Help!!! Heaters cold on Discovery 300tdi

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Hiya,
well you wouldn't beleive it, BUT after all the bloody work we have done on it my mate came over and looed at it and said that it is definately the thermostat that is causing the problem, took it out, ran it, and low and behold the heaters are aired (obviously not hot) and the water is getting round the system perfectly.
The question I have now is, when I put the NEW thermostat into the boiling pan, it opened just fine, so it is obvioulsy working. Wh would it be that it wouldn't work in the car, could it be something in there that is too big to go through the thermostat once open??
Am I running anyrisks keeping hte thermostat out? Will the guage rise at all (I understand that it will be coler and the fuel costs will be higher etc,) BUT if the engine was going to overheat will the temp guage in the cab show it?????
Thanks in advance
 
I think its possible that taking the thermostat out and refilling the system and then running it without the thermostat has probably shifted a very stubborn air lock.
Try putting the thermostat back in again.
Running without a thermostat will not harm your engine but it will simply be cold all the time. Might as well not have a heater.
When you refit the thermostat you will put the bleed hole in the flange to the top wont you.
Persistence pays off eventually.
Theres no possibility of the engine over heating without a thermostat fitted and yes the gauge would respond but probably too late.
 
Last edited:
nicedayforit said:
I think its possible that taking the thermostat out and refilling the system and then running it without the thermostat has probably shifted a very stubborn air lock.
Try putting the thermostat back in again.
Running without a thermostat will not harm your engine but it will simply be cold all the time. Might as well not have a heater.
When you refit the thermostat you will put the bleed hole in the flange to the top wont you.
Persistence pays off eventually.
Theres no possibility of the engine over heating without a thermostat fitted and yes the gauge would respond but probably too late.
Click to expand...

Sorry to question you, but you have put that there is no possibility of the engine overheting, BUT that the guage would respond too late!! Was it suppsoed to say that the engine could still overheat but the guage would respond too late?? Sorry, just want to get it straight in my head!!
Thanks again, and I think your right in the fact that persitance does pay off. Wish sometimes, moeny was no object and I could just stick it in the garage!!! Although this way I suppose we learn more!
Thanks for all your help. I will try with the thermostat back in later on and post back!
Thanks Again
 
viks3457 said:
Sorry to question you, but you have put that there is no possibility of the engine overheting, BUT that the guage would respond too late!! Was it suppsoed to say that the engine could still overheat but the guage would respond too late?? Sorry, just want to get it straight in my head!!
Thanks again, and I think your right in the fact that persitance does pay off. Wish sometimes, moeny was no object and I could just stick it in the garage!!! Although this way I suppose we learn more!
Thanks for all your help. I will try with the thermostat back in later on and post back!
Thanks Again
Click to expand...

Sorry about the confusion regarding overheating, didn't quite come out as I intended.
To clarify all things being equal running your car without a thermostat will not cause it to overheat in itself, won't do the engine any favours mind in the longer term if you leave it like that.
However if for instance the radiator is blocked or the water pump fails or the head gasket fails etc there is then a possibility the engine could over heat for reasons nothing to do with the thermostat. In this situation the temp gauge will respond but unfortunately because of the way the gauge is made to operate by LR in their wisdom, if the engine is allowed to run with a rising gauge above its "normal" position to the extent it reaches the red position the chances are it's then too late to definitely avoid possible over heat damage.
By the way you are fitting an original LR thermostat, for some reason they seem to be more reliable than some other makes.
 
I just bought the stat from the local supplier - don't actually think that it was a LR original - might do a search see if I can pick one up online.
I will try it with the new thermostat in and also buy a new LR one and then put that in!
I am so glad for these forum's hehe - thanks again
 
