Acceptable Coolant Temperatures - help required

Submitted: Sunday, Jan 17, 2010 at 16:58
ThreadID: 75278 Views:13775 Replies:11 FollowUps:12
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Hi all.
I am looking for a bit of advise regarding acceptable coolant temperatures.

I am running a 98 Hilux 3 litre 5L diesel with an aftermarket axt water cooled turbo charger. I have a digital temperature sensor that has a coolant temperature sensor in the top radiator hose.

On a hot day (30+ degrees) , and travelling at high speed (100 - 110 km/h) with the air conditioninng on my coolant in the top radiator hose sits between 95 and 100 degrees celcius. With the air con off 93 - 95 degrees celcius. This only occurs during high speed driving. Normal city driving or idling the car sits on 88 - 89 degrees celcius (the rating of the thermostat). If my car is overheating and I pull over on the highway the car will cool to this temperature very quickly. Driving at 110km/h the turbo boost sits on approx 5.5 psi.

What I have tried to bring down my coolant temps:
The viscous fan appears to be working fine.
I got it Dyno tuned and the boost turned down to 9 and the fueling tuned last week.
I have tried a new 88 degree thermostat just to be safe
I have added redline water wetter.
The previous owner put in a new radiator which looks to be in very good condition - it is now about 18 months and 10 000 kms old.
I have a thermo fan the helps cool the car at idle speed.
I have taken the spot lights off the car to increase airflow

How you can help me:
1) What is an acceptable temperature for coolant running through my top radiator hose? (am I being too picky - can i run hotter temps)
2) What can I do to achieve a satisfactory coolant temperature.

Thanks for any help you can give me.
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Reply By: Member - Kiwi Kia - Sunday, Jan 17, 2010 at 17:02

Sunday, Jan 17, 2010 at 17:02
Hi Malley, I am not familiar with 'Redline water wetter. Is it glycol based and what concentration are you using ?

AnswerID: 399880

Follow Up By: malley - Sunday, Jan 17, 2010 at 17:07

Sunday, Jan 17, 2010 at 17:07
The redline water wetta has got mixed reviews. Its often used in racing. It is not glycol based. It has some anti corrosive properties. It doesn't really have enough anti corrosive properties for a daily driver car. I am running a pretty strong coolant mix with 1 bottle of water wetta added to the 9L tank.
FollowupID: 668903

Follow Up By: Shaker - Monday, Jan 18, 2010 at 09:46

Monday, Jan 18, 2010 at 09:46
If your coolant mix is too strong it may cause it to run a little hotter.
Plain water cools better than when mixed with coolant, but obviously that is impractical.
FollowupID: 669044

Reply By: Member - Mark G Gulmarrad - Sunday, Jan 17, 2010 at 17:05

Sunday, Jan 17, 2010 at 17:05

My 2004 Navara (fitted with a low water alarm) always runs at 83 to 85 deg with or without the air con on.When we went to St George last september travelling at 100 km/h ( well some of the time 90k's to let Hair Fysh in his clapped out 80 series catch up ) ran at 87 deg.

Are you running the correct mix of coolant in your radiator?
Is your thermostsat operating properly?
Nothing blocked between your radiator and your air con rad?

just a thought,cheers.
AnswerID: 399882

Follow Up By: Member - Mark G Gulmarrad - Sunday, Jan 17, 2010 at 17:06

Sunday, Jan 17, 2010 at 17:06
87 deg was towing our c/t with all the gear loaded up :-)
FollowupID: 668901

Reply By: Ozhumvee - Sunday, Jan 17, 2010 at 17:34

Sunday, Jan 17, 2010 at 17:34
Make sure the coolant mix is at the MINIMUM ratio as specified by Toyota for your ambient temperature.
Too much coolant WILL make it run hotter than it should as coolant doesn't conduct heat as well as straight water.
The water wetter will make a few degrees difference but will not compensate for problems.
Do you have an external oil cooler? Fitting one will increase oil capacity slightly and also cool the oil which will remove heat from the engine. If you do fit one don't put it in front of the radiator/a/c condenser as it will cause airflow restrictions and pump heat back into them negating any advantages, try to mount it either below or beside the radiator, if necessary with its own fan.
Basically your problem is that the engine through turbocharging is creating more heat, more power = more heat so to get it to run at the non turbo temps you have to either increase the cooling capacity or its efficiency, or lift the right foot!
Your temps don't sound excessive but different engines run at different temps.
For example the Chev V8 diesel in my Humvee has a thermostat that opens at 90 C the engine is quite happy in the 90- 110 C range and any hotter than that is cause for concern with my engine.
My troopy with 2H a/c on and 35 c day would struggle to stay cool in 5th on the highway at 100kph, drop back to 4th and back to 95k and it would run all day with no problems due to the fact that in 4th the engine was spinning faster, oil and coolant is being circulated faster and removing heat from the engine better.
It may be that you may ahve to get used to travelling slower in hot weather ;-))
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AnswerID: 399886

