3.4 diesel engine coolant running temperature

lesk1946 · Member

3.4 diesel engine coolant running temperature

Cowboy7307 · Senior Member

I am no mechanic but 73c is not that hot ,it is a pressurized system, and as far as i know it will be ok
But some one will know more than me

lesk1946 · Member

thanks mate , maybe I am worrying 4 nothing but best 2 b sure 4 sure

blaze · Guru

lesk1946 wrote:
hello to all , does anyone know what the MAX running engine temperature of a 1992 Toyota coaster 3.4 diesel should be ? my engine guard hit 75c. i am thinking its a bit high but no alarm. no leaks . radiator full . new pump 20ks ago. oils ok.....any thoughts please....cheers les

I would have thought 75 is a bit cold, around 85 to 90 would be more the normal. I have run a 300tdi upto 110 for short periods with no ill effects

Check to see if you have a thermostat fitted

cheers

blaze

lesk1946 · Member

I didn't give a thought to thermostat , I ll get a new one and check coolant date & hoses , thanks mate . sometimes the brain needs a gentle cattle prod

Rob Driver · Guru

Many thermostats used to have a temperature specification stamped somewhere on the assembly.
It is a simple project to remove the thermostat and test it by placing it in water or coolant and heat the coolant, all the while watching for it to open and testing the temperature with a thermometer.
One of those candy making thermometers will work as will many others that will handle boiling water temps.
Of course if you remove the thermostat and it is obviously open when cold then it is unserviceable and should be replaced with one of the correct specification for the engine.
The vehicle manufacturer should be able to provide these specifications.
Good luck with the repair.

Regards
Rob

lesk1946 · Member

we're learning whilst the wheels are turning . so as Bob & Dolly would say , happy motoring......thx les

Peter_n_Margaret · Guru

Of course, the first question to ask is "Is the temperature shown accurate?"
But I agree, if 75C is accurate, it is too low.
The hotter a diesel engine runs, the more efficient it will be, but get it too hot and other nasty things can happen to oils, coolants, seals etc.
Cheers,
Peter

Aus-Kiwi · Guru

As a guard for emergency. Imo the temp is set way too low. Did it alarm on hard work up a hill ? I would set it 10* higher ? Keep an eye it doesnt run high consistently!! Check fan and shrouds are well sealed ? Cap sealing etc Big Hills ? Maybe sit back and cruise in lower gear ?

Jaahn · Guru

lesk1946 wrote:
hello to all , does anyone know what the MAX running engine temperature of a 1992 Toyota coaster 3.4 diesel should be ? my engine guard hit 75c. i am thinking its a bit high but no alarm. no leaks . radiator full . new pump 20ks ago. oils ok.....any thoughts please....cheers les

Hi les smile

The max temperature would be about 115deg C. The normal running temperature should be about 80-85deg. The normal temperature is set as a min by the thermostat which should bring it up to that quickly soon after starting. As has been said all engines should run above the min for efficient running and long life. If it is not getting hot enough the thermostat may be faulty or not even in there furious The opening temp is shown in a catalogue as 82deg C.

Normally the temp will go up a bit on hills and long climbs but should normally peak below 100 or a bit more. It should only go above that in extreme conditions but can actually get up to about 115 by design, depending on having the correct coolant and radiator cap rating. I would set your alarm to go off at about 95 so you can check things are OK then. Note, is the correct coolant in there also not just water.

Jaahn

-- Edited by Jaahn on Saturday 21st of September 2019 03:36:56 PM

-- Edited by Jaahn on Saturday 21st of September 2019 03:52:19 PM

erad · Guru

The engine guard is a thermocouple which will give an indication of the temperature it senses. Where the thermocouple is mounted will affect the reading. Probably the most accurate reading will come if the sensor is mounted on the thermostat housing. These units are not really designed to give a true indication of coolant temperature - they are really a watchdog which monitors the temperature and when it exceeds a pre-set vale, triggers an alarm. Depending on how well shielded the thermocouple has been mounted, it can give a lower reading on a cold day for exactly the same engine temperature as on a hot day. It is an indication only.

Aus-Kiwi · Guru

On my boat LS engine the thermo couple is on the block. Ive had issues with no water (or steam) getting up the thermostat housing . But thats when theres total loss of coolant ! I like the idea of seperate alarm.

swamp · Senior Member

Hi
1st U need to verify temperature . All sensor need to be in flowing water .
No your mechanical history . When was the viscous fan and radiator serviced last ??.
Check thermostat in a gradually heated container to verify opening temp.
USE ONLY genuine or Tridon thermostat. Some after market t/stats are complete rubbish.
Do u no the dry fill capacity of cooling system 50% coolant 50% distilled water .
Correct type of coolant foe engine /vehicle . Some cast iron reacts to some coolants .Use the recommended .

75 deg cel is on the low end of acceptable
95 deg cel is the upper limit for very short periods .
Between 5-10 deg cel above thermostat spec is what your looking for .

Many old school engines will not tolerate high temps eg over 100deg cel if they mostly operate at 80 degcel. Some modern engines run hot under norm operating conditions . These motors will operate at elevated temps longer . They are built for it . Although Longevity is best served by not running engine at its max all the time . Running at max temp gives little or no safety margin.

-- Edited by swamp on Monday 23rd of September 2019 05:32:18 PM

Warren-Pat_01 · Guru

lesk,
We had thermostat troubles at Halls Gap earlier this year (it jammed open).
I had a spare & put it in at my first chance. The original was set to 76 degrees, the new one was 81.

I checked with my mechanic when I got back home - he said the 76 degrees was too low that the one I put in was the best.