Defender 90 200TDI Overheating - Replaced Everything

Firstly, I know there are lots of threads on here about overheating. However, I have an unusual situation I can't get to the bottom of.

My Defender 90 200TDI has started running hot on the motorway. Around town it's fine, but when pushing hard it gets to 98 degrees C (I installed a VDO sender and gauge as I originally suspected the original gauge). I have replaced the thermostat, water pump and have checked the fan runs.

The obvious thing to conclude is that it's the Head Gasket but there is no white smoke, no coolant loss.

Any ideas? Can a head gasket fail in this way?

Thanks

Have you still got the standard fan fitted?
And do you still have the cowl fitted?

Is it a disco engine in a landrover or standard Lr?

Has electric fan. No cowl. Thing is it was running fine for months and has just started with the issue. Original Defender 200TDI engine

Radiator condition?

Take the rad out and back flush it

Could just need a new rad cap

Have a look at the little fins of the rad, if many are missing and others are crumbling.

Thanks for your replies. The Rad is not that old. By new rad cap do you mean new cap on the header tank? How would this make a difference?

I have had new stats faulty from the packet, last one was a 200 one.

Squeeze all the heater pipes some times they get crusty, could bypass the heater matrix & see if it makes a difference.

Thanks again for your replies. The previous thermostat was working (I tested it) and still had the issue. The system has had coolant changed a couple of times - had the radiator plug off and waited for air to escape etc. so I think the system is bled OK. Not losing coolant so don't think it's an expansion tank cap. Baffling.

If I sit on motoway at 70moh my temp will climb. Sit at 60 all good.
No fan on it but at slower speeds electric fan can be used to drop the temp.

Check to see if hot air out the heater blower.

IandelaMare said:

Thanks again for your replies. The previous thermostat was working (I tested it) and still had the issue. The system has had coolant changed a couple of times - had the radiator plug off and waited for air to escape etc. so I think the system is bled OK. Not losing coolant so don't think it's an expansion tank cap. Baffling.

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Once the stat opens they will self bleed, but you do get a massive spike in coolant temperature until the stat does eventually open.
Is the coolant system pressurising?

If you try a search on here there have been at least two and possibly three recent threads of tdi (300 mainly) overheating with no obvious issues, I think one gave up and another fitted another block.

Hicap phill said:

If I sit on motoway at 70moh my temp will climb. Sit at 60 all good.
No fan on it but at slower speeds electric fan can be used to drop the temp.

Check to see if hot air out the heater blower.

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My 200 also does that, though I find 70 hard bloody work in it, 60 ish is much easier.

I had similar symptoms with my old 300Tdi disco. It was fine around town but when it was given some beans on the motorway or up hills it got hot. The fins on the radiator were in poor condition. A new radiator sorted it.

Thanks all for your comments. I think it's looking like a head gasket on the way to failure. Going into Landie specialist in a couple of weeks so fingers crossed the head doesn't need skimming! Thanks again

IandelaMare said:

Thanks all for your comments. I think it's looking like a head gasket on the way to failure. Going into Landie specialist in a couple of weeks so fingers crossed the head doesn't need skimming! Thanks again

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It might need skimming, but I have done a few 200 and 300 head gaskets, and have never skimemd one of them tbh never even checked them, clean up faces new gasket and go, also reused the head bolts, IIrc they can be reused up to 5 times.

lynall said:

It might need skimming, but I have done a few 200 and 300 head gaskets, and have never skimemd one of them tbh never even checked them, clean up faces new gasket and go, also reused the head bolts, IIrc they can be reused up to 5 times.

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Good to know, thanks. Did you get the weird symptoms I am getting?

IandelaMare said:

Good to know, thanks. Did you get the weird symptoms I am getting?

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Every 200 head gasket I have done has blown out the back of number 4 cylinder.
Every 300 head gasket I have done has been due to pressurisation of the cooling system.

lynall said:

Every 200 head gasket I have done has blown out the back of number 4 cylinder.
Every 300 head gasket I have done has been due to pressurisation of the cooling system.

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OK, that's good to know. I have read some research that an HG that blows around a cylinder rather than a complete failure can put more heat into the engine. Not sure why but given my running hot symptom came on unexpectedly I would say this is definitely a suspect. Thanks again!