Engine temperature on 3.5 Pathy

[dududuckling]

Hi,

Tonight while driving the pathfinder on the highway, I noticed the fluctuation of the engine temperature on the ultra-gauge, plugged to OBD-2, whereas the temperature gauge needle stayed constant.

Doing 65 mph (105 km/h at 2750 rpm) or 80 mph (130 km/h at 3250 rpm), regardless of the terrain, the needle would stay around 50% whereas the engine temperature fluctuated between 195 and 215F. When I exited the highway, the temperature went up to 210-215F before going back to 200F moments later. Does anyone know what is the normal engine operating temperature for the 3.5L Pathfinder?

Also, there was once when I was doing uphill at 80 mph with full electrical loads (radio/amp/sub, and fog lamps turned on), and the temperature when up to 230-235F. Rpm stayed constant around 3250-3500. The needle gauge went 60-70%. The temperature went down to 210F as soon as I turned those off.

I know my clutch fan is going bad, the fan sound is getting louder even when the engine is cold. Could this be the problem or maybe a weak stock alternator?

Thanks in advance.

[Simon]

Hey Dudu,
There's definitely something amiss with your truck, and it sounds like you've already got it figured out. Pezzy's 3.5L never gets over half, even towing and loaded. My dads is the same. The high amperage draw increasing temps makes sense, as there's more load on the alternator, and ultimately, the motor, without an increase in cooling (fan isn't spinning faster) That said, the clutch on the fan should engage almost fully under those conditions.

[dududuckling]

Thanks, Simon. This morning when I opened the radiator cap to check the fluid, it was pretty much empty! At the same time, the coolant in the coolant reservoir was way past the maximum. I have a feeling the coolant went to the reservoir and did not come back to the radiator. I intend to buy premix coolant and just keep topping off the radiator until I can get it fixed this weekend, plus the fan clutch.

[Bow_Tied]

X2 on Simon's point, ours never exceeded half way on the gauge at any time that I noted.

I would replace the rad cap for peace of mind. And make sure there are no holes or leaks on the overflow tube and that the tube fits reasonably tight at the rad - just in case it is shunting fluid to the overflow bottle and sucking back air.

[dududuckling]

I replaced the radiator cap with the one from the old 3.3L. I pumped out the excess coolant from the overflow reservoir and refilled the radiator. I went on the highway, did 3000-3500 rpm for 10-15 minutes, and the temperature stayed somewhere between 175 and 195F - it was cold today, about 15C. I popped the hood, looked at the overflow reservoir, and the coolant stayed at the max level and not beyond.

So I went to Nissan, bought a new radiator cap - hopefully that was it.

[Scotto]

The other thing to check is the plastic across the top of the rad. You might not notice a small crack that could be opening and losing a bit of rad fluid. Easy enough to look for, and probably not the problem,as it seems you figured it out. But a small crack would stop the rad from being able to suck coolant back into the system. Mine did this a few years back, and it took me a bit to track down that little crack.

Scott

[dududuckling]

Noted. I pop the hood up and check the oil/coolant level every other day. I read somewhere that the 3.5L is notorious for burning oil. I will keep an eye on the upper radiator too. Thanks!

[Simon]

The 3.5 in the Pathfinder wasn't as known for oil burning as the 3.5 in the Maxima of that generation. Not sure what the difference is, but I haven't heard of nearly as many issues with the Pathfinder motor.

[Adam]

The VQ35 oil burning issue tends to be a valve cover baffle that gets clogged up from sludge. My parents' 05 Maxima has 310,000km and it doesn't burn any oil at all.

[dududuckling]

Not trying to revive an old thread - I recently discovered the hose from the radiator to the overflow reservoir came off and sprayed coolant all over the driver's lower control arm, etc. I refitted the hose, ziptied (of course), and installed a worm-gear type clamp because I did not want to un/re-install the hose again in the middle of the night.

Yesterday, after a 6-hour drive and the engine has cooled down, I discovered that the coolant in the overflow reservoir was higher than normal (it is not returning back to the radiator as it should). The radiator cap is brand new and OEM, only three weeks old.

Is it possible that there's too much air in the system to prevent vacuum, that would otherwise suck the coolant back into the reservoir? I am thinking for as long as the overflow hose came off, the radiator sucked in air into the system instead of coolant from the overflow reservoir when the engine cooled.

When I squeezed the upper radiator hose, there's bubble sound in the radiator. When I opened the radiator cap, there'll be bubble sound in the overflow reservoir. Thanks!

[Bow_Tied]

I guess that is possible? To rid the air you could try this: when cold, remove cap and top up rad. get a drip tray or something under the rad to catch overflow. Start truck and let it get up to operating temp. The coolant should start flowing when the Tstat opens (a chunk of cardboard in front of the rad will speed up the process to get to operating temp). The fluid level should drop a bit and then slowly start rising. It should eventually overflow as the fluid expands with temperature. If it doesn't, add more fluid. When it does overflow then put the cap on (carefully with gloves so you don't get burnt). Running it with cap off, in my experience has been able to get the air out. When there seems to be a lot of air trapped that won't come out I have installed the rad cap loose to first point where it is locked on but not tight and gone for a short drive (watching the temp gauge closely) then tightened the cap as soon as I got home.

Make sure both ends of the overflow tube are tight. Mine was loose at the rad neck.

[Adam]

There should be a bleed bolt somewhere on the intake manifold. I never usually use it as bow_tied's method always works for me but maybe give that a shot? Sometimes a small shot of throttle can force air out as well. Obviously don't stand over it if you do this, though.

[dududuckling]

Thanks! I will try this tomorrow.

Well actually I tried it this morning for a few minutes. I took the radiator cap off, started it up, and coolant began to overflow almost instantly. I syphoned the overflow coolant into an empty container. But I only did it for three minutes or so, was not sure how long it should be. Will try again tomorrow.

There is an air valve right next to the firewall, but its fitted rather tight and I'd rather not mess with it if I could.

[dududuckling]

Oh and this was my clamp job: