Thread: I need every possible option laid out in front of me,

Yes the thermos come on at a certain temp however in my experience if you are reaching that temp even when towing or offroading then your cooling system is faulty.
Mine used to come on as you described but after having the radiator rodded nearly 3 years ago I don't think they have come on in that situation since.

Just do the radiator and take it from there. If you remove and refit yourself it will cost you about $100 to get rodded plus coolant cost.

does the system have a high point like the commodores and need to be bled?
faulty radiator cap can reduce the boiling point. every psi of pressure is a couple degrees hotter the water boiles at.
is it automatic, if so check the colour of the trans oil if it is brownish thentrans has overheated. if trans is faulty and overheating it may heat engine up unless it has a seperate oil cooler not one in radiator

As above , an airlock is something i'd be looking at.

Originally Posted by goingbush

faulty viscous coupling

X2

My first choice, and easy to check.

Leave car overnight. Open bonnet and start engine, there should be a loud rushing air noise and a fairly solid flow of air directed back from the fan. This should disappear after about 30 seconds or so. If this doesn't happen your viscous coupling is shot.

Deano

My 3.5 suffered the exact same symptoms. Turned out to be the viscous coupling - and a heap of leaves between the AC condenser and the radiator. I knew the radiator had been rodded only a year or so earlier, so I didn't bother with this, however, it wouldn't hurt to get that done as well. I wouldn't be pulling the heads off yet, but if you have seriously cooked it on one of its overheating expersitions, then you could be in for some grief - the 3.9's don't like to get that hot, it can cause major issues...

When you say 'gets hot' how hot are we talking, and are you judging this off the dash gauge, or a seperate - accurate gauge?

My VDO gauge can get up near 100 degrees on a hot day with the AC on when heavily loaded, but I wouldn't call that too hot - it usually sits on about 88 to 90 degrees on the flat, etc and drops down quickly back to those levels when the going gets easier - so do you even have a problem? - temperature swings in these aren't all that uncommon.

Car hasn't been started since yesterday so I went out ant started it, let it idle for about 2 mins listening, I could hear it sucking a lot of air through the air flow snout, but as for any air related noise from clutch fan area nothing changed, so it's fairly noticeable? What part does the viscous fan play? (that's the alloy section behind clutch fan?)

What's the job of the clutch fan? Is it to suck air away from the rear of the radiator? Or push air into it? Mine is pulling air away from it!

image-3854168247.jpg

thats a fairly grubby looking radiator, have you got all the leaves and crud out from between the radiator and the AC radiator? and then give it all a good shot with the high pressure washer?

the VC fan pulls air through the radiator and over the engine. had you taken the cowling off for the photo or dont you have one? as this makes a fair difference also.

The fan should make a fair bit of rushing air sond for the first few minutes of cold engine operation untill the VC warms up a bit and the fluid speards evenely through the unit and causes it to disengage to a degree, at which time the fan should slow down and make much less sound.

If there is no cowling shroud over the radiator though the fan is just moving allot of air around the engine bay rather than sucking it all through the radiator.