Disco Overheating

I am at my wits end with my 1997 Disco 1, with some 135,000 km on the clock. I had an overheating problem when my black type expansion tank busted. The tank was renewed .All was ok until I renewed the water pump after finding it had a worn bearing. The overheating recurred. The head gasket was renewed.The overheating stopped for a while,and then suddenly came back. The radiator and hoses were renewed,and the system purged of air countless times. A quick drive up the highway and the temperature gauge shoots past the red mark,and coolant is pushed back through the expansion tank cap. After the engine cools down a bit and I continue on with the expansion tank cap removed, the overheating stops, but subsequently there is a loss of coolant. Any ideas? I am thinking that I may have to renew the cylinder head.

get the head tested and make sure, should really have been done as a matter of course when ya did the head gasket. might still have an airlock though

when you replace the head gasket you would be aswell to have the head skimmed and pressure tested to make sure there are no cracks and the mating surfaces are flat.this would have saved you the bother of stripping it again and buying another gasket. check you dont still have an air lock first before you go stripping it again and maybe check the thermostat isnt stuck.

check compression on the cylinders see if it holds the pressure (within reason)
could be a cracked bore liner or head as been mentioned.
blocked radiator?
viscous fan fitted?

hope any of that helps

Is the quick run up the highway on flat road or up a hill?

have you tried a new thermostat in just out of intrest that could cause the syptoms that you describe could be worth changing it and trying again before you take the head off the car
is there any smoke when running

colinl said:

when you replace the head gasket you would be aswell to have the head skimmed and pressure tested to make sure there are no cracks and the mating surfaces are flat.this would have saved you the bother of stripping it again and buying another gasket. check you dont still have an air lock first before you go stripping it again and maybe check the thermostat isnt stuck.

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Thats a costly mistake. I should have had the head skimmed and pressure tested when the gasket was replaced.

Disco nutter said:

have you tried a new thermostat in just out of intrest that could cause the syptoms that you describe could be worth changing it and trying again before you take the head off the car
is there any smoke when running

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Yes the thermostat was renewed.There is no smoke when running or any mixing of oil/coolant.

ssmn1234 said:

Is the quick run up the highway on flat road or up a hill?

Click to expand...

All flat roads.

andyt109 said:

check compression on the cylinders see if it holds the pressure (within reason)
could be a cracked bore liner or head as been mentioned.
blocked radiator?
viscous fan fitted?

hope any of that helps

Click to expand...

Thanks Andy, a viscous fan is fitted . The radiator was renewed very recently.