I just had an interesting thought for a scenario. I recently changed the oil on my 02 MCS. I'm thinking after I topped off the oil that I didn't close the cap tight enough. This would allow air and pressure to build up within the engine because it was not sealed enough. Would this then in turn make the engine warmer which would then suck more coolant into the engine to help it from overheating? I was just wondering if this could be a connection because I recently saw this happen with my MCS. I'm a newbie so someone please correct me if I'm wrong...

Thanks!

 

There's already a mechanism for venting excess pressure from under the valve cover (the PCV system). Leaving the oil filler cap loose would just provide another way for pressurized air to leave the valve cover, so I don't really think the engine would notice the difference.

Also, I'm not sure what you mean by "sucking more coolant into the engine". Once the engine is up to operating temperature and the thermostat is fully-open, there's nothing you can do to vary the amount of coolant flow - it's totally dependent on the speed of the water pump, which is turned by the supercharger shaft, and therefore proportional to engine RPM.

 

Ah I see what you mean. I guess I was just looking for excuses for why the coolant in my resevoir tank was bone try after the oil change. It could be just coincidence, but I'm not sure...