overheating

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RogueFinder
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overheating

Postby RogueFinder » Sat Jun 13, 2020 7:22 pm

2005 "finder, 154000 miles. Started overheating on short drive during a hot day. Threw P1217 code also. When I ran the heater on max in an attempt to cool it so I could make it back home, little heat produced in cabin. Got it home, and decided to take a look at coolant levels - very low, less than a gallon after I drained it. No wonder it overheated. In the process of flushing, ran the engine at idle with the cabin heat on again, still very little heat coming from the vents; coolant temp after running for 10-15 minutes was 203-deg F. Running it with water and Blue Devil flush right now. The truck has history of temperature spiking on hot days and sitting at idle, like in stalled traffic or long drive-thru waits. But get it under control and in the normal range after normal driving resumed. Does this indicate a thermostat problem? Something else? I haven't seen any indications of leaking coolant either, how did I get so low? was changed last year. Also what triggers the smaller fan on the radiator to come on? This fan never came on when I idled it to flush.


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smj999smj
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Re: overheating

Postby smj999smj » Sun Jun 14, 2020 1:55 am

P1217 is a code for engine overheat, which makes sense. The electric fan is two-speed and powered by the IPDM via two relays. The IPDM gets the command to turn on the electric fan from the ECM via input from the engine coolant temp sensor and/or the refrigerant pressure switch (during A/C use). To test the relays, circuit and fan, you can do an IPDM active test. Turn all of the accessories off (radio, heater, lights, etc.), lift the wiper blades up off the glass and open the hood. Now, if I remember it correctly, open the driver's door and locate the door switch on the B-pillar. Turn the key "on," push the door switch 10x in 10-seconds, turn the ignition key "off" and then back "on." The horn should "beep" to indicate you are in IPDM active mode. The test will automatically turn the wipers on and cycle high and low speeds, then the fog lamps will turn "on" and "off," the low and high beam headlights will flash, then the A/C clutch will engage and disengage and, finally, the electric fan will turn on at low speed and then high speed. The test will repeat three times unless you turn the key "off."
A bad thermostat can cause overheating, as can a bad water pump (pretty rare on VQ40DE engines, but possible), bad fan clutch (will usually cause overheating at idle but not at highway speeds), bad electric fan or circuit, poor airflow through the A/C condenser/radiator cores (look for sand, mud, dirt or debris build-up on or in the fins of the core or between the two cores. A bad IPDM, ECM, fan relays can also cause it, but it's rare. Sometimes, people have accidentally swapped the radiator cap with the coolant reservoir cap (radiator cap has no pressure spring on it; the reservoir cap does have a spring on it). The coolant loss would be concerning. If the water pump (which is timing chain driven) leaked, it should drain out at the front-side of the engine on the driver's side. The plastic, multi-directional part of the heater pipes near the firewall on the passenger side can crack or break and leak coolant. The metal coolant lines to the rear heater can wear through and leak coolant. Once in a blue moon, we hear of a blown head gasket issue on a VQ40DE.
To purge air out of the coolant, I top off the radiator and cap it and then fill the reservoir to the "MAX" line about halfway up the reservoir tank and cap it. I'll raise the front of the vehicle as much as safely possible or park on an uphill with nose forward. I'll turn the front and rear heaters to the highest temp setting and turn the heater on. Then, I'll run the engine at 2500-3500 RPM for at least 10-minutes, or more, if needed, until hot air (about 140 degrees F.) comes out of the heater vents. I'll lower the front of the vehicle down and when the engine is completely cold, I'll recheck the coolant level and top off as necessary.

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ShipFixer
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Re: overheating

Postby ShipFixer » Sun Jun 14, 2020 10:32 am

RogueFinder wrote:
Sat Jun 13, 2020 7:22 pm
2005 "finder, 154000 miles. Started overheating on short drive during a hot day. Threw P1217 code also. When I ran the heater on max in an attempt to cool it so I could make it back home, little heat produced in cabin. Got it home, and decided to take a look at coolant levels - very low, less than a gallon after I drained it. No wonder it overheated. In the process of flushing, ran the engine at idle with the cabin heat on again, still very little heat coming from the vents; coolant temp after running for 10-15 minutes was 203-deg F. Running it with water and Blue Devil flush right now. The truck has history of temperature spiking on hot days and sitting at idle, like in stalled traffic or long drive-thru waits. But get it under control and in the normal range after normal driving resumed. Does this indicate a thermostat problem? Something else? I haven't seen any indications of leaking coolant either, how did I get so low? was changed last year. Also what triggers the smaller fan on the radiator to come on? This fan never came on when I idled it to flush.
With the OEM radiator, my truck could get very low if I wasn't watching it (at least a gallon or more low) and act the same way when it started to go. Especially when you add in the rear heater loop, which adds a hidden volume of either air or coolant. Do you have green dried coolant on the upper or lower side of the radiator? Eventually all plastic tanked radiators fail where the aluminum clamps to them. I was surprised at how much I could lose. While I was putting off changing my radiator last time, I think I was adding somewhere between a half to a full gallon each month.

