Taking it off and flushing may be worthwhile. Thanks. Otherwise I can only think it’s the water pump.

the head was pressure tested hot.

viscous fan fitted
correct stat fitted. now removed and still overheats.
rad gets warm on side of inlet and outlet pipes only but hoses feel full of air only
Head pressure tested hot by an engineering firm?

How are you bleeding it up?

I think last guy who has same issue gave up and changed the engine.
 
Head pressure tested hot by an engineering firm?

How are you bleeding it up?

I think last guy who has same issue gave up and changed the engine.
no tested myself,
parking on a 30degree incline and massaging the pipes. filling rad 1st, fitting the cap, then filling the thermostat housing. trouble is this keeps disappearing and overflowing the expansion tank.

ive tried then filling through expansion tank gradually and loosening housing cap to let air out.

ive ordered a new water pump as there just doesn't seem to be any circulation going on
 
I was once in a convoy with my wife and a load of other members of out Kit car club driving back from the Stoneleigh show. The mrs came on the CB saying how her heater was cooking the poor dogs who were in the passenger footwell.
Kit cars are notorious for cooling problems so we stopped and another mate stopped too.
Hers was a Triumph Herald based kit. I assumed the stat was playing up, although on inspection it seemed fine, but I took it out anyway, made a gasket from some cardboard and grease as you do, (well "did") put it all back together and carried on. In no time at all she came back on the blower saying it was worse if anything, so we gave up and called recovery.
Once back home a couple of days later I gave it another look-see, took the rad out and reverse flushed it, a load of crud came out, put it all back together, all then ran fine.
What is important to note is that before the missus bought the car it had belonged to the guy who built it and he had never done more than short local trips. So it was the length of the journey that shifted the crud out of the engine waterways etc and into the rad.
 
no tested myself,
parking on a 30degree incline and massaging the pipes. filling rad 1st, fitting the cap, then filling the thermostat housing. trouble is this keeps disappearing and overflowing the expansion tank.

ive tried then filling through expansion tank gradually and loosening housing cap to let air out.

ive ordered a new water pump as there just doesn't seem to be any circulation going on
Try this way next.
Remove header tank cap and thermostat bung, fill header tank to the cross mark and then refit the header tank cap (do not remove even to check) continue to fill the system via the stat bung (do NOT remove the header tank cap!) once full refit stat bung and take it for a drive.
You will occasionally get a little temperature climb as the stat opens then it should settle to normal temparature, but most of the time it will just run as per normal.

Reason there is no circulation going on is there is no water at the pump, this is the problem with having a high mounted coolant pump, slightest loss of coolant causes real issues, the P gasket used to be the main cause of blown head gaskets back in the day.
 
Next step would be to check the temps Rad outflow hose. Also, when it's running set up a camera (or have a friend) monitor the hoses and give the engine some quick throttle inputs. You're looking to see if any of the hoses look like they're sort of collapsing on themselves.

This can be indicative of blockage assuming you don't have any long supplemental coolant lines running to heaters in the back of your Defender.
The OP have a has a disco 1 and the engine cooling system is closed circuit therefore no “outflow hose“ I assume that you are referring to an over flow hose that was once fitted the top of the coolant reservoir or rad header tank, so not fitted now also the system is vented via the valves within the reservoir cap.
 
I was once in a convoy with my wife and a load of other members of out Kit car club driving back from the Stoneleigh show. The mrs came on the CB saying how her heater was cooking the poor dogs who were in the passenger footwell.
Kit cars are notorious for cooling problems so we stopped and another mate stopped too.
Hers was a Triumph Herald based kit. I assumed the stat was playing up, although on inspection it seemed fine, but I took it out anyway, made a gasket from some cardboard and grease as you do, (well "did") put it all back together and carried on. In no time at all she came back on the blower saying it was worse if anything, so we gave up and called recovery.
Once back home a couple of days later I gave it another look-see, took the rad out and reverse flushed it, a load of crud came out, put it all back together, all then ran fine.
What is important to note is that before the missus bought the car it had belonged to the guy who built it and he had never done more than short local trips. So it was the length of the journey that shifted the crud out of the engine waterways etc and into the rad.
Regular changing the coolant every year would have helped back then, instead of plain water for the summer and then fill with antifreeze for the winter months… much as winter grade the summer grade oil, as I remember 🤔

RR coolant was changed every 2years at the LR service with their green yell stuff.

