Can't find the coolant leak??

[Jimmy85]

So I have a small coolant leak that I can't seem to pin point. I can trace where its drips from, but able to find the source of the leak. (Or I'm in denial of where it's coming from). I can follow the water drool back to the motor mount, but loose it from there. I also get drops on the drag link. I feel around the water pump neck, radiator hose, and other hoses, but they are all dry. Can a freeze plug have a slow leak?? I've seen corroded freeze plugs, but they leaked like a sieve. The other plugs I see are okay. This leak has been present for a while, but the tahoe is rarely driven.
I wipe of the drops and coolant line, lay under the truck while its running and I see nothing leaking. I only find drops of coolant after diving. Guessing that's pressure related?
It's a 5.7 99 tahoe.

 

[Bent77]

Yes, freeze plugs can leak

What’s that booger spot in the first picture about an inch ahead of the starter nose?

 

[Jimmy85]

But I’ve never heard of a slow leak from a freeze plug?
I believe that to be an oil pressure sensor.

 

[RaisedK5]

That sensor should be a knock sensor and it goes into the water jacket. Might wanna check that.

 

[Bent77]

But I’ve never heard of a slow leak from a freeze plug?
I believe that to be an oil pressure sensor.

This here



And also pay attention to what @RaisedK5 said. It is the knock sensor, threaded into the water jacket

 

[Fastereddie]

Yes, freeze plugs can leak

What’s that booger spot in the first picture about an inch ahead of the starter nose?

Looks like head gasket to me

 

[Jimmy85]

That rusty spot is an empty bolt hole. I believe in the block. But nothing is coming from that hole. At least not when I’m laying underneath.
I’ll be looking again tomorrow. I don’t know which would be worse, freeze plug under the motor mount or a head gasket.

 

[max 02]

Pressure test?

 

[Wes Harden]

Head gasket is definitely worse.
Motor mount isn't that tuff. Only a little bit of swearing, and no tool throwing.

 

[swettysblazer]

Get a pressure tester and test it while it's cold and everything is contracted. If you're looking for it with the truck running most likely with it being so small when it heats up it seals the leak.

 

[Jimmy85]

Pressure tester it is. No more of this hoping to spot the leak.

 

[Jimmy85]

Well the pressure test wasn't that smooth as I couldn't get a good seal at the radiator neck. I borrowed a kit from a friend. But I was still able to find the culprit. Head gasket. Yay....

 

[max 02]

At least you know now.

 

[Jimmy85]

Sometimes in life a guy gets lucky! After digging in I found some moisture at the intake. I was able to get the gaskets changed in a big day. And after 3 days of driving I'm happy to report that my minor leak is fixed!

 

[Jimmy85]

Figured I'd show her off since I also found a better grill and new lamps.