Overheating V8 90 and viscous coupling

Have you had a peek to make sure the radiator matrix isn't clogged with dead insects/grass/mud?

Steve

How do you do?

Cooling system losing any fluid?

aye - that would be a good test.

I second that - my Rangie was overheating a bit, so whipped the radiator out to flush it and removed a forest -load of dead leaves and twigs from in front of it. My rad was also rotten too, the fins were disintergrating. One new rad later and everything is now hunky dory!

Paul

When the engine is cold it should run free usually you can spin it, warm her up and stop the engine it should be very stiff to turn if its still running free then you have a problem - once the engine is running the fan will turn the whether or not its OK the point of the viscous coupling is it will push more cool air as the coupling becomes stiffer Derek

On or around Wed, 21 Jun 2006 21:49:03 GMT, "Derek" enlightened us thusly:

It'll only spin full power once the engine's above normal temperature though

- they're not easy to check for this reason. You could try, on a hot day, running the engine at standstill at a steady 2500 revs or so, and keep an eye on the temperature gauge. The fan should at some point lock up - it might be up near "red" on the dial though. when it does you can hear it quite distinctly - they make a lot of noise at full speed.

The other clue is that when you start off from cold, it should spin at full power initially, then run down to idle, IME. you can hear this, too. The fan will never be actually stationary with the engine running.

However, overheating is more often a rad problem as others have said, external blockages are easily cleaned off, internal blockages, again IME, ditch the rad and fit a new one - I've never yet succeeded in clearing one that's significantly blocked.

"William Tasso" wrote in news: snipped-for-privacy@jupiter.cavern.tbdata.com:

Hi all

Thanks for all your comments

Can't say as I've noticed a noise difference like when it cuts but will have a closer listen.

The rad itself is clean on the outside and I flushed it out and refilled last year with no muck or sludge coming out though the coolant hadn't been changed for quite a few years so I did put a flushing agent in and ran that through before refilling with antifreeze,

The water level stays fine in the header tank - not having to top it up.

The gauge seems to stay just a needle width above normal when idling or stopped in traffic when hot and when running normally but when it's working a bit harder, towing or going up long hills I see it rise to about halfway between normal and the red section on the gauge (standard LR 90 temp gauge). OK I realise it could well rise but it never used too.

I'll try running it at higher revs when standing and see if I can hear the fan lock up and maybe cover the grill with a sack to try and restrict airflow and see if the fan locks up that way.

Thanx again

Jay

Austin Shackles is spot on.

A healthy viscous fan will engage when you start the engine from cold. The volume of air it moves causes a roaring noise, which after about 90 seconds will disappear totally.

A worn viscous unit will no shift as much air, causing the temperature needle to creep higher than centre when stationary or at low speeds. If the temperature needle falls back when you're running at a constant speed this also supports your theory that the viscus unit is worn.

Also, is the car overheating, or is the needle between the dead centre and the red zone? If it's not in the red zone it's not doing any harm, but we get used to modern cars with needles that sit at 90 degrees all day.

With this recent spell of hot weather, mine does the usual of engaging on startup for a few seconds, but if it has been sat in the sun all day it will continue to drive for quite some time.

Its easy to tell when its driving - the wind noise from under the bonnet is quite loud !!