Hilux 4x4 Forum

Hi Guys, I need some advice...

My Hilux is overheating when standing in traffic. Temp is quite normal while driving but if I stand still in traffic it starts to heat up and if I don't get moving it gets very close to the red. When I drive off it immediately drops back to normal operating temp. I have checked the visco fan and it is running, how effectively I don't know.

Is this something I should tackle on my own or should I involve a pro?

Thanks in advance!

I am assuming the viscus has never been replaced? If not, that's where I would start.

We have just replaced one on a 2009 BT50, 120k km....

We also found that the radiator was very dirty on the outside between the radiator and aircon cooler.[IMG]//uploads.tapatalk-cdn.com/201809 ... 887f79.jpg[/IMG]

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Hi Craig.

The bakkie is already 17 years old. Over time all the components contributing to keeping the engine cool deteriorate gradually and it is usually the collective effect that leads to what you are currently experiencing. Without being too lengthy here is what I propose you do. It will entail a full cooling system overhaul in a sense

1. Do an engine/radiator flush with one of the reputable products such as Wynns. You are going to be replacing the coolant anyway.
2. Replace the Thermostat. It is most certainly not up to spec anymore due the the many times it has opened and closed. This means it is probably not opening properly slightly hampering the flow of coolant.
2. Remove and have the radiator properly cleaned (descaled) inside as well as outside and checked for leaks.
3. Replace the water pump. (depending on how long ago it has been replaced) The impeller vanes could have deteriorated due to rust (if anti-freeze levels were not adequately maintained) and other wear such as cavitation. If you fit a new pump you eliminate one of the variables.
4. Check all the rubber hoses for damage due to perishing and replace any suspect hoses. Thoroughly clean all the fittings before you re-fit the hoses.
5. Replace the coolant with any of the reputable brand products. The Toyota product is good but expensive. You can also use one of the VW G12 replacement products sold by Goldwagen

It may sound like a lot but heat is the worst enemy of any engine. Do the above and I can guarantee you that the issue will be resolved.

Thanks for the advice guys. A busy saturday for me.....

Agree with what Marnus is saying, it could be one or a number of causes. The fact that it cools down when driving suggests inadequate airflow to be the, or one of the factors. I would first look at the visco fan and check the cowl around the radiator and fan. Yes by all means do the radiator flush, inexpensive exercise and can only do good, but also check the condition of the radiator fins ... if they are corroding away or even clogged with insects and debris the radiator cannot do it's job properly. Replacement of the thermostat is also a good idea, easy to do and also not expensive.

Many visco fans can be refurbished by replacing the silicone oil in the hub (I think Toyota actually carry it in their spares dept.).

If all that fails, I would then replace the water pump last ... most expensive and time consuming of all the options. IMO the pumps are the least likely culprits - yes the impeller vanes can corrode / erode if there has been a long extended period without anti-freeze but generally they last pretty well and replacement is usually because of a leaking shaft seal.

Good luck.

Mud Dog wrote: ↑Thu Sep 06, 2018 9:30 pm Agree with what Marnus is saying, it could be one or a number of causes. The fact that it cools down when driving suggests inadequate airflow to be the, or one of the factors. I would first look at the visco fan and check the cowl around the radiator and fan. Yes by all means do the radiator flush, inexpensive exercise and can only do good, but also check the condition of the radiator fins ... if they are corroding away or even clogged with insects and debris the radiator cannot do it's job properly. Replacement of the thermostat is also a good idea, easy to do and also not expensive.

Many visco fans can be refurbished by replacing the silicone oil in the hub (I think Toyota actually carry it in their spares dept.).

If all that fails, I would then replace the water pump last ... most expensive and time consuming of all the options. IMO the pumps are the least likely culprits - yes the impeller vanes can corrode / erode if there has been a long extended period without anti-freeze but generally they last pretty well and replacement is usually because of a leaking shaft seal.

Good luck.

Hi Mud Dog, I have unfortunately had a period of about 5 months without anti-freeze.....procrastination is the only reason. I'm hoping the damage is not too bad!

Well the cooling system needs a functional radiator, adequate airflow to cool it and adequate coolant reticulation / flow to take the heat away from the motor.

It also to a lesser degree needs a pressurised system because the boiling point of the coolant is raised if under pressure - anti-freeze also helps raise it further. If you're not loosing coolant then you should be OK in this area.

Airflow is affected by the efficiency of the fan (the cowl plays an important part here) and if there are any obstructions to airflow like spots or stuff mounted in front of the radiator grille and of course debris blocking the radiator fins.

Reticulation is affected by the efficiency of the pump or any obstructions like a partially open thermostat, blocked water galleries in the motor (head) or a chocked radiator.

Given the age of the vehicle and having run without anti-freeze, the possibility of the pump being the or one of the culprits becomes greater. I hope it's not the cause but I'm not holding thumbs on that either now.

I bled the system after using radiator flush. Water was not as bad as I thought it would be. I replaced the thermostat, it looked a bit worse for wear! System was reloaded with water & antifreeze mixture and seems to be working. Big test is tomorrows traffic. I tried idling it to make it overheat but it stayed constant. Hold thumbs!

Drive to work was uneventful but the traffic was very light. The few times I parked at an intersection the temp needle didn't move. I'm hoping the problem is now in the past. I'll find out for sure this afternoon as my afternoon commute is a lot heavier than the morning one!

One thing I failed to mention in the previous post, when I added the radiator flush the water level in the radiator was quite low. I needed to add at least 1,5l of water as well as the 450ml of radiator flush to top up the system. The resevoir bottle was full though. In fact is was about 50% over filled.

