# 2003 Pathfinder Overheating...Please Help!!!



## SDNissanOwner (Aug 28, 2012)

Hi Everybody,

My 2003 Pathfinder started overheating on my way to Yosemite N.P. I was going uphill with the A/C on on a very hot day. Ever since then, my truck will overheat going up a long hill or when the outside temperature is pretty hot. Seems to be OK on short drives or driving at high speeds without going uphill. If I notice the engine starting to overheat, I can turn the A/C off and blast the heater and the temp will go back to normal. It doesn't appear to be leaking any coolant... the radiator and overflow reservoir are always full.

Has anyone else had this problem and found a solution? I've read other posts where people have said that these radiators are prone to failing (getting clogged with deposits), that air sometimes gets trapped in the cooling system preventing proper flow, and I saw one post where someone's oil cooler got clogged causing the engine to overheat.

Anyway, any help or comments would be appreciated, especially if you found a solution to the problem.

Thanks!


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## IanH (Feb 11, 2003)

I also have a 2003 Pathy. I have not had a problem yet.
I suggest you look up the bleeding procedure and bleed the cooling system.

On the forum here others have replaced radiators. blocked cooling tubes. 
Also some head gasket replacements, but these were on already overheating trucks.

There is a table on page LC-26 in the FSM

https://skydrive.live.com/#cid=CE930CA1A1A4B33C&id=CE930CA1A1A4B33C!127


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## IanH (Feb 11, 2003)

BTW I don't think the Oil cooler on the Pathy will cause this, its on the block and is a simple Oil to coolant exchanger, and isn't in front of the radiator. And the O rings leak, so look for Oil leaking around it.


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## SPEEDO (Jun 9, 2003)

I would check the fan clutch, might even replace the t-stat, might take a garden hose, from the engine bay wash the backside of the rad (pushing any debris out the front) or change out the rad... some ideas anyway


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## SDNissanOwner (Aug 28, 2012)

Thanks Ian and SPEEDO,

There's quite a bit of resistance in the fan clutch, so I'm pretty sure that's OK. I think I've read that the fan will spin freely (several revolutions) if the fan clutch is bad. My plan right now is to replace the thermostat, belts, upper and lower radiator hoses, and the radiator itself with a new Koyo. It sounds like Koyo makes some of the best aftermarket radiators.

From the posts here it seems like a bad radiator is the most common cause of Pathfinders overheating and I'm hoping that's the issue in mine since I'm planning on replacing it. Will let you know how it goes.

I had the oil changed at the dealership last week and they alerted me that the oil cooler seals need replacement due to a small leak. Question: could a very small oil leak (one that doesn't drip on the ground) cause an oil loss of half a quart to a quart of oil every 1,000 miles??? If anyone knows the answer please let me know.

Anyway, I'm hoping to get this work done this weekend so hopefully my overheating issue and oil leak will be fixed by next week.

And Ian...thanks for the link. I appreciate it!


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## IanH (Feb 11, 2003)

My Oil cooler seals were leaking for years, they just weep and I had a small drip on the ground. Dealer claimed they couldn't find it, but it was under warranty. They had avoid-warranty-itus on several things I found out later.

The VQ's are not particularly good on Oil, mine varies with heavy use. 
There is a problem reported on the forum here with the baffles in the valve cover that goes to the PVC valve getting full of junk, causing Oil mist being sucked into the intake. do a search.


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## IanH (Feb 11, 2003)

btw it took me 20 mins to change those seals, parts were less than $20.


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## SDNissanOwner (Aug 28, 2012)

Thanks, Ian. Is it necessary to drain the engine oil prior to replacing the oil cooler seals?


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## IanH (Feb 11, 2003)

SDNissanOwner said:


> Thanks, Ian. Is it necessary to drain the engine oil prior to replacing the oil cooler seals?


No, the cooler is held by one center bolt, Oil only flows when the engine is running.
Wipe down the exterior.
Undo the bolt, pull back the cooler leaving the coolant lines attached, and remove and replace the two O rings, I wiped all interior surfaces clean, and reassembled.


