Installed an ebay header Friday night. After install, I drove around the block, parked into garage and noticed drips in driveway. I opened the hood and discovered the leak (see pics). I took off the radiator cap while the engine was running and the coolant was bubbling/going out.

What could I have done to cause this?

Observations and items to disclose:
1. Immediately after the exhaust manifold was taken off (with quite a bit of pulling and grunts), I went under the car to squeeze the ebay header up from underneath for installation. That's when I noticed a few drips of coolant. I dismissed and thought nothing of it.
2. I have to say that I am temporarily pulling the exhaust system towards the front to hookup the pipe to the header (need a longer test pipe). Could the tugging pressure to the engine be causing the headgasket to leak, causing what I observed with the coolant bubbling? HOWEVER, why did #1 observation happen. Maybe it is just coincidence that the radiator went bad the same time I installed the header?
3. Might as well mention that a performance exhaust system was installed about 3 weeks ago.

Any helpful insight and suggestion would be appreciated.

Thank you in advance gentlemen!

 

Well clearly the leak is from something up top. There's not much up there, Just run the motor and watch for leaks, it should stick out since it's up top. Probably just a bad end of a hose. Replace it, bleed coolant, good to go.

The top of the rad might be cracked too, just keep an eye out and you should find the culprit.

 

Clean up all of that coolant, run the engine and see if you can find the source of the leak.

 

Looks like the plastic top is separating from the core. See that long green line of coolant? This happened to my radiator a few months ago and my wife's last year. Probably coincidence. Replace it.

 

Radiator replaced... Problem gone! I was starting to sweat it, thinking that I'd need to replace the head gasket. Whew!

Thanks for everyone's input!