Nightmare! Heater valve, heater tube

So, the heater wasn’t working, not that I need it, but I like all things on my cars to work. Also, nice for fall/early spring driving.

Removed a couple of the HVAC water hoses from the behind the firewall heater tubes to determine if I have a blocked heater core, valve, or something else. This was after feeling the hoses on a warmed up car and determining fluid was NOT running through the heater core. Pulled off the upper heater core hose and the water inlet hose to the valve to test the water valve with compressed air. Not working, air would not flow. Time to remove the water valve (cable working) and see what’s what. Well, what’s what sucks. The whole thing is corroded with the part of the tube piping forward of the firewall “welded” to the valve and now separated from what’s left of the tube. Ugh. Believe me, I was gentle in coaxing off the valve having done some reading here. The parts of the tubes exposed that are projecting from the firewall don’t look too terrible, but need a testing and cleaning. I do see that the firewall plate is missing where new rivets were put in (previous owner) at the heater inlet tube. And the plate on the tube to the left of the corroded valve tube rotates, the tube can be pushed in (rivets somehow sheared). I will bypass the entire HVAC water system for now and probably flush the cooling system.

So, fellow S1 enthusiasts, how do I proceed? How much ripping apart do I need to do to replace the ruined tube from the valve to the heater inlet. Is there a way in? I was hoping maybe from where the heater box connects to the firewall, but from pics I see it doesn’t look that way. With the top off the dash, can I reach down with the windshield in?

My friend, and learned member on this board, Tom D, did point out the silver lining. At least I’m not discovering the problem stranded on the side of the road with antifreeze pouring out from under the dash. I’m grateful for that.

Thanks in advance for any help,

! 20190628_202611|281x500

Replace the tubes, all three of them. SNG has them in stainless, and it’ll be sooo much fun.


EDIT: IIRC, there three differing size of tubes.

1 Like

You’ll need to replace that heater pipe and the others based on the condition shown in the photo. Heater valve as well (ask for the correct o-ring !).

Do your homework and prepare mentally for this project. Access is difficult , I did mine thru the instrument panel after removing the dash. Windshield in place (OTS).

Good planning (there is a good video on you tube), patience, wine, cussing , band aids and before you know it you’ll be done. It can be done in a weekend.

Good luck


1 Like

Retaining the services of a mechanically-minded 12-year old, with small hands and slender arms, is a plus.

I did mind with the windscreen out: not a clue how one does it with it in place.

1 Like


As mentioned before I believe an OTS has the advantage of being able to lower the top…


1 Like

If anything needs refurb in the wiper or screen washer plan on doing that also, as it has to come out.

Morning John,

I’ve done this on a FHC and it wasn’t much fun but it was doable. Heres a link to the blog I did describing it, hope it is useful:
Getting the pieces riveted in was a bugger with the ancillaries in the way but…

Don’t feel bad about having broken it. If it broke just trying to remove a valve from the end then you were living on borrowed time. Imagine what a nightmare it would be if one started leaking inside the bulkhead.

It’s not a super hard job and you’ll learn how to take your dash apart. Everyone loves doing that. It’s as fun as painting a fence.


I may be misreading this, but just to be sure you realize - there is no plate on the water-valve end of the pipe that goes to the heater. This photo should clarify:

Good luck - it’s much easier with an empty engine bay!

I’ll echo what others have already said. I sort of enjoyed doing the tube replacements the first time.

  1. Use stainless tubes
  2. Follow the replacement process in the YouTube video.
  3. Read Lynn’s blog
  4. If a small armed child is not available use one of these when reaching through the access hole into the firewall nether regions:

I always wondered about you.

Not any more.


1 Like

I was referring to the outlet side of the valve/heater tube. Please see my 3rd picture. It has a couple of fresh rivets but no cover plate.

Thanks for the comments so far, I’ll consider the suggestions. My car is a FHC. We’ll see where this ugly journey goes!

Since the next one is a 4-day weekend (in the US) I will agree.

X2 on the Kevlar sleeves:

Here is Cy Stanton’s video on the subject:

“Muah hah hah hah…”

1 Like

given how much time I spent on getting these in, I can understand why he flung the plate away.

Keep track of the order you remove the pipes in and how the bottom two are overlapped each other. It is likely that’s the only order and arrangement that is going to work

And DO NOT drop anything: in those depths of the inner cowl, only demons live.


I put a long string on that little clip on the wiper mechanism and tied the end outside some where although, I believe they are now available.

While you have the heater system apart/drained down, you should put a new heater core in the heater box, and freshen up its innerds. The heater tube replacement job is fiddley, but you will only have to do it once. You may find that the heater valve is too tight to easily slide over the metal tube. If it doesn’t easily slide over the tube, you will end up pushing the tube back inside the firewall space on reassembly. I polished up the heater tube a bit with some emery cloth, and carefully used a large (1/2 inch??) drill bit to minimally enlarge and smooth the heater valve hole on the firewall side. Be careful and manually enlarge the hole by clamping the drill bit in a vise facing up, and hand-twist the valve down on the drill bit, so you don’t get any metal shavings into the valve body.

…and so it begins. I started out needing a windshield replacement. Still can’t get the bonnet on properly

1 Like

I think many can relate: @j_limongelli certainly can!