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noodle650 07-01-19 01:24 AM

r51 pathfinder overheating issue
Hi guys,
been having an odd problem with my 2007 r51 pathfinder for the last 6 months or so.
When driving on main roads up hill putting power down my engine temp rises and can go pretty high towards red unless i back off.
if i back off and once the ground levels off it stops rising and drops down within a few minutes to normal, half way up the gauge.
i changed the coolant about a year ago and bled it etc using methods on this forum, nissan spec coolant and all went fine.
The heater is working without an issue and when driving on the flat the temp issue doesnt arise, its just when i put down power going uphill.

i start to think about the worst case scenario which would be head gasket failing, but i dont have a major coolant loss, ive always topped it up with coolant the odd time to the header tank but i doubt ive put more than 2 litres in over the last year since i changed the coolant.
I also have no white smoke in the exhaust or knocking sounds or coolant in my oil.
I changed the thermostat out but the problem is still there. i tested the old stat and it worked fine. I also swapped out the water pump and viscous fan, all of which didnt change the situation. (i now have a spare water pump, stat and fan!)

what i could think of logically is a blockage in one of the radiator cores thats causing a pressure increase when the engine is being loaded, this would cause a relative temperature increase.
I have a new radiator but havnt fitted it yet.

Could anyone else shed some light or advice on the problem?
im going to swap out the rad asap and hope for the best but id be delighted if someone with more knowledge could shed some light!

i should definitely add that the problem hasnt got worse since it started and i never let it go to the point where its in the red as i dont want to cook my block, i just lay off until the hill levels out. i distinctly remember the first time i noticed it one day on the way home on a long (fast) motorway drive, i pulled in to let it cool and drove on noticing the temp rise a few more times after that.

thanks for any help/advice

landmannnn 07-01-19 08:53 AM

I think you are doing the right thing, the symptoms would indicate a cooling flow issue.
The other bit to consider is that you shouldn't need to top up the coolant, in nearly 13 years of Navara ownership I have never added a drop of coolant.

I would suggest that once you have replaced the rad (they can block up) that if the problem persists that you get a garage to carry out a pressure test.

On the head gasket, the common issue is the gasket only leaks coolant just above the alternator, the leak can be very gradual.

noodle650 07-01-19 05:01 PM

Thanks alot for the reply. I definitely appreciate that I shouldn't have a coolant leak, I had put down the drop in coolant down to some tiny Leak somewhere from a hose that was removed when I did the stay or changed the coolant out. Or some small leak around the new waterpump or stay cover that just couldn't be seen. Or evaporation from the header tank when the temp rises up.
But it could very well be so small through the gasket that it wouldn't show up in exhaust smoke or just be totally burned off in combustion.
I'll swap the rad out and hope for the best. Don't fancy getting the head skimmed and putting new gaskets in!

diydave 07-01-19 08:50 PM

Interesting regarding hills/engine loading.
I've had this years ago and it was the viscous clutch had failed on the cooling fan, the fan wasn't doing the job at all, maybe worth a spin, see if you have any resistance.

noodle650 07-01-19 09:01 PM

Thanks for the reply. I also swapped out the viscous clutch for another unit and the problem persisted!
It didn't feel bad beforehand but I swapped it out anyway but no difference.
Thanks though

noodle650 12-01-19 03:03 PM

I solved the issue of coolant loss today. This morning I decided to give the engine bay a once over as I've my nct tomorrow and wanted to check fluids etc and see how much my coolant needed topping up. I ran a flashlightbover the guts and down on the bottom right where the underbody guard is I noticed a wet line where something had been flowing. Small pool under the engine bay too of coolant. Hopefully now I've solved the problem and the overheating issue will dissappear once I swap the rad out. I found another post on the forum where a user had been having the exact same issue as me and turned out to be a duff rad.
Here's hoping!

noodle650 04-02-19 02:12 PM

Problem solved. Rad was screwed inside but still circulating coolant to some extent. and 2 tiny leaks visible once removed from the bay. relieved it wasn't head gasket!
Thanks for the help.

diydave 04-02-19 09:25 PM

Pleased you found a less painful fix.

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