Heater
Hi everyone. I'm having an issue with my 2001 disco II. My heat tends to fluctuate hot and cold while driving. Mostly stays hot while moving and cools when stopped. I know this sounds like a thermostat issue however my engine temp needle stays in the middle and doesn't fluctuate up and down. Any help would be appreciated as its starting to get cold out. Thanks in advance!!

 

I'm so glad you asked.

1. The D2 stat has a "regular" valve that opens starting at 180 F, and is fully open at 204 F. To do that, it samples hot coolant through four sampling holes in the top end of the stat. That coolant flow heats up the stat so it will open.

2. When stat is "closed" (below 180F) a bypass valve inside the same housing cuts off the main coolant flow at idle, when the water pump pressure is low. This opens when pump speed is increased.

3. Coolant moves through the heater core whenever the engine is on. See attached flow chart. Heater core could be restricted, so that you don't get enough flow in idle conditions. You can remove hoses and flush both ways with a garden hose. If you use or used Dexcool, could be the orange sludge. Pix of sludge.

4. If your coolant level is low, or your thermostat thinks it is too cold to open the main part of the stat, there will be reduced flow at idle. If the metering holes are full of trash the flow to warm up the stat can be impacted. Pix of stat.

5. The gauge is not a "real" analog gauge. It gets a computer generated signal from the ECU, which tells it to point at 9:00 for a very wide range of temps. You can see exactly what temp you are getting by using a data reading scanner or an Ultra Gauge. Pix of Ultra Gauge on the ultra high MPG test truck belonging to Spike.

6. If replacing stat go with an oem, worth the difference.

7. IMHO the design allows engine to get too warm, I'd like to see those four metering holes increased in size or number, so hot coolant could make stat operate sooner.

 

thank you savannah for the quick response. i looked at my coolant level earlier and looked to be okay however i think it may have been color staining on the plastic. i added some coolant and water and things seem better. will keep an eye on it over the next couple of days. thanks again, BK

 

Loss of coolant, and bubble noises under dash can be indicators of worse things. On leak place that fools some owners is the clamp ion the bottom side of the coolant container.

 

thanks for the hint. i will check there today. At first i didnt think it was low coolant because on another vehicle i had air in the system and I "did" hear the sloshing noise. thanks again.