Isuzu Trooper Owners Club UK™

[Mike_S]

Before I start I'll mention that I've read most of the overheating threads here without being any the wiser as to exactly what my problem might be, so please bear with me.

My vehicle is a 97 3.1TD Bighorn Trooper with an auto box, and the facts are:

i) In normal running conditions, and on most hills, the temperature guage sits at about 1/3 of the way across towards hot.

ii) Sometimes, on either short steep hills or long hills, the temp starts to rise, but it's never got beyond about 3/4s of the way across - on the long hills the temp may start to rise at any point, either near the bottom or near the top. It is also quite possible to climb a long hill with no temperature problems at all, and there are certain hills I know will cause problems and some that I know won't be a problem.

iii) Under normal driving conditions the top radiator pipe is too hot to touch and, immediately after stopping, the bottom pipe is cool enough to hold for an extended time without any discomfort. I'm guessing from this that the radiator is doing its job adequately.

iv) When the temperature does rise it falls very quickly once the top of the hill is reached.

v) After reaching the top of the hill, although the engine temp drops back to normal, the gearbox will not change into higher gears for a while - the length of time it takes to come right seems to be proportional to how long the engine experienced a higher than nornmal temperature - I'm guessing that the gearbox is also hot and is entering a limp mode until its temperature goes back to normal.

vi) On occassion after descending a long hill the gearbox also seems to inhibit higher gears for a short period.

vii) The radiator was, to the best of my knowledge, disassembled and the core cleaned about 12 months ago, after an overheating episode (a replacement engine was fitted at this time by the Isuzu agents).

viii) Sometimes, when the temperature starts to rise, I can prevent further rises by backing off on the throttle.

ix) When descending hills the engine temp does not drop below normal - this used to happen in my Toyota, but may have been just a feature of that model.

x) On a recent summer holiday extensive soft sand driving was done, with high revs and low speed in 4WD, without any signs of temperature problems.

xi) There is no sign of gas bubbles in the coolant, and no excessive consumption of coolant.

At the moment my personal thoughts are that when climbing or descending hills the gearbox is getting heated due to "churn" in the torque convertor, and this in turn is causing the water going back in the engine to be too hot, thus causing the engine temperature to rise.

I am happy to get a new radiator core, and/or an external oil cooler fitted to the transmission, but I'd appreciate any insights from the forum that could help me avoid unnecessry expenditure ie., what is the best order to spend money in order to fix the problem with the least expenditure - is my theory about the gearbox heating up and raising the engine temperature even possible?

Mike.

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Sorry no expert on the auto box.

But my 1995 3.1 manual commercial had overheating probs about 5 years ago and it was the radiator, i have flushed many rad's out with no sucess, you usually have to replace them.

take it you have done the usual checks, thermostat & fan belt, (cheaper options), try running it without thermostat on a known overheating hill?

From what you are saying about the temp difference between the top & botton rad hose's, sounds like you could have a coolant restriction, could be caused by clogged rad core or thermostat not opening fully.
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2011 3.0l Hilux Invincible
94, 3.1 duty
95, 3.1 commercial, Agricultural licence
04, 3.0 citation

[Mike_S]

Thanks - thant's the sort of info I'm after.

To me, a radiator that is hot at the top and cool at the bottom is one that's working efficiently, but if more experienced opinion is that it's a sign of a clogged radiator then I'm happy to investigate the thermostat/radiator path.

I must admit I did have my doubts about whether or not it woulod be possible to properly clean out a core once it had seriously blocked.


Mike.

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Not allways! ive just had same symptoms with rad hoses on a forklift and i was the thermostat not opening properly.

Forgot to mention, u checked that the rad is clean on the air side?, can look clean from the outside but you must be able to see through fins, (put lamp behind rad and look through)
_________________
2011 3.0l Hilux Invincible
94, 3.1 duty
95, 3.1 commercial, Agricultural licence
04, 3.0 citation