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01 Pathfinder overheating


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Hey Guys,

It's been a while since I've posted anything, but I have an overheating issue. I noticed the other day that my temp was way high. Pulled into an autoparts store and got some coolant. I noticed there was a significant leak so I  got a radiator and had the truck towed to the house and replaced the radiator. It was fine for a few days and then today it started chugging for a second. Looked at my temp guage and it was way up again. Nothing from the radiator and couldn't see any leaks. So i limped a few blocks to the house and thought it must be the thermostat. Put in a new thermostat and housing. Started to pour in the coolant and could hear it coming out. I looked underneath and it's pouring out from behind the oil pan. Does that tell anyone anything? Is that the water pump or what am I looking at? Any help on this would be great because as it sits, I have no way to get to work without this old beast. 

Thanks guys!   

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Behind the oil pan, as in the back of the engine? Check heater hoses etc to rule out the easy stuff. If it's not that, there's a crossover pipe between the heads on the back of the engine, might be that.

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For the leak definitely check what Slartibartfast mentioned. Hopefully it's not the crossover pipe...

 

I dealt with some overheating issues last year as well. Things to check based on my experience if you are able to find/fix the leak but it's still overheating. As with anything start with the simplest potential issue and work your way up:

 

1. Check the radiator cap. For some reason the old owner of my Pathfinder had the wrong cap (too low pressure) installed and I think this was at least part of my issue

2. VQ35 Pathfinders have 2 thermostats - one in the front of the engine, and one in the back of the engine. The one in the back is a PITA to get to and replace. If you have significant miles on yours there is a good chance the back is factory original and needs to be replaced anyway

3. Double check that the fan clutch is working properly

 

If that doesn't work could be the water pump, although to answer your question it's on the front of the engine behind the timing chain cover. 

 

Hope that helps...

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Thanks you guys. I bought the water pump, took off the cover for the pump and the tensioner. Took out the tensioner but put it back in because I'm nervous about top dead center. I'm going back out to check it again but it's been 110 degrees plus the last few days and not a lot of fun as soon as I get home from work. I'm curious what these marks mean exactly. I'm scared to death that if I take the tension off of the chain on the pump side and it isn't on tdc, the cams will roll and the chain jumps a tooth and I'm completely screwed. I had no idea there was a thermostat on the back of the motor? I think since I'm this deep, I'm going to keep going with the pump if anyone can tell me the best way to get tdc? I'll look on google but you guys usually have more info!! Here are the timing marks on the top of the crank pulley. What exactly do they mean?

timing marks.jpeg

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I got the pump in after I found tdc. Just took a little longer than expected. Now I'm going to start pulling hoses. All of the hoses I've looked at looked ok and as fast as it was coming out, it has to be either off, or torn pretty bad. It was pouring out with it not running. I was just trying to fill it and it was coming out from behind the oil pan. It reminds me of when I had 2 bad O-rings on my Isuzu Trooper. They were O-rings on the inlet to the thermostat. Coolant came out of the housing, ran down the valley and out the back by the oil pan. I've got an endoscope that i can look down inside to a degree. I'll try that first and maybe I can save a little money.

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I wonder if it could be the one below the intake manifold? That's pretty big and far back there... could it flow in a way that ended up behind the oil pan? 

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I had a very similar issue in 2018. If you get under the truck, behind the front wheels, and look up behind the engine and see coolant on the transmission bell housing its likely the coolant crossover pipe gasket. There are two gaskets, one for each cylinder head port/flange. Legend has it some people, like @02_Pathy  , have been able to replace it without dropping the transmission but I was not one of those lucky people. The pipe is basically backed up against the firewall with little more than a fingers width of space to work with. If you're lucky it'll be the water control valve gasket (2nd thermostat) in the coolant crossover pipe. You'll need to tear down the intake plenum to reach that one. 

 

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Edited by TowndawgR50
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When I get home from work today, I'm going to pull the manifold. If you've got upper and lower intake off, is that pipe within reach? As I said before, this coolant was pouring out just like I was pouring it in. I did read about a guy who had the small hose that is under the manifold blow. I'm hoping that's what I'll find. I pulled the heater hoses last night and they were old but definitely still viable. I tried to reach back there last night while I was doing the heater hoses and that's not happening. I really don't want to drop the tranny but if that's what it takes, so be it. I can replace the rear main seal while I'm there. The other thing that makes me think that it was something on the outside(like that damn pipe) was when I used my endoscope last night to look inside, there wasn't a drop of coolant in the valley. I think I'll put the new heater hoses on and pour a jug of water in the radiator and be ready to watch on the back of the motor. This is a real PITA!! 

