Seeking Heater Box Refresh / Coolant Work Advice

[Richie G]

I'm at the point I need to pull the heater box out so I can finish my interior work and figured while I'm at it will rebuild it and replace the valve / hoses.  I've found a fantastic thread on here for the restoral steps and gasket templates but still have some newbie questions to go along with it.

Before disconnecting anything I'm assuming a smart first step would be to drain the coolant to avoid a mess (and check the quality of the fluid / refresh it in the radiator).  First question is around that process / how far I need to go.  Is it necessary to drain the radiator and the engine block both and how much should I expect to collect from each?  Assuming both, once those are done would there still be fluid in the core itself to deal with and any advice on how to get that out without a coolant puddle in the interior?  My initial thought is leave the hoses connected to the core but disconnect them in the bay.  Seal them off maybe with ziplock / tape and feed them into the interior and take the whole thing hoses and all out of the car?

Andy detailed advice before I dive in would be appreciated.

[Yarb]

Take lots of pics!!

[siteunseen]

I used a shop vac on the return hose to suck the coolant out of the heater core.

My advice would be a good set of 1/4" drive sockets with at least a 10" extesion. Take the passenger's seat out then lay cushions over the door sill and the seat's mounting brackets. Then a bottle of ibuprofen or your preference. Just changing the valve and new hoses about killed me.

Another thing with the shop vac is you can "pull a vacuum" on the brass core and check for leaks. 90% of coolant in the cabin is from the valve not a busted heater core.

[Richie G]

Thanks.  Seat and glove box already out as this all started with a need to replace the sound deadening and firewall pad as part of interior work.  The dash is still in but since i removed the front / center vent assembly the main heater box seems to be able to slide out past the dash bracing without need for the dash removal.  The valve looks corroded as heck but I am not sure there is a leak so this job really is about refreshing the box/valve as needed just because i am pulling it anyway.  Last time i used the heater was for a brief moment or two just to verify it works when i bought it two years ago.  Blew warm but didn't really fire it up for all that long as living in CA don't really need it much.  Now I'm dealing with the snowball effect of thinking hey the box and hoses are out so lets change out to the correct braided look, oh and btw the rest of the coollant and radiator hose could use a "makeover" as well so thats where the questions began around drainage.  If my intention is to replace all coolant/radiator hoses as part of this mini-makeover I'm assuming we drain every drop and what's the best way to do that in what order?

[Richie G]

Got to this today and it was much easier than anticipated.  I've been procrastinating this due to worry of leakage and mess and had zero drops.  What i did was drain the radiator completely with the heater valve in the open position.  I contemplated draining the engine block as well but that drain plug is locked tight and in a tough spot to get leverage on without removing pipes or a lift.  So at that point the plan was to "minimize" the mess by loosening the two heater hoses from the engine bay three way and supply inlet and seeing if I could drain the core from the engine bay.  I was either going to use a shop vac or a handpump as suggested.

i started with the return hose and what i came to find was that it came off relatively easy and only had less than a shot glass of fluid that leaked out into a drain pan i had at the ready.  At that point i got some duct tape and sealed the end.  moved on to the other hose expecting fluid from both the hose and the engine block but nothing at all.  Sealed it as well and proceeded into the car. I had already removed the blower and the front vent box of the heater so all that was left was the 6 screws holding the box to the firewall / tunnel brace.  Undid those but also had to remove the small brace that holds the dashboard to the tunnel.  With that out of the way i simply slid the box out to towards the passenger side and fed the taped up hoses into the car from the engine bay.  No mess no fuss!  

The box certainly needs all new gaskets, a new valve, and a general cleaning.  there is liquid in the core I can hear sloshing around but it doesnt seem to be leaking as of yet.  When i take the box apart I can inspect it better for signs of previous leaks and deal with it.  All this work is probably a bit of a ways off as the primary goal is to get to the bare tunnel and firewall so i can complete my floorboard and interior work.  thanks to all with the advice.

[Richie G]

Following this up with potentially a silly question. But I'm at the point where I'm deciding if I want to pull the radiator and when I was looking at it and comparing it to some others I've seen either online or in the forums mine looks a little bit different. It seems to be original but I don't have the two threaded connections on the bottom side facing the engine down near the drain plug. What are those for and how come my model doesn't seem to have the? were there different versions over the years? It certainly is not an aftermarket I can take pics when I have some time if someone wants to look at it but I was just curious what those were for and why mine doesn't have them

[inline6]

I believe those are fittings are only on radiators for the 240z with automatic transmission.  They seem to be more common than automatic 240z's, in my opinion.  I think it's possible that for a number of years after production of the 240z ended, many, if not more than most of the replacement radiators were made with those fittings, as they are simply not used when the radiator is used in a manual transmission car.  Easier to manufacture and/or stock one part vs. two is how I see it. 

They are for running tranmission fruid through the radiator - this functions as an "oil cooler".

[Richie G]

Ah the oil cooler okay I saw mention of those. So because mine doesn't have them I would think it's safe to assume that it's original to the car or at least the correct version for a mid-71 240z manual

[inline6]

Yes, I think that is accurate.

[Zpenman]

Refurbished the heater box in my '71 last winter. Discovered a few pinhole sized leaks in the heater core and decided to use some Bar's radiator stop leak in lieu of replacing the core. So far, so good, no leaks with the heater going (never cold enough here to use it, but I do test it when I take the car out). My car is an auto transmission and does use the transmission oil cooling. Sorry for the late addition.