Heat kind sucks

[Mv7fd]

I have an 84 bronco ii and the heat just kinda sucks with the blower motor speed set at like half way maybe a setting less it blows luke warm air at best but with the blower motor off it'll blow a little warmer heat what could cause this

 

[RonD]

3 possible causes:
Heat control valve on heater hose is not opening all the way.

Heater Core is partially blocked so has poor flow.

Engine itself is not warming up.

Engine is easy to check........look at the temp gauge, is it above 1/4 and just below 1/2, that is usually about 200degF and the correct operating temp for Ford with 192degF thermostat.

Next time engine is warmed up set heat to HOT and fan on high, then open the hood and feel the two Heater Hoses at the firewall.
One will be warmer than the other, the warmer one is the IN hose, the other is the OUT hose, remember which is which, or mark them.
Let engine cool off now.

Heat control valve, if you have one, will be on one of the heater hoses in engine compartment.
It will either have a cable attached that goes to COLD/HOT dial/slider in cab or it will have a Vacuum hose going into cab.
Drain a little coolant and separate the heater hose at the valve, operate the valve manually and make sure it is opening and closing as it should.
The valve fin can come loose and not open as it should.

Heater cores are just like a smaller version of a radiator, so they have large tubes where the "water" comes in and then goes out, in between are smaller tubes, these can get clogged over time.
First thing to do is to Back Flush.
Google: Back flush heater core

Lots of videos of how to do this, model of vehicle isn't important they all work the same way.

You are going to remove heater hoses at the engine or valve end.
Point the IN hose down at the ground
Put a garden hose on the OUT hose
Turn on the garden hose with low pressure at first

What you are doing is trying to push out any larger debris that may be blocking the smaller tubes, so you have to "reverse the normal flow", you are Back Flushing

You can increase pressure as you see fit.
If flow is still not very good get some CLR and mix it with warm/hot water.
Blow out water in the core, just using your mouth is fine
Pour CLR/water mix in the core
Let it sit for 20min.
Then Back flush again

Repeat the CLR/water mix as you see fit.

New heater cores are not expensive but they can be hard to remove and install on some model vehicles.
I haven't done an '84 Bronco II so can't say.
On my '94 Ranger the core was $28 and took only 20min to change.

 

[Mv7fd]

thanks i will check that out. my temp gauge doesn't work factory or aftermarket so that i can't do but i will try the rest like i said it puts out ok heat with the fan off but you turn the fan on and its kinda cool. maybe the heater core hoses are on wrong i haven't been able to find a diagram to check them against yet. i thought about just replacing the heater core and thermostat all at once and hoping that fixes everything

 

[WarHawk-AVG]

did this to my 1997 Ranger...blows hot hot hot now!

 

[RonD]

Ranger Heater core doesn't have a direction so where each hose goes doesn't matter as far as heating up goes.

 

[Mv7fd]

Replaced the thermostat and still nothing jus cool warmish air im starting to get pissed

 

[drsvox]

there shouldn't be a control valve on the heater hoses, but there is a flap/door that should open when you switch from cool to heat...could be that it's stuck shut. Either that or it's a bad heater core like Ron said.

also, i'm pretty sure coolant should circulate through the heater core no matter if the thermostat is open or shut. this probably isn't the case, but it is possible your water pump is shot...but, the engine isn't overheating, right?

The heater core isn't overly difficult to replace...you'll have to remove the glovebox, and you'll pull some odd angles to get up underneath the dash and open the box.

p.s. if you find out it's a bad heater core, when replacing, would be a good time to drain and flush the whole system.

 

[RonD]

Replaced the thermostat and still nothing jus cool warmish air im starting to get pissed

Have you felt the heater hoses at the firewall????
Easy to do

Next time engine is warmed up set heat to HOT and fan on high, then open the hood and feel the two Heater Hoses at the firewall.
One will be warmer than the other, the warmer one is the IN hose, the other is the OUT hose, remember which is which, or mark them.
Let engine cool off now.

If one is hot and the other cool then core is blocked.

If both are hot then "Blend Door" in the cab might be stuck

 

[Mv7fd]

Replaced the heater core and all is good I have heat again. I have a minor coolant leak down at the coolant bypass hose. That heater core was the easiest one I have ever replaced

 

[RonD]

Good work

 

[Mv7fd]

Now I have anti freeze leaking in the area of the coolant bypass hose. I noticed when I put the thermostat housing on that there is like a plate or something on there other side is there a gasket there that I need to replace I guess it would be on the other side of the block now really sure what it would be called

 

[kimcrwbr1]

Mine the fitting for the intake manifold fitting was half plugged with rust. Inoticed it when I put the water pump in. I also ran high pressure water through the metal tube that goes to the water pump. I cant set it up much past half on the heat select without having to open the windows it get so hot.

 

[kimcrwbr1]

If you go to replace the bypass hose be real careful of the fitting going into the intake manifold. If you break it you will likely have to remove the manifold to fix it or even have to replace the manifold if you cannot remove the fitting. It gets welded in there pretty good otherwise ream it out when you have the hose off it is surely restricted with rust also.

 

[Mv7fd]

The top one is fine no leaks at all the bottom is leaking either from the hose or the back side area of the thermostat housing where the bolts come through

 

[AndyB.]

The lower rear thermostat housing is held on with the same three bolts that hold on the lower front thermostat housing. There is a gasket that goes behind the back of the front cover and rear stat housing that could have loosened up when removing the front one.