98 sierra oil leak
 

98 5.7 has oil leak somewhere in the front left of truck (drivers side). Thought it was oil cooler lines, changed those but oil leaks from somewhere else. Help

Hmm. My 98 HAD a mysterious oil leak similar to the one you're referring to.

I was leaking 6 drops of Tranny fluid and 2 drops of engine a night. I had the transmission flushed and a new pan put on, but they didn't replace the gasket so they both continued to leak. I took it back to the dealer a bit PO'd at GM for not replacing the gasket and saying it was reusable, so they promptly changed my engine oil. WTF??? I went to pick it up and they said "oops, wrong truck, we'll get on that". (I literally had just changed the oil 200 miles ago) Well, they fixed the transmission, and for some reason, the engine oil leak went away... I can't explain it, but I'm wondering if it wasn't the fact that they put Mobil 1 synthetic in... I'm too cheap to go with anything more expensive than Quaker state if I'm paying. I don't know. I won't complain, but I have been known to speculate.

Also, magically, after the second time they filled the tranny with fluid, the clunk I'd been getting while going into overdrive magically disappeared. I'm wondering if the new fluid didn't relublicate it or something???

So basically, for some strange unexplained reason, I attempted to fix one problem, failed, tried again, and fixed three. I've not helped you on this subject one bit, but you could try putting Mobil 1 synthetic in your engine..?

Front left has to be oil cooler or possibly valve cover. Look to see if it is running from somehwere else. Could it be power steering fluid? An oil leak in the front of the motor is almost always the oil cooler, nothing else up there has engine oil in it.