Unusually Coolant Leak

[AJ Frontier]

I have a 2001 Nissan Frontier 4x4 108000mi and have had a very unusually coolant leak. It only leaks after the engine has shut off - but not everytime. It appears that the coolant is coming from the weep hole at the water pump (not 100% on this). I realize that if coolant is coming from the weep hole then a seal has failed, but what I don't understand is why it isn't consistent?

A few weeks back I had a new radiator put in becuase I was having over heating issues. Once the new radiator was in the over heating disappeared. Then two weeks later I suddenly have a huge coolant leak. Would there be any connection here?

I also replaced the radiator cap (the old one was faulty) in hopes that would fix the problem, but not sure if it has yet. As of this morning I have had no leaking.

The Water Pump was replaced at 90,000 miles when I had the timing belt replaced so it seems like a failed seal is unlikely unless the radiator replacement would somehow cause a seal to fail.

Anyone have any thoughts on this? I really don't want to replace a water pump and if anyone knows of any other things that would cause coolant to leak only after the engine is shut off I would greatly appreciate it.

Thanks
Happy Trails

 

[Turtle]

I hate to say it, but that sounds exactly like a water pump gone bad. Had the identical scenario that happened on a '97 Jeep that I had. I'd shut the engine off and the coolent would start leaking out the weep hole. Replaced the water pump and issues all gone. Can't say why yours is doing it with so few miles on the last replacement though.

 

[08whitex]

Sounds like a water pump to me. Since you replaced a faulty cap your system is now building pressure. That pressure is now going to find the bad seals.

 

[off.track]

either the water pump or the notorious by-pass hose.

 

[Strizzo]

your coolant temp actually peaks about 15 minutes after you shut down as the heat in the block continues to transfer into the coolant, but the coolant is no longer moving. this could be why the pump only leaks after shutdown. it will keep getting worse until it leaks out the weep hole all the time. where was the replacement water pump bought from? a lot of the aftermarket rebuilt pumps have a tendency to be bad out of the box.

 

[Bogo]

your coolant temp actually peaks about 15 minutes after you shut down as the heat in the block continues to transfer into the coolant, but the coolant is no longer moving. this could be why the pump only leaks after shutdown. it will keep getting worse until it leaks out the weep hole all the time. where was the replacement water pump bought from? a lot of the aftermarket rebuilt pumps have a tendency to be bad out of the box.

Yep, yep, and yep. Unfortunately way to true. No name aftermarkets are the worst.