New advice on Inline mod without thermostat. p0126 Code
Camel Trophy
Joined: Sep 2017
Posts: 3,820
Likes: 1,337
From: Mission BC Canada
@davidpx858 OEM grey soft spring or 78C Black, but if everything is already bypassed you can order a housing from @Extinct and use a standard North American thermostat and have lower and more stable temps that the LR thermostats
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Drifting
Joined: Jun 2020
Posts: 32
Likes: 7
this is great info....so the turns on P0126 code means "difference in Radiator and Engine Coolant temps too small" which makes sense since there's no thermostat.
so i wonder why if i warm up the vehicle to 170, it won't trigger a p0126 code.
Thank you!
so i wonder why if i warm up the vehicle to 170, it won't trigger a p0126 code.
Thank you!
Recovery Vehicle
Joined: Jul 2012
Posts: 978
Likes: 154
From: Mideast US
The 'time frame' specified to time-out the temperature reading is unknown to users. Software writers at LR design will not reveal such.
The thermostat, inline or bypass type does not change, reduce nor increase the temperature of the coolant after has changed state to normal running conditions.
When engine coolant reaches 'normal' running conditions (say above 180F-82C), the inline type thermostat is fully open and directs all the flow towards the radiator, doing nothing, it is open and does not change from that condition.
When engine coolant reaches 'normal' running conditions, (say above 180F-82C), the bypass type thermostat is fully open towards the radiator and fully closed to return loop, doing nothing, it is open and does not change from that condition.
Temperature of the coolant would have to decrease below the thermostat rating for any flow direction to change. That is likely only after a couple of hours parked.
The thermostat does absolutely nothing at normal running conditions, other than placing some flow restriction to coolant path.
I do have a 180F-82C inline thermostat because I do not want the risk of hot coolant to flow back into the block trough a bypass loop if ever gets stuck and for system simplicity. There is no bypass path in my vehicle, was eliminated looong ago.
Engine block----->in-line thermostat-----> radiator-----> pump suction-----> engine block
Without a thermostat the engine runs cooler a longer time until engine stabilizes its operating temperature, then the heating factors take over and the thermostat or no-thermostat-presence does exactly nothing as it is in open flow state towards the radiator.
The thermostat exists to manage very cold ambient temperatures to allow the engine to reach efficient warmer combustion operating temperatures and closed circuit operation.
A thermostat is a very good thing to have in polar climates. Nearly useless in tropics.
To run modified without a thermostat, the bypass path must be eliminated, plugged, condemned to coolant flow and will not harm engine operation unless it is winter in Alaska.
The more coolant mass flowing trough the radiator per second, the more heat is dissipated. The lower temperature is not created but achieved by releasing heat; by the coolant heat exchanging.
A 180F-82C thermostat installed does not mean that the engine coolant will be regulated at that temperature. It means coolant will not get colder than that temperature.
A 180F-82C thermostat installed does not mean the coolant temperature will stay below or at that temperature.
The thermostat rating is the coolant temperature that changes its state of flow, towards the bypass loop or towards the radiator.
The working engine coolant temperature obeys to other factors. An engine with or without thermostat cannot get cooler than to a certain limit. That limit comes from ambient temperature, rpm, air flow, coolant mass flow, climb rate, tow load, lead feet, fuel mixture ratio...
There isn't a thermostat that can make the engine run cooler for a while since start-up than having no thermostat at all.
In other words; the "number" stamped on the thermostat has no relation to the coolant/engine running/operating temperature. It tells at what temperature it changes coolant flow direction and nothing else.
A hose that collapses on suction from coolant pump at radiator outlet/pump inlet is a commonly overseen cause of overheating. Has to be witnessed by accelerating a hot engine while looking at that hose if collapses or not.
Too slow warming or cold running can also be managed/tricked by placing a piece of cardboard in front of the radiator.
The thermostat, inline or bypass type does not change, reduce nor increase the temperature of the coolant after has changed state to normal running conditions.
When engine coolant reaches 'normal' running conditions (say above 180F-82C), the inline type thermostat is fully open and directs all the flow towards the radiator, doing nothing, it is open and does not change from that condition.
When engine coolant reaches 'normal' running conditions, (say above 180F-82C), the bypass type thermostat is fully open towards the radiator and fully closed to return loop, doing nothing, it is open and does not change from that condition.
Temperature of the coolant would have to decrease below the thermostat rating for any flow direction to change. That is likely only after a couple of hours parked.
The thermostat does absolutely nothing at normal running conditions, other than placing some flow restriction to coolant path.
I do have a 180F-82C inline thermostat because I do not want the risk of hot coolant to flow back into the block trough a bypass loop if ever gets stuck and for system simplicity. There is no bypass path in my vehicle, was eliminated looong ago.
Engine block----->in-line thermostat-----> radiator-----> pump suction-----> engine block
Without a thermostat the engine runs cooler a longer time until engine stabilizes its operating temperature, then the heating factors take over and the thermostat or no-thermostat-presence does exactly nothing as it is in open flow state towards the radiator.
