Defender 90 2.5 TD 1989 Head Gasket or Something Else - Help

[Fixanything]

Before I start, a 200tdi conversion is not an option at this time, as the vehicle is totally original with matching numbers etc..and would very much like to keep it that way.

My 1989 2.5TD 90 County:
135k miles
Starts fine
Little smoke at start-up, but none once moving/warm.
Does 29mpg and will easily get to 75mph and hold there
Bit of crankcase pressure and a little oil in airfilter box

Problem:
I have done about 5000 mile since purchased 7 months ago, first thing I noticed was the temperature gauge would fluctuate with speed i.e. the faster I go the hotter the temperature gauge reading. Then I noticed that the coolant system would hold a lot of pressure even if not used for a few days i.e. I believe the coolant system is being over pressurised in someway, probably by combustion gases through head gasket. Just recently it has started to force a small amount of coolant out of the header tank overflow once I stop after a run out.

Note: No evidence of water in oil

The help I need, understanding that this is a late/up-rated Block, could this problem be anything other than the head gasket ? All help and advice would be much appreciated.

Many thanks
Mark

[camel_landy]

The evidence is pointing towards a head gasket. It's also worth noting that you don't always get oil in water when you have a gasket failure as it depends which part of the gasket has failed.

M

[Fixanything]

M,

Many thanks for the response, the reason I metioned the oil/water thing is if it helped narrow down the problem. I'm guessing (hopefully) head gasket failure between cylinder/pistion and coolant passage.

Any other suggestions welcome

Thanks again
Mark

[pikeyboy]

Sounds like a leaking fire ring in the head gasket allowing combustion gases to pressurise the cooling system. My 300 tdi disco was doing exactly the same, swapped head gasket 20 pounds and a days work all sorted.