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BORDERTREK 4X4 & FABRICATION
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Please forgive me for my ignorance, but my understanding of the purpose of a thermostat is to bring the operating temperature of the engine up to an efficient operating temperature in a cold climate.
Any climate actually. It's to bring the engine up to normal temp as quick as possible as everything is designed to work the most efficiently at certain temps. Running an engine cold all the time is bad for it, that's why constant short trips where the motor never warms up reduces the engines life. You probably know all that but some may not.
 

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The nutty professor
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8,299 Posts
Discussion Starter #42 (Edited)
Exactly thats what ime saying theres no coolant flow up to 60 deg. or when under preasure, Only when it hits thermo temp opening and it opens then the whole motor circulates the coolant. Thats why they put it above the thermostat, Its a great deign either on the Q or GU, just on the Q you dont have to take anything of to bleed the cooling system, Its there on the GU to take off for bleeding otherwise they would have just blanked it off.
there would be no coolant flow through the thermostat until it starts to open ie: an 82 deg thermostat starts to open at around 80 deg, and opens enough to maintain the temps at 82 deg

i would dare say it there for servicing ie: at the mechanics , cause i dont think they want to send a customer off and have them come back the next day asking why the overflow bottle wasnt topped up

either way the system will still bleed the air out itself , just my way takes a couple of trips and then you top up the overflow, even with that hose connected you probly will have to top up the overflow as it will take a while for all the air bubles to get to the radiator
 

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nissan patrol
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144 Posts
Please forgive me for my ignorance, but my understanding of the purpose of a thermostat is to bring the operating temperature of the engine up to an efficient operating temperature in a cold climate. Once the maximum temperature rating of the thermostat is reached, it is fully open, allowing maximum flow of coolant through the thermostat housing, the engine water jacket and the radiator. I really cannot see how restricting the flow through the radiator (to cool the coolant more) will be effective when by doing this you are also restricting the flow of coolant through the water jacket, thus increasing the temperature of the coolant that has to be cooled. Catch 22. Shoot me down in flames.:D
The purpose of the thermostat is also to control the operating temperature of the engine after the initial warm up period!

When I purchased my Y60 Td 42, it had a stuck thermostat and the temperature gauge never went over the C mark! I replaced it last year with a Nissan tropical thermostat (76.5 C) and the temperature gauge now rises to quarter and stays there. This indicates that the thermostat does not stay fully opened all the time because if it did, the temperature of my engine should drop below the C mark during normal operation as it did when the thermostat was stuck open!

I noticed that you guys were installing a higher temperature thermostat when the engine is overheating; my view is that you should be installing a lower temperature thermostat!
 

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KICKEN BACK IN THE BUSH
nissan gq
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4,690 Posts
Used to always run the coldest rated thermostat in my early holdens that i could get
And yes i lived in QLD

Not a huge temp difference,but the difference is you get a bit more warning
The difference between getting home and walking
 

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Gone Fishing
NISSAN 1989 GQ PATROL
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6,203 Posts
there would be no coolant flow through the thermostat until it starts to open ie: an 82 deg thermostat starts to open at around 80 deg, and opens enough to maintain the temps at 82 deg

Youre repeating what i said!,You said theres flow all the time through the bleed hose when its presurised at around 60 degrees, when i originally quoted you I was saying theres not till the thermostat opens!!!!!!!!:confused:
 

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The nutty professor
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8,299 Posts
Discussion Starter #46
CARIB... i see what you are saying and normally it makes sense, but i did try running a colder thermostat early on and all it did was to make the motor run hotter on the hwy, i even tried drilling holes in the thermostat to get more flow but all it did was make it worse, this is when a light bulb lit up in my head and i thought " if a colder thermostat is only making the motor run hotter when on the hwy , then a hotter thermostat should make it run cooler on the hwy" well that was my thinking at the time, so i got myself a 91 deg thermostat, and yes it did run hotter around town (about 10 deg) but it did also stop the temp from getting really high and also kept the temp more stable, which is was what i was after in the first place,

another side effect of running the hotter thermostat was the clutch fan wasnt locking up like it did with the colder thermostat and all i can work out is that the coolant must be traveling slower through the radiator and not needing the fan to draw extra air to cool the coolant, and yes the fan is/was working properly

