jimleshed said:

Yep, early on (4). That was before I realised that the problem seemed to be airlocks caused by extra air/gas. Bleed system, run for 5 miles, stat housing has filled with gas/air, no chance of stat opening. Havent checked that again (run with no stat) recently, to see what happens. May try when i get the head back!

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the thin pipe going from the top of the theremostat then thru a Y junction to the filler bottle is meant to facilitate any air in the system being expelled thru the filler bottle
the other side of the Y goes to the radiator

that Y piece is a possible issue

Thanks D1, but I checked that pipe (ejector assembly I think its called), and it's clean and clear. It blows through easily too. But, as it was a possible suspect I replaced it with a new one. And checked the new one before fitting. Also triple checked the 3 spigots (expansion tank inlet, stat housing outlet and rad outlet) to make sure they were clear too. When I bleed the system, which I've done a lot over the past few months, I can see coolant flowing very freely into the expansion tank, from the inlet connected to the thin pipe, which also implies that the pipes are clear.....

D1Nut said:

the thin pipe going from the top of the theremostat then thru a Y junction to the filler bottle is meant to facilitate any air in the system being expelled thru the filler bottle
the other side of the Y goes to the radiator

that Y piece is a possible issue

Click to expand...

whereabouts in SA are you? Last time I was there I drove up Prince Alfreds pass in a hired Audi A3 automatic!

Checked the water pump? There have been cases of replacement water pump impellors coming loose on the shaft when warmed up.

tottot said:

Checked the water pump? There have been cases of replacement water pump impellors coming loose on the shaft when warmed up.

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Thanks tottot, yes, old pump was working, no loose impellor. Changed it anyway. New one pumps water round fine. Or seems to, I question everything I have done on this.

Brief update.
Went to steam show monday, made myself a real pain with every 300tdi owner. 15 odd people (read that either way!) Got a couple of new variation on bleeding (jack up front as much as possible, and bleed from empty with engine running) which I might try. Consensus was that I seem to have tried most things right. Last conversation i had was with 3 old guys, sitting in thier caravan. Went through lots of options, but ended up hoping its the hoses (bottom hose most likely) but expecting its a cracked block. Anyway, they know a man who hopefully has a couple of motors if it comes to that.
new hoses arrived today, more stuff to play with at the weekend. I'll have to test the block somehow.

Got myself some block test fluid, put it in a wine fermenter bubbler, warmed up engine, fitted bubbler to exp tank.
Yes, slow release of gas, fluid slowly changed colour (20 mins) red to yellow.. So some exhaust gas in cooling system. Got to be cracked block.

Will look for another engine.

Unlucky, you'd tried everything else. Glad you got to the bottom of it.

have you checked the temperature with a probe or laser to confirm it is overheating and where the hot spot s are or is it not the gauge telling lies ,for it to over heat it would force the coolant to be pressurised and you say it's not

Thanks. Yes, both gauge and sender checked for accuracy, off vehicle, and on vehicle (to confirm loom and any earths). As exhaust gas is present in coolant, and head has been tested, cylinders compression tested, I am happy that the block is cracked. Probably very fine crack well down in the bore, where although it will get high pressure, it will only get it for a small percentage of the engine cycle.

ive had this same issue and it was my thermostat not opening at the rite temprature,ive since had 4 thermostats and not one of them open at 88 degrees i pulled a thermost out of a 300 tdi engine laying around and it worked perfectly overheating issue gone ive even removed the viscous fan still not overheating i do have a backup electric one anyone know were i can actually get a thermostat that works as it should ive bought waxstat ones both didnt work cheap ones still didnt work causing me to over heat if i use them am sick of messing about with it ,i need to replace the thermostat i robbed out the other 300 pref a one that works would be good

Mine is certainly not the Thermostat. I've tested all three, and they open correctly at the right temperature.

Anyway, its academic now, as I have to sell the landy.
Block was skimmed and inspected by an engineering company, but the problem still persists. (everything to do with the cooling has been changed - rad, pump, thermostat, all pipes, head gasket (4 times?)new head, gauges removed and checked, water temp checked with different sender and gauge, and physical thermometer. It gets a small amount of exhaust gas in the cooling as shown by bubbling through indicator solution.