Well , here we go, this is either going to be good news OR really bad news.
We ran the car this morning for about 20 miles or so, running sweet as a nut, air in heaters aired but not hot, and temp gauge didn't move out of the bottom quarter without the thermostat in.
Went and bought a GENUINE LR thermostat, put this in and hey presto, the same problem. Water is not circulating and the heaters are cold! The water is not going from the thermostat housing to the rad. I understand that this is OBVIOUSLY a blockage of some description around the area of the thermostat housing!! The small pipe that comes out of the thermostat housing near the bleed screw was removed and hot water came out of this, (although this didn't happen yesterday with the old thermostat in!) so the water is reaching the thermostat housing, just not getting past it!!!
I really don't know what is happening now!! Am I missing something??
I have spoken to my local land rover repairer and they have said with my symptoms they would not suggest a "Pressure test" as the symptoms don't warrant it!!!! (they will not take my money for it! How odd!!). I have heard a lot about this "sniff" test, but when I mentioned this to them, they said the same. They suggested the P gasket, but logic in my mind, says that if it works fine with the termostat out, but not when its in, then there lies the problem!!!
Thanks
 
Last edited:
viks3457 said:
Well , here we go, this is either going to be good news OR really bad news.
We ran the car this morning for about 20 miles or so, running sweet as a nut, air in heaters aired but not hot, and temp gauge didn't move out of the bottom quarter without the thermostat in.
Went and bought a GENUINE LR thermostat, put this in and hey presto, the same problem. Water is not circulating and the heaters are cold! The water is not going from the thermostat housing to the rad. I understand that this is OBVIOUSLY a blockage of some description around the area of the thermostat housing!! The small pipe that comes out of the thermostat housing near the bleed screw was removed and hot water came out of this, (although this didn't happen yestaerday with the old thermostat in!) so the water is reaching the thermostat housing, just not getting past it!!!
I really don't know what is happening now!! Am I missing something??
Thanks
Click to expand...

I think from what you describe you have a significant but partial blockage in the water ways in the head.
With the thermostat in place, with a cold engine, the thermostat should be fully closed so no water should go to the radiator. Only what bleeds thro the thermostat bleed hole should go thro the thermostat to provide a flow for the thermostat sensor to measure.
The flow to the heater doesn't go thro the thermostat but goes out thro the bottom of the thermostat housing before the closed thermostat directly into the head circulates thro the head and engine body and is sucked directly back into the pump. From the head a proportion of water comes out of the top rear pipe and goes to the heater thro the heater and back along the metal pipe on top of the head to the suction side of the pump.
The way to check for a blockage in the head is to remove the heater flow connection at the back top of the head, clamp the rubber hose, fit a garden hose to the pipe rising off the head, undue the plastic bung in the top of the thermostat housing and turn the hose on. If all is clear you should get a fountain out of the thermostat housing, if not you have a blockage.
You might clear it if you have.
 
nicedayforit said:
The way to check for a blockage in the head is to remove the heater flow connection at the back top of the head, clamp the rubber hose, fit a garden hose to the pipe rising off the head, undue the plastic bung in the top of the thermostat housing and turn the hose on. If all is clear you should get a fountain out of the thermostat housing, if not you have a blockage.
You might clear it if you have.
Click to expand...

Thanks for this - I am going to try it tomorrow. Just out of curiosity (and really sorry for being a pain) but do I have the thermostat in or out for this process, Don;t want to make it worse by not doing as I am supposed to.
Thanks
 
Hello,
Next update and i have to say, this seems to be a good one.
My hubby has blasted the head with a hose and magically the blockage has dislodged. With the termostat back in engine running fine (and sweet as a nut I may add) no overheating, sounds fine now (Have also touched the fan belt with soap to stop it squeaking) so it is all good - HOWEVER the heaters are now going from hot to cold to hot, and at one point the passenger side was aired and the drivers side warm, then they both went cold. I am really tempted to buy a portable heater for the cab - BUT it is also intriguing me as to why it's still doing it. They are going from hot gradually to cold, to warm, to aired, back to cold. This is all a gradual motion, not instantly. Is it still air in the system that may just need bleeding, as it was only done this morning.
Should I just leave it till morning to cool down and check coolant levels?? The thermostat housing is now full of water and no air in it so this seems to be a breakthrough in itself.
Thanks
 
viks3457 said:
Hello,
Next update and i have to say, this seems to be a good one.
My hubby has blasted the head with a hose and magically the blockage has dislodged. With the termostat back in engine running fine (and sweet as a nut I may add) no overheating, sounds fine now (Have also touched the fan belt with soap to stop it squeaking) so it is all good - HOWEVER the heaters are now going from hot to cold to hot, and at one point the passenger side was aired and the drivers side warm, then they both went cold. I am really tempted to buy a portable heater for the cab - BUT it is also intriguing me as to why it's still doing it. They are going from hot gradually to cold, to warm, to aired, back to cold. This is all a gradual motion, not instantly. Is it still air in the system that may just need bleeding, as it was only done this morning.
Should I just leave it till morning to cool down and check coolant levels?? The thermostat housing is now full of water and no air in it so this seems to be a breakthrough in itself.
Thanks
Click to expand...



