92 Astro - No/Low coolant flow thru heater core

Hi.

My 92 Astro has 209,850 (TBI 'Z' eng.) & runs great except heater only blows cold air. What I've done or know; chemical (prestone) & power flushed cooling system (flushed eng & radiator separately by filling w/ water from bottom to top w/o thermostat in outlet housing, & shooting short 15PSI bursts air, forcing water out in gushes), installed new 195 deg thermostat & 50/50 cooolant/water. Engine warms up fine, thermostat opens & closes normally; temp gauge shows needle in center of 2nd bar from left when warmed up. Blower fan & flaps in heater & (vacuum controlled) heater valve work right, can blow [with mouth] freely thru heater core w/o hoses connected, replaced water pump (new [was leaking]). Water flows freely through heater core to water pump hose, but dribbles through back of intake to heater core hose. Outside (threads & O-ring to hose/pipe seal) of Intake 'Quick Disconnect' fitting are not leaking. Inserted 'flushing T' into top heater core line (return to water pump) to attempt to fill sys & avoid air lock. When start eng., coolant level in flushing T goes up & down, but apparently not enough flow to warm core. Heater hoses at core don't get warm/hot. There's no info in Haynes manual nor found any on Internet. Is there a check valve in core feed line (from intake)? How does one remove the airlock from heater core/lines? Try to suck the coolant/air out of intake (or both hoses & heater core connected) with a wet-dry shop-vac? (I haven't replaced Quick Disconnect fitting, heater hoses or intake manifold). If intake is blocked inside, is there another way to route a feed line to heater core? Can someone please help me? I'm totally stumped. (Guess I'll remove the Intake/core line, try to run coat hanger through it, carefully check same on Quick Dis. fitting (try not to break fitting - i hear its a bear if i do).

Thanks (in advance, of course) for your help!
Best regards,
Jon

Wow, you have tried a lot of stuff.
The way to burp a cooling system is to run the engine for 15 - 20 minutes without the rad cap on, and every few minutes rev the engine a little bit. Keep on eye the rad level because after it burps anti-freeze will spill out a little then disapprear, so you have top it up.
The other thing you might want to check is if the proper lines are going into the heater core. By that I mean the line that fills the heater core should be connected to the bottom of the heater core, so it forces air up and out as it fills. Good luck

I've had some interesting problems from "easy" repairs too. What a pain!
I was wondering, I've seen old hoses, connected to the "suck" side of the water pump collaspe with the engine running. This stops the flow obviously. Might it apply here?

:grinyes: Had same problem on delivery van (92 Astro). Took two years, not consistently looking but suffered with it and after taking almost everything apart discovered problem. Fluid not going through heater core from top of manifold exit. Solution: disconnect the factory swaged fitting to the manifold; I found that the hose expanded to plug the hose where it was swaged; took a 3/8" to 7/16" rod and heated it up red hot and plunged it into the blocked off hole; a nice clean opening resulted with the minimum of effort; the fluid flowed, the heater blew warm air and I was happy as a clam. Now I have another AWD 92 Safari loaded and have just discovered the same problem so hopefully this will work again. Good luck
Bryan

FRYIN' EGGS ON THE DASHBOARD... well, not quite, but 132-138 degrees Fahrenheit coming out the dash vents now when its 20 outside isn't bad either.

tableman, Thanks a LOT!!! for your excellent and speedy help!! (I apologize for taking so long to get back to you.) I figured it out and did what you said, ie, checked the lines, - and your advice on filling the system worked well. Anyway, it turns out that inside of a (OEM) factory Quick Disconnect fitting (in the back of the intake on a 4.3L V6 - 'Z' eng.) is a CHECK VALVE, (of all the strange things - ya never know what's going' on in the brains of people who design this stuff! ) that under certain conditions (which I don't know what they are) is DESIGNED to STOP the coolant flow in the NORMAL direction its supposed to flow!!! - Is that WEIRD, or what!!??? Anyway, so as it turned out, the fix was SUPER SIMPLE and CHEAP and easy!

What to do: Basically, you disable the check valve by removing the rubber flat washer and letting the ball fall down into the intake's coolant passages, reinsert the QD line, fill and burp system, get out yer fryin' pan.

Details: Drain just enough to open the quick disconnect line fitting connection (a 7" slip-joint pliers works well), disassemble the parts of the fitting, taking care to remember their order for reassembly, and under the nylon/plastic cylinder (that fits over the aluminum line end) inside the fitting, is a flat rubber washer (the seal face the ball seals against from under the washer). Just pull the washer out with a small wire, etc., let the ball fall down into the coolant passage, put the parts back on the line (except the flat rubber washer), put a little Vaseline on the O-ring and snap the Quick Disconnect line back into place. Fill and burp the system and you're ready to go.

Thanks again for ALL your help!
J

:grinyes:
Bryan

Hi Bryan,
Thanks a lot for the idea! As I'd replied to Tableman, the OEM Quick disconnect fitting has a check valve inside of it, but the afermarket fitting one only has the 1/4" (or so) ID hole with the 180 degrees 'bar' over/across the center of the hole insid the fitting - to prevent the ball bearing from sealing the hole. I'm not quite sure what you mean by the line being swaged, but understand if one melts the plastic out of the inside of the bottom of the quick disconnect fitting, it will open up the hole (and increase the flow rate dramatically).

Best regards,
J

[QUOTE=drew300]QUOTE]
[B]drew300[B/] Thank you very much!!! as much as it was 8 degres outside when I received your post, I checked it anyway; they weren't, but I appreciate your help anyway. :)

Best regards,
J

PS - please see my answer to tableman for THE solution.