My heating doesn't seem to be working properly, I do a run about 12 mile to work and use the car regularly, its got plenty of antifreeze in and for the last 6 months the heater only gets luke warm. Ive tried running the engine for ages without a the cap on the expansion tank and squeezed the hoses at various intervals to try and burp the system but its not made any difference. Do I need to bleed this off in any way? I also noticed since doing some work underneath the temp gauge doesnt register properly, it stays in the cold position even though I know it should have moved into normal. would this affect the heating matrix in any way?

 

Hex, what you are describing sounds like the thermostat has crapped out on you and it is maintaining the engine too cool. So, instead of the thermostat regulating at say 180F, it is controlling at say 120F. This will cause all the symptoms that you are seeing. It is possible that the thermostat has simply stuck open. I had this same sort of indication when I had my thermostat fail. If you want to prove your thermostat good, you simply have to pull it out and then put it in a pot of water on your stove. PUt a thermometer in the water and allow the water to heat up. you will see the thermostat start to move and that should be roughly the temp on the thermostat. Along those lines, it should be closed when at room temp.

 

Humm not considered the stat, as I could feel heat through the hoses on both sides of the housing. I might just replace it as a given as its probably old anyway, and not expensive or hard to do, would this cause the engine to run cool even after a blast down the motorway? If its stuck open wouldn't the engine heat the water as normal just after a longer time? It takes me about 30 minutes to get to work in traffic jams etc so I would have thought it would warm up to normal temp?

 

Hex, the thermostat simply works as a blockage to the radiator. So, you have a loop of water going from the pump, through the block, back to the pump. But then, you have the thermostat that will take some of the water and force it through the radiator to cool it off and then force that through the engine. So, when the thermostat is functioning properly, the engine is getting a mix of hot engine water and cooler radiator water. If your thermostat sticks open, it will allow an excessive amount of water through the radiator, attempting to cool it off to atmospheric temperature and not recirc any of the engine water. Now, your engine will not cool off that far, but you will find that it will run much colder than it should because you are allowing too much flow through the radiator. With the colder temps for this time of year, it is very possible that the engine will not get up to temp because you have lots of air flow through the radiator due to the car moving down the motorway. In town, you may see it rise some because you are stopping and going. If you were to sit and let the car idle, it is possible that it would get up to temp, but this may take say 15-20 minutes to happen due to the excessive flow through the radiator allowing some heat to escape.