SOLVED: Diagnosing/replacing a leaky radiator + flushing coolant (for the inexperienced GMT400 owner)

[Keeper]

This thread is an oldie but goodie from @Mangonesailor that may have some new fans.

Heater core coolant strainer.

I figured some of you guys may find this to be a decent solution to keeping your heater core free of debris if you've had dex cool in the past or just have scale buildup in your motor. Months ago I replaced my intake manifold gaskets. A month or so after that I satisfied that I had...

www.gmt400.com

 

[slow_c1500]

Since I flushed it while the truck was parked on a slight incline facing uphill, should I be worried about water being in there that never drained out? (Bumping the question because new page)

 

[JDGMC]

I've lost track of what exactly you did to flush the system and exactly where you're at now . What is the current state of the truck - premix antifreeze added, system is drained and and empty (as much as it will be without pulling block plugs)? A recap would be helpful.

 

[slow_c1500]

Used a garden hose to the flush the heater core, did the block as well through the thermostat hole (with drain plugs and upper/lower hoses removed.) Today I got the new radiator bolted in and the trans cooler lines in. Upper and lower hose and T stat aren’t hooked up yet, no coolant in it yet. I am ready to reconnect everything and fill her up except for one thing that came to mind at the last second:

Since I did my flushing process on a slight incline (truck facing up), should I be worried about any water still in the block and heater core that may not have drained out? (Aside from the potential leftover water from flushing, the cooling system is empty of fluid). I guess I could re-park to get the truck facing down on the incline, (or just level ground, whatever is better) to ensure everything drains out, if needed.

 

[movietvet]

Yes, make sure all is clear and you can run it to turn around or park somewhere close and flat and then proceed with your work.

 

[slow_c1500]

Also how tight does everyone torque the thermostat housing studs? The Haynes manual says 20ftlb but that seemed excessive to me

 

[termite]

Also how tight does everyone torque the thermostat housing studs? The Haynes manual says 20ftlb but that seemed excessive to me

I'd just snug them down. As for the remaining water in the system, I'd pull the block drains and blow out (or shop vac) the heater core. Don't beat yourself up over getting every drop of the flush water out.

Are you using premixed or concentrate coolant? Concentrate is cheaper, distilled water is cheap. Using concentrate will give you more control over the coolant mix your running, especially if you still have some straight water remaining in the system.

Since the thermostat is already out, I'd fill the block there up to just below the housing then install it. Doing so reduces the chances of trouble with bleeding the air pockets out others drill the t-stat to address. (I've never drilled one, had cracked a t-stat loose to bleed air in a hurry though)

Probably goes without saying but, when you fire it up after filling, keep an eye on the temp guage as well as for leaks.

FYI, the factory service manuals are available on this site for download in the engine forum as a sticky.

 

[JDGMC]

That's not excessive. Service manual spec is 28Nm (21ft-lb). You should use the service, unit repair, electrical etc. manuals when working on your truck. Download here if you haven't already done so. Moving forward browse the manuals much like you browse the internet to learn more about the maintenance schedules and repairs for your truck. Good luck

 

[AuroraGirl]

would I just pour the thermocure into the thermostat hole, have the block drains screwed in and lower hose blocked off, let it sit for a few days, and then drain out later? I can’t run the motor.

no, it has to be run.

 

[AuroraGirl]

IIRC, the sealant tabs are for aluminum blocks. I could be wrong though.

the sealant tabs were for lazy gm, tolerances, poor owner maintenance, and "why not" lol ,
then it found out the hardway they werent compatible with dexcool, despite having them added as a preventative measure as a procedure lol.