Reply By: Davewest - Sunday, Jan 17, 2010 at 17:43

Sunday, Jan 17, 2010 at 17:43
Shouldn't be a problem. On a hot day under heavy load a/c etc it is quite normal for an engine to get this hot. If you wanted to get it cooler you would need to fit a bigger radiator or a thermo fan.
AnswerID: 399892

Reply By: howesy - Sunday, Jan 17, 2010 at 18:32

Sunday, Jan 17, 2010 at 18:32
I wouldnt be relying on a hose read temp anyway. The critical temp is best read on the head itself. An egt guage and a head reading is what you want to make sure that the temps around your pistons are not up too high. Doing it this way is good insurance the other way i reckon is not much better than relying on a factory guage.

When I had my lux I got an aussie desert cooler triple bypass radiator. Some one told me that when your at highway speed the water in that motor doesnt spend long enough in the radiator when your spinning the motor a fair bit and the triple flow forxces it to stay in the radiator a tad longer resulting in cooler temp. They claim 15% cooler. Dont know about that but I definately noticed the difference and was more than happy to spend the $450.

Anyway these are just my thoughts some will disagree but I hope this helps a bit.
AnswerID: 399900

Reply By: Road Warrior - Sunday, Jan 17, 2010 at 18:51

Sunday, Jan 17, 2010 at 18:51
With all of that stuff you should notice some sort of improvement in coolant temps

Seems to me that there could be a circulation issue - have you checked out the water pump?
AnswerID: 399908

Reply By: Member - Scooby (WA) - Sunday, Jan 17, 2010 at 18:55

Sunday, Jan 17, 2010 at 18:55
Hi Malley,
I have a 5L without a turbo and my coolant temps are very similar to yours. I did have higher temps until I put on a new Davis Craig viscous fan hub and that made a difference.
AnswerID: 399909

Follow Up By: malley - Sunday, Jan 17, 2010 at 20:23

Sunday, Jan 17, 2010 at 20:23
Hi Scooby.

Thanks for the response. Your post is actually the most relevant to my car. I am very very interested in the temperature of other 5L non turbo hilux's. It gives me a guage to go by

I follow my temperatures closely - on a 30 - 40 degree day i get the following

90 km/h without ac = 91
100 km/h without ac = 94
110 km/h without ac = 97

90 km/h with ac = 93.5
100 km/h with ac = 97
110 km/h with ac = 99+ (never really gone there)

How do you measure your temperatures? The standard toyota guage or something else?

Are you getting similar results?


FollowupID: 668973

Follow Up By: Member - Scooby (WA) - Monday, Jan 18, 2010 at 18:51

Monday, Jan 18, 2010 at 18:51
Hi Dan,
I am getting similar results to you, 84 to 87 at 60km/h, on the free way tonight, 41degrees outside temp and 92 engine temp at 90 km/h. The highest temp I got was 104 degrees climbing the hill on Mills Rd Gosnells, towing my camper trailer. It was a hot day and I had the foot flat, 2nd gear, 40km/h. I measure my temps with an Engine watchdog, digital readout and the thermocouple mounted under the thermostat cover bolt. At 104degrees the stock temp gauge had moved off the centre and was getting towards the top of normal.
FollowupID: 669182

Follow Up By: malley - Monday, Jan 18, 2010 at 21:26

Monday, Jan 18, 2010 at 21:26
Thanks heaps for your feedback Scooby. It makes me a bit more comfortable knowing others are pulling similar figures without too many drama's.

Sounds like I might have to accept my temperatures on a hot day will rise to 96/97
FollowupID: 669220

Reply By: Member - Phil G (SA) - Sunday, Jan 17, 2010 at 19:09

Sunday, Jan 17, 2010 at 19:09
I think its most likely normal.
Your is 88 degree thermostat is 6 degrees hotter than the 82 degree thermostat found in other vehicles, like Landcruisers. Yours opens at about 84 degrees and is fully open at 95 degrees. Mine opens at 76 and is fully open at 90.
AnswerID: 399913

Follow Up By: malley - Sunday, Jan 17, 2010 at 20:40

Sunday, Jan 17, 2010 at 20:40
Hey Phil,

I like your thinking.
After reading your comments I actually took out my thermostat today and boiled both my thermostats in a cooking pot(my old one and my new one - [don't tell the wife I did this]) today after reading your post. I put the thermometer in the pot with them. Both thermostats stay fully closed until around 87 degrees. They gradually open. Both thermostats did not fully open until around 94 degrees.

