Auto Repair Q&A



Cooling System










Auto Repair Products

Finding, Fixing Coolant Leaks


Coolant leaks are sometimes a real problem and, if the coolant is leaking into the environment (on the ground), they can be a serious violation. Most of the time, finding a coolant leak is as simple as locating the drip and tracing it to the leak point - usually a seal or loose cap. Other times, it's not so easy.

Other signs of a coolant leak are a low coolant indicator lamp, engine light, low fluid levels found on a routine check, white-colored exhaust smoke ("fog"), or a hot coolant smell in the cabin or engine compartment. Some coolant leaks are so small that the fluid boils off (evaporates) before dripping to the ground. Others are internal and not easily spotted because they may not (yet) be big enough to affect the exhaust noticeably.

Common Leak Points

Coolant most commonly leaks from those areas where seals and equipment the most vulnerable to breakdown. The seal around the water pump is one of those, as are corroded radiator fittings. Loose-fit or punctured hoses are another common leak point. Finally, the heater core for the cabin's heat is a common culprit in leaks.

Less common, but still possible leak points are the intake manifold gasket, which can deteriorate and begin allowing coolant to enter the engine. Freeze plugs can also corrode from the inside out, eventually causing a leak of coolant out of the block. Bad head gaskets, of course, cause coolant to mix with the fuel:air mix and is the most common cause of "white smoke" from exhaust. Not as common, but similarly, cracked head blocks do the same.

Testing for Leaks

Coolant leaks can be tested for using a pressure test. When the leak is not easy to find, but you know there is one (missing coolant, low fluid levels), a pressure test at least confirms the leak. Often it can point out where it might be as well.

A pressure test of the radiator finds leaks in the radiator itself, if there are any. You can also pressure test the radiator cap (recommended). Finally, you can pressure test the entire engine block's coolant circulation system - also recommended. Confirm a head gasket leak with block check fluid or leak detection dye.

Fixes for Common Leaks

Leaks at common points such as hoses, fittings, etc. are obvious fixes. Replace the leaking part. A radiator with leaks should usually just be replaced with a new or recored radiator. This is usually more sure and simpler than attempting to repair the leak itself. Same with bad radiator caps, leaking coolant reservoirs, etc.

Finally, leaking gaskets usually mean a lot of tear down to replace, but it must be done. Many service points can e covered during these disassembly/reassembly procedures as a preventative measure or as early maintenance interval work. For example, replacing the water pump seal may be close enough to the interval to replace the timing belt as well. Draining the radiator to replace hoses is another point at which perhaps a radiator flush and fluid replacement is a good option. Perhaps a replacement of head gaskets could include a new timing belt, new valve fittings, etc.