Join Date: Feb 2013
Location: Near London
Vehicle: 1997 SLK 230 (In H352 Linarite blue)
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1997 R170 low/no heat at idle
Of course I usually drive my SLK on nice sunny days with the top down but this morning even though we had a very heavy frost) and because I have my annual MOT coming up I thought I would take her for a spin. A quick blast to blow some cobwebs away and give her a bit of an Italian tune up! I don’t want to fail that wretched emissions test again for a high LAMBDA value through lack of use…
Cruising down the motorway the heating is fine but whenever stationary in traffic the heat falls away quickly and is soon barely warmer than the outside temperature. I have searched this and haven’t found anyone reporting it on an SLK but quite a few occurrences on other models – especially those with an electric pump in the system mounted by the Duovalve.
Anyone had (and fixed!) this or similar issue?
I fitted a new thermostat about two years ago as the original was stuck open and the engine was taking forever to warm up and giving rubbish fuel economy. It now heats up quickly and the temp gauge is stable at just over 80 degrees. My current thoughts are:
• There is still air in system somewhere from when I changed the stat. Seems unlikely given the water level is stable and the engine doesn’t under heat in winter or overheat in summer and the heating works well at faster engine speeds.
• The duo valve is causing some impediment to coolant flow at tick over. I guess this is the first and easiest thing to check but it seems to affect both passenger and driver sides equally. Also at tick over all hoses into and out of the Duovalve are hot and feel to be about the same temp.
• There’s some sort of partial blockage in the heater coolant circuit somewhere.
• The water pump just isn’t working as well as it should be.
Does anyone have any other suggestions – they would be gratefully received.
Cheers to all