Sorry, 1998 GMC 2500 4x4, Suburban; no mods. Will try for a pic tomorrow but the plug in the hose appears to be a “tighten only” style fitting. It reminds me of a lot of the fasteners used to hold restroom stall panels together. ones that can only be turned clockwise.
The radiator drain on my 98 is on the lower drivers side, facing in the engine compartment. It is the stock plastic petcock valve. No tools needed. Just grab the finger tab on petcock and turn it open or shut. Mine is finger tight. You can unscrew the valve assembly all the way out if you want. The drain outlet body on the radiator is threaded on the inside.
Maybe someone broke the valve and replaced it with a threaded fitting, tube, and plug on your truck.
OK, here’s a pic from my iPad so you may have to zoom in. (This is no longer a major priority as I finally found a set of pliers that could pull off the spring clamp on the lower pax side hose.) I would like to get a proper peacock put in as it was a mess draining by just pulling the hose off.
Turns out the heater core was clogged. After initial draining, I drove around for a couple of days with two bottles of Prestone coolant system flush w/clear water in the system. Then undid both the front and rear heater hoses at the firewall and blew them out in the opposite of normal water flow direction; refilled with clean water, drove more and then final drain. I used a water hose and compressed air to blow everything out before final
filling with fresh antifreeze and H2O. Presto, HEAT!
I have the same on my '97 3500HD 6.5L. It looks like some kind one-way "tighten only" fitting, and at first I thought the petcock was broken. After getting a close front-on look with my phone camera, I was able to use a 3/16" allen wrench to insert and give it a 1/4 turn CCW to open. There's a port immediate below the valve that you can use some tubing to connect and drain cleanly into a 5 gallon bucket. Good Luck!
Thanks Blahey, appreciate the info. I drained it the hard way by finally finding the “right” channel locks to fit into the restricted area on the lower right and get the spring clamp off The 2”(?) hose. Fortunately a couple of well placed drain pans caught most of the old coolant for disposal; reverse flushing with air and water through the two (front and rear) heater hoses up top cleared the clogging material and old coolant (with Prestone flush). I replaced the factory spring clamp with a screw type band clamp.
Now Alaska driving is not the challenge it was for the first half of this winter!
This rig is a great vehicle with two row seating and a huge cargo (and winter survival gear) area. I am impressed with GMC‘s construction/materials as it has no underbody rust after now 23 years, all of which look to have been in northern climate areas.
Thanks for this forum and to all who responded. Let’s keep the brotherhood of diesel trucks rolling along!
A forum community dedicated to Chevrolet and GMC diesel truck owners and enthusiasts. Come join the discussion about duramax engines, performance, builds, modifications, classifieds, troubleshooting, maintenance, and more!