Heater isn't... hot?

[Skunksmash]

I've never had a heater in a car die on me so I hope someone here can help. My heater in my 87 TBI 5.7L 2WD isn't functioning correctly. It won't ever actually get hot. It gets... a little warm. Sort of. You can definitely tell its working half @$$, because when you switch it over to cool vent, it starts blowing the cold outside air. So its working, but not very well. The air is just barely warm.

Is this a dead or dying heater core? What exactly causes a heater core to die anyway?

[J Knight]

The main reasons for heater not getting hot is;

the blend doors are not funtioning or sealing properly.

you could be low on coolant and not getting sufficient flow through the heater core.

[INSIDIOUS '86]

X2^

Pull of the hoses and run a garden hose through the heater core
Posted via Mobile Device

[Skunksmash]

Will do. Would that be the top, or the bottom heater hose to run the garden hose through? Probably doesn't matter.

[meatwagon83]

check your coolant level

[Dylan86]

take off both upper and lower coolant hoses going to the heater core and run water through it alternating in both directions- it will usually dislodge any particles that have accumulated in it...

[67swb72klb]

x2 on the flush both ways

[Skunksmash]

Nice I never knew that. I'll do that tomorrow. And I'll check the coolant level. Although, it has not been overheating.

[bk2life]

Is the truck getting up to operating temperature? As in is the t-stat working? If no, it won’t blow hot..

[bk2life]

Originally Posted by bk2life

Is the truck getting up to operating temperature? As in is the t-stat working? If no, it won’t blow hot..

we can play guess all day long, has the OP checked to see if the motor is hot? vacuum bad gauges, stuck t-stat, blocked heater core is all useless advice if the motor is not getting hot..

[buffle]

My 87 had the same problem. I replaced core,water pump and flushed everything. It ended up the cap was no good and overflow tank leaked. After repairing these it works like a champ.

[INSIDIOUS '86]

You can have low coolant and not overheat.
Gm designed it that way. Water is sucked from the bottom (cool side) and pumped to the top. (Hot). This way water has to be below water pump level before nothing is pumped.
But before that level air pockets will get big enough and steaming and overheating in this pockets occurr
Posted via Mobile Device

[Rich84]

Originally Posted by INSIDIOUS '86

You can have low coolant and not overheat.
Posted via Mobile Device

I didn't think that this was possible until it just happened to my Tahoe..Truck temp never rose above normal but it would not throw any heat. Checked coolant level was low...Real low..but it never overheated.

[Skunksmash]

Well yall were right as usual. Low coolant. It just never dawned on me cause the truck never started to get too hot. Just stayed right there at 187 degrees. Don't know where the coolant went though lol. Its Not in the oil, cause I just changed that last week and I was already having this problem at that time.

And its not leaking anything on the ground. Well, not fast enough for anyone to ever see, anyway. There is one weird problem though, that it could somehow be related to. Though I'm not sure how. If I fill up my overfill jug to the proper level, it will puke out most of the water in the jug. All runs out the cap somehow. I have to leave the coolant level in the jug at the very bottom, cause there is no point in filling it to the line. It will all just be coming out anyway.

[CSGAS]

Also make sure you don't have any vacuum leaks in your heating system. That not only can lead to the heater/vent doors and flappers not working the way they need to; but also prevent some heater flow valves from opening and allowing heated coolant into the core. Check the valve to make sure it is still working, too.

If your core has gone bad, on our trucks at least it doesn't leak (much) into the interior. You'll see a puddle of coolant where you park, under the spot where the heater core resides (it will drip slowly)

Corrosion can cause blockage in different parts of the system too, but if there's corrosion blocking up the tubes in the heater core it should still get hot; and I can't imagine corrosion causing blockage in any of the areas that would prevent the heater from warming up, because most areas are flowing too openly.

[sethv]

T-stat could be stuck open not allowing the engine to fully warm up and causing the coolant to not be hot enough

[J Knight]

You may want to get a new rad cap.

[Skunksmash]

I did lol. Got one cause I read here in this thread, a member said it was his cap. And then I remembered a buddy had one go bad on his firebird and leaked. Nice easy fix for them and hopefully for me as well. Wish they were all that simple.

[piecesparts]

Check your T/stat and check your radiator core level. If you find the level is low, refill the radiator. Watch the radiator level to see if it goes low on water again. If it does so, then there is a possibility that you have a head gasket leak. This will pull or push water out of the radiator and replace it with combustion gases. This can be tested bya aradiator shop, by having them read out the gases in the radiator and see if it is something more that steam or air.

[Skunksmash]

Ok thanks I'll see what happens.