Shortly for sale. **** load of new parts: Galv chassis, Galv bulkhead, tyres, springs, shocks, all the engine parts, clutch, loads of seals and stuff, bushes etc, etc etc.
Anyone interested in fitting a different motor (or block - as the crank/rods/pistons/flywheel have been balanced too) will end up with a very good landy. Make me a sensible offer!

jimleshed said:

Mine is certainly not the Thermostat. I've tested all three, and they open correctly at the right temperature.

Anyway, its academic now, as I have to sell the landy.
Block was skimmed and inspected by an engineering company, but the problem still persists. (everything to do with the cooling has been changed - rad, pump, thermostat, all pipes, head gasket (4 times?)new head, gauges removed and checked, water temp checked with different sender and gauge, and physical thermometer. It gets a small amount of exhaust gas in the cooling as shown by bubbling through indicator solution.

Shortly for sale. **** load of new parts: Galv chassis, Galv bulkhead, tyres, springs, shocks, all the engine parts, clutch, loads of seals and stuff, bushes etc, etc etc.
Anyone interested in fitting a different motor (or block - as the crank/rods/pistons/flywheel have been balanced too) will end up with a very good landy. Make me a sensible offer!

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what a nightmare i feel for ya my 300 is coming out soon gonna go m57 auto as left leg cant handle the clutch anymore i do have a spare td5 laying around but i feel the m57 will be better for me do a lot ow towing heavy stuff and my 300 just aint got enough guts anymore so its going into a build for my daughter she wants a double cab so i will have to make it happen lol

My problem is not so much getting another engine as due to personal reasons I have nowhere to do the job and need the cash!

i get ya i think money is tight for a lot of people these days i do all my work on my front drive in the crap weather lol i even painted my double cab base coat and laquer came out spot on too i was shocked that was about 5 years ago i think its due another paint the ally rust worm has started under the paint,latest one i am building has gaskets on all touching sufrfaces of ally and steel meeting .

If you are losing fluids from the cooling system and the engine runs hotter than normal then it is likely to be the head or a cracked block!!! I had a TD5 Def with the same issues. A new head cost me £1300 plus fitting!!!! It cured it as there were holes in my head as shown in the attd pic and combustion pressure was leaking past the head gasket into the cylinder head waterway. You can see the hole in the head between the top two head chambers about an inch to the left. It ran like a ferrari after having the new AMC cyl head fitted so was well worth doing after all.
I can also add that the previous owner had a garage rebuold the engine and they skimmed the head and said it was all good to re-use. A rebore and new pistons and a new water pump was also done at the same time. So i guess the previous owner had a coolant issue and didnt tell me when i bought it!!!!!
When i had the problem, it lost coolant over a few days so i started to monitor it. After doing a couple of longer trips i looked under the bonnet and it was pumping a bit of coolant out of the header tank overflow past the cap. Then i started to notice i had a orange/brown film and spots on the engine bay and bulkhead where the bonnet is attached to the bulkhead. It is that colour as the OAT coolant for the alloy head is that colour so not rust. With that as a clue i did all the stuff like you have done to no avail so ordered an AMC cylinder head which is made in Spain and said to be better then the LR originals are. Expensive but it cured my problem.
The head gasket looked fine when i took it off the engine but when i cleaned up the head surface it was obvious what the problem was. I had two holes in the alloy head so it was a useless lump of alloy. The previous owner had it skimmed according to the bill he produced when i bought it so i guess the garage didnt pressure test it and just did a visual and it had gotten much worse since then. That was 18 months before i bought it and just 8000 miles driven by the last owner.
All i can say is good luck and if the new head is just £200 its well worth doing it as it makes the engine run like new again.
The head problem is caused by people adding just water or ordinary a/freeze into the coolant instead of paying for OAT fluid which is what LR tell you to use as water or a/freeze rots the alloy like on my head. Saving a quid or two cost me close to £2000 so wasnt a good move .

Thanks for the comprehensive reply!
99% certain that its a cracked block.
Anyway, its academic now. Change in personal circumstances is forcing me to sell it as is. Advertising it as "needing new engine", but as its new galv chassis, bulkhead, shocks, bushes, springs, tyres, etc, etc etc, it will sell