I have a 2000 Disco II with about 170,000. The heat blows cold at idle, but when I rev the engine, it warms up. The engine never overheats but I do hear a gurgling sound from under the passenger dash. Any ideas? I tried bleeding the coolant from the valve on the top hose, but that didn't help any.
Thanks

 

Air in the heater core, you just need to bleed and top off. It can be a b!tch of a system to bleed, but with normal driving the air should accumulate in the ET and then you just top off as needed... How long have you had this truck and how long has this issue been going on? There are a few schools of thought on the proper way to bleed the system and none are really foolproof. I'd offer advice, but the first thing I do with any D2 I get nowadays is modify the factory plumbing! A search on how to bleed the cooling system should yield hours of reading material... LOL

 

You also need to ensure the heater is on full heat, maximum, to ensure the thermo valves are open when bleeding the system.

 

Gurgle is air in heater core, needs to leave.

If you base "truck does not overheat" on the gauge, you are walking down a false path. The gauge is programmed to point at 50% until engine is really overheated. Like it stays at 50% from about 140 - 240F. Use a scanner to be sure.

A new thermostat may be in order, the Land Rover (not motobad brand) 180 soft spring is a good choice. It drops temps across the board, and the soft spring makes it more responsive at idle for letting water into the heater core. The bypass spring is normally strong enough to not open at slow idle. Yours may be sticking completely. Your thermostat metering disk (has holes in it) could be clogged, so no coolant flow to heater except when main stat opens. The bypass disk normally passes some hot coolant. The soft spring lets it slide down for more coolant flow. When the main stat opens, it slams the bypass disk shut.

 

Thanks for the responses. I'm gonna try bleeding it out again. I'm familiar with the gauge not reading correctly, but the engine is truly not overheating. I had an older disco that overheated. I wound up replacing pretty much the entire cooling system- radiator, water pump, thermostat, electric fans and even the overflow reservoir. Just wasn't sure about the gurgling sound issue. Wish me luck!

 

as long as you hear gurgling you have air.