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

[454cid]

I figured while I had the coolant out I would flush the heater core and heater hoses, long story short I don’t remember what order the rubber o rings and plastic gasket rings for the heater inlet tube go. I can’t remember if it goes: plastic, rubber, plastic? Or rubber, plastic, plastic? Anyone know? I can only get the quick connect to fit back in if I do the rubber, plastic, plastic order. (Meaning rubber o ring going onto the inlet tube first, and being furthest away from the intake hole. But I don’t know if that’s correct. Anyone know?

Should I consider changing the fitting to something non quick connect while I got the coolant out, or not even risk breaking the fitting?

F*ck quick connect

Those fittings are an issue. The Dorman replacement is supposed to be better made than the GM original. So that's the way to go if you want to continue using the quick connect. I opted to get rid of it entirely and use a hose barb.

Removing the original could break it, but leaving it isn't going to help your chances of it not breaking later. If you do break it there are options for removing it.

 

[slow_c1500]

My fitting wasn’t leaking so I’d probably just keep it for now. I just need to get it back together properly, with the rubber and plastic o rings in the right order. Anyone know how those go in there? There are 3 total: 2 plastic and 1 rubber. I know the furthest inside the fitting is plastic, I haven’t touched that one. But I can’t remember the order of the other two that go before it. Does it even really matter if the plastic or rubber o ring goes first?

 

[JDGMC]

If I understand correctly - spring clamp (plastic), collar (tapered plastic), o-ring. The o-ring is seated at the bottom of the fitting/adapter.

 

[Martin Evans]

I filled the rad with water and held it up to see if it leaked at all. Turned it over to test the other side. No leaks. I’m really confused how the truck could spit coolant on top of the motor and fan shroud if the rad and its hoses aren’t leaking, even more puzzled if it was a coincidence or if mixing coolant caused this.

You need to pressure test your cooling system, like Termite said. Your radiator may have cracks that won't leak until there is pressure in the system. I had a bad water pump that i tested for leaks like you did with your radiator. It didn't leak when I put water in it, so it re-installed it. After the vehicle had been running a while, I could see that my water pump was leaking at the shaft and had to pull it again and replace it.

 

[slow_c1500]

You need to pressure test your cooling system, like Termite said. Your radiator may have cracks that won't leak until there is pressure in the system. I had a bad water pump that i tested for leaks like you did with your radiator. It didn't leak when I put water in it, so it re-installed it. After the vehicle had been running a while, I could see that my water pump was leaking at the shaft and had to pull it again and replace it.

I already said in the thread that the rad was leaking, your right it had to be under pressure to show up

 

[slow_c1500]

Okie dokie I got the sh!tty quick connect back in. Starting to flush the block, water is almost clear but I noticed a new hole that water was draining out of, and I didn’t remember taking a plug out of. This is probably a really dumb question but what is this hole, and why is water coming out when I flush the block? Like I said I don’t remember taking a plug out of it. It is right behind the oil pan.

You must be registered for see images attach

 

[movietvet]

That is the transmission inspection cover and if you have water draining out of there, you likely have a freeze/welch plug leaking, at back of engine block.

Or is coming from up above somewhere and getting in there some how.

 

[1998_K1500_Sub]

Starting to flush the block, water is almost clear but I noticed a new hole that water was draining out of

@movietvet's observations may be spot-on. Then again, I assume the engine wasn't leaking coolant into the transmission inspection cover before, so it probably isn't leaking now. I might be wrong, but...

In your picture there's water hanging off MANY things on the underside of the engine bay, so it's obvious there's ample water being used.

I would guess there's water draining down the passenger's side of the engine and finding its way around the nose of the starter and into the transmission inspection cover, where it then drains to the bottom of the cover and out that hole.

I doubt you have a serious problem b/c, if you did, it would have made itself evident before you started this project.

 

[slow_c1500]

Yes I removed the cover and confirmed it is just water coming from the driver side block drain riding along the top lip of the oil pan, and then ending up inside the cover.

 

[movietvet]

@1998_K1500_Sub is spot on as well. I was not 100% convinced that it was a freeze plug as well. Water leaking will follow a trail and eventually drop somewhere and can be far away from the place it started.