overheating bighorn
overheating bighorn
My 1990 isuzu bighorn overheats when going up long hill climbs (on the motorway). They are not particularly steep sections of highway and I don't try to thrash it, but it still gets very hot. It cools down fast enough at the top of the hill and doesn't get too hot normally. I have flushed the radiator. I intend to replace the thermostat in case that is the problem. Any ideas?
No, I only got muddy the first week I had it. Took it down to fiordland and got bogged well and truly.
There is an radiator in the front, it looks pretty clean. Like I said it is only when I am going up big, steep runs (like the crown range) that it overheats, and drops rapidly once I stop or start going down hill.
There is an radiator in the front, it looks pretty clean. Like I said it is only when I am going up big, steep runs (like the crown range) that it overheats, and drops rapidly once I stop or start going down hill.
Once I had taken my radiator out and cleaned out both of them, the crown range @4500 rpm will get it warm but not hot.... it never used to do that, but from what I've gathered I may have slightly cooked the engine, when I hit the red.... one you've done it, it will never be the same....
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Who knew Prados could fly?
Who knew Prados could fly?
Same thing used to happen to my 2.4d Hilux. I added an electric fan in front of the rad (between radiator and the grille) with a switch on the dash. Fixed it straight away. I only use it when going up steep hills or towing. Seems like the rad aint flowing enuff air, specially when the ole 2.4 is stuggling up a big hill at about 70kph 
A simple way to test all your cooling system components:
Drape a tarp or other plastic sheet over the front of the vehicle, the idea being to restrict the airflow to the radiator as much a possible. Run your engine at about 2000rpm, the hand throttle is good for this and sit in side and whatch the temp guage.
The fan should cut in just over half way on the temp guage at the latest, you should hear a roar as it goes to work.
The temp should then drop back below half and the fan should stop working. If that doesn't do what it should, you may need a new viscous coupling for the fan, or ask me and i will tell you how to rebuild it for about $60.
Continue with this again, but when the fan cuts in, go out and look to see if the tarp is being sucked into the radiator grill strongly. If not, find some one with a high volume high pressure hose and wash out the radiator fins and the same with the aircon condensor which sits in front of the radiator and is commonly over looked even though its the one which tends to get blocked with bugs, grass and feathers. Leave that in place when you wash it, wash from in side the engine bay.
As for your thermostat, what temp does your engine run at when on a straight flat road at 100km/h. It should sit just below the half way mark.
What im getting at is, if it usually runs just above cold, it may be sticking open, then if it overheats, it may be that the thermostat has jammed.
If while testing, the fan is working, and the tarp is getting sucked in strongly, and the temp continues to increase, i would ;look at the thermostat. For the sake of $20 for the thermostat, it may be worth doing anyway???
Drape a tarp or other plastic sheet over the front of the vehicle, the idea being to restrict the airflow to the radiator as much a possible. Run your engine at about 2000rpm, the hand throttle is good for this and sit in side and whatch the temp guage.
The fan should cut in just over half way on the temp guage at the latest, you should hear a roar as it goes to work.
The temp should then drop back below half and the fan should stop working. If that doesn't do what it should, you may need a new viscous coupling for the fan, or ask me and i will tell you how to rebuild it for about $60.
Continue with this again, but when the fan cuts in, go out and look to see if the tarp is being sucked into the radiator grill strongly. If not, find some one with a high volume high pressure hose and wash out the radiator fins and the same with the aircon condensor which sits in front of the radiator and is commonly over looked even though its the one which tends to get blocked with bugs, grass and feathers. Leave that in place when you wash it, wash from in side the engine bay.
As for your thermostat, what temp does your engine run at when on a straight flat road at 100km/h. It should sit just below the half way mark.
What im getting at is, if it usually runs just above cold, it may be sticking open, then if it overheats, it may be that the thermostat has jammed.