Sounds to me like you have an airlock still.
 
thebiglad said:
Sounds to me like you have an airlock still.
Click to expand...

Great :-(
I have just driven it for about 20 miles, no overheating, no heaters hot though, OTHER than when I went up a steep hill for about 1/4 mile, and when I pull out at the top, the heaters are hot, for about another 1/4 of a mile then go cold again. This was the only time on this whole trip that the heaters went warm. ALSO when I checked the coolant level this morning it was up to the top of the expansion tank, and it was left at half way yesterday.
Any ideas?
Thanks
 
viks3457 said:
Great :-(
I have just driven it for about 20 miles, no overheating, no heaters hot though, OTHER than when I went up a steep hill for about 1/4 mile, and when I pull out at the top, the heaters are hot, for about another 1/4 of a mile then go cold again. This was the only time on this whole trip that the heaters went warm. ALSO when I checked the coolant level this morning it was up to the top of the expansion tank, and it was left at half way yesterday.
Any ideas?
Thanks
Click to expand...

It appears you still have air in the system.
Bit concerned that you appear to have more water in the system than the night before. Only 2 things could cause this, your are drawing air into the system somewhere or you have a small head gasket leak allowing combustion gases into the coolant,
Both of these could cause an air lock to the heater and an increase in water level.
Might be worth having a garage check the coolant for the presence of exhaust gases.
Check all the hose connections for tightness and also the expansion tank cap. Then fill the system from the heater flow pipe as before.
 
Hi, your still having the same symptoms as me....i tried everything that you have tried over and over and over.
I think your gonna have to bite the bullet and take the head off and have it skimmed as i bet you its warped:rolleyes:
Every mechanic i took mine too were saying stat or blockage....turned out it was the warped head causing it!:(
 
Well touch wood, hubby realised a bit ofair in the termstat head and wow the heaters are warm, engine comes up to temperature fine and as of yet it is running fine. No more problems with water level or cold heaters for the minute.
D6Jay I was in exactly the same thought process as you, thought it was going to be the head!!!!! BUT if it stays like this then happy days, if it doesn't I will most certainly be taking the car to get it sniffed and taking the head off I think!
I am trying to stay postiive in the hope that this is the last of this particular problem for now but if it isn't I shall be back.
Thanks to you all for your great help, and I will more than likely be back on soon as I am having problems with my doors hehe
Thanks again
 
Hello,
I am back with my tail between my legs and thinking very very quickly that this is now going to be a problem with the head!!!!
We sorted it, heaters hot and all air out the system, run to the bloody cor shop today (only about 10 miles away) and by he time we got half way back, the damn thing had started to overheat and YET again NO bloody water in the thermostat housing!!!!!
Although I have to say, once it was tightened the thermostat bleeding plug seemed to be hissing a little, which i am presuming can let air in!!!!
So if it is not that, then it is going to be the head isn't it. Just mightily annoyed as I have no other symptoms of head gasket/cylinder head failure!!!
Never mind.

If anyone else has any ideas, please let me know.
Thanks
 
Just a quick update.
I took the disco to the garage, and the mechanic there was extremely nice, and told me that he would be very surprised if it was the head, as there are no other symptoms. The P gasket was definately leaking, so I booked it in for the work to be done. When he took the old P gasket off, there was hardly anything left of it! However driving home, the bloody thing began to over heat, I pulled up, left her idling for a while and she came back down to temperature. Managed to drive the 1 mile journey to get home, and she is now on the road outside, having filled her through the thermostat housing and rad, with the expansion tank cap off, hoping that this is definately just an airlock and not the head!!! We shall see in the morning (please all pray for me that the water level proves it was just air!!!)
I will let you know the next instalment tomorrow!
 
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