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## SDNissanOwner (Aug 28, 2012)

*Overheating Issue Solved....Probably*

Just an update to my overheating problem. Over the past couple of days I replaced the radiator, thermostat, belts and hoses. It appears to have fixed the problem, but I probably won't know for sure for maybe a week since the overheating was intermittent. However, after doing all of the repairs and refilling the coolant my Pathfinder overheated again and *I learned how extremely important it is to bleed the cooling system properly*. If air pockets are left in the system it can cause your engine to overheat rather quickly and may cause your heater to blow cold air (both of these happened in my case). Here's how I bled/burped the system. The attached picture shows the purge device that I created using clear 1/4 inch tubing (Home Depot, about $3.50), a half-gallon bottle and a little duct tape.

1. Topped off radiator while engine was cool.
2. Removed air release plug at back of engine (tube sticking up near firewall)
3. Disconnected radiator overflow tubing at the radiator cap
4. Attached purge device (see picture)
5. Started engine
6. Revved engine (2500 rpm for 10 seconds) - did this 2 or 3 times [a little bit of coolant may spurt out of air release tube at back of engine]
7. Capped air release tube at back of engine when there was a constant flow of coolant coming out of it (usually happens when engine starts to warm and coolant expands)
8. Ran engine for at least 20 minutes and watched air bubbles escape through the tubing on the air purge device. Revved engine several times while doing this to dislodge any trapped air bubbles.
9. Turned off engine, let it cool, then removed air purge device and reconnected radiator overflow tubing.


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## smj999smj (Jan 1, 2006)

Nice setup! They used a similar setup for purging the cooling systems on the L31 Altimas but what they did was use the coolant recovery bottle by unbolting it and suspending it, like you have. Another thing they did, which you could also do, is get a brake shoe horseshoe clip (like those for attaching the parking brake lever to the aft side rear brake shoe) and wedge it in the radiator cap spring to allow it to vent the coolant directly to the overflow hose. There's a TSB out there somewhere that explains it. For those that do a lot of coolant servicing, Lisle Tools makes a Spill-free funnel kit (#24610) that works great for purging air out:

Great deal on Lisle 24610 at ToolTopia.com


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## SDNissanOwner (Aug 28, 2012)

The Altima TSB is actually where I got the idea for the purge device. It's a great bulletin on how to bleed/purge the cooling system. For everyone else, the Technical Service Bulletin is NTB02-047c and can be found here:
http://ww2.justanswer.com/uploads/baddad1/2009-03-03_155546_NTB02-047c06heater.pdf


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## IanH (Feb 11, 2003)

Is it possible someone replaced the thermostats with ones that don't have the bleed hole / valve?
I know we have 2, and trapped air / bleed issues can result from this.


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## SDNissanOwner (Aug 28, 2012)

I used a genuine Nissan thermostat which has the jiggle valve. I believe that's supposed to allow air through.


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## SDNissanOwner (Aug 28, 2012)

*Coolant won't return to radiator from reservoir*

OK, now I'm having a new problem. The overheating issue appears to have been solved, but now the coolant won't return from the overflow reservoir back to the radiator when the engine cools. Has anyone here had this problem? I've read that this could be caused by several different things....a bad radiator cap, a small leak in the overflow hose that allows air in but doesn't leak coolant, or an internal cooling system or engine problem. I should note that there doesn't appear to be any coolant leaking externally. The overflow reservoir keeps getting fuller and fuller if I add more coolant to the radiator.


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## Marian Hill (Dec 8, 2014)

*Coolant won't return to the radiator.*

It's the Radiator cap !!!!!! Buy the original! Trust this female owner of a Nissan Pathfinder, automatic, 1997. Proof of the pudding is in the eating. I've been working on my overheating problem for 2 years with no help until finding this forum. Who's got the radiators for sale ex. Sydney for 100 dollars? Don't know where to look in the forum. 
Cheers, Marian Hill.


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