If while testing, the fan is working, and the tarp is getting sucked in strongly, and the temp continues to increase, i would ;look at the thermostat. For the sake of $20 for the thermostat, it may be worth doing anyway???
Nah, since my fiancee left me for a life in auckland, i seem to spend far to much time on the net and in the garage 
Pretty good page on rebuilding a viscous fan:
http://www.off-road.com/~estegall/tech/ ... lutch.html
and the part number for the oil from Toyota:
Silicon oil P/N 08816-03001.
It took about 3 bottles at $20 a bottle for the Safari. There is abit more to it than that page lets on.
You have to drain the resoviour in the hub of all the old oil else the fan ends up working non stop. The resoviour is on the half with the bi-metal strip attached, not the half that has the shaft to the waterpump.
The fan starts up straight away, even when cold. On the open road the needle never goes above 1/3. Sounds like the thermostat could be to blame. It seems a simple job to replace it. I am getting into a lot more DIY as far as home renovations go and may as well have a crack at simple mechanical jobs. May take twice as long but certainly less than half the price of a mechanic.
Hmmmmm. Just check that fan.
Start your engine and run it 2000rpm for a while with no covering on the grille.
Its normal for the fan to run for a few minutes when engine first started up. It takes a while for the oil to be pumped out of the hub into the resoviour, as it seeps back into the hub slowly as the centrifugal forces stop when you turn the engine off.
Just make sure your not getting confused by the fact the fan is spinning. It will always spin, but you should be able to stop the fan easily. I use a car washing brush to stop it, you don't risk your fingers, and the bristles are gentle on the fan. Just be carefull.
If you can't stop the fan, an aftermarket hub should cost no more than $200, i wouldn't bother trying to rebuild it if it is locked all the time, sounds like a bearing may have siezed or something in there.
As it runs at 1/3, it would make sense that the fan is running all the time.
Try the test i mentioned before, it will definatly let you know wether its running all the time, as you won't hear it cut in and the temp will just keep climbing, or it won't heat up at all. Its very obvious when it does, it makes a hell of a racket.
Definatly replace the thermostat, might as well do the radiator cap to for the small cost involved.
If it were me i would do the test, and if the fan proves satisfactory, the pull the rad out again, give the A/C condensor a good wash out.
Try the test again.
If no better, install the new cap and thermostat.
If all this still doesn't improve it, take the radiator to a specialist and get them to flush it for you. They remove the top tank and flush the core each tube at a time.
Thats about the best we can do for you online i would say. I would love to have a look at it my self.
Do the test
Start your engine and run it 2000rpm for a while with no covering on the grille.
Its normal for the fan to run for a few minutes when engine first started up. It takes a while for the oil to be pumped out of the hub into the resoviour, as it seeps back into the hub slowly as the centrifugal forces stop when you turn the engine off.
Just make sure your not getting confused by the fact the fan is spinning. It will always spin, but you should be able to stop the fan easily. I use a car washing brush to stop it, you don't risk your fingers, and the bristles are gentle on the fan. Just be carefull.
If you can't stop the fan, an aftermarket hub should cost no more than $200, i wouldn't bother trying to rebuild it if it is locked all the time, sounds like a bearing may have siezed or something in there.
As it runs at 1/3, it would make sense that the fan is running all the time.
Try the test i mentioned before, it will definatly let you know wether its running all the time, as you won't hear it cut in and the temp will just keep climbing, or it won't heat up at all. Its very obvious when it does, it makes a hell of a racket.
Definatly replace the thermostat, might as well do the radiator cap to for the small cost involved.
If it were me i would do the test, and if the fan proves satisfactory, the pull the rad out again, give the A/C condensor a good wash out.
Try the test again.
If no better, install the new cap and thermostat.
If all this still doesn't improve it, take the radiator to a specialist and get them to flush it for you. They remove the top tank and flush the core each tube at a time.
Thats about the best we can do for you online i would say. I would love to have a look at it my self.
Do the test