Hilux Surf 1KZ-TE Engine Running Temp?

[bronx89]

Just installed an aftermarket water temp sensor and gauge to get a more accurate reading of the real water temp when off-roading (and on-road). But having never owned a diesel before I'm unsure what the "normal" running temp range would be.

Is anyone able to tell me? It's a '95 Hilux Surf KZN130 1KZ-TE Auto.

- What would the normal road temp range be?
- What would the normal off-road temp range be?
- What point/temp is where it's getting too high/hot and the engine should be given a rest?
- Also, any experts agree that when an engine is overheating it should NOT be turned off and should instead be left on (stationary) until temp decreases to help prevent warping etc.?

Cheers.

[kbushnz]

I too have an aftermarket gauge and a std thermostat installed 86C ?

Anyhow here are my observations.
- What would the normal road temp range be?
Tends to sit on 85C but will creep up to 90C and settle there if pushing it hard like blasting up hills but it soon settles back down to 85C when off the gas.

- What would the normal off-road temp range be?
As above....

- What point/temp is where it's getting too high/hot and the engine should be given a rest?
I have set the alarm for 100C, its never hit it yet...but if it did, I would slow down and watch it, if its still climbing then pull over and let it idle, if its still going up, turn off engine and investigate.
You also need to keep an eye out if the temps suddenly drop. As depending where the sender unit is, if you are losing coolant the sender could end up in an air pocket / gap and then it wont read tru water temp, only the air temp around it........

- Also, any experts agree that when an engine is overheating it should NOT be turned off and should instead be left on (stationary) until temp decreases to help prevent warping etc.?
I don't see any harm in turning it off if its overheating, if you don't it may do more damage as there may be no coolant...And its only going to get hotter..
I think the biggest thing is not to throw in cold water to top up the system while its overheated. Let it cool... and put in hot water...(if you can)

[bronx89]

Cheers for the info! I haven't had time to drive mine with gauge in yet so if I can get it out tomorrow I'll see if mine settles around same temp as yours with normal road driving.

Sender/sensor is in an adapter in the top radiator hose as this will show the true inside water temp with the thermostat being by the bottom hose.

Yea I just heard somewhere that turning an overheating engine off ceases water flow which can lead to variable core temps inside the engine which can lead to warping of heads etc. Apparently it's best to leave engine running to keep water flowing (yes as long as there is water and coolant in there lol) so it can cool down at a steady and uniform rate.

Anyone else got any similar or conflicting info on the 1KZ-TE?

[kbushnz]

Obviously this all depends on how well your system is working...
Good radiator, hoses, clean water / glycol and good water pump and vicious fan...

[tweake]

i think you will find the idea behind not turning an overheating engine off is from heat soak. when you turn it off the engines temps go up a bit as the existing heat now can't escape via the cooling system.
i've tested that myself and had temps go up a little bit after engine off.

can't help with what running temp tho 90c sounds about right.

[bronx89]

Heat soak - those were the words I was looking for! Yep exactly what I had heard; if the heat can't escape thru the cooling system it can start to warp stuff.

Just went for a decent drive. Temp gauge had the water temp sitting at about 90-95'C. Normal road driving. Cool-ish weather and minimal traffic. Have cleaned out top hose when I put adapter in and has fresh coolant and water. Does that seem a tad too high? I'm just a tad obsessed with engine water temp as my old Sigma cracked a head about half a year ago

Might take both hoses off, thermostat out, flush water with pressure thru the radiator and thru the engine cooling system to see if any gunk comes out or if there's a blockage - just need the time to do so! 90-95'C seems high to me but I'm used to my rebuilt Sigma runnig a lot cooler. Do diesels generally run hotter than petrol engines?

[tweake]

i think 95c is getting hot for such cool weather and minimal load. also the fact that its changing that much while driving would be of concern. my old 2.8 will sit with a degree or two even up hills.
not sure about comparing to petrols but a lot of diesels are designed to run hot for emissions purposes.

[Sadam_Husain]

I havent got a clue what temps 1KZ's should run at but to keep it in context your thermostats probably opening around 80-85C and with a 15psi radiator cap your boiling temp is around 120C

[evolution02]

I have 94 1kz surf and have done most things to the cooling system
Have fitted a 82 degree thermostat and VDO gauge. It normally runs in the mid 80's. Driving hard can get it to 90
Off road should stay low as normally driving slower and in low range
If yours is high I would fit a genuine thermostat and check the viscous fan. You should be able to hear it roar on first start up especially if you rev the engine a bit
You could also fit an external transmission cooler for your auto to remove heat from the bottom of the radiator

[skidmark]

i have a 185 surf(non intercooled) that has a aftermarket guage tapped into the top hose out of the engine..sits at 90-95 degres and will hit 100c up hills if i put my boot in in.or towing etc.

