83 Chev pu heater issues

[iamblueboy]

305V8 50K miles original
New 195 t-stat, heater core, anti-freeze.
both heater core hoses hot.
Never had decent heat in 2 yrs of ownership, after seeing wet floor knew I needed heater core.
Had work done at a shop, no difference in temperature output at floor :(
Was wondering if a cold air intake flap or diverter could not be operating properly?
Would air in the rad. or heater core give only luke warm air output?
I'm baffled, never done a heater core before... :noidea:

Thanks in advance
iamblueboy

[Nostradamus]

air in there would reduce heat because it would mean fluid levels are low and not circulating properly. At the same time running the motor for awhile should pretty much bleed the air out on it's own but then you would need to top up the rad with fluid

[Terryl]

Had a problem like that with my 85, it turned out to be a plugged heater core, it was full of small leaves and other junk, cleaned it out and it was back to normal.

[oak]

Air in system would cause low temp from core.

Also there is a flap that could not be operating properly. Could be that the guy at the shop forgot to connect it. It is operated by a cable from the temp selector lever on your dash. Follow the cable and see if it is connected.

[ru_knuts]

I used to be a parts mgr at a gm dealership, seen this many times. It is almost 1 of 2 things. Is the thermostat installed correctly? Cone side up cone end should be pointing up sitting in the intake manifold. Is it actually coming up to temp (193-195) degrees? A hose being hot, doesn't mean it is coming up to temp 193 degrees, 193 is to hot to hold your hand on it for any length of time. Most the time a cheap thermostat is exactly that, a cheap thermostat. If it's not coming up to temp, and you have drove it enough to bleed the air out of the system (reservoir full?), put a good thermostat in it. I have won bets with customers about cheap thermostats many times.

[justeric1agn]

can't add much to that except i am so tired of getting bad parts. just because you just bought a new thermostat doesn't mean its good. we have been thru bad starters bad alternators control boxes and several other parts that just come defective. low water level will make it not heat. a rusted out or stuck water valve will also make it not heat up good. i'd get a higher temp thermostat and put in a another one. check the water valve. and there isn't much more to them. checking the cable to see if the control unit is good is also a good idea. just see if it is opening all the way unhook the cable and open it manually. if its all the way open and you have good water and a different thermostat you have probably got a rusted or plugged control valve. hope this helps and good luck

[justeric1agn]

had one more thought if you have a candy thermometer or a digital meat thermometer.you can get a pan of hot water about 150 drop thermostat in it and see if it opens then turn up heat watch thermometer and thermostat until it opens and look to see what temp the water is. you can take off the return line from the heater core and put it in a bucket to catch antifreezze and have someone crank it to see if your getting a good flow of water.the return should be the one that doesn't come from the water pump.

may want to use a double boiler one pan on top of the other so the thermostat doesn't open because of the heat from the bottom of the pan or tie a string to it and keep it off the bottom so you can get an accurate reading of what temperature it open up at. testing the thermostat like this will save you buying another bad one and knowing it can't be the thermostat because its new.lol i'm glad i get paid by the hour to work on cars instead of commission all the bad parts you get nowadays drives you crazy.lol

all you can do is figure out what it isn't and then fix what is left.lol

[Terryl]

One other thing is how long has it been since you did a back flush on the heater its self?

Just flushing out the radiator may not get all the junk in the heater core, I've disconnected the two hoses to the core and done a reverse flush on it*, be careful not to use too much water pressure as you may get your front seat wet.

This will also tell you if its plugged or the valves are not working.

* This has to be done with the engine running on some cars and trucks, due to vacuum assisted valves and controls under the dash, a small jumper hose (don't kink it) from the water output to the return input on the engine block will keep things from getting all wet.

[swingbozo]

On top of the other suggestions, check the air flow and make sure there's not a ton of leaves/dead squirrels, etc stuck in your heating air vents. It's also highly likely that you may have a broken/disconnected door vent cable causing the air flow itself not to be directed through the heater core. This is easier to check when the heater core is out of the vehicle but you may be able to verify enough things are working/not working with it still installed.

You can verify this by turning on heat to the floor full blast then moving the HEAT temperature control back and forth. You should be able to feel and/or hear your control physically moving something and also hear air flow changing as you move the HEAT temperature control back and forth. If you aren't hearing clicks under the dash or air flow "changes" of some variety, I'd check the physical control of the heat flow ductwork as determined by the heat temperature control itself. I've had the physical cable that controlled the heat door flapper simply fall off causing this exact same problem.

I'd also see if there is a heat control valve inline that controls the coolant flow through the heater core ON TOP OF the thermostat itself. My "fancy car" has physical flappers, a heater core temperature controller and the usual thermostat. Luckily failure mode for my heater core temperature controller is open full blast so problems in the heater core temperature control system simply mean the control valve is always wide open.

[no-one]

305V8 50K miles original
New 195 t-stat, heater core, anti-freeze.
both heater core hoses hot.
Never had decent heat in 2 yrs of ownership, after seeing wet floor knew I needed heater core.
Had work done at a shop, no difference in temperature output at floor :(
Was wondering if a cold air intake flap or diverter could not be operating properly?
Would air in the rad. or heater core give only luke warm air output?
I'm baffled, never done a heater core before... :noidea:

Thanks in advance
iamblueboy

k so if both heater hoses are hot then there is no engine issue .

your have a hot bold blend door issue . if some thing like a pen has slid down the defroster vents it can and will jam the door from opening or closing ....
instead of re inventing the wheel the best teacher i had always said follow the KISS theroy .... keep it simple stupid...no dis respect here usually its something simple and we try to over complicate it . look at blend door control and disconnect from flap and move by hand you may be suprized ay what u find. jmho good luck:thumbsup:

[iamblueboy]

Didn't know mice enjoyed eating holes in plastic flapper doors ;)
New part unavailable from dealer.
Epoxied the hole shut and all is well, even at -20F:yeaah:
Thanks to all
iamblueboy

[oak]

Glad to hear you got it fixed. You'd think the guy at the shop would have noticed that?

[justeric1agn]

Glad to hear you got it fixed. You'd think the guy at the shop would have noticed that?
lol you would think. unless he wanted it to have a problem so you'd bring it back so he could say oh here it is another problem i have the cure this huge bill.

[swingbozo]

Thanks for reporting back! Is there nothing a little glue won't fix? :okay:

[satchick]

lol you would think. unless he wanted it to have a problem so you'd bring it back so he could say oh here it is another problem i have the cure this huge bill.
Normally they would replace the blend door during a heater core replacement, or when the dash is off, since they are almost a wear item and in most cases it can be done with no additional labor. I would think parts availability was the problem in this case...

You should take a look in the LMC truck catalog next time you need a part not stocked by the dealer, they have new parts for trucks as old as '47.

[Terryl]

Didn't know mice enjoyed eating holes in plastic flapper doors ;)
New part unavailable from dealer.
Epoxied the hole shut and all is well, even at -20F:yeaah:
Thanks to all
iamblueboy

Duct tape works wonders on mice nibbles, works good on mice too, keeps them still till the cat gets there.

Thanks for the report back on the fix.