A couple weeks ago I replaced the timing belt, tensioner, water pump, thermostat, etc., and cured a water leak down the front of the motor. I suspected the water pump. Anyway, looking good, feeling good, no more leak or so I thought.

Well, after driving in the Texas heat, the motor was still losing coolant and overheating. Upon shutting the car down, the engine would heat-soak, build pressure, and start puking coolant, this time from the rear of the motor... WTF.

I modified a differential cylinder leak down tester to pressurize the cooling system and hopefully find the leak. FOUND IT!

Even though I replaced the coolant overflow/expansion tank, it had a pinhole in it that shot a steady stream of coolant while under pressure. The previous tank had a lot of cracks and leaked as well. I replaced the tank (again) and NO MORE LEAK!

Moral of the story... if you have a phantom water leak, and if you live where it gets really hot, inspect the coolant overflow/expansion tank for any cracks or pinholes.

Hopefully this post will save someone some grief...

By the way, I purchased my parts from Autohaus, and they sent me a replacement tank and refunded the price of the defective one once I sent it back. Good people.

 

I modified a differential cylinder leak down tester to pressurize the cooling system and hopefully find the leak. FOUND IT!
ingenious 10/10