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With the upper and lower plenum, fuel rail, and the intake manifold off, the rear thermostat and hose is easy to reach. The back pipe is not easy to reach. 

 

 

If you're going to hunt for it, make sure you have an intake gasket set though - you can't reuse them. Not a bad idea to have some vacuum line handy - I just went through this repair myself and there were a couple rotten hoses. You're right behind the PCV valve too, so if you've never done that you can replace it. IF that hose was the one that was ruptured, it surely would have spilled coolant all over your knock sensor. I'm not sure how happy it would be after that. 

 

See if you can source the thermostat too - its a different model than the one you just put in the front. It took me a couple days to find one locally. 

Edited by Jotegir
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11 hours ago, ryjaytay38 said:

When I get home from work today, I'm going to pull the manifold. If you've got upper and lower intake off, is that pipe within reach? As I said before, this coolant was pouring out just like I was pouring it in. 

The pipe is within reach but there is not enough room to pull the pipe off the studs and replace the gaskets. The water control valve is reachable and can be changed without removing the coolant crossover pipe.

 

I had the very same conditions. Poured water in, it came right out the passenger side cylinder head coolant crossover port. 
 

A great way to check before tearing everything down is to pressurize your coolant system and listen/look for the leak. I made one with a spare radiator cap and schrader valve but they may even have something you can rent for free from an auto parts store. 

Edited by TowndawgR50
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Good call Slartibartfast-I checked and they are all completely solid. Thanks for the diagram Towndawg. I'm ordering the parts tonight. It looks like I need 2 gaskets. I'm looking for #11062 correct? 

Ok fast forward a few hours. I thought I had one more chance to not have to drop the tranny and that was if that hose underneath the manifold was blown and here it is!! I think I need to get a little better with my endoscope because I didn't see a drop of coolant  and it appears as though I might have missed something?!?!  What would you guys suggest? Replace the thermostat, the hose obviously, the knock sensor, PCV valve, the square gasket for the other housing(I'm not sure what it's called) that the hose connects to, and there are a multitude of other hoses that need to be replaced. Any others that you guys suggest? Thanks for all of the advice so far by the way!

Resized_20210811_205149_189328955627046.jpeg

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Good find! Glad you don’t have to drop the transmission, thats not a fun job.  

 

As for recommendations- Any item that requires taking off the intake to replace or is made easier by the current level of access. I believe I did my spark plugs, valve cover gaskets, some vacuum, coolant and fuel lines, fuel injector O-Rings as well as a few other items that were easily accessed with everything off the top of the motor.


It definitely adds to the time and money invested but its well spent if you plan on keeping the rig for the long haul. 
 

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I've got all gaskets(including valve cover), multiple coolant hoses, need to go get some more vacuum lines. Did the injector rings a few days ago. I just cancelled the order for the water valve. These guys were taking forever and I couldn't get any response from them. Nissan that's a few miles away has it in stock so I'm going to pick it up this morning. Also, knock sensor should be here today. While I'm at Nissan, I'll get the water neck outlet gasket for the lower side. Btw, when I took that blown hose off, the inside was like mush. I'm checking everything and replacing. I don't think my engine would be all that happy having any of that rubber slurry/paste down inside of it. Yeah that's an absolute load off my mind to not have to drop the tranny. I had to on my other truck to put in a torque converter which wasn't terrible, but the difference is that was done in the garage- I'm doing the Nissan out in the rocks on the side of the house. Not the ideal situation, but it could definitely be worse. 

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  • 2 weeks later...

Hey guys, I'm finally putting the Pathfinder back together. All is together except one thing:  I didn't mark where all the vacuum lines go. (I'm not the sharpest knife in the drawer). The one hose that I can't find a port for is coming from the swirl valve vacuum box. One goes straight up to the top plenum and the one to the right of it comes out of the box, does a hard left and it goes about as far as the regulator and damper but there is no port. I'm wondering if it goes down into the intake manifold? I've looked everywhere online and there is no destination for this *!?@# hose. Ilooked in the manual to no avail. I didn't want to post this because I'm pretty embarrassed, but if anyone can tell me where it goes, I'd be forever grateful!

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