I did blow out the siphen pipe in case there was a blockage in there. I'll be checking the water levels daily now to make sure the engine isn't using water. As a side note...I've not previously had any water or oil usage issues.

The overheating at stops could have pushed that water out. 1.5 lit is a lot, even half a litre short will make a difference.

What concerns me is that it wasn't sucked back into the radiator from the reservoir ... could be that the radiator cap is also faulty, so I would replace it anyway - just to be sure.

Check the coolant levels (radiator and reservoir) in the mornings when the motor is properly cold.

Good luck, hope your problem is solved.

Yes that is good advice to replace the radiator cap. I forgot to mention that and make sure that the surfaces where the radiator cap mates on the radiator are clean and smooth to ensure a good seal there.

Make sure you replace with the correct rating cap...

I know this sounds silly, but I was losing coolant on my 1HZ. Replaced the cap, nothing changed.

Then I saw online that my vehicle uses a 0.9bar cap and not the 1.1 that was on.....

Changed again and problem solved!

Not sure why though...

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The system is designed to work as a specific maximum pressure. If you get a cap that is below that rating it is going to release pressure with the accompanying coolant.

Mars wrote:The system is designed to work as a specific maximum pressure. If you get a cap that is below that rating it is going to release pressure with the accompanying coolant.

Mine worked the other way around...cap rating was lower than the cap it had.

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Sorry I did not read your post properly. Yes that is strange.

Shane, the probable reason for loosing coolant with the higher rated cap is that the resulting additional pressure in the system could have pushed coolant past a hose clamp or even the pump seal. If that was the case then you would have lost coolant.

Mud Dog wrote: ↑Mon Sep 10, 2018 8:28 am The overheating at stops could have pushed that water out. 1.5 lit is a lot, even half a litre short will make a difference.

What concerns me is that it wasn't sucked back into the radiator from the reservoir ... could be that the radiator cap is also faulty, so I would replace it anyway - just to be sure.

Check the coolant levels (radiator and reservoir) in the mornings when the motor is properly cold.

Good luck, hope your problem is solved.

I'm going to check the levels now during our lunch break.

Good point on the radiator cap. I'll check the condition of that too and call around for a replacement! Would a normal spares shop stock it?

Radiator level is low again.....it is a 1.1 bar cap. I'll calll around for a replacement!

Don't stress too quickly. The level will drop after you have done a coolant replacement even if you bled the system. Top it up, drive it home and check again tomorrow morning. The spares places should stock them. Was the higher pressure cap on there all the time before?

the level may drop to a air pocket that may have formed when refilling it, as commented above, top it up and monitor it

Sylvester wrote:Radiator level is low again.....it is a 1.1 bar cap. I'll calll around for a replacement!

Not saying yours is incorrect. Just confirm that 1.1 is the correct rating....

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Lorry wrote: ↑Mon Sep 10, 2018 4:30 pm the level may drop to a air pocket that may have formed when refilling it, as commented above, top it up and monitor it

That is a good point and exactly as you implied, the water level seems to be consistant now. I'll keep monitoring though. I am going to do another flush in a week or two as I am now unhappy with the ratio of water/antifreeze with the recent top ups it has been pure water.

Baasvark wrote: ↑Mon Sep 10, 2018 4:34 pm

Sylvester wrote:Radiator level is low again.....it is a 1.1 bar cap. I'll calll around for a replacement!

Not saying yours is incorrect. Just confirm that 1.1 is the correct rating....

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It is the same radiator cap that has always been on the vehicle for the last 5 years since the radiator was replaced so I am hoping/assuming it is correct.

Thanks for all the advice guys, really great to have it "at your fingertips"!

One final question...

What is the ratio of water to Antifreeze supposed to be?

Depends if it says Premix on the bottle or not. Premix (such as Castrol Radicool and Toyota OE) you put in neat. Additive coolants are often 50:50 with water. Those will most likely tell you on the label.

I have the same problem just the other way around.Cools down on idle and heats up on driving.

Hi.I know its been over a year but here is some feedback from my side.I replaced radiator cap and no change.Then I flushed the cooling system and the problem was worse.I then send the radiator in for a service as I also had a leak on it and replaced the thermostat.Still not fixed.I then bought a new water pump and viscous coupling.When I took the old water pump off it looked better than the new one If bought,so I put It back .Then I changed the viscous and problem solved.Just a side note on the viscous.It may seems to work but its not always efficient.

Thank you for the feedback! Always learning.

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How many kms on the engine?

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317000 and going strong.

legend35 wrote:317000 and going strong.

Great! My 2.7 only on 118k. 2004. No issues.

Glad you got it sorted!

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just a question,what is the right coolant for this type of bakkie and ratios to mix it

mine was overheating ,replaced with toyota parts,viscous fan ,water pump and thermostat overheating problem solved.drove across Botswana at 47 degrees inside bakkie all was good

As mentioned before, the Toyota brand coolant is probably the best way to go. Not only that it's recommended by the manufacturer but also because it compares well against other leading 'off-the-shelf' brands IRO of price.

The brand of coolant / additive is however not that important when it comes down to the efficiency of the cooling system. Yes, it helps by raising the boiling point by comparison to pure water and it lubricates the pump seal as well as inhibits corrosion, particularly the aluminium surfaces.

The efficiency of the system (in either hot or cold ambient temperatures) depends on the effectiveness of a couple key things.
They are:
Efficiency of the radiator
Sufficient airflow through the radiator (not obstructed or choked)
An effective fan and cowl to draw the air
Effective pump
Effective thermostat
Correct radiator cap.

Your problem was that one or more of the replaced components was faulty or on it's way out, and resolved by replacement.

I thank you