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Leaking Antifreeze

My 98 chevrolet cavalier is leaking antifreeze overnight. I have replaced the cap and the surge tank, however, it’s still leaking. I have discovered that it only leaks overnight, but not every night. The mechanic has checked the car three times, but can not find the leak. He said that he doesn’t think it’s the head gasket or water pump. It leaks about 1/4 of antifreeze every time that it leaks. I have noticed puddles both on the driver and passenger sides of the front of the car. Any suggestions on what else this could be and the associated costs?

Many thanks in advance for your time and assistance with this matter!

Are you saying 1/4 of the antifreeze in the radiator leaks out at night, and there are puddles of antifreeze on the ground, but no visible leak?

If the antifreeze is leaking from the cooling system, and puddling on the ground, there should be a visible sign of leakage.

How do you know the coolant isn’t being lost as you drive?

Yes to your first question. I don’t know for sure that it’s not leaking when driving, except that I am constantly checking the antifreeze level iteself (where you fill up the antifreeze) and it does not appear to go down. It’s puzzling as to why the leak can not be found. Do you have any ideas as to what this could be?

You need to check the ACTUAL level in the radiator, as the reservoir bottle can b e inaccurate for many reason…Remove cap from Radiator only when engine is cold. If you have a leak on both sides of front of car there will be evidence of the source. Start at the top of the engine and work down. it could be in the plastic tank, hoses connections fittings plain old corrosion or holes. This should not be hard to find.

Thank you very much for your help!

How many miles on your Cavalier? Do you check the level in the radiator itself, or in the surge tank?

Losing 1/4 of the coolant each day is a pretty substantial leak. Have you tried opening the hood after turning off the engine and watching to see what happens?

If you’re getting puddles on the floor it has to be dripping from somewhere, and if you watch and look around under the car you should be able to see where the drips are falling from.

This should provide a clue as to what’s leaking. You could also look around under the car while the engine is running. I think the leak is constant, and that coolant is being lost all day, not just at night.

There are tests to determine whether or not a head gasket is leaking. A mechanic should not “think” the head gasket is leaking or not leaking. Test to be sure.

Water pumps have what’s called a “weep hole” and coolant will leak from this hole if the pump seal is bad. Coolant coming from a bad water pump should be visible (at least from under the car) at the end of the engine where the belts and pulleys are.