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The nutty professor
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8,299 Posts
Discussion Starter #1 (Edited)
spent hundreds if not thousands trying to stop it running hot ???

well i have the answer for you and it is fairly cheap , no need for multi pass alloy radiators or anything like that , although i do recommend that all cooling system componants be in good running order

this fix is for most if not all bypass type thermostats ie: looks like this ( specs will vary)



how the bypass thermostat works is ... that it will allow coolant to recirculate through the motor without having to go through the radiator as well as allowing coolant through the radiator

what i have found is that the bypass valve isnt blocking the flow of coolant that gets recirculated through the motor ( bypassing the radiator ) soon enough, basicly the thermostat has to open alot further before stopping this recirculation bypassing the radiator, this may mean the coolant temp has to reach around 100 deg or more before all the coolant has to go through the radiator

now the above pic shows some specs

54mm is the thermostat flange diameter

35mm is the closed thermostat hight between the flange and the bypass blocking plate

the 27.7 mm is the blocking plates diameter

now on my car the distance between where the thermostat flange sits and the surface where the bypass valve/ plate is to sit is 40mm , this means my thermostat would have to open 5mm before it will block the flow of coolant that bypasses the radiator, and in my case this means the coolant has to reach over 100 deg

what i have done is increased the closed thermostat hight between the flange and the bypass blocking plate to 38 mm , this means the thermostat now only has to open 2mm before all coolant has to travel through the radiator and the coolant temp is only around 90 deg at this stage

the results are impessive to me , i can tow my camper trailer up a mountain range with the temps maxing out at around 92 deg , i only have a falcon thermofan set up with the fans set to turn on at around 90 deg ( about 1/2 way on my factory guage) , and they easily kept up with cooling , hwy driving saw the temp guage sit around 1/3 and not needing the thermo fans at all to keep it cool

what i recommend to people who are having a hot running issue is to take some measurements to see how far your thermostat has to open before the blocking plate/ bypass valve makes contact with its intended seated surface, if it is 4mm or more then this mod is for you, reducing the closed thermostat gap to about 2mm should mean all the coolant will be traveling through your radiator by the time the coolant reaches about 90 deg, instead of recirculating hot coolant through the motor

this mod should allow coolant to recirculate and bypass the radiator when the motor is cold and force more coolant through the radiator once the motor is at running temp

any questions just ask away and i will try to answer them the best i can

Posted from the thread, So it is easy to find this data.

updates?

anyone else done this?
reviews and what not?

IAFNAN, would this help my case?

currently, temp gauge hardly moves a needle width about C on the gauge,
im guessing my thermostat is farked and locked wide open..

you prob have done this over and over..
but can you explain it so a dummy can understand?

i have no idea what temp it currently runs, i should hook up my mechanical temp gauge.

my factory gauge tends to move with the speed i do..

0 - 60kph the needle sits below the C line.
60 - 80kph the needle sits on the C line.
80 - 100kph the needle sits above the C line.

or do i just go to my mechanic and have him put in a 82 degree thermostat and see what that does first?

any imput would be appreciated.

from what you have posted it looks like your thermostat is stuck wide open, and as you are not having any heating issues as yet i would just replace with a new thermostat, tridons TT228-180 is an 82 deg thermostat for the later model td42 and should work fine, or there is the high flow version TT2028-180 which is the same specs just high flow, both of these are just a strait put in and forget no mods needed.

the only uncertainty is how well the standard thermostat will cope under high load and/or heat situations, this is where (if your temps are fluctuating wildly) i recommend fitting a different thermostat or modding your standard thermostat so it can control the coolant temp better, now a factory thermostat which has the following specs



has to open up 9mm before closing the bypass hole so all the coolant flows through the radiator (ie: the 31mm distance in the diagram has to open up to 40mm to close the bypass hole), this is why alot of people have hot running issues with there TD42`s as the coolant temp has to rise about 20 deg before the bypass hole closes and the temp guage is all over the shop when the car looks at a hill.

