26 ·
I've always watched the coolant at the cap to see if it starts "bouncing" as it gets hotter. This is indicative of a thermostat on the edge of opening up. Once it does, coolant level should drop immediately.

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#29 ·
Here's what I do with these vehicles when servicing the coolant:
-Remove the radiator and reservoir caps.
-Fill the radiator and install the cap.
-Fill the reservoir to the "MAX" line and install the cap.
-Jack up the nose of the vehicle as much as safely possible.
-Start the engine and turn the heater to the highest heat setting (if you are working on a Pathfinder with rear heat, make sure the rear heater is "on" and set to the highest heat setting).
-Fix a suitable tool (an adjustable hood prop rod works well) between the gas pedal and the driver's seat cushion to keep the engine RPM around 3000 RPM and run for about 10 minutes (or longer, if needed) until hot air is coming out of the heater vents.
-Remove the tool between the gas pedal and seat, shut the engine off, lower the vehicle down.
-Let the engine cool down and top off the reservoir, if needed.

If the heater performance is poor, repeat the process. So far, I've never had to do this twice.
 
#30 ·
smj999smj that is what I did just without the use of the gas pedal tool. Instead I just slowly rev'd it to 2,500 rpms a few times per try. After the 3rd time burping it I drove it to fill it up with gas, and I'm happy to report I am now seeing some of the coolest temperatures I have seen in a while. I drove it pretty hard with the AC on for about 20 minutes and couldn't get the temps over 207º. Sat in my driveway with the AC on for 20 minutes. Usually I would see it running at around 215º but it ran at a cool 199. I guess the ultimate test will be to try and tow the boat when in it's in the mid 90's (it was 90 yesterday), but I'm fairly confident that I have this taken care of. Thanks for all the suggestions and help guys.
 
#33 ·
Are you reading your coolant temps thru an OBD 2 scanner?
I'm reading the temps from my Bully Dog GT. Which yes, plugs into my OBDII port.

Something a little weird I'm seeing now though, with no heat or ac on, I can see temps hitting 222º (The dash gauge starts climbing after I hit 225º) while driving into work (mostly highway)... but when I turn on my AC the temps go way down into the 197-200º range.... which is almost the complete opposite it was doing before. I've never heard of an engine running cooler with the AC on. My only guess is that with the AC on the electric fan is kicking on and pulling more air through the radiator. I imagine I still just have a bubble somewhere, so I will do the coolant burp process once again. I'm getting good at it hahah
 
#34 ·
Just thought I'd give this a little update. After i swapped out the tstat it seemed to run a little cooler for about a day, and then started getting hot again. So then I replaced the fan clutch. Still ran hot. So THEN, I had the idea that maybe somehow my radiator was clogged on the inside, or just not working as well as it should. So... I put a fancy CSF Aluminum radiator in it. Since I wheel a lot, and tow my boat during the summer, I figure it wouldn't hurt to get the upgrade. So, swapped it out.... and guess what... STILL ran hot. With the days getting hotter and hotter here in Nashville I was seeing temps all through the 220s, even saw 230 once before i turned the heater on. I was beginning to get discouraged to say the least and was actually contemplating taking it to the dealeship (shame on me). But... before I did that, I wanted to try one last thing. The thermostat that I put in was one I got from Oreilly's, and I had read a few threads where people used a non oem tstat and had problems with it. SO... I ordered a genuine nissan tstat and put it in.Well... that completely fix it. Ive been running around for 2 days now with temps never running any higher than 193 with the AC cranked and heavy footing it. I bought the Oreilly's part against my better judegment because I wanted to replace it THAT day. So, I replaced a fan clutch, and put a radiator in that I most likely didn't need, but hey at least it looks good!

I know some people have had no problems with parts store parts, my I've learned my lesson, and will NEVER put a non OEM part on my truck again...well, besides suspension components ;-)

Just wanted to share and give this thread some closure.
 
#36 ·
I did. It started to open around 180 and looked to be fully open around 200, so I'm not 100% positive that the original was actually bad. I guess I will never know with certainty which part actually fixed it, but I could've saved myself a lot of grief by just using the right part in the first place. In the passed month, I have completely torn apart the front engine of my truck FIVE times. I'm actually quite good at it now though.
 
#37 · (Edited)
Thanks for the update!

I know some people have had no problems with parts store parts, my I've learned my lesson, and will NEVER put a non OEM part on my truck again...well, besides suspension components ;-)
Non-OEM electrical parts, fuel pumps, fan clutches and thermostats seem to be the main cause of problems.

Just about everything else aftermarket usually works OK, as long as you choose a quality brand.
 
#38 ·
I haven't had any issue with Stant thermostats on any of my vehicles. I'd buy those or factory.
 
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