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Old 09-06-2019, 11:52 AM   #4
shifty's Avatar
Join Date: Mar 2005
Location: Atlanta
Posts: 13,241
Re: 1998 5.7L Sierra SLE, 91k miles, TONS of xtras, loaded w/leather

Originally Posted by pitterpat View Post
Any pics of cowl and leaking area?
No pics b/c I don't know where it is. But here's what I can tell you:

This past weekend when I replaced the driver's exterior door handle, I did a crapload of testing. with the cowl plastics off.

I setup a waterhose full blast physically inside the cowl so the water was rushing over every seam of the air intake box. Ran it for 5 minutes. No leaks.

Then I took the water hose out. I ran it across the flat area around the hood hinge. Nothing after 5 minutes.

Pulled the coolant overflow (replaced with NOS one) and hit the entire area behind it, nothing.

I ran it on the firewall, found a leak where the A/C and blower motor wiring bulkhead hits the firewall - but that's a spot water isn't even supposed to really be. Still, I added a new foam gasket seal similar to OEM.

Then I took and ran water below the windshield seal around the two cowl screws everyone complains about leaking down into the box. Sure enough, within 2-3 minutes I started seeing a slow drip, about 1 drop every 45 seconds or so. But I checked, it wasn't leaking from the screw holes and down into the air intake box like everyone else explains. So there's something going on above/around the cowl that's letting water drip down onto the interior firewall. I'm almost positive it's more cracked seam sealer. Really, the entire cowl needs to be re-seam-sealed. The seam sealer GM used cracks to hell pretty quick.

I reckon the only way anyone would ever find the leak is if they removed the dash - which needs replacement anyway - and tested with the dash off, traced the water back.

EDIT: And I'm sorry for the late reply, life's been a little nuts this week getting the truck ready to list. Did a lot of work on it, including replacing the oil pressure sending unit, replacing the coolant overflow jug, new exterior door handle, new driver side interior door handle and reinstalling the interior.

Planning on washing it up, taking pics and listing on eBay at a 3400 start price, $5700 BIN. Still willing to sell here though if anyone is interested. I'll post back here if it sells over there.
I randomly sell stuff at stupid prices:

Here's $300+ stuff for $125 || huge early-mid 2000s truck magazine stash

I'm probably still around even if not posting. Drop me a PM! I'm (hopefully) still alive.

Last edited by shifty; 09-06-2019 at 12:02 PM.
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