[mudbugga]

Here's some info on modifying the factory temp guage
http://www.toyotasurf.asn.au/techsite/tempgauge.htm

Might be helpful for some.

[mudmike]

Mine sits at 80 if all clean and running well, pushing hard been up to 100 so just pull it back and it cools fast, when mine started to run up at 90 on the road I pulled the rad out gave it a good clean and it was back to 80.
Also will depend on where in the system you run it. I'm in the top hose have been told that the bottom hose will give slightly different readings

[kbushnz]

I have put my sender unit in the top hose connector (alloy casting) on the head.
I didn't like the adaptor thing with more hose clips to potentially fail.
There was enough meat at a boss location for a drill and tap...

[bronx89]

Just to confirm it DOES sit at one temperature, I just put 90-95'C as I wasn't exactly sure where the needle was sitting. Just got home from another drive and it looked to be about 93'C it would settle on.

When I fired it up this morning I popped the bonnet to check radiator water level and the fan was roaring.

Does between 90 and 95'C sound too hot for normal road driving in average heat weather here in Auckland, New Zealand? Should I take all hoses off, radiator out, flush the radiator and cooling system in engine with high pressure hose, test thermostat in pot on stove and also get the rating for it and change to a lower temp one if it's too high?

What is the stock thermostat rated at? And what's a good one to have to help it flow earlier and run cooler?

Yea thought about adding external trans cooler in series before the radiator one but I really need to get the radiator one taken out or find a manual radiator as keeping the trans cooler in there restricts radiator water flow when off roading which aids in overheating. Strikes me as stupid having an oil cooler inside a radiator which blocks off the outlet flow of the radiator water itself..

[bronx89]

Just finished doing a few things.. here's what I did/found..

Took top and bottom radiator hoses off, used high pressure hose to flush water thru the radiator - flow was fine, no blockages and no junk/gunk came out, was all crystal clear water.

Took the thermostat housing off and the thermostat out. The thermostat is already an 82'C one.. so are these the factory rated ones? Put thermostat in a pot on stove with water (had it suspended not touching pot or air) and it opened just as the water started to bubble - didn't have a thermometer so couldn't check if it really opened at 82'C though. Snipped off the little restrictor in the hole and drilled it out a tiny bit bigger, did the same 180 degrees on the other side (I know this doesn't effect anything when thermostat is open but it does until it opens). Used high pressure hose to flush water thru top of engine and came out the bottom absolutely fine, no gunk and no blockages. Did it from the bottom up too (as well as on radiator).

Put it all back together and when I take it out this afternoon I'll see if the temp is the same as before (90-95'C-ish).

Anyone know why mine would be running this temp if someone with the same rated thermostat and no cooling mods is running 80'C?

Sensor/sender adapter in top hose gives a more accurate reading of inner-engine water temps than bottom hose as thermostat is at the bottom and you're really wanting to know the temperature of the water exiting the engine not the freshly cooled water from the radiator (or dormant water after the radiator if the thermostat is closed). Yea?

[Sadam_Husain]

you've also got to allow for gauge accurecy of at least 5% mate so chances are your chasing your tail and going to start throwing time and money at a problem that might not exist.... the moneys probably best put aside for a new head when it finely does go

[bronx89]

Haha 5% would still have it running cooler than it is/was. Yea that used to be my attitude until I cracked a head. Why save for a head when you can spend a shit load less preventing that issue happening in the 1st place!

Will see how it goes when I drive it this arvo. Hopefully runs a tad cooler now that it's been flushed out and had a few holes in the thermostat.

[SMOKEY]

As you are so worried about cracking a head and you should be as it will crack, for one more time I will share some advice with you, your motor will cook it's self internally from combustion temperature, It doesn't matter how good or clean you keep your cooling system even working 100% it will still fry, you can't avoid it but you can monitor it. FIT an EXHAUST GAS TEMPERATURE GAUGE pre Turbo and drive by it, it has been all documented on this forum have a search and read. I think I should save this reply and just paste it each time I answer this question.

ONCE AGAIN,

FITZY.

[bronx89]

Righto, cheers for that. And what is the safe range of exhaust temp's pre-turbo for one of these engines?

[Ginzu8]

My kzj78 sits around 80-85C. On the motorway cruising at 100kph it sits at 81-82 C, not once does my temp goes above 85 in traffic or going slow around town. If I go up a hill doing 50kph my egt sits at average 560C and the water temp goes up to 87 but never go near 90C.

