fj62 front heater help (1 Viewer)

[franklin40]

So I recently had a 1hdt swapped into my fj62. it has a new thermostat and the heater lines are run as close to the original set up as the new engine allows. the heaters both worked well prior to the swap. now the rear one works fine but the front won't heat up if I have the fresh air on. it used to heat hot in this configuration and would help keep my windows clear. now if I put it on recirculate I can get it to blow close to hot but the windows frost up that way. I figure my heater core is fine as it heats the front when on recirculate just not with fresh air!! any suggestions as to where the problem might lie. it's my daily driver so I dont want to pull the heater and dash all apart without having something to look for. can't find any threads with this exact same problem. engine will heat well above 1/2 up the gauge with cardboard up front and it'll still blow cold with fresh air on.

 

[red66toy]

It sounds like either the heater control valve is not opening enough when you are turning on the heat or there is a blockage somewhere. You probably only kind of feel heat when the recirc is on because the inside air is not cold enough to mask what little heat the heater core is putting out.

 

[Elbert]

have you made sure you have all the air out of the cooling system? are both heater hoses that feed the problem heater core hot to the touch. Does your heater control valve control coolant flow to both heater cores

 

[franklin40]

by heater control valve do you mean the water valve on the fire wall? the heater slide control wouldn't slide all the way if that was stuck would it. my heater slide moves fully and opening it manually goes to the end of the cable throw. it can't open further. it's got the rear heater on a seperatel valve. I'm pretty sure all air is out of the system. how steep of a hill do I need to be on to burp the system. I have tried this but maybe my nose was t high enough. it would seem to me that if there was air in the system it would affect both heaters wouldn't it?

 

[red66toy]

Correct, the firewall mounted valve. Well the control wire could have been slipping through the mounting point on the valve if the slider was actuating the whole range, was just a thought. That would have given you a false impression of function. If the valve is opening all the way then I vote for blockage/air bubble.

 

[Output Shaft]

Turn off the rear heater valve. Then slide the front heater valve to HOT to purge the front heater core of air. Keep the rear heater valve off until the front has purged and is blowing hot air.

Running the engine at a higher RPM increases the water pressure and will help it purge.

 

[franklin40]

thanks output shaft. I'll have to find a steeper ditch that I won't get stuck in!! I have about two feet is snow to contend with! how long do I need to run the truck with the front end up and rad cap off? do I need to rev it at all to get the pump pushing extra fluid?

 

[Output Shaft]

What has likely happened is that the lower rear heater plumbing has purged itself of air and is flowing coolant as it should. Everything about the rear heater is lower than the front, and if the rear heater valve is open when the engine is filled with new coolant and started up for the first time, the coolant will take the path of least resistance.... downhill, via the rear heater plumbing.

Once the rear heater plumbing circuit has purged itself of air, the front core, which is higher than anything in the rear is now a big empty trapped air bubble.

The return pipe (for both heaters) joins up to the radiator outlet pipe, just before the water pump. It is a small inlet that does not provide much suction.


What may be happening is that the low pressure of the water pump at the fitting at the back of the head does not have enough pressure to overcome and push out the trapped air in the heater core, which is an uphill proposition. It now will have to push the air DOWN to the return plumbing.... Which is filled with coolant.

My guess is....
If you keep the rear heater valve always off and the front valve always on.... and just keep on driving the cruiser, eventually it will purge out the air in the front core.

That's my guess any way.

 

[franklin40]

my return is actually into the drivers side of the block so probably no real sucking neg pressure at all. I'll give your suggestion a go and report back.

 

[Elbert]

by heater control valve do you mean the water valve on the fire wall? the heater slide control wouldn't slide all the way if that was stuck would it. my heater slide moves fully and opening it manually goes to the end of the cable throw. it can't open further. it's got the rear heater on a seperatel valve. I'm pretty sure all air is out of the system. how steep of a hill do I need to be on to burp the system. I have tried this but maybe my nose was t high enough. it would seem to me that if there was air in the system it would affect both heaters wouldn't it?

yes...that is universally called the heater control valve (out under the hood on the firewall)... no to your questrion about air pocket...what if you have an air pocket in the heater core not working right... get the front of the truck up high, make sure the coolant is full, turn on both heaters all the way hot...let run until thermostat cycles and fill full with coolant and top off your overflow bottle.

Is the heater hose hot that feeds the problem heater core.

 

[Elbert]

thanks output shaft. I'll have to find a steeper ditch that I won't get stuck in!! I have about two feet is snow to contend with! how long do I need to run the truck with the front end up and rad cap off? do I need to rev it at all to get the pump pushing extra fluid?

certainly long enough for the thermostat to cycle....its not just a 5-10 min thing...

 

[franklin40]

just a follow up my heater still not working. had it checked out while in the shop for some other work. the core is plugged so getting flushed

 

[MacGYVER1979]

get one of these kits at walmart for 4 bucks, cut the hose and install the T with the cap, start engine and loosen cap till the air comes out, simple effective burp, also helps when doing a flush.

 

[franklin40]

i had some a/c work that needed to be done so just had the shop do it for me. i trust them so at least its done right.