Losing Coolant over time

My 1994, automatic, 1.0 L, 120,000 mile Geo has consistently had a coolant issue.:frown:

The reserve tank remains full (it appears the system is not sucking fluid out when it is needed) and I have to refill the radiator itself at least once every two weeks. When I do it takes a probably a quart to do so.

There are no signs of a leak on the ground or on the bottom side of the engine, radiator, or compartment.

Oh yeah, the water pump WAS replaced less than 7 months ago due to a leak and hasn't had problems since.

Check the back of the water pump where the coolant tube enters the block. Take the car for a drive, get it to operating temp and let it sit and idle while you look around the engine for any illusive leaks.

Check the radiator along the top and bottom where the core meets the plastic tanks. Your radiator cap may be bad, depressurising the system into the overflow and then spilling it out of the overflow tank on the road.

Remove and inspect your spark plugs for heavy deposits white to brown in color.

-MechanicMatt

Thanks Mechanic Matt. I'll do all of that tomorrow. If there are deposits of that type on the spark plugs, what does it indicate is happening?

If there are deposits of that type on the spark plugs, what does it indicate is happening?

It indicates that coolant is somehow leaking into the combustion chamber(s) and being burned, along with the fuel in 1 or more of the cyliners. The cause of this is most likely a blown head gasket or warped head. a light tan color on the spark plug electrode means a normal burning spark plug. Heavy buildup or deposits as Matt said is most likely from coolant being burned in a cylinder or more than 1 cylinder. Do you see any signs of white smoke from the tail pipe after the car is fully warmed up on a warm day?

OK, did everything except the radiator cap (how do I tell if it's the problem?)... on that note, I don't see any evidence of the reserve tank overflowing, either from the lid or the hose that hangs down from the tank... though I guess it's possible...

No leaks that I can see anywhere, neither on the water pump or surrounding area OR on the radiator, top, bottom, or hoses. Nothing near the thermostat either.

Spark plugs - right to left looking into the engine compartment...

Right - thinish (not at all heavy) white residue
Center - same but not as much
Left - same but not as much

Regarding smoke from the exahust - NONE at all...

replace cap and check the line from the radiator to the overflow tank and make sure no holes and tight on both ends and make sure the hose going to radiator is hooked to the part that goes all the way to the bottom of overflow tank

...make sure the hose going to radiator is hooked to the part that goes all the way to the bottom of overflow tank

!

-MechanicMatt

Lines from the radiator to the reserve tank were in the right places... BUT the one going to the bottom on the in side was full of some kind of gray gunk. I cleaned it out, so we'll see if it starts pulling from there as needed.

The radiator cap is on order...