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  #1  
Old 5th-November-2009, 00:53
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Join Date: Nov 2009
Location: Bacup, Lancashire
Posts: 41
Default Help!!! Heaters cold on Discovery 300tdi

Hi,

I am new to the forums on here, and am by no means a mechanic, so any replies would be appreciated in laymans terms hehe (I am a lady after all, and relatively new to the underneath of a bonnet).

My 1996 discovery 300tdi started blowing cold air from the heaters when they were set to hot. Initially I thought that there was no water in the system, but the header tank showed normal level when I checked it. I was at a loss as to why this was happening for a week or so, the heaters would sometimes blow hot, but then go cold. Eventually I realised that I was loosing coolant and the water pump began making a kind of "dry bearing" sound.

Sure enough the water pump and gasket had failed. I bought a water pump, gasket, antifreeze and blue gasket sealer, and my friend proceeded to take the water pump off to put the new one on. The gasket had previously been superglued on, and it took him ages to get it off and get a good seal again for the new gasket and pump. Anyway we bled the system using the radiator plug, thermostat housing plug technique and left it overnight to cool down. This seemed to do the trick, once my husband had filled the header tank to the correct level with water this morning. We ran it for over an hour, driving round locally, heaters blew hot and temp gauge stayed just below half as normal. The only thing different was that when we stopped the temp gauge dropped slightly and then when we set off it would rise again to just below the halfway mark. But just as we got excited thinking we had solved the problem, the heaters went cold again!!!!! The engine is not over heating, however the pipe that runs from the thermostat housing to the rad is cold, until the rad cap is taken off then it seems to fill with warm water.

Little bit confused as to whether this is still an air lock or rad problems, or thermostat problems. Praying that it is not head gasket (no smoke, and oil filler cap is fine!!!). The only other thing we noticed about the coolant in the car when we have checked was that it was a very rusty colour!!!

Please please can someone help, or point me in the right direction as to what I can do!!

Thank you (and sorry for the long post, just wanted to be thorough)
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LZ
  #2  
Old 5th-November-2009, 01:38
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Join Date: Sep 2006
Location: cardiff
Posts: 194
Default Re: Help!!! Heaters cold on Discovery 300tdi

check after running it that all hoses are hot and expansion tank is hot also check that the thermostat bypass hose is not blocked that rust coloured stuff can block the valve at the middle of those hoses and screw the water pump up again and check the 2 hoses going into the bulkhead are hot when you run the disco again keep heaters up on hot also check to see if carpet is wet in footwell as heater matrix can leak on these motors. you could try a rad flush toget rid of the dirty water
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  #3  
Old 5th-November-2009, 10:12
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Location: Bacup, Lancashire
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Default Re: Help!!! Heaters cold on Discovery 300tdi

The bypass pipe from the thermostat housing to the rad stays cold, as does the header tank after running. The pipes that go over the bulk head are not particularly warm, but the pipe that goes from the rad to the water pump is hot. Forgot to mention as well, it seems to have developed a squeak around the pulleys for the fan belt and pas (I think thats what these are), although this sounds totally different from the noise that the water pump developed when it was on it's way out!
My hubby is totally draining the system as we speak. With regards the rad flush, can I do that with normal water, or do i need to buy the actual rad flush fluid to do it!!!
I have toyed with the fact that the termostat wasn't working correctly but the car doesn't overheat now!!! I do feel like there could be a blockage in the pipes at the thermostat housing though.
Thanks for your response. I have read so many threads on this problem, but they all seem to have the motor overheating, and mine isn't!
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  #4  
Old 5th-November-2009, 10:33
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Location: The village of the dead
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Default Re: Help!!! Heaters cold on Discovery 300tdi

Quote:
Originally Posted by viks3457 View Post
The bypass pipe from the thermostat housing to the rad stays cold, as does the header tank after running. The pipes that go over the bulk head are not particularly warm, but the pipe that goes from the rad to the water pump is hot. Forgot to mention as well, it seems to have developed a squeak around the pulleys for the fan belt and pas (I think thats what these are), although this sounds totally different from the noise that the water pump developed when it was on it's way out!
My hubby is totally draining the system as we speak. With regards the rad flush, can I do that with normal water, or do i need to buy the actual rad flush fluid to do it!!!
I have toyed with the fact that the termostat wasn't working correctly but the car doesn't overheat now!!! I do feel like there could be a blockage in the pipes at the thermostat housing though.
Thanks for your response. I have read so many threads on this problem, but they all seem to have the motor overheating, and mine isn't!
I don't think from what you describe that you have any major problems.
300tdi heaters can be very difficult to bleed properly.
After you have flushed the system, water will do, fill the system with water and antifreeze as you did before and then gio and have a run in the car. When you come back let the engine cool and then check the coolant level again, it will probably have dropped a bit. This just air in the system-it takes a little while to collect at the top. Go for another run.
Let the engine cool again but this time undo the heater flow connection off the top of the cylinder head. This is the pipe that rises vertically off the head at the back, not the metal pipe running along the top of the head.
Hold the rubber pipe up vertically and get someone to put their thumb over the pipe connection on the head.
With a jug fill the vertical pipe slowly until its overflowing and then quickly put the pipe back on the head connection and tighten the jubilee clip.
Your heater should now be vented and full of water. The heater should now work(!)
Keep checking the coolant level for a couple of days just to make sure all the air is out.
Best of luck.
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  #5  
Old 5th-November-2009, 12:28
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Default Re: Help!!! Heaters cold on Discovery 300tdi

