Classic 3.9 V8 - Over heating - still

If you haven't already done so, check the condition of the radiator. Check the vanes are solid and clear.

I cooked mine when I first got it. I put it under load and it overheated and warped the heads!! When I touched the radiator the vanes just turned to dust!

Dr Strangeglove said:

If you haven't already done so, check the condition of the radiator. Check the vanes are solid and clear.

I cooked mine when I first got it. I put it under load and it overheated and warped the heads!! When I touched the radiator the vanes just turned to dust!

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Second to this, any debris caught in between rads or the vanes

If it's an old radiator it may well be full of crap - esp if previous owners haven't bothered using anti-freeze or have dumped any of the various leak stoppers into the system.
You could try flushing, back flushing, chemical cleaners but it rarely succeeds in completely unblocking it.
When I replaced the rad on my Range Rover Classic (3.5EFi) the difference in weight between old & new was remarkable - as was the improvement in cooling!

Ratae said:

If it's an old radiator it may well be full of crap - esp if previous owners haven't bothered using anti-freeze or have dumped any of the various leak stoppers into the system.
You could try flushing, back flushing, chemical cleaners but it rarely succeeds in completely unblocking it.
When I replaced the rad on my Range Rover Classic (3.5EFi) the difference in weight between old & new was remarkable - as was the improvement in cooling!

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Hope you didn't flush it before weighing it in for scrap.

Looking increasingly like the rad as I've fitted a new (82 degree) thermostat with the jiggle pin at 12 o'clock and it's made no difference, although I couldn't get it to 'burp' as I'm sure it should (front end on ramps and rad screw cap checked) it will still go to HOT on cold heater setting after about 5 miles (it's not cold!) but drops down as soon as heater is set to max. Rad or burp?

peanuts01 said:

Looking increasingly like the rad as I've fitted a new (82 degree) thermostat with the jiggle pin at 12 o'clock and it's made no difference, although I couldn't get it to 'burp' as I'm sure it should (front end on ramps and rad screw cap checked) it will still go to HOT on cold heater setting after about 5 miles (it's not cold!) but drops down as soon as heater is set to max. Rad or burp?

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Maybe take the rad out and flush it in both directions to see if any crap is evident or try a funnel that sealed around the filler neck and slightly over fill the tank and run it while squeezing the jeepers out of the pipes. It may help to get rid of any air.

The funnel's a new one on me Mark, always looking for the easiest (ok cheapest) alternatives so thanks, it got to be worth a try. nothing ventured, nothing gained

peanuts01 said:

The funnel's a new one on me Mark, always looking for the easiest (ok cheapest) alternatives so thanks, it got to be worth a try. nothing ventured, nothing gained

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Like this, I used my old funnel. And put some rubber tube around the neck so it can be jammed into the opening in the coolant tank. It allows you to bring the coolant level above everything on the car and run it and squeeze the tubes as much as you like.

If I can't find a big enough funnel, I'll buy one, got the oven gloves ready for squeezing the pipes

Ok, found a thick plastic bottle with a disc around the neck that, with a bit of force, fitted exactly in the filler cap hole. Topped it up as seen in photo and started her up, as temp rose there was movement in the bottle so I started squeezing the top rad pipe, sure enough, bubbles left it running for 5, squeezed again, more bubbles, then it started to bubble on it's own, when that stopped I squeezed again more bubbles, left it a few minutes squeezed again, more bubbles, then it went mad and bubbled like crazy, water came over the top of the bottle but it died down as quick as it had come up. I was pretty please at this point I must admit. Squeezed again, no bubbles, that's when I now assume I should have stopped and turned her off (damned hindsight) because very soon after it blew everything as it totally boiled over, water over the bottle, the bottle out the hole (it was in tight!) and me diving to turn her off being sprayed in somewhat hot water. Filled her up as she cooled down, started her up, watched the thermostat open via the expansion tank, put the cap on and watched the temp gauge rise, even putting the heater on full didn't stop the rise this time. I think I may just be back to square one, perhaps even square zero

There is always coolant flowing through the heater matrix. If turning the heater to hot causes a drop in engine temp then it's because it's doing the job of the radiator

Have you tried the UV dye in the coolant yet or a sniff test for hydrocarbons?

The heater doing the job of the radiator is not something that's been mentioned before but it's a very valid point, I've been steered toward burping as it only started going wrong after the viscous fan broke and she boiled over big style (running perfectly ok prior to that), thus presumably causing an air lock when trying to refill it as I lost so much fluid, much the same as I just have again!
The sniff test was something I did a week or so ago before starting this thread, no bubbles coming in to the expansion tank so zero result, not tried the UV dye to date as I can't envisage doing 100 miles yet.

Have you run it up to the opening temperature with the expansion cap off?

Yep, several times to check visually that the (old and) new thermostats are opening.

Ok and it didn't spew coolant when it got hot, unlikely to be an exhaust gas problem

No, it ran quite a while without the cap on, only spewed coolant when it got very hot as in first time when the fan bust and second time today while I was burping it, and that was after over 30 mins with no cap, just the bottle of coolant sticking out the expansion tank.

Right then, when the engine gets really hot is the viscous fan pulling in the cooler air?

Do you have a reliable method of reading the actual temp? Are you able to pressurise the coolant while it's cold? If you can, you'll see whether the coolant drops in the expansion tank or not. If it does significantly then you have an air lock, otherwise it's ok.
Are you sure the radiator is not blocked internally or externally? Are you sure the water pump is actually pumping water?

On most coolant reservoirs the little pipe should be a return from the pump circuit and should be returning fluid to the reservoir to maintain a heat balance. A none return could symbolize a none functioning pump.. If you haven't already verified the pump impeller, maybe do so.