Hello,
Wonder if anyone could help me out. I was leaking engine coolant from my Discovery and it would begin overheating. I switched the temperature controls to high heat, and the overheating stopped as well as the leaking. Any ideas about what could be wrong? Thanks

 

Well, you came to the right place, despair and repair under the same shade tree.

1. If you have a Discovery 2, the coolant alway is flowing in the heater core. Turning on the fan to high pulls some heat away from that. So the overheating backed down a notch, and the temp dropped just enough to lower the pressure and slow the leak.

2. "begins overheating" means different things to different observers. If you mean that the red warning light came on, and gauge went way past 50% on the scale, yep, serious overheating. Sometimes just once can warp heads, cause a cylinder liner to begin slipping forever, head gaskets to fail, etc. The gauge is programmed to point at 50% from about 140F to 240F. So you don't see it slowly get hotter each day as your coolant loss increases. A scanner or Ultra Gauge can give you a more exact picture.

3. Your overheating IMHO has not stopped, it has just backed off a little by running the heater. A scanner would show this. If your electric fan is operational under the hood, it should come on a 212F. That is one signal that things are warming up, however lack of that operation can also be siezed front electric fan, blown fuse, etc.

4. You may have had a sound under dash like water rushing thru pipes. That is bubbles in the coolant. Might be air (from the leak) or might be exhaust gas from bad head gasket. Bubbles need to be purged from system (the bleeder valve on the "T") and coolant should be at proper level. A big cushion of air inside the cooling system allows engine to overheat. A steam pocket can also place the heat sensor out of contact with the hot coolant, yielding a lower than expected gauge reading.

5. If you have full coolant system, and a radiator that is not blocked with mud on the outside and sludge on the inside, and your radiator main fan is working; idle temps can be expected between 190F and 205F. Low coolant pushes that higher, and quick.

6. One way to test for coolant leaks is to rent/borrow a pressure tester, and pump system up to 15-18 PSI. Leave for 30 minutes. Leaks should be come obvious. Don't go above 18 PSI, which is the vent pressure for the coolant cap. The coolant cap can also be venting at a lower than spec pressure, allowing coolant loss while driving, just not noticed so much when parked.

7. The plumbing chart is attached. Any clamp or gasket can be suspect for a leak.

8. If you are loosing coolant you need to fix the leak. It will always leak faster than you planned. Some carry spare water in their truck just in case. Don't drive when overheated or near overheat.

9. If coolant is full, and bled and overheat continues, could be radiator (check top to bottom on fins, more than 10F change = sludge inside usually); could be viscous fan clutch (at idle or slow speed, very little impact at 50 mph); and a host of other annoying minor issues. And of course the major issues like head gaskets and cracked block.

 

Thanks so much for thew information. That is a great help. Appreciate it. Thanks again...

 

Try not to drive it till you find/repair the problem so you don't do any more damage to the engine.