Mmmmmm... what to you reckon ????

[Mellemel]

Will a simple "burping" fix this do ya think ? My rear heater wont blow hot. I disconnected the pipes in the engine compartment to the rear blower and sent water thru from the hosepipe, got a good flow in and out ! Great, now the in pipe gets hot under the car to the unit, but the outlet pipe under the car is still cold ! Is there an airlock in the system ?? or something sinister going on ?
Does the car need to be raised at the front also for this burping ?

Thanks.

 

[LIVEVIL]

Had the same issue and burping was the fix.

 

[Mellemel]

I tried burping it and now there is no flow from the outlet pipe from the rear heater ?? There was a good flow with the hosepipe too !! I got a lot of bubbles in 5 mins with the rad cap off, I'm gonna try raising the front and burping again. I wonder if the valve is opening properly under the seat on the blower unit ? It looks as if it is. The inlet pipe gets hot so I'm half way there.

 

[TheDurk]

I tried burping it and now there is no flow from the outlet pipe from the rear heater ?? There was a good flow with the hosepipe too !! I got a lot of bubbles in 5 mins with the rad cap off, I'm gonna try raising the front and burping again. I wonder if the valve is opening properly under the seat on the blower unit ? It looks as if it is. The inlet pipe gets hot so I'm half way there.

There is no separate rear valve. The rear core is hot all the time as long as the front heat is on. It's the air damper and the fan that control whether that heat moves into the cab. Did you have the front heat on? Follow the second diagram closely...

If that's not it, you might check for obstruction at the small leg of the divider fork (87265B in the second diagram.)

 

[3bears]

thanks Durk, you always seem to have good info and photos, I wondered exactly how this all worked.

 

[Mellemel]

That's awesome, Thanks. Tried burping again, it feels like both in and outlet pipes are getting hot but I think it's from engine heat under the hood ! There does not appear to be hot air from the rear blower yet ! Def got a few small bubbles from the rad cap. How long should the burping process last ? Would it help to squeeze the upper hose to the rad or is that just going to suck air back in ?

 

[ShooterMcGavin]

Did you try raising the front of the vehicle off the ground? I'm just curious if that method helped you or not.

 

[TheDurk]

Did you try raising the front of the vehicle off the ground? I'm just curious if that method helped you or not.

That's been key for me, although I just park uphill or with the front wheels up on a curb. Get the engine hot enough to open the thermostat and you can see flow in the top of the rad, and that does it for me.

My son's BMW 323i is famously hard to burp. Those forums recommend squeezing both hoses and it does help, but I've never needed to on the 4Runner.

 

[Mellemel]

Well I raised the car up on ramps about 10 inches which helped some but not many bubbles came out, so I squeezed the top hose and bubbles galore came out ! I think I still need to "burp" it some more to be honest.
What's annoying is that there is a free flow of water from the hosepipe in the in and out the out that I shot thru it, so there is no blockage ! It's just gotta be an airlock in there when I put the hoses back on. Grrrr.

I assume I am burping it correctly, I take off the rad cap when cold, start the motor, let the engine temp get hot, the water in the rad slowly rises and spills over and a bubble pops out, if I squeeze the top hose more air bubbles appear, so I top up with coolant . The overflow reservoir is at the full mark. I guess I keep doing this until all signs of air bubbles stop ?