M

monodedo

New Member
Helo there...

I have a disco 99 which I love!!! but not so much lately... my heating sistem is not working properly... it blows cold air!! yes... I'ts winter here and I'm freezing I realize that it starts to blow hot air only when the car is runing on hi rpm... 2000+ But if reduce the speed and the rpm go down the cold air comes back... any ideas of what is going on with it.

Thanks!!!
 
Mine was doing the same. I was going to look at it the next weekend when I had time. Unfortunately, before then it overheated & the head gasket went:(

Don't risk leaving it like I did!!!
 
if the thermostat is jammed it can change the routing of the cooling circuit of the engine, which is where the heat comes from in your heater.
 
Check for your coolant level and possible air locks in the system. Also check your thermostat for being constantly open as suggested above. If those are in order, suspect blockage in the heater matrix.

Petrol 4.0 heats up pretty quickly. It's -7oC here now and the my 3.9 RRC heats up in 5 km drive starting to heat up the cabin. At -20oC the engine heats up even faster, due to increased friction in the driveline.
 
Get a V8 guru to talk you though it, but you may be able to whip it out all together for now or at least to see if it's jamming and try to free it.... best check...ask the question...
 
Reading this i'm beginning to get a little worried about my TD5. I noticed it doing just the same recently. When sitting in traffic on tick over the heater blows cool air. Raise the revs to about 1500rpm and it blows hot instantly. Also occasionaly you get a cool draft when on the motorway. I posted about it and came to the conclusion that it could be the aircon temp sensor. Maybe the 2 problems are linked??
 
accywingy said:
Reading this i'm beginning to get a little worried about my TD5. I noticed it doing just the same recently. When sitting in traffic on tick over the heater blows cool air. Raise the revs to about 1500rpm and it blows hot instantly. Also occasionaly you get a cool draft when on the motorway. I posted about it and came to the conclusion that it could be the aircon temp sensor. Maybe the 2 problems are linked??
Click to expand...
Is it the same if you switch off the aircon? I don't think there are any sensors involved in the basic heating system. On the TD5 the heater receives warm coolant in preference to the radiator, so if it's not the aircon it's probably a stuck thermostat or an airlock.
 
Really daft question - are you losing any coolant at all and when was the last time you checked it.

Low coolant levels can give the same issue of sporadic heating - engine speed may provide enough waterpump spin to push an air lock around.

My understanding of a thermostat is to regulate engine temperature and to restrict coolant to the engine block to get it up to heat quickest, then to open at the right temperature and help disapate excessive heat from the engine.

thermostats open at set temperatures - i.e they go from closed when cold to open when hot.

I ran my last car for 5 years with no thermostat in it - no issues. A lot of imports come over like this.

Try (from cold) running the engine with the coolant cap off and filling the system. Make sure your heater controls are all fully open and fill to between your low and high marks.

Check to see if you get constant bubbles coming up - if yes it may mean the engine is pressurising the cooling system.

If you are losing water, check for excessive steam from the exhaust, and the inside of your oil filler cap - if emulsified (white gloopy stuff) your losing water into the engine oil (NOT GOOD). If excessive steam - probably a water jacket issue.

Main thing is to check now - cooling issues only lead to bigger problems unless sorted.
 
Dippydiver said:
thermostats open at set temperatures - i.e they go from closed when cold to open when hot.

I ran my last car for 5 years with no thermostat in it - no issues. A lot of imports come over like this.

Try (from cold) running the engine with the coolant cap off and filling the system. Make sure your heater controls are all fully open and fill to between your low and high marks.

Check to see if you get constant bubbles coming up - if yes it may mean the engine is pressurising the cooling system.

If you are losing water, check for excessive steam from the exhaust, and the inside of your oil filler cap - if emulsified (white gloopy stuff) your losing water into the engine oil (NOT GOOD). If excessive steam - probably a water jacket issue.

Main thing is to check now - cooling issues only lead to bigger problems unless sorted.
Click to expand...
On the TD5 it's a bit more complex - the engine tends to run cold and the stat is designed to increase running temperature by up to 10 degrees. This is achieved using a complex water jacket around the stat housing. I wouldn't advise running a TD5 without a stat, although it's probably fine for a V8. On my TD5 the stat jammed shut, leading to blown head gasket. Follow DippyD's instructions - if only to put your mind at rest!
 
Silly question, is the aircon turned off when you run it in econ mode?? (It's the old digital type aircon/climate thingy) I must admit i'm worrying a little bit lol
 
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