I then took the Lux for a spin (its a hot day in Perth - perfect testing conditions) on the freeway without the thermostat in the car meaning full water flow. The car temperature behaved the way it has been with the thermostat in. The car ran 88 degrees in idle and around town. Once I hit the freeway with the a/c on and went 100km/h the coolant temps went north of 97 degrees until i dropped my speed and turned off the air con.

So in summary - My thoughts are: I agree that given I have an 88 thermostat I should give my temps some leway - and expect my car to run between 88 and 91 (maybe even 93 to 94).

But these 97+ temps have me worried - and any car that can't do 100km/h with the a/c on is pretty useless in my book.

Thanks for your comments - got me thinking. I'm still a bit unsure on what to do next.
FollowupID: 668978

Reply By: qubert - Sunday, Jan 17, 2010 at 20:52

Sunday, Jan 17, 2010 at 20:52
they have weak heads, a little bit of hotness will crack them
AnswerID: 399924

Follow Up By: snapper49 - Sunday, Jan 17, 2010 at 22:56

Sunday, Jan 17, 2010 at 22:56
running without a thermostat isnt a good way of testing either as ther is no restriction the water flows through the radiator too fast and doesnt stay in the radiator long enough to cool
FollowupID: 669008

Follow Up By: howesy - Sunday, Jan 17, 2010 at 23:43

Sunday, Jan 17, 2010 at 23:43
Also if its the thermostat with the little foot on the bottom then thats there so when it opens it comes down and blocks a galley so the water will go through the radiator and not bypass it like it does when cold. If this is the design running without it can actually make it run hotter.
FollowupID: 669014

Follow Up By: malley - Monday, Jan 18, 2010 at 00:04

Monday, Jan 18, 2010 at 00:04
Yeah, I realise that running without a thermostat does cause too much water to run through the cooling system - therefore not cooling the coolant enough. However the car seems to heat up similar with restricted flow (thermostat in) or unrestricted flow (thermostat out)...I have already purchased a new thermostat. The thermostat is now unlikely to be the problem.

I did some more testing of the viscous fan tonight - appears to be fine.
FollowupID: 669015

Reply By: JAZZY - Monday, Jan 18, 2010 at 09:35

Monday, Jan 18, 2010 at 09:35
I work for a radiator/air conditioning shop. Why don't you take it to a local radiator shop and have it all checked out? Why risk cooking your engine?

They will completely check out your cooling system, including thermostat, radiator & water pump as well as the fans and give you a diagonisis for FREE.

A lot of radiators look "new" but I have seen a lot that have blockages and need to be replaced. They are manufactured in China these days so don't last as long as they used to.
AnswerID: 399972

Reply By: Bob of KAOS - Monday, Jan 18, 2010 at 18:41

Monday, Jan 18, 2010 at 18:41

You seem very keen to keep temp below 100 degrees. It is a pressurised system so boiling point is somewhat higher than 100. My gut feeling is that 105 degrees is OK. But I'd be asking a guru from Toyota what they think.

AnswerID: 400061

Follow Up By: malley - Monday, Jan 18, 2010 at 19:06

Monday, Jan 18, 2010 at 19:06
I would love to know what other temperatures people with Toyota 3L and 5L diesel motors are getting from their coolant at the top radiator hose. I'm sure there are a few people with a similar set up around. Or the advise of a Toyota guru.
FollowupID: 669185

Follow Up By: Thermoguard Instruments - Saturday, Jan 23, 2010 at 13:07

Saturday, Jan 23, 2010 at 13:07
Hi All,

I'm with Bob on this one. No need to get too hung up on 100 C. It's the boiling point of pure water at sea level (1 Atmosphere absolute pressure). At any other pressure and/or with additives the boiling point is different and, as mentioned, at cooling system pressure the boiling point is much higher. From my experience anything up to 110 C isn't too much trouble but this may differ from vehicle to vehicle.

This whole tread explains why the standard coolant temp gauge in most vehicles is designed to reach about mid-scale at the thermostat opening temp and then stay there until the actual temp is well over 100 C before it starts to creep up to the "Red". Stops owners worrying about 'normal' temperature variations during different driving situations.

While not necessarily relevant to your vehicle, our '97 Land Rover Discovery 300Tdi saw 114 C coolant temp (in the radiator side of the thermostat housing) a few years ago before I noticed it. We were towing 2.2T in 45-ish ambients in the NT at the time. We then eased-off a little to keep it under 110 C for the next few hours until things began to cool down.

Since then the vehicle has done at least another 100,000km (292,000 in total now). About this time last year the head was off for a pre-emptive gasket change and the condition of the engine was excellent: no warping of the head surface, no cracks and the cylinder bores still showing good cross-hatching. No reason why it shouldn't do another 200,000.

Now I know other vehicles may not handle these temps as well, but surely even Toyotas can't be THAT weak? (Yes, this is BAIT!...)

FollowupID: 669941

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