overhearting problems...heater core maybe?

[BDog21]

i have a 99 yukon that ive been having lots of overheating problems with lately. i fill the radiator and reservior up and drive it it will start overheating after about 10 min of driving. the whole time i have no hot air from my heater either. i was just driving it a bit ago and saw the temp gauge goin up so i tried to hurry home but it was pretty much to the red line when i got home and there was steam pouring out of the hood, coming from the lines that lead back to the heater core almost like it was just building up a bunch of pressure there and had to vent there cuz it was stuck, im assuming this is just a plugged heater core? i know u can flush em but how do i go about doing that? just hook a hose to reverse flow at the heater core outlet tube i know but do i need to rig something up to make my hose fit my heater hose or will it be enough pressure to just hold a hose up to it? ive never done it before and any help would be appreciated

---------- Post added at 04:39 PM ---------- Previous post was at 04:38 PM ----------

i just put a new thermostat and radiator cap on it as well btw

 

[kcb37]

You got it for the heater core.
You could buy a cheap hose cut the end off and clamp it on. If you have high water pressure you may want to be a little careful starting out.

Sounds to me like your water pump may be bad too, or the radiator is plugged.

 

[livingez_123]

Well, the heater core itself wont cause an overheating problem. even if it was completely plugged. Now if you have an overheating issue I would start at the front of the truck and work your way back. if you have a 5.7, you can take 1/8 drill bit and put a hole in your thermostat. it will burp any air out of the system and not effect the function of the stat. Get all of the air out of the system first. then you might be surprised you will get heat out of the core.

 

[retorq]

^^^ What he said, Vortecs have a bypass coming out of the intake and going into the pump itself, even if your heater core was plugged or missing the coolant system would still be able to survive. You have a problem elsewhere ... provided of course the system wasn't massively altered in any other way.

I would say that 1/8th inch hole is too big on the thermostat, I say that from personal experience. Get one with the lil hole and lil brass piece already in it.

No heat could be caused by that bypass setup on the firewall too, those have been known to lock up when they are old or it could be that there is no vacuum applied to open that up.

Just gonna throw this out there too since it's common, once you red line those Vortecs you can just about bet you cracked a head. If there was no coolant flow in the block and it redlined like you said you more then likely cracked something between the 4 and 6 cylinder. the water jacket there is thin and SBC Chevy heads get HOT there.

You may want to fill up the cooling system and see where the coolant is going if it's disappearing on you ...

 

[BDog21]

well the temp gauge went way past redline a few times but it seems like the gauge might be off or something or maybe theres a blockage somewhere right by the temp sensor or something cuz the engine never feels that hot when i pop the hood...?

 

[retorq]

Get an infrared temp gun and verify, I would be my ridiculous govt paycheck that the head between those two middle cylinders is way too hot and more then likely compromised. Trust me I've been there.

 

[God]

Before you go drilling holes, I'd try burping it by running it for 10-20 mins with the radiator cap off.

 

[livingez_123]

Drilling a small it the thermostat has been done before most of you guys were even born. Pre Ls engines have a real issue with getting all of the air out of the system. And a simple hole in the stat gets most of it out. Leaving the radiator cap off does nothing if you can't get the air past the stat. When I was building engines I would leave the Tstat housing off and fill the block that way. It would also fill the radiator up to that point. So before you go and knock something that is proven to work, maybe you should try it. Even some of the aftermarket Mfg's have put the hole in.

 

[BDog21]

wel, now ive gt a whe new problem...the damn thing wont start...and i mean NO electrica power whatsoever..sometimes when i hook my batt charger to it it saysits charging correctly, but no matter how long i let it charge i turn thekey on, everything comes on fine, try to start it, CLICK and dead again, no power...sometimes jiggling the pos cabe gets thelights 2 come back on but try to start it CLICK and dead again...when it was dead i check voltage from batt posto batt neg and got 0, but pulled the terminals out andwent straight t the battery and got 12.something so i replaced the terminals and clieaned all the connections with a wire brush same prob now idk what 2 do

 

[retorq]

If you went terminal to terminal and got 12V your battery sounds OK to me. Replace the cables, not just the terminals. If you replaced the cable ends and and they aren't done correctly that corrosion will just creep up inside the cable to where you can't see it.