the easiest thermostat to fit (no mods) is what i recommended to you first up "TT228-180 or TT2028-180" specs are

and is an improvement over the factory spec thermostat as they will control coolant temps a bit better because they only have to open 5mm before blocking the bypass hole, (the bypass hole is 40mm below the flange of the thermostat) , but even this thermostat allows the coolant temps to fluctuate a bit although not as bad as the factory thermostat

this is where i got a different thermostat again (couldnt find one with the specs i wanted so i had to get one and moddify it) the only one i could find close enough to suit my needs with minimal mods needed was a dayco DT79H which has the following specs

now this thermostat has a 41mm distance from the flange to the bypass blocking plate, if i fitted it strait in it would mean the bypass hole is always blocked which is not what you want, you need to change the 41mm distance to about 37-38mm so when the motor is cold the coolant will still circulate through the motor, basicly you need to space the bypass blocking plate up about 3 to 4mm

the DT79a rated at 82deg
http://www.eziautoparts.com.au/dayco-thermostat-dt79a.html
the DT79h rated at 85deg
http://www.eziautoparts.com.au/dayco-thermostat-dt79h.html
the DT80g rated at 89deg
http://www.eziautoparts.com.au/dayco-thermostat-dt80g.html


the other option is to weld in an alloy washer/ring on top of the bypass hole to reduce the distance the thermostat has to open before blocking the bypass hole, this way you could still use the factory thermostat and have better control of the coolant
 

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Gone Fishing
NISSAN 1989 GQ PATROL
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6,223 Posts
Is yours a TD42, and how hot was it running?
 

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The nutty professor
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8,299 Posts
Discussion Starter #3
Is yours a TD42, and how hot was it running?

yes , td42, and on hills it would get up to the first line of the "H" (115deg) when i had an 82 deg thermostat in , i then changed the thermostat to a 91 deg which stopped the guage getting to the "H" but still up to 3/4 (104 deg)

i believe this shouldnt be aimed at only the td42 as all bypass thermostats behave in the same way
 

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BORDERTREK 4X4 & FABRICATION
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8,552 Posts
the results are impessive to me , i can tow my camper trailer up a mountain range with the temps maxing out at around 92 deg ,
Maxing out at 92? The workshop manual says 118 is within normal range on a TD42.

i only have a falcon thermofan set up with the fans set to turn on at around 90 deg ( about 1/2 way on my factory guage) , and they easily kept up with cooling , hwy driving saw the temp guage sit around 1/3 and not needing the thermo fans at all to keep it cool
Have you got a separate coolant gauge to the factory one that you know what the temps actually are in relation to the position of the needle on the factory gauge.

Like what you've done to reduce the temps though.
 

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Gone Fishing
NISSAN 1989 GQ PATROL
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6,223 Posts
yes , td42, and on hills it would get up to the first line of the "H" (115deg) when i had an 82 deg thermostat in , i then changed the thermostat to a 91 deg which stopped the guage getting to the "H" but still up to 3/4 (104 deg)

i believe this shouldnt be aimed at only the td42 as all bypass thermostats behave in the same way
Yeh that is hot!!! Mine seems OK,Done a new rad, wtr pump at 300 thousand as it was all still original but never had heating up probs, Got a Drift gauge and 82 degree thermostat, and she slowly gets to about 70 ish and shoots up to 82 and stays there, around town! On the highway with trailer on a hill aircon going got up to 98 on a hot day and sitting on 115 K's on hway sits around 85-90 depending on head wind etc. When mine was at 98 the orig. gauge was about 3/4. Best thing i ever done getting the drift gauge those original gauges fark ya up.
 

