Over Heating

I'm thinking that to Bob - in the same situation actually , with 250k up I noticed that I have lost a little water and will be watching carefully things like temp gauge also.

If a car is going ok and then it starts to overheat then there is a logical reason why - putting bigger radiator etc may just cover things up for a while and you need to find source of problem.

Thanks for feedback Guys, Only done 95,000 k's and doesn't use fluid at all, it was the first place i looked, but again thanks for the thoughts.

Cheers

Gday Brocky05fj,

Yep I am thinking along those lines also, it is set to come on well below halfway mark for temp and all the ""experts"" tell me the fan makes no difference at highway speed, but I am tending towards trying the old fan back on it.

Cheers

Hi there brocky05fj, firstly going by your user name I presume the old VS was a 5L V8 as the V6 ecotec come with electric fan from the factory for cooling plus one up front for the aircon ?? S.A. Blaze, I would piss the electric fan off and go back to the viscous coupling you had, you obviously had no cooling issues prior so why change what was working fine ?? Also people who say either electric fans or viscous coupling fans dont operate when vehicle is moving dont know what there talking about. Wether sitting still or crusing at 110k if the engine coolant requires cooling they will operate. As brocky05fj has found out some of these so called electric cooling fans will not draw the air through that is required compared to the 7 huge blades on a VS V8 commodore. Most modern cars today do come with electric cooling fans and work extremly well, but generally when fitted from the factory not aftermarket. Silly question but have you checked the operaton of the thermostat ?? Maybe not opening write up so not allowing full flow of coolant from radiator to engine block ?? I have also heard of some of these super dooper radiaotrs actually causing more problems due to reducing airflow through the radiator, this might be totally crap as I have never dealt with aftermarket modified radiators. My theory is if it was cooling fine for the last how many years then all of a sudden its not cooling then either some thing is stuffed/blocked/ or not working how it was. As mentioned above, just adding a bigger radiator is probablyjust hiding some thing and allowing it to run a tad hotter before it shows up. Get the heads checked, but I would put it all back to normal then start with the basics/cheapest parts first, thermostat etc. My prado turned out to be blown head but I had obvious symtoms like pressure in over flow bottle, and besides that was common in the 1kz prado/hilux motors............

Yeah I noticed no mention was made of the thermostat and this sounds like a thermostat issue if everything else has been replaced, unless the water pump is playing up. I presume the cooling system has been flushed and the correct AFAB is in place.

Gday Kimba,

Most of what you said is exactly what I am doing, putting a new thermostate in, even though current one is only 30K old, also putting old fan back on. The only reason I did any of this was it had a small leak with the original Radiator, so it needed replacing, so I thought with some hot weather driving in the forecast, I thought I may as well put in a larger one, never again....

G'day Kimba10,

You are correct, it is the V8 that I have and the V6 does have the electric as standard.
The electric fan is still just sitting on a shelf and the old girl is still going strong with the viscous fan.

Cheers

Sorry Muff, I neglected to say its a Challenger PA model.

Hi,
New radiator = new everything else. Including clips on all hoses.
You may have to watch the heater hoses but if age is the thing than they will need to be on a replacement schedule too.

Bill

Gday Al, I did all the clips and hoses etc but didn't do the thermostate as it seemed to be working fine with old setup, It also had one put in 30,000 k's ago but I have decided to do as you say and fit one so i can tick it off the possible cause list.

Cheers

Change the thermostat.

Hi,
I had a new radiator done in Townsville in July and the account said the thermostat was replaced. Eight months later the water bottle was losing water due to the block/head boiling.
New thermo and it was back like new.
The Townsville repairer wouldn't entertain the thought that he may have missed the thermo and I couldn't find anyone who thought the thermo I took out was perhaps OME or old.

Bill

Sounds like it's not getting enough air flow through the radiator, I remember hearing people that had extra core radiators had troubles with air flowing through, yet the standard tank did just fine.
You could try using a lower gear which will make the motor rev higher which should cool it better , or are laboring the motor when loaded going up the hill after all

Hi Kenny,

I did a drive today in 26deg just out of home town with camper attached, up a short hill. Vehicle dropped down a gear on the hill and was doing about 90kph at 4900rpm, as i said it is a short hill, only 300mtrs. Total distance from home is 3klm's and it ran up to the nearly boiling mark in that distance.

I have decided I will replace Thermo in next 2 days and try again.

Geez you would be lucky for it to be even runnng at normal operating temp after 3 k ?? I would definately be checking the thermostat out, also when replacing coolant did you use two different types ?? this is s a common cause of blockages as the two different brands can form a gel like substance in the radiator causing blockage even if you have put in new radiator. Also have you checked hoses to make sure there not sucking in together ?? Water pump ok ?? I know the mitsi's have a different set up for water pump compared to majority of vehicles. You would have to be unlucky for it to be a head/heads, at those klms, its possible but would think highly unlikely ?? Good luck with it all, but I would start off with putting it all back to how it was and go from there..................