From a heat transfer perspective, air switches between a really effective insulator and a conductor with the smallest amount of velocity, and more velocity makes it much better pretty quickly...so a partially effective heat exchanger system can appear effective at speed but get very, very ineffective when slow or stopped (with no fans).

Stuff I noticed, especially since putting in a radiator with more cooling capacity than stock and some previous problems. The ECU will do a bunch of things to manage temps before it gives you an actual overheating indication (dummy lights or codes). Includes turning off A/C, but before that it will dial back power a bit. That one is noticeable on hills.

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palmerwmd
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Re: overheating

Postby palmerwmd » Sun Jun 14, 2020 3:07 pm

I have noticed before that for no reason I may be a quart low if I dont watch it.

its not sufficient to judge by the overflow container.
I dont think it ever actually sucks anything back into the rad from the overflow like it supposed to.

I had my overflow full and the rad a quart or more low on couple of occasions.
Just one of the idiosyncrasies that every design seems to ave.

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ShipFixer
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Re: overheating

Postby ShipFixer » Sun Jun 14, 2020 6:19 pm

So long as the rear heater loop is full (this is the big "if"), then the reservoir tank will tell you your fluid level. The Pathfinder has the "European style" coolant system where the pressure cap is on the tank. So long as you don't routinely take off the radiator fill cap after initial fill/flush (this actually screws up the level and makes it look like you're never getting there...confused me and a master mechanic friend at first), then the reservoir tank should line up with the top of the system. It's only tricky because the rear loop can be empty, affect your radiator uphill, and not affect the reservoir when you are on level ground trying to figure it out. ( I know this game really, really well unfortunately.)

You run into problems when you lose enough that you start getting air in the rear loop as the fluid goes down and you run downhill, etc. If you have small leaks in your radiator or elsewhere, it can happen pretty fast. I spent a lot of 2017 filling my reservoir and checking it weekly for that reason. When my system is watertight, it burps itself down to somewhere between the min and max lines in the reservoir pretty quickly, and sits there for plenty of months. I rarely have to top mine off...today, for the last however long. I haven't filled mine in at least ten months and it's fine right now.

Stuff to check:

- Do you get heat out of the rear loop? (Heat on max, fan on max, vehicle at temperature.)
- Have you burped your rear loop? (Sit truck pointing up hill, like 10-20 degrees, foot on the gas in neutral with all heat on max to flush backwards). Super easy, if your system is watertight, it maybe takes me one or two minutes to get a bubble out. Refill when cool, and do it again later. If it takes longer or heat never comes out...other problems may exist.
- Do you have any signs of leaks? Look top-to-bottom for green, crusty, dried coolant. Top and bottom of the radiator, in the fins, both ends of both hoses, and the supply and return lines under the truck to the rear core. If you see it on the radiator, when it's hot, the aluminum will expand and let coolant out as steam slowly around the plastic tank. This was the source of most of my problems. If you see it on the hose ends, tighten or replace the clamps. I had to tighten mine a couple different times after installing the all-aluminum radiator as everything settled in.
- Really look at the rear supply and return lines. Bet there's some green crusty stuff in the straps holding them in place under the body of the truck. That's the one spot I am watching closely in my truck, and planning on replacing that section with heater hose or something else easy.

If all of that is good to go, then an overheating problem is coming from somewhere else. This has been my main culprit in the last few years. The last time it was an issue, the radiator (the original one I bought with the truck) was partially plugged or something. And I actually didn't go in to have the radiator checked, I brought it to the dealership because the A/C was randomly turning itself off. Since it was a year or two after I bought the truck, it's possible the original coolant had been sitting in there for four plus years. And no idea what else was happening to the truck before I owned it. If I recall correctly, I paid Nissan for the radiator, but then they refunded me under the extended warranty they put out due to SMOD, even though I never had that problem.

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palmerwmd
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Re: overheating

Postby palmerwmd » Mon Jun 15, 2020 1:47 am

I am not really seeing over heating issues.
But I do check the level on occasion.
... gonna do it right now :)

EDIT: All levels good today.


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