disco 300tdi overheating

I changed the thermostat, water pump, head gasket and flushed everything I could but it overheats. When the engine runs, the expansion tank gets up to pressure, but if I remove the plug on top of the thermostat housing, it has almost no pressure. The heater does not work and the top pipe out of the radiator is almost cold. It almost points to the thermostat but it is new and I tested it. I assume there is no electronic control of any type anywhere which could stop water flow.

So what can it be???

With no diagram of the water system in front of me i'm only assuming, but could it be the heater matrix thats blocked????? i've had this before and managed to clear it by removing the pipes where they go through the bulkhead and forcing water in each way with a hose pipe. If water flows through its fine but if theres back pressure its blocked. The water should flow easily with very little resriction.

I tried this and it flowed OK. I tried flushing water through everywhere and it all seems to flow OK. I removed the cylinder block drain plug underneath the manifold and drained the block too. One odd thing perhaps is that when I changed the head gasket, the front half of the head drained and the back half did not until I removed the drain plug. This may be by design. Is there another drain plug perhaps. I am baffled frankly. the local agent is not much use (I live in France btw)

so....

i'm having to think about this one a bit??? i will have a ponder and see if i can come up with any more... Best of luck

sounds like you have air in the cooling system needs bleeding make sure you have heater set to hot when filling system had same problem on other cars also make sure that temp sender is ok may be reading hotter than it is good luck

Hi Guys,
I've got a similar problem. Had 3 head gaskets on then a new head. Still seems to overheat. New Thermostat etc. Only symptoms since the new head - the heater doesn't get hot. I drove it yesterday and it got near the red on the gauge. Checked the hoses -both seemed warm. Maybe the sender is shot. It melted the plastic around the connector the first time it got hot. After harsh braking and some gurgling the heater worked!! Not tried it since though. Maybe they are proned to air locking???

Try this site the guys on there are very helpful

www.landrovernet.com

Hi, just had same prob. Head gasket removed, gas tracking across to water system forcing water level below thermostat,

Replaced gasket but now need to know valve guide settings before testing. Anyone help?

Do you mean valve clearances ?

Stuarth , I would think that considering all you've done that the system is suffering from airlocks and the water can't circulate properly . I've come across a wide range of cooling problems over the years which were all down to air in the system .
I have some times found that a good way to solve the problem was to give the water plenty of time e.g . fill it up and then leave it for a few hours ,then top it up and leave it for another few hours and so on until it is full. Time consuming I know .
This got me out of trouble a few times and I'm not sure why it works but it did - the first time I discovered it by accident : I had tried all methods on a car and had it topped up with water but had to leave it overnight . Next morning it took more water (no leaks) but once topped up the problem was solved !!!

another trick to try, is to run the engine with the rad cap off.
let it get hot, then replace the cap. this trick usually gets rid of any airlocks.

ps.
make sure the heater is set to hot when doing this. too many peeps leave it on cold. this alone can cause airlocks.
also squeeze/pump the hoses whilst filling with water. all helps.

From what you say your engine block seems to have some form of obstruction.Suggest you try opening the block drain plug again and force water back the wrong way through system You might be lucky and loosen the obstruction and cure peoblem. Washing soda crystals are a good old fashioned trick for cleaning out stubborn and dirty systems. Melt about half a packet in hot water put into radiator drive around for a few days drain and flush out system. Hope it helps----BB

where is the block drain plug as i have this problem also

have you checked rad core is hot all over it rad is biggest cause of heating faults on 300s ive come across

jamesmartin said:

have you checked rad core is hot all over it rad is biggest cause of heating faults on 300s ive come across

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Bloody ell James you noticed how old this thread is

i see now but why did someone bring it back today

Foooked if i know matey but good answer though thats what i was gonna say would be nice if people would come back tell us if they sorted problem and what the cause was we might all learn somthing new

my fault it's back but had the same issue and didn't want to start new thread and get a b******ing

stuarth said:

I changed the thermostat, water pump, head gasket and flushed everything I could but it overheats. When the engine runs, the expansion tank gets up to pressure, but if I remove the plug on top of the thermostat housing, it has almost no pressure. The heater does not work and the top pipe out of the radiator is almost cold. It almost points to the thermostat but it is new and I tested it. I assume there is no electronic control of any type anywhere which could stop water flow.

So what can it be???

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its air locked. drain cooling stysem, refil at the radiator .leave the expansion cover top on while through this process . once rad is ful, remove plug from thermostat housing an top up. close both plugs on rad and thermostat housing then open expansion tank an fill 1/2 full. problem solved

The problem is due to the bonnet. I jest not because allegedly the Defender 300 TDi does not have anything like the problem that the Discovery has because its header tank is higher up. I plan to put a bulge in the bonnet of my Discovery in order to raise the header tank. At the moment the design relies on the head, block and gasket making 100% perfect hermetic seals that will not pass a single molecule of gas. In actual fact metals (particularly aluminium) are often porous and they need to be vacuum impregnated with resin. Skim the head and the resin is gone! The low header tank can also result in the water pump being starved of water as IMHO the pump is too high up. The design is basically rubbish but as I cannot afford over £50K for a good 4x4 I'll have to raise the header tank. Wonder if the same cooling system designer also did the Triumph Stag and Dolomite Sprint? (both of these vehicles were notorious for cooling problems) In actual fact most vehicles that have engines mounted north-south can have troubles on steep hills because the water pump can get to be the highest thing in the cooling system, FAIL.