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Can antifreeze leak from your catalytic converter?

I have a 93 ford taurus 3.8L V6 automatic GL. I had my car up on ramps the other day to change my oil and filter when I saw drips of antifreeze coming from the bottom of my catalytic converter. I knew before that I had a antifreeze leak because my coolant reservoir has to be refilled completely ever couple of weeks. I could not find where the leak was starting. I inspected my radiator, all hoses, coolant reservoir and water pump. They were all leak free. I thought it was possible the leak may be coming from my heater core or maybe a freeze plug. Can antifreeze leak from your catalytic converter and if so is this a sign of a leaking head gasket?

It’s going to be hard to say where the coolant leak is. It could be leaking from anywhere on the engine or a hose up on the engine. This can cause the coolant to run down the exhaust manifold/pipe to the lowest point which is the catalytic converter and drip off.

The quickest way to find this leak is to introduce a tracer dye into the coolant. And then after driving the vehicle for a while, put it on a lift, and then use a UV lamp to trace the dye back to where the coolant is leaking from.


Can antifreeze leak from your catalytic converter and if so is this a sign of a leaking head gasket?

I suppose that it probably could somehow. But it’s not something that you run into every day. Or even once in a lifetime. It’d require coolant getting into the cylinders, being pushed through the valves, condensing in the catalytic converter then leaking through a hole in the catalytic converter that probably shouldn’t be there. It’s far more likely that the coolant is leaking down the outside of something, dripping onto the catalytic converter and then dripping off the bottom.

The most likely sources of a leak would be a hose, the temperature sensor, the thermostat, the water pump, or, just possibly a cracked head gasket that is leaking coolant to the outside world. Radiator leaks are common also, but where’s the path from the radiator to the catalytic converter? The good news – it’s probably not the heater core.

I’d start off by examining the ends of every coolant hose I can see. If you don’t see leaking coolant there, examine the hoses, sensors, thermostat housing, etc.

If you have a tool for pressure testing the cooling system you might hook it up and pressurize the system. If you are lucky, coolant will squirt out where previously it had been seeping. Otherwise tracer dye will probably work.

If you have a blown head gasket, yes, the fluid might leak from your gasket onto a cool exhaust and you might find dripping fluid that has traveled from a blown head gasket by way of path of least resistance to your catalytic converter, so that it drips when your car is cold but always steams away coolant while you are driving.
I guess the best thing I can tell you is that, unlike many cars, your problem cannot be maintained. You need to fix the leak right away or give up on the car. This engine cannot withstand even moderate overheating. The head gaskets go if the engine is overheated. Other than that, the coolant system is difficult to flush, and it requires a long time to flush the system completely. A Jiffy Lube version for ten minutes is not going to do it.

I would think that if an intake or head gasket was leaking coolant into the combustion chambers badly enough to cause coolant to drip out of the converters that you would see a healthy cloud of white smoke out the tailpipe.

Coolant into the combustion chambers can also bleach the tips of the spark plugs and give them an abnormal color.

External leakage from a head gasket or even a block plug leaking are possibilities.

Antifreeze leaks can be tough to see. It really will not be out of your exhaugst until it is way too late. That said these engines are famous for head leaks. Due to pressure it is more likely that the AF goes into oil. Remember that water flows down hill and that water can be blown by wind. The best time to look for a leak is right after you turn off the car. Also look at the area of the water pump as you may have a leak(normal) on the shaft bearing that get put on to the engine belts and flung around the engine on the passenger side when the belts are running. You might consider an inexpensive sealant product, if the shaft seal is leaking it will not help much. On the other hand it could stop the leak before you spend time and money chaseing the bad boy down.