The thermostat exists to manage very cold ambient temperatures to allow the engine to reach efficient warmer combustion operating temperatures and closed circuit operation.
A thermostat is a very good thing to have in polar climates. Nearly useless in tropics.
To run modified without a thermostat, the bypass path must be eliminated, plugged, condemned to coolant flow and will not harm engine operation unless it is winter in Alaska.
The more coolant mass flowing trough the radiator per second, the more heat is dissipated. The lower temperature is not created but achieved by releasing heat; by the coolant heat exchanging.
A 180F-82C thermostat installed does not mean that the engine coolant will be regulated at that temperature. It means coolant will not get colder than that temperature.
A 180F-82C thermostat installed does not mean the coolant temperature will stay below or at that temperature.
The thermostat rating is the coolant temperature that changes its state of flow, towards the bypass loop or towards the radiator.
The working engine coolant temperature obeys to other factors. An engine with or without thermostat cannot get cooler than to a certain limit. That limit comes from ambient temperature, rpm, air flow, coolant mass flow, climb rate, tow load, lead feet, fuel mixture ratio...
There isn't a thermostat that can make the engine run cooler for a while since start-up than having no thermostat at all.
In other words; the "number" stamped on the thermostat has no relation to the coolant/engine running/operating temperature. It tells at what temperature it changes coolant flow direction and nothing else.
A hose that collapses on suction from coolant pump at radiator outlet/pump inlet is a commonly overseen cause of overheating. Has to be witnessed by accelerating a hot engine while looking at that hose if collapses or not.
Too slow warming or cold running can also be managed/tricked by placing a piece of cardboard in front of the radiator.
Last edited by Externet; Jun 9, 2020 at 11:58 AM.
Hopefully I can clear up the confusion a little bit instead of adding to it. The 2003 and 2004 models have what can be thought of as a thermostat stuck open subroutine in the ECU. It looks for the engine to reach temperature within a defined time. And if it does not it throws the code. In my experience it requires at least a 180-degree thermostat to not throw the code, even if you have a 170 degree thermostat which I run in my 2000 model it will throw the code with that thermostat in a 2003 model because it is looking for a minimum of 180 degrees. if if you already have an inline thermostat housing you just need to install a 180 degree thermostat in the housing and the code will never come back.
As far as damage to the engine from running colder temperatures until you can get that done you don't need to worry about that. There might be slightly more fuel dilution of the motor oil do to the piston and cylinder walls not expanding as much, but it is relatively minor. Marine inboard outboard engines that use sea water for the cooling water typically run 140 degree thermostats because the salt precipitate out of the salt water if you run hotter temperatures. I did Boyle analysis on my boat and it would frequently show a higher than normal fuel dilution rate that I attributed to the colder thermostat.
As far as damage to the engine from running colder temperatures until you can get that done you don't need to worry about that. There might be slightly more fuel dilution of the motor oil do to the piston and cylinder walls not expanding as much, but it is relatively minor. Marine inboard outboard engines that use sea water for the cooling water typically run 140 degree thermostats because the salt precipitate out of the salt water if you run hotter temperatures. I did Boyle analysis on my boat and it would frequently show a higher than normal fuel dilution rate that I attributed to the colder thermostat.
Thread Starter
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Drifting
Joined: Jun 2020
Posts: 32
Likes: 7
Hopefully I can clear up the confusion a little bit instead of adding to it. The 2003 and 2004 models have what can be thought of as a thermostat stuck open subroutine in the ECU. It looks for the engine to reach temperature within a defined time. And if it does not it throws the code. In my experience it requires at least a 180-degree thermostat to not throw the code, even if you have a 170 degree thermostat which I run in my 2000 model it will throw the code with that thermostat in a 2003 model because it is looking for a minimum of 180 degrees. if if you already have an inline thermostat housing you just need to install a 180 degree thermostat in the housing and the code will never come back.
As far as damage to the engine from running colder temperatures until you can get that done you don't need to worry about that. There might be slightly more fuel dilution of the motor oil do to the piston and cylinder walls not expanding as much, but it is relatively minor. Marine inboard outboard engines that use sea water for the cooling water typically run 140 degree thermostats because the salt precipitate out of the salt water if you run hotter temperatures. I did Boyle analysis on my boat and it would frequently show a higher than normal fuel dilution rate that I attributed to the colder thermostat.
As far as damage to the engine from running colder temperatures until you can get that done you don't need to worry about that. There might be slightly more fuel dilution of the motor oil do to the piston and cylinder walls not expanding as much, but it is relatively minor. Marine inboard outboard engines that use sea water for the cooling water typically run 140 degree thermostats because the salt precipitate out of the salt water if you run hotter temperatures. I did Boyle analysis on my boat and it would frequently show a higher than normal fuel dilution rate that I attributed to the colder thermostat.
Camel Trophy
Joined: Sep 2017
Posts: 3,820
Likes: 1,337
From: Mission BC Canada
