Heater valve replacement

[Ellie]

Hi, Having read several threads here I know I am not alone in the unpleasant experience of having a floor pan full of coolant. So I have taken out the console and can see the coolant coming out of the heater valve. Does the whole heater box need to be removed to replace the valve? or is it just as easy to do the replacement working under the dashboard?

[spider2081]

I have changed the heater control valve in the car and didn't remove the center console. I think being physically a small stature person helped. I pushed the passenger seat all the way back and went for it. The nuts holding the valve to heater core can be a pain. I soaked them with penetrating oil and was very careful removing them. If the stud brakes off the heater core then the whole box has to be removed changing an hour + job into 4-6 hour job.
There are special seals the go with the valve to the core and pipe. Also if you have an original valve the replacements are different and require either bending the original pipe or making the hole in the firewall bigger. Another alternative is to buy special pipe sold by some vendors to mate new valve to existing firewall cutout.

[Ellie]

Hey thanks for the confidence boost. I was under the dash and figured I could do the job from there, upside down of course, but if I could avoid having to take out the whole box it would save time and avoid disrupting components that haven't seen the light of day for 30 years.

[wizard124]

Hey thanks for the confidence boost. I was under the dash and figured I could do the job from there, upside down of course, but if I could avoid having to take out the whole box it would save time and avoid disrupting components that haven't seen the light of day for 30 years.

But, dropping the box provides the opportunity to:
1) clean the grime out of the inside of the box;
2) clean and lubricate the fan motor,
3) inspect and flush the heater core

[Ellie]

Absolutley true. Having seen the years of dust and grime under the console I think a thorough clean out will do a lot of good.

One question... Although the manuals all say to drain the cooling system first, there are some suggestions that this is not neccesary. I could just catch the coolant that flows into the heater core when disconnecting it. Is there any merit to this plan?

[DanD]

If you clamp the hose to the water pump return shut, you can disconnect the hoses in the engine compartment, and do the repair. However, you should take a really good look at those hoses, particularly the little bent one.

If that hose looks in any way tired, you should replace it. If you are driving along and it fails, you will overheat your engine in a flash. Also, be aware that you can install the new heater valve two different ways. If you install it the wrong way, it will fit, but the pipe going out to the engine compartment won't line up right.

[Ellie]

I want to make sure that everything is in top shape after this so all the hoses are going to get a check over.

Great advice, cheers.

[Ellie]

Ok so I've had a really good look under there and I may be missing something, but is there a trick to taking off the heater valve? I cant see any way possible in getting a wrench to the four bolts holding it in there. Also, how difficult should it be to remove the whole heater box? I reckon that after I have unbolted it, there will not be enough room to slide it out. Is this a tricky manoeuvre? do all the cables to the heater controls stay attached and the whole lot comes out?...so many questions...

[timspider]

I just did my 78 over the winter. I avoided taking the whole thing apart as long as I could and eventually just took the core out and the whole box.
I'm really glad I did. The core had a birds nest sitting on it. The little vent door was rusted in the slightly open position, so that never worked at all. Now the 3 cables are all refurbished and the fresh air vent door opens and closes.
the difference is huge.
so my suggestion is pull it if you have the time.
start by unclpping the 4 clips that hold the upper and lower box together. The lower portion should drop down if wiggled.
the thing that helped me at this point was loosening the heater hose pass through gasket on the firewall from the engine compartment and removing the 2 heater hoses.
that freed up the core itself so I could wiggle that out of the box, with the 2 short pipes still attached.
not sure that's the best way as its the only time I've done it but it worked.
if you take the core out then you can attach the new valve and pipes to it as an assembly, then slide the whole thing in.
for me that was a lot better than trying to do it upside down in the car.
also suggest taking passenger seat out. 4 bolts and makes access a LOT easier.
good luck!

[fredguaz]

Totally agree with Tim.
Pull the box, lube the cables, lube all hinge points and flap, clean the core (for 80 bucks, I would replace it with new and be done), replace the foam, lube the blower motor to stop the squeal, etc. it will all work like new and you'll never have to mess with it again.
It's easy to do and you won't regret it.
I was able to re align the short tube to fit the new valve with oxy acet torch and lots of trial and error. Also, your heater box attaches to underside of cowl by either 3 or 4 studs depending on the mood of the factory workers!

[So Cal Mark]

I offer re-designed heater pipes that properly fit the replacement heater valves. Stainless steel of course so they won't corrode like the originals

[Ellie]

Thanks Tim and Mark, In your post Tim, you say the heater core wiggled out from the top part of the box, is there any further clips, screws, etc holding the core in? Or is it really just the case of "wiggling" it out? It feels like it should but I usually break something I can't see when I get to this point of removing parts.

[Ellie]

Ignore that last post, job done. The problem was the ground wire for the fan was at full stretch and wouldn't budge. However the annoying thing was that the air con unit was covering the connection. All the trouble I had revolved around accessing that screw. Once that was done everything else came out, including bits of straw and 30 years of dust and grime. The fan and heater core are on the workbench now getting a thorough cleaning and testing. It's all good! Hopefully I'll remember how it all goes back in.

[timspider]

sorry for delay- been offline for a bit- great to hear that you had a break through.
for me, it went back together a lot easier than it came out, but I'm not dealing with A/C.
once it's back together, it will feel great every time you adjust any of those three cables

[Ellie]

I'm now in the process of putting it all back together. Heater core is all good, and the fan had a service too. Just noticed that the fan blades draw air away from the core, is that right? I guess the fan fan pulls the air through the core and blows it down and out the vents.