Overheating - heater blows cold

[Olaf]

Hey, so my 2003 LS spontaneously started overheating while i was driving. I pulled over and waited a while then drove home once it was cooled to the middle. I ran the heater on full, and temp stayed in the middle, but the hot air wasn’t blowing hot.
The coolant seems at a normal level. I’m just letting it cool fully now. Any ideas what this might be?

 

[joegr]

Yeah, the same thing that has happened at least once to every other LS. Search the forums.
The only real solution: GenII LS8 Cooling System Overhaul

 

[Olaf]

Oh no. Well, that’s a bummer to hear that. Is this a “don’t drive even a foot until you’ve done it all” situation? Or can I do short trips with the heater on?

also thanks for your help joe.

 

[joegr]

The amount of risk you want to take is up to you. (Personally, I wouldn't.) Having the heater on is very unlikely to help (unlike most cars), since trapped air is keeping coolant from circulating in the heater cores anyway.

 

[Olaf]

Ok thanks joe, I’ll start ordering parts.

 

[04_Sport_LS]

BUY OEM... not aftermarket parts. THAT is the biggest mistake most members make on this forum. Depends on whether or not you want to do it again in a couple years... or 7 years.

 

[Olaf]

Hey, not sure if you’ll see this, but I finally got all the parts together and started this project. I discovered clay like gunk in the radiator tubes while disassembling. (Step 10c or so).
Does this indicate blown head gasket? That’s what doctor google is telling me.

 

[joegr]

Is there a chance that anyone ever put any kind of stop leak in there? Warped heads (more so than actual head gasket failure) is a possibility, but it is very rare on this engine, in part due to the fail safe cooling.

 

[jerryg2112]

Maybe mixed coolant in the past.

 

[Olaf]

It is definitely possible someone put another coolant or stop leak in there. Is there anything I can do to clean it out? I guess I’ll have the intake manifold coming off tomorrow anyway, so I’ll get to see what it looks like inside a little.

Also those hose clamps are the devils work.

 

[joegr]

I guess you could try lots of flushes with tap water and maybe some of the radiator flush chemicals. In addition to replacing all the usual plastic parts, I'm sure you'll need a new DCCV, aux pump, and radiator. I'd replace the water pump too. I strongly recommend Motorcraft for most of the above, but the aftermarket radiators seem to be okay. The aftermarket DCCVs and thermostats are terrible.
In case you missed it:
GenII LS8 Cooling System Overhaul
Definitive GEN 2 Cooling System Thread

 

[Olaf]

Ok, well, after far too much hemming and hawing and delays, I’m in to the manifold, and the news is... I don’t know. There’s no fluid in here, but there’s plenty of charring. Am I fine to just scrape this stuff off and call it good?

And that insulation bag seems cooked, is there a way to get another two to replace it?
I’ve attached a photo of the charring from above, I’m going to work on cleaning the other half for now. Is there some good way to clean that out without letting it all fall in?

I will replace the other stuff you mentioned, and I’m only using motorcraft for anything.

 

[joegr]

That insulation bag looks fine.
I'm not sure what to make of the line about the manifold. No coolant runs through the V8 intake manifold.
It's normal to have some crude in the intake passages. It's mainly from the PCV pulling oil vapors in, and maybe a tiny bit from the EGR. It's probably too late now, but you really don't want to disturb it in any way that lets any hard particles fall into a cylinder, where they might scratch the cylinder wall and cause an oil consumption problem. The trick is to turn the crankshaft till the intake valves on that cylinder are fully closed. Then clean what you can and vacuum all the crumbs out before turning the crankshaft to close the next set of valves to work on the next cylinder.
For what it is worth, the buildup is usually much worse on GDI engines. Some of those have to be walnut blasted.

 

[Olaf]

-It's probably too late now, but you really don't want to disturb it in any way that lets any hard particles fall into a cylinder, where they might scratch the cylinder wall and cause an oil consumption problem.

gotcha! I have only cleaned the ones in the upper manifold, and I’ll do as you say with the crankshaft and vacuum to clean the lower ones. Thanks, I knew there was a right way to do that.

I was confused about the coolant flow, for some reason I thought it was up in there too. Once I have this cleaned up I’ll move on to the pump, dccv, radiator, and all that. Thanks for your help and support.