[SMOKEY]

If you can find the max EGT for any motor please let me know, the research I have done gives max of 700deg C for a few seconds don't hold it there, up to 650 once again no longer than 20 seconds, go for 550 ---600 when hard acceleration or uphill. I have made 800+ by mistake/not looking while towing Caravan with my Prado 1KZ. You will find a new style of driving using an EGT gauge and prolong the life of your HEAD,

AND THE VEHICLES,

FITZY.

[rangimotors]

Flushing a radiator with a hose is not the same as taking it in having the tanks pulled off, rodded, flushed and flow tested. 90 is to hot imho because you run out of room to play when things get warmer.

[bronx89]

Flushing a radiator with a hose is not the same as taking it in having the tanks pulled off, rodded, flushed and flow tested. 90 is to hot imho because you run out of room to play when things get warmer.

Yes I'm aware it isn't the same as that. In saying that, doing what I did reduced the normal road driving temp to about 80-82'C, so I'm happy..

[bronx89]

Max of 700deg C for a few seconds don't hold it there, up to 650 once again no longer than 20 seconds, go for 550 ---600 when hard acceleration or uphill.

Cheers for that.

[DDAN]

I've been through the 1kzte Manuel head to to toe. And all I can find out about temperature, is on the turbo and it say. The turbocharger has been design to withstand the high operating temperatures (800c) from the exhaust gasses
And then talks about coolant temperature limit of 110-120 c

[tweake]

what ever is mentioned in the manual will not be relevant because they fail while in factory tune.

generally speaking the heads fail due to overheating. overheating is a combo of egt's and lack of cooling. reducing egt's will help a lot but it won't stop it overheating due to blocked radiator etc.

i would be looking at max of 700c pre turbo.
water temps, i can't remember what the surf guys recommend but keeping it on the cool side helps stop it heating up so quick.
not to sure how to explain it but its much harder to keep it cool if its running hot. if you run it a measly 5-10c less its a whole lot easier for it to stay cool.

one of the big problems with the surf is the trans cooler heating up the water that goes into the engine to cool it. cooling with hot water doesn't work very well.

[bronx89]

Yea shitty trans cooler design on Toyota's part I reckon. Exactly the reason the next thing I'm doing is looking for a manual radiator and fitting an external trans oil cooler!

[kow1]

I have spent a fair bit of time with the cooling system on my ‘KZ & read A LOT about them on the websites. A few thoughts:

The standard thermostat opens at 82°C and should be fully open at 95°C. As the engine comes under greater load (hills, towing etc.) the cooling system has to dissipate more heat through the radiator. It does this by opening the thermostat further to allow a greater volume of water to flow through the radiator. The only way the thermostat can open further is by being surrounded by hotter water. The water temperature is to an extent proportional to the load the vehicle is under and the radiator can’t do much heat disapation unless the water temperature is elevated.

The thermostat is located in in the cooler lower part of the engine. It is also ‘hit’ by the cool water coming in through the lower radiator hose. Most people are measuring the water temperature at the hottest part of the engine – at the top at the water outlet which is attached to a great chunk of hot aluminium.
The difference in temperature between the top and bottom of the engine varies. At low load like when driving around town, only about 2°C is added, but on a hot day under load there is a far greater difference. This makes it a hard job for the thermostat to regulate the water temperature as it doesn’t know what’s going on at the top of the motor.
It makes me wonder what the water outlet temperture would be when the thermostat is fully open at 95°C – possibly well over 105°C

If the thermostat opens at 82°C and a minimum of 2°C is added to this by the flow of water through the engine, then the water outlet temperature must be at least 84°C when the vehicle is warmed up.

Many people with cooling system problems, especially over seas, change the thermostat to one with a lower operating temperature. Toyota make a 71 - 90°C and a 76 - 90°C. These are said to be an option that Toyota put out for the Hilux and Prado in Oz, but I am yet to see any official parts listing from them other than the usual 82°C. I think there may be value in these in hot climates under high loads, due the large temperature difference across the engine under these conditions. The problem is under light loads in NZ, which is where most of the running is done, would mean a water outlet temperature of only approx. 73°C or 78°C. It has been said that the idealoperating water temperature for a diesel is 88°C.
On a brighter note the Toyota Technicians tell me with that with the new heads they fit (superseded part number), the vehicles don’t come back again…

[mudbugga]

The genuine part number for the 76-90 degree thermostat is 90916-03119.
I've fitted a few to vehicles that do a fair bit of towing.

There are only the 2 options available here, the 76-90 degree and the 82-95 degree (the standard type).

[bronx89]

Sweeeet will definitely look into that lower rated thermostat thanks