full coolant tank, engine overheat
 

Does anyone know what these syptoms could be:

Was driving around for an hour, and after hitting traffic, car started to overheat. Heater was cold at idle. Had to rev the engine to about 2000rpm before heat came on and engine started cooling down.

I figured it was low coolant, so the next day I filled it back up. After another hour drive and when i came to an idle, car overheated again. I figured I didnt fill the system up correctly. So i refilled and bled the coolant according to the rave manual. I had to do this for about 10 minutes until I got a steady flow of coolant. I took a 5 minute drive and my heater was hot at idle .

The next day at lunch, i checked my coolant level. All looked well in the coolant tank. However when i loosened the bleed screw, there was air pressure in there. So I figured it was just another air bubble and bled it out.

When i got home, after letting the car cool, I again loosened the bleeder and air came out.

Now, this morning, I went for a 5 minute drive and noticed the cold heater again. The car began overheating on my driveway. I shut it off and checked the coolant level in the coolant tank, and it is full.

I do not see any white smoke coming out of my tailpipe, and do not see any milky residue on my oilcap or dipstick. There are no signs of coolant look on the driveway.

Am I screwed? Could this be a cracked block or slipped sleeve that a lot of people talk about?

Its a 2000 land rover discovery II 150k miles. Head gaskets have not been changed yet. I have the head gasket kit all ready to go. Should I even attempt changing them with these symptoms?

your problem started with no heat, so i will assume you have a leak in your system which started your problem. When you bleed the system it was stone cold and the overflow tank was elevated? at 150k i would think head gasket are in you near future. but just to rule out a lot of little things "I" would refill the system borrow a cooling system preasure tester and see if you find any other leaks before going directly inside the engine. do you have any codes and what do the plugs look like?

I bled it when it was stone cold. I also tried bleeding it while idling and engine at operating temp while heater was full blast When I bled, i did lift the tank overhead.

There are no fault codes. I will pull the plugs out and take a look.

If you have a plug in scanner that can display live data, watching the coolant temp can tell you when temps start rising, before gauge will move off the 9:00 position. So while testing you don't need to let it go to 240 F, you can stop at 210, etc.

You may be having a loss of coolant while underway, but not at idle. A coolant pressure test (pump up to 20 PSI) will show where a leak is, or if system is holding pressure. Borrow this tool from auto parts store.

You may be leaking into the oil, this kind of quantity should make oil level increase on stick, even if you can't see the milky stuff yet.

You could be leaking from heater core onto carpet on other side.

It may not be air that you keep having, it may be exhaust (combustion gas in coolant) - there is a $50 test kit that tests the coolant for that gas being present, can make maybe 16 tests. With that present head gasket is certainly in the future, but possibility of cracked head or block.

Here's a cooling layout for a D2, note that hot water is always in the heater core, no valve. If you are dropping enough coolant to turn off the heat that is a good quantity. Might want to do an oil drain to confirm no milky streaks or green coolant droplets. Note that I said drain, if it is not milky and is fairly new oil, it can be poured right back in after inspection.

But you could just have a loose hose clamp, like under the coolant bottle.

Some mechanics put a dye in the coolant, run truck, and then examine the spark plugs for any green flecks. HG leaks are most common at front and rear cylinders.