# T31 M9R Engine temperature



## Richard91 (Feb 12, 2020)

Is it normal for this engine to not reach the thermostat spec of 89 degrees? When i first noticed the engine at around 75 degrees i thought it was the thermostat, so i changed it, but it made no difference. So i connected a temp sensor on my multimeter and put it inside the top hose to see when water gets through the thermostat, there is a slight opening at 80 degrees, which sounds normal to me. Took a drive, at 30% load(normal driving,flat road, 90km/h) the engine is around 74-75 degrees, at 60%(uphill), the engine eventually reaches 80 degrees, the thermostat opens, and 10 sec later the temp drops to 70, and slowly climbs it's way back to 75. This is with an outside temp of 5 degrees and low heater fan speed, 0 degrees or lower, with high fan speed i can barely get 72 degrees, i never reach 80. Is this normal? Is there anything i can do so i can keep a decent cabin temp when the outside temp drops to -10 or lower?


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## rogoman (Dec 16, 2004)

It's possible that the heater core has trapped air preventing good heat output. There's an article somewhere in this forum posted by SMJ999SMJ describing a procedure to purge the air from the heater core. You can do a search to find it.

If the heater core has been purged of air and the coolant system is working correctly, then another thing you can do is place a large piece of cardboard in front of the radiator to block a certain amount of air flow. You'll have to experiment with sizing the cardboard by watching the temp gauge. Initially start with blocking about 75% of the radiator surface and if the temp gauge shows too hot, keep trimming until you have reached a decent cabin temp.


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## Richard91 (Feb 12, 2020)

I can't seem to find the article you are referring too. But 2 times now i have parked the car uphill and opened the radiator cap, shouldn't that be enough? 
Also, correct me if i'm wrong, but the problem here seems that there isn't enough heat produced in order to have a good heat output, rather than something preventing a good heat output?
The cardboard trick is more of a last resort, so i'll wait a little longer in hopes of a better solution before implementing it.


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## rogoman (Dec 16, 2004)

Here's the posting by SMJ999SMJ in the thread I'm referring to:








2015 Pathfinder Platinum, no heat at idle.


Hi, and thank you for taking the time to read this article, as I try to resolve the problem, I will seek help from anyone that will offer it. NOTE: I continue to go the dealerships and complain of not having any heat. To date, nothing has been actually done to fix the problem except a heater...




www.nissanforums.com


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## Richard91 (Feb 12, 2020)

No difference after bleeding one more time.
I have now covered 77% of the radiator, and i am now keeping a more stable temp closer to 80 degrees with normal driving, holds steady at 81 degrees under continuous 70% load(110 km/h uphill), this is with an outside temp of 9 degrees.


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## Richard91 (Feb 12, 2020)

I'm still looking for tips regarding temp issues. I have done several more bleedings, where i park uphill and hold 3000rpm, i then noticed that after about 10 min the temp would start to go past 81 degrees, hitting 84 before the temp drops again, the second time i can go beyond 90 degrees, and it will hold at 89 when idling, it will also hold this when driving for about 5-10 mins before slowly going down to 70-75 again. I could then repeat the procedure several times, and get the exact same results. To me, this suggests the coolant system can't maintain correct pressure, either a faulty reservoir cap or maybe a leak, but this would probably make the engine hotter, not 20 degrees cooler?

Here is a flowchart of the coolant system, the red line indicates a hose on my engine that is not included in the original chart for some reason, any idea what it's for? It looks like it would increase the amount of colder coolant from the radiator before the thermostat opens, thus cooling the engine? Whould it do any harm removing it?









If i can't figure this out soon i'm tampering with the idea of wrapping copper tubes around the exhaust and connecting it to the cooling system to increase heat generation. However, if this is wrapped before any lambda, would that cool the exhaust pipe enough to affect the readings, and therefore also affect engine controll? 
Another idea i have is connecting a 1000W coolant heater and running it of the battery, if i'm not mistaken the generator is rated at 150A, so it should be possible. But would it be enough? 1000W is not that much.


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## VStar650CL (Nov 12, 2020)

Just a guess, we have no Exxie DCI's here in the 'States, but it looks like that line is bypassing the EGR cooler. Who knows why, but I'd imagine the cooler would sink quite a bit of exhaust heat into the cooling loop. So it seems plausible that could be the reason the engine can't keep itself warm. I'd try pinching off that line and see what happens.


