Intermittent overheating problem

[sudso]

Well after the long saga of getting the Rodeo back on the road after the comp another problem has reared its ugly head.

The temp gauge rises up on occasion where I've had to stop and let it cool down before continuing my journey.

This has happened 3 times now, the most recent being yesterday while on a short wheeling trip with my son and nephews.
I was in 4th gear, 2wd on a semi soft sandy track doing about 40-50kmh the motor wasn't struggling when the temp started to rise. I stopped and let it cool down to normal temp, it didnt rise up again on the trip home on the bitumen.
It has never got hot doing hard work before.

It has a new fan clutch, replaced coolant, flushed radiator (was clean as anyway) and cleaned out fins of radiator and a/c condensor, all this before yesterdays incident so now me thinks the thermostat may be sticking shut when it feels like it.

It looks like I have to remove the intake manifold to get to the thermostat (V6) but I'm wondering if there may be another cause of the temp rise, I dont want to remove the manifold for nothing.

cheers, sudso

[Guzzi]

Sudso,
Not being a prophet of doom here but another cause for the intermittant over heating is a leaking head gasket .
A mate just went through this with his disco, turned out to be the head gasket.
Do you have any cream sitting under the oil filler cap? Coolant occasionally needs topping up?
Another possibility is an air lock in the coolant system(clutching at straws with that one).
Water pump drive belt not slipping?
Bite the bullet and change the thermostat first and then work your way up to the bank breaking options. Sorry I cant help further.

[sudso]

Sudso,
Not being a prophet of doom here but another cause for the intermittant over heating is a leaking head gasket .
A mate just went through this with his disco, turned out to be the head gasket.
Do you have any cream sitting under the oil filler cap? Coolant occasionally needs topping up?
Another possibility is an air lock in the coolant system(clutching at straws with that one).
Water pump drive belt not slipping?
Bite the bullet and change the thermostat first and then work your way up to the bank breaking options. Sorry I cant help further.

Not at all mate, I am now used to the inetivable worst
Well there is no coolant been leaking or need topping up, belt doesn't slip, fan clutch works fine, no cream under oil cap and no bubbles in the radiator.

I drained a couple of litres of coolant out and put more concentrate in, I may have had it too lean though when I replaced it a week ago, the book says 50/50 coolant/water, I use demineralised water too.

One thing I found just before was a small vacuum hose at the rear of the engine was off it's nipple again, it comes off sometimes when on a rough track and may have cause the mixture to run lean making it hotter but I would've thought the ECM would compensate the fuel mixture for things like that.

Anyway I've got a 600km trip to take my lad back to his mums now so I'll see how it goes.
I'm not worried about the distance, I'm an RAA premium member just in case

Cheers

[lay80n]

Ages ago i had a rodeo like yours doing this at work. When we fulshed the cooling system and changed the thermostat (yes its under the inlet manifold , gotta love clever isuzu engineers lol) i sent teh radiator off to get cleaned, as it had cold spots on it (i.e. was blocked in certain areas) and found it was filled with chemiweld. Did compression test and all good. Ended up the water pump was buggered and leaking slightly, and the previous owner had filled with chemiweld instead of fixing leaking pump.
Dunno if this is any held. Coolant mixture does is not as important as keeping the system under pressure. From memory the rodeo system is very low temp anyway, hence low pressure. The lean mixture will not always be corrected as the computer is not always using the o2 sensor to set mixtures, only during certain run modes.
Layto....

[sudso]

layto80,
Didn't get hotter than normal since it happened Saturday.
you being ex Holdens service you probably know about those "exhaust restrictors" in each bank of the Y piece pipe, those perforated cone shaped things that are spot welded in there and reduce that part of each pipe to about 1&1/4 inch.

Well when I had the exhaust off to do the clutch I got to the spot welds with the die grinder and removed them. A few blokes have done this to their V6's and claim they just notice a bit more power.
It could just be the placebo effect they experience cos I notice no difference at all but what are those restrictors thingy's there for anyway?

One thing has changed though, always when I run on LPG the check engine light would come on soon after but go off soon after switching back to petrol.
Apparently it is common on some cars with LPG to do this but it's nothing to worry about, it says in the LPG manual for mine that it will probably happen.
The check engine light doesn't come on at all now since removing the restrictors when I run LPG.
So now I'm wondering if the exhaust "restrictors" have something to do with the O2 sensor working properly.

BTW thanks for sharing your knowledge on this, I'm finding there's a lot that the manuals don't tell you.

cheers, sudso