...FJ60 heater question, "...bonk..."... (1 Viewer)

[rfc2307]

Good Morning, I am slowly resurrecting a Rootbeer Brown 81 FJ60, the heater controls (HOT <--> COLD) does not seem to work. In the past, when I started my down hill roll out of the neighborhood, I would tap the break, hear a "bonk" noise, and PRESTO! hot air out of the vents. My rig was sidelined for a week, parked uphill, nose up and now when I roll down hill and tap the brakes, no more "bonk" and no more heat.

In a perfect world, I would like the HOT/COLD slider to work as designed (any assistance here would be appreciated), but in the short term, just getting my "bonk" back would be great.

Anyone had a similar issue, or fix?

 

[Slow Left]

On the PS firewall in the engine bay, you should be able to locate the heat control valve. The heat control valve opens/closes when you actuate the HOT <-> COLD heater control inside the cabin of the vehicle.
If you set the heater control (inside vehicle cabin) to COLD, note the position of the heater control valve at the firewall.
Then move the heater control to HOT and confirm that the heater control valve at the firewall has changed.
If there is no change in the position of the heater control valve on the firewall, then try lubing the cable/piston at the valve (maybe a graphite type dry lubricant, or Seafoam...but graphite shouldn't attract as much dirt over time) to try and 'unstick' the response of the valve...

Does the rear heater work? Or is just the front that doesn't work?

 

[Slow Left]

Also, if the heater control valve is actuating correctly, the other thing it might be is air in the line of the cooling/heating system. You might try burping to remove any potential air blocks. And having that nifty funnel for burping is a good tool to have on hand any time you break a line in the cooling system to replace a hose/thermostat and need to burp...

Burping:

For burping (this is after you have done the fix and are ready to test/run the truck again):
Before you start the truck, take the radiator cap off and get that funnel on (see below for information on funnel). Fill through the funnel until the coolant fills the funnel up about 1/2 to 3/4 full. That should be higher than any point on the rest of the cooling system (assuming you're parked on flat ground).

Start the truck and TURN BOTH HEATERS ON FULL BLAST. Keep heaters on full blast during burping procedure, you want the coolant flowing through the heaters to push through any trapped air there and move it out to your funnel.

As it sits there idling, keep adding coolant to the funnel so it is at least 1/2 full. As the engine comes up to operating temperature and the thermostat SHOULD OPEN and remain at operating temp and any trapped air should start to bubble out through the coolant in the funnel and release into the atmosphere (...burp...). Add coolant if you need to as the air comes out and the level in the funnel drops, but not too full, because as the truck gets hot, the coolant is going to expand naturally and will move up higher in the funnel. Your gonna want to run it for a good while (45 mins or more) to let that thermostat continue to cycle and release trapped air. When you are convinced the air is out, remove the funnel and cap the radiator. Fill the overflow container 1/2 full will coolant. Should be good to go.

Funnel:
Get one of these - http://www.amazon.com/dp/B001A4EAV0/?tag=ihco-20

Additional directions for using funnel/burping (if mine weren't clear enough) - http://www.instructables.com/id/How-to-Burp-your-cars-cooling-system/

 

[rfc2307]

Thanx for the quick reply. I have "burped" it, no change. At the firewall, the heater control valve is operational. The "bonk" noise seems to be coming from the plastic box at the foot of the passenger leg area. It COULD be the cabin air, vice exterior airflow control? Or does the HOT COLD slider, also control an air flow valve?

 

[Slow Left]

OK. Is the engine coming up to operating temperature (as indicated on the temperature gauge on the instrument panel)?