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## Richard91 (Feb 12, 2020)

VStar650CL said:


> Just a guess, we have no Exxie DCI's here in the 'States, but it looks like that line is bypassing the EGR cooler. Who knows why, but I'd imagine the cooler would sink quite a bit of exhaust heat into the cooling loop. So it seems plausible that could be the reason the engine can't keep itself warm. I'd try pinching off that line and see what happens.


I'll test that on a colder day, almost 30 degrees celsius in the shade today.
Is it normal for the reservoir to become completely empty when warm, while at Max when cold? If i loosen the cap it is rased half way to Min.


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## VStar650CL (Nov 12, 2020)

Richard91 said:


> Is it normal for the reservoir to become completely empty when warm, while at Max when cold? If i loosen the cap it is rased half way to Min.


No, that's definitely abnormal. The reservoir should be higher when warm, not lower. The only way it can drop is if there's an abnormal amount of suction on the main coolant return line between the oil cooler and the water pump when the engine is running. Pretty weird behavior.


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## Richard91 (Feb 12, 2020)

VStar650CL said:


> No, that's definitely abnormal. The reservoir should be higher when warm, not lower. The only way it can drop is if there's an abnormal amount of suction on the main coolant return line between the oil cooler and the water pump when the engine is running. Pretty weird behavior.


How do i start diagnosing this? When you say abnormal amount of suction, i imagine a partial or complete blockage somewhere. I did clamp the hose we don't know what is yet, i'll try warming it up again without.


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## VStar650CL (Nov 12, 2020)

Richard91 said:


> When you say abnormal amount of suction, i imagine a partial or complete blockage somewhere.


Yes, but the thing is, if there's a blockage, you'd expect the engine to run hot and not cold. That's why this doesn't make sense. That screwy crossover line has to be doing something weird to the whole system.


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## Richard91 (Feb 12, 2020)

VStar650CL said:


> Yes, but the thing is, if there's a blockage, you'd expect the engine to run hot and not cold. That's why this doesn't make sense. That screwy crossover line has to be doing something weird to the whole system.


No difference in coolant level with the crossover line open, it still goes to empty when hot.


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## VStar650CL (Nov 12, 2020)

Richard91 said:


> No difference in coolant level with the crossover line open, it still goes to empty when hot.


Did it make a difference in the temperature, though? Looking at the diagram, I'm wondering if that EGR cooler isn't blocked and they added that hose to restore flow through the heater circuit. The loop to the EGR comes from the heater, so if it was blocked the heater would quit working with it.


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## VStar650CL (Nov 12, 2020)

And the lack of heat from the EGR cooler still might explain your abnormally cold temperatures.


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## VStar650CL (Nov 12, 2020)

Hmm, you should be able to test that by seeing if the heater still works with that bypass hose pinched off. If it doesn't, then the EGR cooler is clogged.


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## Richard91 (Feb 12, 2020)

VStar650CL said:


> Did it make a difference in the temperature, though? Looking at the diagram, I'm wondering if that EGR cooler isn't blocked and they added that hose to restore flow through the heater circuit. The loop to the EGR comes from the heater, so if it was blocked the heater would quit working with it.


It's to hot out to test the temperature as it will reach 89 at idle either way, at the moment i don't have anything to pinch the hose that i can drive around with, so can't check it right now. But you are thinking that the EGR cooler might be clogged, and some moron wanted to save money by bypassing it instead of changing it? It does sound plausible. Is it easy to take the EGR cooler out and check it?


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## VStar650CL (Nov 12, 2020)

Richard91 said:


> But you are thinking that the EGR cooler might be clogged, and some moron wanted to save money by bypassing it instead of changing it? It does sound plausible. Is it easy to take the EGR cooler out and check it?


Morons happen, as anyone in this business knows.  

If the diagram is right, then the simplest test for the EGR cooler is to use the heater as I said. The cooler is in series with the heater outlet, so if the cooler is blocked then flow through the heater is also blocked. Pinching off the bypass hose will tell you. If the heater works badly or not at all with the bypass pinched off, it means there's little or no flow through the EGR cooler.


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## Richard91 (Feb 12, 2020)

There is no difference in heater temp when pinching the hose. Also, the hose looks a bit too professional to not be standard from factory in my opinion.
















I've done some searching on the dissapearing coolant, this is often caused by trapped air, but this has to be at least 1litre, that sounds a bit much to me, but should probably be checked either way. The only way i can think of that allows air to be trapped in there now is for the vacuum to suck it in from a leak somewhere, so next step would probably be a pressure test?


