I've been battling this all summer. Does anyone else experience hot air seeping out of the vents (dashboard and floor level) while the air conditioner is off? I like driving w/ the A/C off and windows down but when it's hot out it's hard to control/stop the heat from coming through the vents into the cab.

The temp setting gets set to "LO" or 60 degrees. Then powered off. Still hot air finds it way through.

Also, the trim areas by the cigarette lighter and window controls get really hot.

It could be from when I cut out the shifter surround plate during the CDL install. Engine heat must be finding it's
way in. I thought I sealed it up pretty good, but...

 

Yup.

I find that if I turn on the A/C for a moment, it gets a little better for a short while.

 

Bypass you're heater core with one of these.




then apply vacuum in winter / unplug vacuum in summer.

 

It's normal I wouldn't worry about it - the heater core on these vehicles is no joke, and made worse by the bizarre coolant bypass loop cooling system which sends more (and hotter) coolant through the heater core than conventional systems; albeit mostly at idle, but still. Also due to the nature of the system there is no "valve" to shut off coolant flow like many people seem to think there is. 200 deg water is always being pumped through your dash even in the middle of summer.

The air pressure at the front of the vehicle is higher than the rear obviously, which is why air flows while the blower is off. Why the heat side of the system never fully closes is beyond me, but might also be due to the temperature build up on the hot side.

Once the heater core flaps "shut" (any temp below current cabin temp) putting it all the way to LO won't change anything, the flap for the heater side of the HVAC is still shut.

If you're experiencing heat that far into the dash system it's almost certainly NOT from the engine - again, you're pumping hot coolant into a heater core which resides inside the center of the dash exactly where you're talking about - which is a FAR more concentrated source of heat than radiant heat from the engine bay.

 

Same here. Must a "Rover" thing. I see your stock. So, that means you didn't hack into the metal plate underneath your shifter. Hmmm!

 

Has anyone used this? Should I be concerned about adverse effects. I shouldn't, right? Does the heater core play an intricate part in the exchanging/disposing of heat?

 

In short yes, but that hasn't stopped plenty from bypassing it before.

 

Chevy Chrysler jeep dodge ford BMW have all bypassed the heater core when not in use since the dawn of time. Whats the super complicated engineering mystery behind land rover not doing it? They're retarded.

 

That's how I felt when I bypassed my heater core. It can't negatively effect cooling temps that much, and I would think if it did it would just be cherry on top of another hidden cooling problem. I just had mine bypassed for a short span anyway, I wanted it back to it's original cooling design and temp, plus I need heat !)

In short OP, as someone who has replaced their heater core() yes. I've bypassed my heater core and drove to and from while waited for parts. But I always checked my setup and hose clamps. I fashioned my own bypass with hoses. The one RMT posted is a good bypass set up and sturdy.

 

Rover used to cut off flow to heater core, the current system is a way to please folks that want a little heat, etc. If bypassing the heater core, keep the coolant flow going as a loop, don't stub it off. On a D2 you don't need to decrease the coolant flow entering the top of the thermostat. That small flow mixes with coolant from the radiator, and warms up the stat to open. You certainly don't want the stat opening later.

The problem of fresh air ventilation and heater cores has been around a long time, back in the 60's Chevy owners who did not have AC would install a plumbing valve at the firewall to kill the hot flow to the heater core. And plenty of Rovers in warm climates have the heater core bypassed.

Two potential problems come to mind. First, the diagnostic for air in coolant or exhaust gas in coolant is removed (bubbles thru pipes under dash). Second, when servicing cooling system, will need to remember to flush out the heater core. Heater core needs antifreeze. Replacing a heater core introduces the technician to the concept that the truck is built around the heater core.

I think the vac operated valve is an elegant solution. There will even be some flow from time to time under wide open throttle, which might be a plus.

Plumbing flow diagram attached.