2003 Discovery overheated, had a cracked reservoir which was replaced today. After my husband replace the tank, I took it out for a test drive (with ac on) and within 3 minutes, the gauge went right up to red, stayed there for a minute, then went back down to cold but the red light is still on. Tried bleeding the system...still on!
-what is the best/correct way to bleed the system
-why won't this damn light go off?

Thanks!

 

from the RAVE tech manual -

If the engine coolant temperature gauge receives no input or the input is out of range the

temperature gauge will read cold and the high coolant temperature warning lamp will be illuminated.

Translation from the original Klingon Roverspeak - the wire to temp sensor could be bumped loose, or you could have so much air in the system that the thermal element is located in an air pocket. Venting all possible air while letting some coolant out from the bleeder screw will help, when cool. Unbolt container Prince Charming replaced, and raise it to help with this. Then re-attach. You probably are quite a bit low. Perhaps by a gallon or more.

 

Going that long into the red, you may have damaged a head, head gasket or a sleeve, these engines can't take going into the red.
Do not restart it till it has been bled properly.
PM me your number and I'll call you back this evening.

 

@savannah buzz- yes, was quite low- have added and bled...added and bled...added and bled until steady stream of fluid was coming out of the bleeder. Did lift up reservoir as well.

@Disco Mike - I didn't run it for long while it was on red, literally about 5 minutes total-That's 5 minutes from COLD so in reality, if it was actually overheating, it should have taken a bit more time, no? the strange part was, as soon as I saw the gauge rising, I turned the heat on full blast...no heat which made us think to bleed again. By time I got into my driveway, the gauge fell to cool and light was stuck on. She sounded fine and was running fine. Now the heat is working but light still on. Good news is...no more leaks ;-)
My poor prince charming is frustrated and off to bed while my poor disco is sitting in the driveway!

 

Did you not read Buzz' post? Your sensor isn't working properly.

 

I actually missed that... Will check the sensor next.

 

Where is the sensor located?

 

Between alternator and compressor on top of engine. As you have a D2, the heater core always has fluid circulating in it, so turning on the heat has little impact as compared to some old school systems that had a valve, and actually added more water to the system.

 

Did testing on the sensor and it was good. Went back to bleeding again (even after bleeding the first time for an hour) and just needed to be bled more! She's fine now!

Thanks for all your help!! This forum
Is great!!

But now I have a new problem with 3 of the dash (break lights?) lights coming on which I will post in another thread

 

You have not fixed anything yet.
My money is on the fact that it will over heat again cause of a blown head gasket that you have not tested for.
Not sure how you are bleeding the system, but it only takes less then 10 minutes when done while stone cold.
I would not drive it far from home and just be aware of the fact that one more red ligh indicator, if it hasn't already damaged the engine it will and you will be looking for a replacement.