Gday Kimba,

Starting with that tonight, I was going to do the thermostate first but have to wait for one as they are OEM. So have decided tonight I will put the old Viscous Fan back on with the shroud and give it a go, if its still yuk I will do the thermosate before the weekend, if that still fails it swap the radiator back, after that we start looking at pump, but I have my doubts here as it will run on flat ground for over 260k's without excesive temp and no it is all Mitsi Coolant.. Just Sux, am certainly learning to leave things standard, but the Radiator did need replacing, just didn't need a heavy duty.!!

"No thermostat means water travels through the radiator too fast to cool down properly."

No Andrew, that is incorrect. It is not in accord with fluid & thermal dynamic physics. Certainly the coolant flows faster through the radiator and spends less time in passage but every volume of coolant passes proportionally more often as it cycles through the system. The result is that the flow-rate increase has no effect on the cooling efficiency. It may be the case on a single pass heat-exchanger though.

You are however correct regarding the redundancy of the fan with increasing air speed. When the wind speed reaches the same velocity as can be achieved by the fan then the fan can no longer contribute and actually becomes a hindrance as it partially obstructs the air-flow.

Thanks Allan

Can't argue on fluid & thermal dynamics however insufficient exposure to sufficient temperature differential to remove the heat load results in a rise in the mean temperature of the total fluid volume. At least that is what I was taught. The net result is that two conditions seem to occur (probably supports your point actually)
With no thermostat to regulate the coolant flow
The vehicle either overheats because the engine is adding heat faster than the coolant loses it

or

it runs cold all the time because the engine can't add heat fast enough to overcome the coolant losing it


From experience I have seen both conditions and they were rectified with fitting the correct thermostats.

Regards

A

Andrew, your use of the word "exposure" is central to the equation. Because the fluid is flowing faster it has less time (- exposure) to transfer heat, but because it is moving faster it comes around more often (+ exposure). The two cancel and the result is no net change.

Certainly if the thermostat does not regulate coolant flow the engine will take longer to "warm-up" and may even fail to reach prescribed operating temperature in some circumstances.

Not sure on your thermostat theory. I removed mine when I was having over heating issues on the prado and with the thermostat removed the temp guage would jump all over the place, huge variance compared to when it had thermostat in it, it then ran just under halfway, didnt show any signs of over heating till I hit the freeways and worked it that bit harder. Could run around all day in town and never showed a single sign of a problem. In regards to fans running or not wether electric or viscous coupling they will run if needed even if your cruising at 100k or more. When pulling up hills with aircon running, 40c outside, 1 tonne + camper on back and I would hear the clutch fan cut in while pulling hard and you could hear it reving its nut out then would fade back off again and you would see about a 2 mill variance in temp guage, if the hill was big enough you would hear it a few times. The spirn in the middle of the coupling is what determines the temp, as it picks up the temp of the coolant as the wind pushes through the radiator and onto the spring which will then determine wether the coupling locks up or not. Get a 40+ day, find yourself a tonne or so to throw on the back, a nice long gradient hill and take off your fan coupling and see how far you get before the guage starts to rise, not long I bet..... Same goes with electric fans, obviously have temp senders here and there, block,head,radiator, aircon condensor, etc there every where detecting temps. Most radiator fans have two stage speed control so they are only ticking over then if needed they will roar up to second speed to cool down. Eg stick your head under the bonnet of a toyota with electric fans with aircon running, you will see the fans turning very quitly round, if its hot enough the sensors will even detect the gas in the aircon system is starting to get hot so even though the radiator is ok and still below swithc temp the fans will roar into second speed action to cool down the gas in the aircon system. The cooling system these days are pretty good compared to years ago, not as often you will see a bonnet up on the side of the road with steam coming out, if you do its generally due to blown hose,belts or simply neglect, which I saw a lot of, the tolerances of the correct cooling product used can also be vital. The cooling system have a bloody hard job to do

I was running LPG and Premium, both reacted the same.

Hey Tony,

Thanks for the info, I would also have been like you at the point of selling if mine kept doing this, but glad they sorted it so easily in the end. On one of our trips across the Simpson about 12 years ago, couple of the guys had Tritons.

Both had 150k on the clock and within a day of each other the viscous fans stopped working. We solved this in the desert by stripping them apart and using a silicon and let it set over night, no more problems as this made it that they had solid fans. They did sound like Cesna' as they crested the hills though after the fix.