Quote:
Originally Posted by nicedayforit View Post
I don't think from what you describe that you have any major problems.
300tdi heaters can be very difficult to bleed properly.
After you have flushed the system, water will do, fill the system with water and antifreeze as you did before and then gio and have a run in the car. When you come back let the engine cool and then check the coolant level again, it will probably have dropped a bit. This just air in the system-it takes a little while to collect at the top. Go for another run.
Let the engine cool again but this time undo the heater flow connection off the top of the cylinder head. This is the pipe that rises vertically off the head at the back, not the metal pipe running along the top of the head.
Hold the rubber pipe up vertically and get someone to put their thumb over the pipe connection on the head.
With a jug fill the vertical pipe slowly until its overflowing and then quickly put the pipe back on the head connection and tighten the jubilee clip.
Your heater should now be vented and full of water. The heater should now work(!)
Keep checking the coolant level for a couple of days just to make sure all the air is out.
Best of luck.
Thank you very very much, I love laymans terms and you description is very easy to understand. Hubby has flushed rad with water and sure enough loads of "bits" came out. Put it all back together and filled up again. Left it sat idling for a few minutes with header cap off and then he's going to go for a run in it then check coolant. Thanks again and I will post once I have done the heater pipe venting as you have suggested. Thanks again
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  #6  
Old 5th-November-2009, 14:43
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Location: Bacup, Lancashire
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Default Re: Help!!! Heaters cold on Discovery 300tdi

HI, just a quick update.
The thermostat appears to be a problem. We have bled the system, but the pipe from the thermostat housing to the rad is still cold. Took the stat out, dropped into boiling water - nothing!!!!
Could this be the problem??
Thanks
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  #7  
Old 5th-November-2009, 15:17
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Default Re: Help!!! Heaters cold on Discovery 300tdi

Quote:
Originally Posted by viks3457 View Post
HI, just a quick update.
The thermostat appears to be a problem. We have bled the system, but the pipe from the thermostat housing to the rad is still cold. Took the stat out, dropped into boiling water - nothing!!!!
Could this be the problem??
Thanks
The chances are your thermostat may be faulty due to the age of your car, while you have it out you might as well replace it for what they cost.
Unfortunately it has no bearing on your heater problem. The pipe from the thermostat housing to the top of the radiator probably is cold, it simply means the thermostat hasn't opened for what ever reason. 300tdi's are vastly over cooled such that the radiator rarely comes into play in cool/cold weather. My radiator is almost never used .
If your thermostat housing is hot, check to see if the metal pipe running along the top of the head is also hot.
If it is you have water circulation thro the heater, if not you still have an airlock, or the heater matrix is blocked with debris. They can block.
When did the heater last operate?
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  #8  
Old 5th-November-2009, 15:38
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Location: Bacup, Lancashire
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Default Re: Help!!! Heaters cold on Discovery 300tdi

Quote:
Originally Posted by nicedayforit View Post
The chances are your thermostat may be faulty due to the age of your car, while you have it out you might as well replace it for what they cost.
Unfortunately it has no bearing on your heater problem. The pipe from the thermostat housing to the top of the radiator probably is cold, it simply means the thermostat hasn't opened for what ever reason. 300tdi's are vastly over cooled such that the radiator rarely comes into play in cool/cold weather. My radiator is almost never used .
If your thermostat housing is hot, check to see if the metal pipe running along the top of the head is also hot.
If it is you have water circulation thro the heater, if not you still have an airlock, or the heater matrix is blocked with debris. They can block.
When did the heater last operate?
It last operated fully for over an hour yesterday but this morning it only got luke warm after about quarter of an hour of running but then went cold again.
Thermostat has been replaced. There was no movement at all in the thermostat when I dropped it in to the hot water.
Unfortunately the water pump seems to be squeaking again now. This does come and go this noise though?????
Sorry to seem a bit vague!
Thanks
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  #9  
Old 5th-November-2009, 17:13
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Location: Bacup, Lancashire
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Default Re: Help!!! Heaters cold on Discovery 300tdi

Hi,
Just another quick update - new thermostat fitted and the pipes are now hot - the only one that isn't is the metal pipe that runs to the heater matrix - so we are going to let it cool and then do the pipe removal on the back of the head, and fill it up with water.
Hopefully this will solve the heater issue.
The odd squeaking noise is still there though.
Wasn't there before water pump was changed!!!!
Thanks
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  #10  
Old 6th-November-2009, 10:57
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Location: Bacup, Lancashire
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Default Re: Help!!! Heaters cold on Discovery 300tdi

Just another quick update - filled the pipe that rises vertically off the back of the head with water (as my hubby had his thumb on the bit I took it off). Put it back on very quickly, and low and behold, the heaters are still cold!!!!!! lol
That pipe that we filled up is getting hot, but the one that runs from the metal pipe on top of the head is cold!!! Any ideas??
Thanks
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LZ
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