look at it this way... the greater the differance between the coolant temp and ambient air temp the easier it is to remove a certain amount or percentage of heat given the same amount of airflow

so , lets say with your 82 deg thermostat being just open , it is passing say 20 liters of coolant p/m (eg. only) and the engine fan is drawing 100cfm of air and the ambient air temp is say 32 deg , it will only remove a set amount or percentage of heat , to remove a higher amount or percentage of heat you need to change one of the figures above, increasing the coolant flow wont remove any more heat because the air flow also has to increase to keep up with the increased coolant flow, air flow would be fixed and cant change, running a colder temp thermostat would only reduce the temperature difference between ambient air and the coolant meaning it would remove a lower amount or percentage of heat, the only other option is to increase the temperature difference between the ambient air temp and coolant temp by fitting a hotter thermostat, the greater the difference the greater the percentage of heat would be transfered to the air
 

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The nutty professor
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8,299 Posts
Discussion Starter #47
there would be no coolant flow through the thermostat until it starts to open ie: an 82 deg thermostat starts to open at around 80 deg, and opens enough to maintain the temps at 82 deg

Youre repeating what i said!,You said theres flow all the time through the bleed hose when its presurised at around 60 degrees, when i originally quoted you I was saying theres not till the thermostat opens!!!!!!!!:confused:

sorry but i was tired , when you said
"Exactly thats what ime saying theres no coolant flow up to 60 deg. or when under preasure,
thats when i replied changing the 60 up to 80, i dont recall saying there is coolant flowing all the time through the bleed hose, but i did state that any excess pressure will go out the radiator cap

, and near the radiator cap is where any air should be trapped in the cooling system, thus the air should be forced out
 

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nope , just the thermos, i would dare say that the coolant temp would be more stable and lower if i had the factory fan and shrowd instead of the thermo fans
I did the top up thing on my viscous.
I now hear it kick in at just (and I mean just) over half on the temp gauge, so basically it doesn't get hotter than that.
If the thermo kicks in whilst going up hill on a hot day, you still see the needle drop.
 

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The nutty professor
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8,299 Posts
Discussion Starter #49
I did the top up thing on my viscous.
I now hear it kick in at just (and I mean just) over half on the temp gauge, so basically it doesn't get hotter than that.
If the thermo kicks in whilst going up hill on a hot day, you still see the needle drop.
and thats how it should be, last friday during testing it was faily warm but my electric thermos still brought the temp down from just above 1/2 to just below when i was labouring it up the mountain range and trying to get the motor hot,

if i plan a beach trip i might fit the factory fan on for the extra cooling but otherwise the electric fans are keeping up easily
 

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93 SWB Maverick
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1,390 Posts
mine never gets hot. completely stock cooling system. 60/40 water/coolant mix, on a long hike, sitting on 100km/h for over an hour and turbo boosting at 5-6psi the whole time, even more on hills, turbo running at 300C egt's non intercooled my motor only runs at 75-85C tops. Thats a hair over half on the stock gauge, and the digital gauge plumbed into the top hose of the rad is .3C off spot on.

On my Jeep i had a problem with overheating. Removing the thermostat is one of the worst things to do as all the coolant just rush's over the hot spots and doesn't allow it to cool. One thing people actually did was removed the top hose and put a nylon restrictor in. Which brought the top hose diameter down from 38mm to 15mm and it greatly improved the temps. I personally think that its when you start messing with the stock cooling systems you will get problems. Granted you want elec fans for water crossings and such. but sometimes you cant beat all the stock components.
 

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nissan GU iv 2006
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1,717 Posts
Factory specs(thermostat)

Hi itsa and all.
Just got a new thermostat from nizzbits- 76.5c- 21200-58G04
Width at top- 54mm
width at bypass bolcking plate-28mm
height between top flange and bypass-32.5mm
 

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The nutty professor
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8,299 Posts
Discussion Starter #52
Hi itsa and all.
Just got a new thermostat from nizzbits- 76.5c- 21200-58G04
Width at top- 54mm
width at bypass bolcking plate-28mm
height between top flange and bypass-32.5mm
sweet , when you fit it , would it be possible for you to get another measurment

the distance between where the thermostat sits (54mm flange) and the surface of the hole under where the blocking plate would sit when the thermostat is open

cheers
 

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nissan GU iv 2006
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1,717 Posts
sweet , when you fit it , would it be possible for you to get another measurment

the distance between where the thermostat sits (54mm flange) and the surface of the hole under where the blocking plate would sit when the thermostat is open

cheers
No worries mate. It may be 2 weeks or so because............
 

