Heater Blowing Cold

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Hi,
I have a 2002 Discovery TD5 ES with air con although I rarely use it. I have recently found that the heater takes ages to blow warm air. I have suffered a slow coolant loss but the problem persists even when full.
I have heard strange noises from the heater matrix area and the system does not appear to be under any pressure. There are no obvious leaks in the system. I have noticed that the top hose is soft even after prolonged running and whilst it gets warm it is not as hot as I would expect. I have undone the top hose bleed valve and it only lets out fluid (i.e. no air).
The temperature gauge struggles to climb to 1/4 at a standstill but will climb to normal (1/2) after a good drive.
Any suggestions?
Regards,
John
 
Sounds classic head gasket failure, or cracked head, but try a stat first
 
replace the thermostat then bleed it well, lift the tank above the bleed hole while you refill it and put it back to it's place just after the coolant flows out through the bleed hole, refit partially the bleed screw, rev it up to 1500rpm then tighten the bleed screw when no bubbles are showing there...tighten well the tank's cap...job done ...but if it's cold outside it can take up to 10 miles to warm up properly
 
Thanks for the very quick replies. I don't appear to have water in the oil or vice versa so I'm hoping it is just the thermostat.
Cheers,
John
 
I had the same a couple of weeks ago. It turned out to be the water pump. It was letting water seep past the seals when it was cold through the little drain hole in the housing. No leakage when warm as the seals were plyable and doing there job. If it is the pump, you should be able to see staining just below the drain hole. Put a washing up bowl underneath when you park it up at night and see if any drips into it. Mine was about an eggcup full each night. Not a lot, but enough to stop the heater working properly.
Replaced the pump and all is now well.
 
I had a similar problem a long time ago, and eventually found I had a pinhole leak in the core plug at the rear of the head. I can only assume it was letting water out and also possibly air in?

Probably nothing to do with your problem, but just goes to show that a leak can be a bu99er to find!
 
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