Tom's Corner Garage: Coolant Leaks - Avoid Excessive Repair Bills
This weekly feature for Edmunds Daily about car repair and maintenance is written by Tom Torbjornsen, the popular host of America's Car Show on satellite radio.
Dear Tom,
I own a full size 1996 GMC conversion van. I have to add antifreeze at least once a month but I never see any antifreeze on the driveway. Do you have any idea where it's going?
John from Batavia, NY
John writes in with a commonly asked question over the years. Based on the fact that John doesn't see any coolant on the ground, he should have someone perform a cylinder leak down test on the engine. These signs point to a potential head gasket leak.
It's worth a closer inspection because an internal coolant leak is one of the repairs where customers frequently pay for unnecessary parts and labor. Why does this happen? Repair shops tend to assume a course of action before performing proper diagnostic tests. Needlessly replacing parts can cost big bucks when it comes to engine repair.
How do you check for a coolant leak?
There are a few tests you can run to diagnose a coolant leak. Namely a pressure test, a dye test, and (in the case of John's vehicle) a cylinder leak down test. During a cooling system pressure test, you apply air pressure to the cooling system at the mouth of the radiator to try and force a leak at the weakest point in the system. Then you inspect the hose and cooling system components for external leaks. With the dye test, you add a fluorescent dye to the radiator, run the engine, and then shine an ultraviolet light on the system in an effort to find the leak.
If you find no leak at this point, what should you do next?
In John's case, the van has an internal leak in the engine. It's probably due to a blown head gasket or a cracked or warped cylinder head. Proper diagnostics are necessary to confirm these suspicions before embarking on a quest to repair the leak. When a head gasket starts to go bad, the water can leak into the combustion chamber and exit out the tail pipe without leaving any coolant on the ground. This would account for coolant loss without a visible leak. In extreme cases a cracked engine block can cause an internal leak.
Is there a way to stop an internal leak without major work?
No. Either the head gasket material is gone or the metal is cracked / warped. There are companies out there that claim they have developed chemical additives that stop coolant leaks. These companies prey on consumer ignorance and their desire to avoid a major repair bill. These products may provide a temporary fix, but the real problem still needs to be addressed- the engine has lost its internal sealing ability. Mating and sealing surfaces must be restored to stop the internal coolant leak. Major repair is required, period.
'Til next time...Keep Rollin'
- Posted by
- Ron Montoya October 7, 2009, 11:00 AM
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- Car Maintenance
I had a coolant leak like that. There was never any coolant on the ground and the oil was clean not milky. Yet I was loosing a litre of coolant a week.
I found it running the truck fast on the hwy at night, pulling into a parking lot and with the engine off shining a powerful flashlight at the rad. I could easily see a fine mist of steam coming from a pin hole in the rad.
It disappeared as soon as the pressure dropped a bit.
A rad shop fixed it for a small charge.
Sometimes there are happy endings.