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KICKEN BACK IN THE BUSH
nissan gq
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4,690 Posts
Colder thermostat makes it run hotter on highway
But a hotter thermostat makes it run cooler on highway ?

Mite be from the country but doesnt sound logical
Colder thermostat will be working harder and more often
Hotter thermostat will be working not as hard and less often
The airspeed goin thru the radiator at highway speeds will reduce the water temp in the rad dramitically
Sounds right,yes ???
When was your radiator flushed properly
I dont know what thermostat is in the GQ,but doesnt ever move bugger all on the guage
When pulling up hills with 2 odd tonne , yeah but still not alot
Its an auto without a tranny cooler,so id expect a temp rise
It does however have a brand spanker radiator,as the plastic tanks split on the old radiator
 

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The nutty professor
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8,299 Posts
Discussion Starter #55
Colder thermostat makes it run hotter on highway
But a hotter thermostat makes it run cooler on highway ?

Mite be from the country but doesnt sound logical
Colder thermostat will be working harder and more often
Hotter thermostat will be working not as hard and less often
The airspeed goin thru the radiator at highway speeds will reduce the water temp in the rad dramitically
Sounds right,yes ???
When was your radiator flushed properly
I dont know what thermostat is in the GQ,but doesnt ever move bugger all on the guage
When pulling up hills with 2 odd tonne , yeah but still not alot
Its an auto without a tranny cooler,so id expect a temp rise
It does however have a brand spanker radiator,as the plastic tanks split on the old radiator
that was my experiance , when ever i tried a colder thermostat it would get hotter when pushed hard, the only thing that stopped it from getting so hot was a hotter thermostat

i know it sounds backwards but when you think about it you realise that the coolant will be traveling slower with a hotter thermostat as it wouldnt open as far compared to a colder thermostat at the same temp, this allowed the coolant to have more heat taken out,
i also noticed with the 82 deg thermostat that along the hwy the clutch fan was constantly engaged , with the 91 deg thermostat the clutch fan only engaged when going up hills or when pushed hard , or around town

new radiators , both 2 core and 3 core no difference

i dont know why some td42 motors run hot , thats what i am trying to figure out, all i have figured out so far is that it is a coolant flow issue on mine where too much hot coolant is comming out of the head and going strait back to the water pump via the bypass valve, it may be just that the motor is old and i have a lot of scale build up inside the motor ??

but i do know that a different thermostat with different specs can keep my motor cool no matter how hard i push it, and that is with thermofans that have probly 1/2 the cfm of the factory fan, i must be doing something right
 

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The nutty professor
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8,299 Posts
Discussion Starter #57
IMHO, I think people removing their shroud when doing a bod(ge)y has a massive effect.
I also think the topping up of the viscous fan oil is important every now and then.
yeah but i am talking about when everything is new, been replaced to factory spec, shrowd , fan etc,

some motors just run hot
 

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yeah but i am talking about when everything is new, been replaced to factory spec, shrowd , fan etc,

some motors just run hot
Does anyone know of someone with a completely standard vehicle that runs hot?
I'm interested because I have seen threads were people talk about 'the problem' but when you ask more questions there always seems to be something they didn't mention originally (wound up turbos, bigger tyres (without gearing changes), body lifts, shrouds off etc).

I used to have a shortie Pajero which had no drama's until bigger tyres and a body lift were done on it. Those two mods alone were enough to push up the temps.

I do like the detail that itsa is putting into this thread though!
 

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Nissan
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Tires I can see but I am curious why the body lift would cause so much trouble?
 

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Think I can fess up to that. Mine is pretty much standard ('cept I've taken out the thermostat);) Driving at 100KPH on a hot day with the air conditioner on, the temp gauge tends to creep up to 3/4. I turn the air conditioning off when it reaches that stage, and temp drops back down to half. I suspect my radiator is stuffed but at this point I don't have the readys to replace it.:(
 
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