I-6 heater problem

[gearboxx70]

Forgive me if I'm beating a dead horse here, but I did try to search for answers first...

I've been having problems getting my heater to work. The truck is a 67 with the 292 I-6/ SM420, non-AC cab.

I cleaned the mouse nest out of the heater box. I installed a new water pump. Checked all the control cables and doors. Installed a thermastat (since there wasn't one in there when I got the truck). After all that, the heater blew "warm" air. It had a hard time defogging the windshield.

Yesterday, I replaced my radiator. (Griffon "Direct-Fit" radiators are anything BUT direct fit! And this is my second in 6 months!). While I was in there, I put in a 195* thermastat (as was suggested to me several months ago). The thermastat and electric cooling fan work perfectly, but now the flow to the heater core has slowed drastically! I waited for 25 minutes for heated coolant to reach the heater core, and at least another 10 before any heat was felt at the return hose. Yet, even after heat was felt at the return, there was no heat blowing from the heater in any direction.

The truck is my daily driver, and there are no signs of rodent activity. Before the thermastat was changed (a 2 hour difference in time), the heater was stil blowing "warm" air. After the change, to the higher heat thermastat, no more "warm" air.

[geezer#99]

Do you have your heater hoses hooked up right. From the thermo housing to the bottom of the core and out the top of the core back to the water pump or rad.

[CST10]

Your heater core my be plugged inside also.

[gearboxx70]

The hoses are correct. I verified that this morning. I'm leaning toward plugged heater core. The heat moves very slowly through the hose to the core, like a few minutes to travel the couple feet from the block to the core inlet.

I just took about a 50 mile round trip this morning. I stopped for awhile in the middle of the trip, and noticed when I started moving again the air was warmer. But that only lasted for a few minutes. Once I was on the highway again, it cooled off quickly. When I stopped, I could grab both hoses, and hold them. The inlet hose was slightly warmer.

I also rechecked the blend door in the box, and its working properly.

[zeldman]

If it cools off after moving, check the thermostat. I have had brand new ones stick open.

If you have a water temp gauge, what is the temperature of the water?

Have you tried blocking the grill to reduce the amount of air going through the radiator? If the heater warms up doing that, again, thermostat. (don't drive it, just run it in the driveway)

If still no heat, then I would suspect a heater core blockage. How old is the heater core?

And lastly check the water level. Too low and you might not get heat. But I suspect you have already checked that.

Oh, does the electric fan run all the time or at set temps?

[gearboxx70]

No temp gauge. Well I have one, in a package, buried somewhere in my parts piles.

Have not tried blocking the grille. Ran the truck in the driveway for over half an hour yesterday. The radiator is 28" wide with a 16" electric fan on it. The fan is controlled by a temp switch. The switch isn't set by actual temp, but by "feel".

Not sure of the age of the heater core. Could be as old as the truck. I've only had the truck for about 4 years.

[hamjet]

If all else fails,try disconnecting the heater hoses at the engine and take a garden hose to one of the heater hoses to see if it flows well or if any thing comes out..one time I unhooked the hoses and poured CLR into the heater core and let it set for a while to loosen up calcium deposits from many years of people using well water instead of antifreeze..

[Zeke's Garage]

Yeah, your best bet is to disconnect the heater core, and hook a hose to one side, then the other to make sure you've got good flow and no blockage. Also if you get a chance, post a picture of your hose routing.. I know I've seen some questionable hook-ups that look factory, but aren't connected to a pressurized source on the coolant system for flow, so the heater only gets hot through conduction.

[gearboxx70]

The hose may have to wait a few days. I've got all the outside water shut off for the winter, and there's suppose to be the worst storm since 1985 blow through in the next couple days.

As for hose routing... The hose that goes into the bottom of the heater core comes from the front of the head, just below the thermastat housing and temp sender. The hose that connects to the top of the heater core, goes to the water pump, a cast-in fitting just above the lower rad. hose entry. This should be pushing the water in a circuit that flows from the head to the heater core, through the water pump, into the block, back up to the head, and back to the heater core. All while mixing with the other coolant in the water pump, block, and head. Hope that's as good as a picture, because its too cold and dark outside to be fumbling with my stupid fartsmone.

[hamjet]

Cold in Cali? That does not compute....

[69chevy lwb]

Drive around for a while and then feel the upper rad hose if it's hot then the thermostat is working. If that's working you have a flow issue at the heater. Pull the hoses off and make a loop that eliminates the heater core. Run it and see if it gets hot. If not you have a problem with the flow inside the motor. In that time flush the heater core if it gives much resistance to the water it is plugged and likely to burst. The heater in my truck was so damn hot I couldn't handle it even in the winter.

[gearboxx70]

Originally Posted by hamjet

Cold in Cali? That does not compute....

HAHA! So many people think Cali is all beaches and sun tans. I've lived in Grass Valley for 6 years now, and have yet to see the California coast. I live in the foothills of the Sierra Nevada Mountain range, at about 2300' elevation. When big storms march in off the NorCal coast, they tend to slap us in the face as they head for Reno.

[gearboxx70]

Went to the parts store this morning, and picked up a new heater core, just in case...

Came and tore into the heater box. Found a clogged heater core, and a pile of pine needles up against it. Cleaned out the pine needles, and went to work on the old heater core. (The new heater core is much thinner, and of lesser quality than the one it would be replacing. I opted to try to clean the old one.)

With the other half at work, I was free to use the kitchen sink and a whole bottle of vinegar. Took about an hour. Flushed, soaked, shook, flushed, soaked, shook,... Over and over, until nothing came out but clean water.

I had to "manufacture" a few new seals, but all is well in my heater box now. It blows hot enough to cook an egg on the dash!

[hamjet]

Thats great to here. Now whats it worth to you for us not to tell your better half about the sink thing going on there..LOL

[gearboxx70]

I told the other half about the sink. She's cool with it as long as I don't drag a bunch of harsh chemicals into the house and stink up the place. (This, from the future Guinness Book of World Records "Woman with the worst gas record holder"!)