I still change the coolant with one of my cars, that hardly goes anywhere now, every 2years using the blue stuff.
Now the modern OAT antifreeze is highly recommended, my D1 has been using it for the last 24 years and the coolant is always changed at the recommended 5 years, which is good. 😊
 
Regular changing the coolant every year would have helped back then, instead of plain water for the summer and then fill with antifreeze for the winter months… much as winter grade the summer grade oil, as I remember 🤔

RR coolant was changed every 2years at the LR service with their green yell stuff.

I still change the coolant with one of my cars, that hardly goes anywhere now, every 2years using the blue stuff.
Now the modern OAT antifreeze is highly recommended, my D1 has been using it for the last 24 years and the coolant is always changed at the recommended 5 years, which is good. 😊
You are right of course, I never let a car run with plain water, but I don't change the antifreeze mix as often as you do.
Praps I should.
The trouble is so many cars come with the "filled for life" label as regards coolant.
 
You are right of course, I never let a car run with plain water, but I don't change the antifreeze mix as often as you do.
Praps I should.
The trouble is so many cars come with the "filled for life" label as regards coolant.
A good buying point for some, and only if serviced by the main dealer, no doubt it would be replaced when some part of the cooling system part is replaced I expect at £xxx including a alloy radiator comes to mind.
Well the company Honda Civic I drive now now and again has a 10 OAT coolant life.

Wasn’t the D2 auto box fill for life, thats why there wasn’t a dip stick, as we were told when being nosey in the LR showroom in the early days of the D2 and my disco was in for its annual service 😊
 
replaced the water pump today - no issue found

found water under the rubber in the footwells both sides. could be a coincidence as went through some flood water the day before but that was 3 weeks ago now. im hoping the heating system is the cause
 
found water under the rubber in the footwells both sides.
On a disco 1??? can just about gaurantee the seams up the A pillars have sealer that has cracked and causing rust, plus at the windscreen base there is a massive gap and the sealer will have cracked and lets rain in. From the windscreen base, under the scuttle and right down the A pillar , behind the guard will need stripping, cleaning up and re-sealing/painting. Can almost gaurantee every single Disco one needs it sorting by now.
 
On a disco 1??? can just about gaurantee the seams up the A pillars have sealer that has cracked and causing rust, plus at the windscreen base there is a massive gap and the sealer will have cracked and lets rain in. From the windscreen base, under the scuttle and right down the A pillar , behind the guard will need stripping, cleaning up and re-sealing/painting. Can almost gaurantee every single Disco one needs it sorting by now.
Was hoping it was a leaking heating system which would explain the overheating
 
the water pump today - no issue found

found water under the rubber in the footwells both sides. could be a coincidence as went through some flood water the day before but that was 3 weeks ago now. im hoping the heating system is the cause
@timbr00 the water / coolant just sits there or did with mine. I just ripped it all out to be sure to allow it to dry. It will only rust the floor pan and store up drama for a later MOT.

Have you tried bypassing the Heater yet?

The pipe joinner i mentioned in my earlier post was the larger one in the below kit.

Pipe join

This would certainly rule out the heater, you just join the two pipes going into the bulkhead together and put a clip on each one.

Once you rule out the heater you can forward and back flush it in situ to remove the crud. If its not the heater that is leaking you can certainly rule it out and it should function alot better. My heater caused a blockage in my heating system and temp to spike as it was full of crud.

The O ring's fail between the heater and pipe from the bulkhead and leak into the carpet. Its the low point in the car so you just loose coolant.

Ben
 

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