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## VStar650CL (Nov 12, 2020)

Richard91 said:


> so next step would probably be a pressure test?


Yep, back to fundamentals. That's a good place to start.


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## Richard91 (Feb 12, 2020)

VStar650CL said:


> Yep, back to fundamentals. That's a good place to start.


There is definitly a leak, but i don't have time to locate it yet. But i noticed something maybe strange about the pressure cap on the reservoir, it is rated at 1,37bar, but it started to slowly let air out at 1bar, the amount sounded unchanged until right before 1,4bar where it fully opened, is it normal for it to leak tiny amounts of air before it's rated pressure? This will make it more difficult to find small leaks.


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## VStar650CL (Nov 12, 2020)

The best thing to do for small leaks is some UV dye in the coolant. That will show up things like bad pressure caps and tiny "vapor" leaks that won't show up in a conventional pressure test.


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## rogoman (Dec 16, 2004)

Richard91 said:


> There is no difference in heater temp when pinching the hose. Also, the hose looks a bit too professional to not be standard from factory in my opinion.
> View attachment 7449
> 
> View attachment 7450
> ...


Probably your first order of repair is to replace that hose as shown in your second picture. That hose looks somewhat mangled and appears to have a bulge near the clamp. Where the clamp is, you might have a *pisser* in that area when the engine is fully warmed up and the coolant system is at full pressure; that may be where the coolant leak is. Hoses that have a bulge are doomed to early failure.


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## VStar650CL (Nov 12, 2020)

rogoman said:


> Probably your first order of repair is to replace that hose as shown in your second picture. That hose looks somewhat mangled and appears to have a bulge near the clamp. Where the clamp is, you might have a *pisser* in that area when the engine is fully warmed up and the coolant system is at full pressure; that may be where the coolant leak is. Hoses that have a bulge are doomed to early failure.


Good thought. Could be delaminating and collapsing on the inside, too, which might explain the strange suction behavior.


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## Richard91 (Feb 12, 2020)

rogoman said:


> Probably your first order of repair is to replace that hose as shown in your second picture. That hose looks somewhat mangled and appears to have a bulge near the clamp. Where the clamp is, you might have a *pisser* in that area when the engine is fully warmed up and the coolant system is at full pressure; that may be where the coolant leak is. Hoses that have a bulge are doomed to early failure.


It did leak a bit at first, but it stoppet after i tightened the clamp. But it doesn't look too good, so i will definetly replace it.


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## Richard91 (Feb 12, 2020)

rogoman said:


> Probably your first order of repair is to replace that hose as shown in your second picture. That hose looks somewhat mangled and appears to have a bulge near the clamp. Where the clamp is, you might have a *pisser* in that area when the engine is fully warmed up and the coolant system is at full pressure; that may be where the coolant leak is. Hoses that have a bulge are doomed to early failure.


Changed the hose, and fixed a few small leaks, there is no leaks when pressurized to 1,3x bars, the cap seems to open fully at 1,37 as the spec says. There is no difference in temperature or suction. When i was purging the air from the system i took it a bit further this time, 3700rpm, eventually reached 98 degrees, and held it there for 10 min, maybe more, i checked the reservoir and now there where probably 2-3dl of coolant there, this was sucked back in by the time the engine cooled down to 93 degrees, i have done this 3 times now, the front end is probably lifted 1 meter. There has to still be air in the system, otherwise the coolant from the reservoir would not have anywhere to go right? But how do i get it out?


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## Richard91 (Feb 12, 2020)

Finally got the air out of the system. Ended up with topping the reservoir, then bubles came out, kept filling it until it stayed topped. After a few days of driving the coolant have settled at the max mark, when the engine is hot it rises slightly, as it should. But it is still not possible to get above 75 degrees while driving, this was with an outside temp of 10 degrees. Standing still and revving i can get to 89, and it will stay there for 20 minutes at idle, with the heater on it dropped to 80 after 20 minutes, and was still dropping. To me it does not look like the engine is producing enough heat in order to get to normal temp. Unless anyone has any other ideas to find any fault it would be great if someone could comment on my ideas for generating more heat. 
1. Mounting a 500W or maybe 1000W coolant heater to the system, but not sure this would be enough. Might be better to just mount a cabin heater.
2. Wrap copper tubes around the exhaust pipe and connect it to the coolant system, not sure if this will catch enough heat, but alot cheaper than the first option. And i am thinking if wrapped before lambda it might cool down the exhaust enough to affect the readings and screw up engine control?


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