Coolant problem

[Keira's Dad]

My 94 Chev Cavalier is having problems . . . It's been snowing the past few days and my heater has been blowing out cold air. I noticed that the coolant was low so topped it up and I now have heat again.

I have gone through half a jug of coolant in a week - there is no leak I can see and it would show in the snow.

The temp gauge shows that the thermostat is working as it rises to halfway and falls again. I touched the rad cap this morning and it was stone cold.

I think I have had this problem with this car in the past and believe that rad sealant worked but the problem has resurfaced since a rad flush two weeks ago.

So I am leaking coolant but the thermostat is okay and the engine is not overheating but the rad is cold . . . what's the problem?

[formula1]

You have a coolant leak, that is pretty apparent. Coolant can leak from many places, not just the radiator or thermostat housing. There are the upper and lower radiator hoses, hoses to and from the heater core, the heater core itself, possible bypass hoses/pipes on the engine, water pump, manifold gaskets, and head gaskets to name a few possibilities.

One way to check for leaks is to fill the system full, put the rad cap on, and run the engine till the temp comes up and the system pressurizes. You will be able to feel this by the upper radiator hose getting hot as well as taught from being pressurized. Then shut the engine off and start looking for external leaks all around the engine. There is a manual pump-up kit that can be had to test cooling systems as well. One possible leak that will be hard for you to see will be the coolant pump. There is usually a weep hole on the bottom of the pump shaft/bearing housing that if any leakage is present indicates the need for replacement. On my son's Cav, we didn't see his leak until we pulled the plastic shroud away from the pump, then it was obvious.