Overheating

[kiwiinmelbourne Lurker Find all posts View Profile Close kiwiinmelbourne]

Hi all,
I was hoping I could get some help on here.

Lately I have noticed my Prado Overheating when the workload slightly increases from normal eg, towing an unloaded single axle trailer or even driving on some hilly/windy roads. Once back on the flat or trailer removed the temp comes back to normal.

I have also noticed a gradual increase in fuel usage, from approx 14-15L/100km to around the 18L/100km over the same period as the overheating has started occurring.

I will be changing the Thermostat/Radiator cap and hoses first. Any ideas?

Cheers all.

P.S Vehicle is early 1999 3.4L Prado (Snowy), Auto with Trans oil running through seperate cooler and bypassing radiator, Mud tyres and Auto Lokka. N/B nothing has changed with vehicle before overheating started.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Thermo fan? if so I would check that first, fuel usage might be coincidentally though you could
check for dragging brakes etc.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

First step is to reconnect the inbuilt transmission cooler in line with your additional one. You should never disconnect the standard cooler as the larger part of the radiator itself is what assists with keeping the temps down. Talk to a specialist in transmissions and they'll tell you how many transmission rebuilds they have to do after people have disconected their factory one.

I'm running the stock plus a secondary cooler, and the transmission has still once overheated, but under heavy conditions - all day sand driving and winding up the supercharger a lot.

Secondly the radiators only last 200,000km / 10 years by which time they crack and/or stretch resulting an inability to hold pressure, thus, resulting in high temps under heavy load.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

As mentioned the viscous fan is also a potential issue. Ensure the fan runs noisy at startup (cold) and quietens down when you start driving down the road. If it is doing this, I'd start with a new radiator.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

X 2 for radiator.

It sounds like your radiator is partially blocked and can cool the engine when under normal load (for you) but cannot handle any increased load.
Viscous fan issues tends to show when your stationary or driving slowly when there is insufficient air flow across the radiator to cool and the fan "should" provide air flow but doesn't due to a faulty viscous coupling.

Lee

[kiwiinmelbourne Lurker Find all posts View Profile Close kiwiinmelbourne]

Hi all, Thanks for the input guys, really appreciate it. Will be ordering a replacement Radiator tonight I think KOYO 2 row, Copper core.
Will change top and bottom hoses as well.
Cheers

[kiwiinmelbourne Lurker Find all posts View Profile Close kiwiinmelbourne]

Hi Glen_ep, just rang 2 Auto Specialists and they said to leave the inbuilt transcooler disconnected with an external oil cooler? differing opinions ?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Well there's always room in the world for different opinions, but these articles support what I've been told...

http://myautomatictransmission.com/d...stallation.htm
http://transmissionrepairguy.com/transmission-cooler/
http://www.bulkpart.com/transmission-cooler.html

[topic97 Senior Member Find all posts View Profile Close topic97]

Yeah I wouldn't leave it disconnected, you have to keep in mind that if you have no airflow over the external cooler it will only be cooling marginally if that.
Plus, the radiator adds extra transmission cooling - especially when you have it in sequence from trans to radiator to external cooler.

[kiwiinmelbourne Lurker Find all posts View Profile Close kiwiinmelbourne]

Have all the gear on the way to cover my bases. Radiator, Hoses, Thermostat etc.

Today the car got real hot. That close to the "Red zone" I nearly shit myself.

I got her home, left it idling and opened the bonnet. I managed to grab the viscous fan and quite easily stall it.

How do you know what the operating characteristics of the viscous fan are? Should I have been able to stall it?

[topic97 Senior Member Find all posts View Profile Close topic97]

If it's overheating, the fan clutch should well and truly be engaged.
It basically works the same as a thermo fan, in that the heat from the radiator expands an oil inside the fan & engages the clutch when it heats to a certain temp then disengages when it cools.

One of two things could be happening here, it could be either the viscous fan has lost oil and isn't functioning correctly - which they do over time.
Or the other thing is that there could be blockage/restriction internally and/or externally in the radiator which isn't allowing sufficient airflow and therefore heat to get to the viscous fan to engage it.

Id start by replacing the radiator & all the other bits you have ordered and see how it goes after that, because it could just be blockage in the radiator that's causing it.
Worst case its the fan as well, and they are a very easy job to replace.

[kiwiinmelbourne Lurker Find all posts View Profile Close kiwiinmelbourne]

Yeah, thats the plan. Ill change Radiator, top/bottom hoses, thermostat, flush system and put in new coolant. I'll have a new Viscous unit arriving, but i want to see if those things will fix the issue before changing it over.
Want to also see if this will reduce the hi fuel consumption.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

The ECU constantly adjusts timing (power) according to many things, one such thing is temperature. So technically speaking, cool it down and you'll get more power with less fuel. Whether it'll be noticeable or not is the question!