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G'day, Does anyone have an idea as to why my 1990 L series is overheating. It overheats/boils in approx. 10 kms. There does not appear to be a leak from a hose or the radiator but the gauge goes up quickly and you can hear a loud "hissing" noise slowly building up? Many thanks Newsoob.

mmmm headgaskets?

take the thermostat out and see if it still overheats. The ones i've had around that age seem to block up and stop opening.

Hissing noise might also be low coolant level.
Just hope its not a blown head gasket

It could be that the Radiator needs a good clean. I had a similar problem but after a good clean all is good now.

SEARCH! its your friend, this has come up sooo many times before

alex

- check the fans are working
- bleed the cooling system, see if you have a big air bubble somewhere
- flush the cooling system, see if it's clogged up with brown stuff
- if it's clogged then get the radiator "rodded" (they take the end tanks off and shove a rod down each water gallery to clear out any muck)
- check you have enough coolant, it might be low
- take out thermostat and test it by boiling it in a pot on your stove, see if it opens up. Run the car without a thermostat too to see.

If these aren't it then it might be something more expensive like a failed water pump or a breach of the head gasket(s).

I'd put money towards on the radiator that is blocked! and replace thermostats.
Cheers
AP

Gday again, Thanks for all the replies. Changed themostat, Flushed radiator. refilled with new coolant then started and ran car. After few mins noticed small coolant leak from 6" long small diameter hose tucked away at base of carby.It appears thats where I was loosing coolant from.Pulled out hose to find 1/2" long split. Repaired and all appears to be OK. Thanks heaps for all help and ideas!!

Ah yep that little hose is a real bugger, I had that problem on my old wagon and plenty of other people too! Hopefully it's all good now.