It is possible for the temperature to affect the fluids but if the foaming and bubbling is excessive, the more likely cause would be air being drawn into the system.
Air can be drawn into system from 2 areas:
1. Supply hose and connections to pump. Ensure the hose and joints are good with no signs of oil seeping out.
2. Pump. When pump show signs of leaking, air can be drawn in via poor sealings, usually hardened sealing O-rings.
Wednesday, January 12th, 2011 AT 4:13 PM