Reply #8: Time for a compression check [View All]

[The Traveler]

Easy to do yourself if you have the guage, a quick job for your local mechanic. If the block is cracked or the head gasket blown, you should see a real loss of compression. The fact you have good non-idle performance seems to contraindicate that.

Hmmm .... theory: Your water pump may be dying.
If you have access to a stethoscope, listen to your water pump while idling. If you are losing coolant, and having noise at low RPM, then you might have some pump bearings that are getting ready to die. They are binding at low RPM but free up as you apply power. If this is the case, the pump is almost certainly leaking a bit ... there is a drain hole on the underside. Check around there for signs of moisture.

Check your water for signs of oil seeping into the coolant. Check your oil for signs of coolant seeping into the oil. That would take you back to the cracked block/blown gasket theory.