If so, then with the heater control valve on HOT (valve open to allow hot coolant to flow to heating units), you should still be able to feel heat at the vents (depending if it is switched to VENT, DEFROST or HEAT - as long it is not switched to FRESH AIR)
If it is set to VENT, with the engine at operating temp and the HEAT set all the way in the red, you should feel heat at the vents on the dash.
If it is set to DEFROST, with the engine at operating temp and the HEAT set all the way in the red, you should feel heat at select vents (the outer ones) on the dash.
If it is set to HEAT, with the engine at operating temp and the HEAT set all the way in the red, you should feel heat at the vents in the footwells.

...and if you turn the fan on, you should really feel the heat blowing.

Is it just that the fan isn't working, but that the heat is being generated in each of the above conditions?

And is the rear heater working (blowing hot air)?

 

[Output Shaft]

Sounds like maybe the heater control cables inside the cab needs some TLC. Something may be sticking.
On a properly functioning heater, when the temp slider on the front dash is slid from blue cold to red hot, a "bonk" can be heard down near the passenger foot area.

 

[Slow Left]

Ooohhhh...that 'bonk'...now I understand what you are referring to...

Yeah, not sure what makes that sound...sorry, about as helpful as all the other info I've given you above...

...but I would think that the 'bonk' is the heater control valve opening/closing...you can confirm by either using a helper or checking the position of the valve under the two condtions (as mentioned above) HOT or COLD

 

[rfc2307]

"Output Shaft" is on the right track, If I move the control cables, no "bonk" noise, only (in the past) when tapping brake going down hill

 

[Slow Left]

I think that 'bonk' sound is only when actuating either the 'Recirc/Fresh Air' or 'Vent/Heat/Defrost' controls...not the 'HOT COLD' or fan speed controls...

Not sure how the downhill/uphill factor fits into the cause and effect. Could that just be a coincidence based on timing in your normal routine?

 

[Output Shaft]

I think that 'bonk' sound is only when actuating either the 'Recirc/Fresh Air' or 'Vent/Heat/Defrost' controls...not the 'HOT COLD' or fan speed controls...

SL you are absolutely correct. I makey boo boo.
Hot to Cool never made a 'bonk' for me. Always has been silent.

 

[Slow Left]

SL you are absolutely correct. I makey boo boo.
Hot to Cool never made a 'bonk' for me. Always has been silent.

What is the cause of that sound? Some sort of 'diverter' plate opening/closing within the air/heat ducts? If so, I reckon there is some wire that goes between the selector at the dash and the plate that is opening/closing...maybe the cable is bent/broken, or needs some graphite lube...

But either way, once the engine reaches operating temp and if the heater control valve in the engine bay is working, and the heaters are working, then I would think that there would be heat, just not blowing full blast, but should still be able to sense it...

 

[rfc2307]

So.....the heater control valve on the firewall is golden. However, after the engine is warmed up I cannot feel any heat from the vents, no matter which combination the control sliders are in. Does one of the sliders control a "diverter plate" apparatus? In a perfect world, I'd pull her in the garage and get out of the cold and make some headway, however my sweetie is currently using the Garage as her HOARDING zone.

 

[Mace]

On my 60 I have a cable down by the 4wd shifter. This cable controls where the incoming air is sent, either through the heater core or the AC core. When I push or pull it, it makes the "thunk" that you describe.

I cannot think it is a stock setup. However, I have never bothered to look into it enough to see where the cable "should" go..

 

[gregnash]

I get the same bonk when I switch the vent/defrost/heat positions and believe it is a diverter plate in the air system. You may need to take you system apart and will probably find something blocking it.

 

[Mace]

Here is the cable

 

[Slow Left]

Page 12-90 in the Body chapter of the 1980 Body_Chassis FSM shows that there a are 4 wires leading from the controls to different components

You can download the FSM here:
https://forum.ih8mud.com/threads/fsms.743084/

 

[jeffsclan]

Funny, that just happened to me last night. After a thermostat replacement and a heat core flush I was ready to roll it off a cliff. My brother noticed the cable to the diverter door was unhooked. Like in Mace's pic. He hooked it up and in five minutes fixed what I'm been dealing with for days