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The nutty professor
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8,299 Posts
Discussion Starter #8
sudso...

i do realise that 118 is still within spec, thats sort of why the title is "Motor running hot???" rather than "Motor over heating???" and yes i do have an aftermarket digital temp guage to compare temp readings ,

the main reason for doing this experiment was to get the temps more stable as i believe varying temps are not good for the motor due to the expansion of metals at different rates, plus once the temp is high it isnt much to go if you suddenly blow a radiator hose or something

madk1w1...

i actually modified an old thermostat i had lying around ( keeps my experiments cheap) but i will be useing a thermostat which has these specs



this is a dayco thermostat (highflow) with an opening temp of 85 deg (also come with an opening temp of 82 and 89 deg)

tridon has one similar but will require some grinding/trimming of the bypass blocking plate down to 28mm or so



and to adjust the height of the bypass plate i will use some C clips to space the blocking plate up to the desired hight, making sure the C clips are a nice snug fit so there is no risk of it falling off (the one i experimented with uses a C clip from factory to stop the base plate from comming off)

just for info sake , this is the thermostat that tridon specified for my car



as you can see , the thermostat would have to open 9mm before it would cut the flow of bypass/recirculated coolant through the motor, i dont think the thermost would even open that far, thats for models 93 to 97 td42`s
 

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Registered
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i wish it was that easy , tried it and my car ran hotter on the hwy

Yeah, I must admit, I am running without a thermostat at the moment. Still get hot. I read on here somewhere that the thermostat regulates the coolant flow through the radiator, and if it's faulty, the coolant doesn't stay in the radiator long enough to cool down. Seems plausible.
 

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nissan
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You live in Queensland. You don't need a thermostat. Take it out and throw it away.:D
the problem with that remark is that half the reason the things overheat is the coolant flows that quick thru the motor than it doenst have time to remove heat. so removing the thermostat isnt a good thing imo.
 

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BORDERTREK 4X4 & FABRICATION
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8,552 Posts
the problem with that remark is that half the reason the things overheat is the coolant flows that quick thru the radiator than it doenst have time to remove heat. so removing the thermostat isnt a good thing imo.
Fixed :)
Same thing when cores are blocked. Less cooling efficiency.
 

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Quickest Tyre Deflator On The Market
nissan
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3,026 Posts
the problem with that remark is that half the reason the things overheat is the coolant flows that quick thru the motor than it doenst have time to remove heat. so removing the thermostat isnt a good thing imo.
X2 , you are exactly right, but wot would I fkn know, another ""uneducated opinion"":(
 

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KICKEN BACK IN THE BUSH
nissan gq
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4,691 Posts
Running a car without a thermostat , regardless of which state you live in,
Thats fuggin funny LOL LOL LOL

Its an ol myth from many moons ago,back when we all had cast heads and not alloy heads
Cast head will run alot hotter before it cracks
Never ever run a car without a thermostat thats asking for trouble
 

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nissan
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4,780 Posts
Geez Itsa we're pulling teeth today ! c'mon mate this is the info hwy
What's the part number of the one you're going to use?????????????

A little of topic, what sort of temp change do/should you get from radiator inlet to outlet.
Checked mine the other day with infra red temp gun, i know they aren't accurate, but was only
6 deg diff and temp was up at 105deg
 

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The nutty professor
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8,299 Posts
Discussion Starter #17 (Edited)
Geez Itsa we're pulling teeth today ! c'mon mate this is the info hwy
What's the part number of the one you're going to use?????????????

A little of topic, what sort of temp change do/should you get from radiator inlet to outlet.
Checked mine the other day with infra red temp gun, i know they aren't accurate, but was only
6 deg diff and temp was up at 105deg
the dayco thermostat pictured above is DT79H
, here is a list of available thermostats from dayco

Dayco Thermostats

the tridon thermostat is a tt480 , here is a list for tridon

Thermostat | Tridon
 

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The nutty professor
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8,299 Posts
Discussion Starter #18
A little of topic, what sort of temp change do/should you get from radiator inlet to outlet.
Checked mine the other day with infra red temp gun, i know they aren't accurate, but was only
6 deg diff and temp was up at 105deg
something wrong there, where were you taking the temp readings from, and was the bleeder still connected from the thermostat housing to the radiator filler neck? as this will give you high readings on the cold side of the radiator, i recommend blocking the air bleeder hose or putting something into the line to restrict the flow of coolant

as for the temp difference i would expect to see atleast a 10 deg difference
 

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The nutty professor
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8,299 Posts
Discussion Starter #20
Do you run the factory viscous hub, fan and shroud as well as the thermo's?
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
 
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