Water control valve replacement - HVAC removal?

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Theotherotter
Posts: 13
Joined: Mon May 15, 2023 6:16 pm

Water control valve replacement - HVAC removal?

Post by Theotherotter »

In attempting to replace a broken U-joint on my '77 530i, my water control valve (which had a tiny leak, but was fine) broke and left me needing to replace that (sigh). I did find a new valve - yay! I've read the FAQ here, read the old thread that touched on this, and I found a post on unofficialbmw.com that also touched on it.

It seems to be the case that if you don't have AC, it's not too hard to do; if you do, it sucks. I do have the AC hardware behind the dash, but nothing forward of the firewall - it was removed when the B35 swap was done ten years ago, I imagine. I can see how much of a pain it is to attempt to replace the valve with everything in place under the dash - my head wants to go where the pedal cluster is, bent 9mm wrench, etc. But given that my HVAC isn't actually hooked up to a working AC system, am I better off removing the HVAC unit from inside the car and replacing the valve once its out? Can this be done with removing the center console alone? Only the heater hoses would have to be done on the engine compartment side.

thanks,
D.
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Mike W.
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Location: Sonoma County

Re: Water control valve replacement - HVAC removal?

Post by Mike W. »

First off the HVAC is two separate components although they do share some things including the face level output. Removing the A/C would do nothing to aid you except allow you to then remove the heater.

However, while a bear of a job, it is not necessary to remove the heat or A/C. You have just enough room to get in behind and loosen, then remove the nuts. So little room you can't use a box end wrench, it's got to be a 9MM open end. It does require laying on your back across the door threshold, foam or towels to cushion things might be a good idea. And some sort of a light in there. A magnet wouldn't be a bad idea either as it's easy to lose one of those nuts, but while I've done the job at least half a dozen times now I've only lost one once. Having a spare 5MM nut or two on hand isn't a bad idea either, just in case.

It's doable without taking much apart, but no fun at all. And I presume you also have new O rings to seal it with?
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
Theotherotter
Posts: 13
Joined: Mon May 15, 2023 6:16 pm

Re: Water control valve replacement - HVAC removal?

Post by Theotherotter »

Yes, my assumption going in was that I’d do it with everything in situ - I’ve read (possibly from you) that it can be done that way, and I’m usually not a fan of extensive parts removal if I don’t have to do it. I have a brand new valve, new O-rings, Molykote, and five extra nuts. Two of the three nuts on the valve that I can see are 8mm (so I guess it’s been replaced before), and one is 9mm. Don’t know about the fourth. I figured I’d stuff a towel or something underneath to catch a nut if I lost it, and I have an LED work light, my headlamp and a magnet on a stick. I have thin hands and long fingers but I have no idea how I’m going to start those hidden nuts. But I’ve done jobs before, on other cars, where sometimes it’s just worth removing stuff so you have easy access to the one thing you actually need to change. So I wondered if that might be worthwhile here. I’m not about to remove the dash - hell no. But if I could remove the console and then pull the AC, blower and heater core out without spending tons of time - say no more than two hours - I might just prefer that to trying to do everything in place.
dutch
Posts: 27
Joined: Sat Apr 15, 2023 8:22 am

Re: Water control valve replacement - HVAC removal?

Post by dutch »

just wondering... where did you find a valve..? My non air 76 is mostly in pieces but the dash and heater are still in. I have no leaks but I thought about replacing the valve and core now... I have not seached very hard yet but it seemed the valve it no longer produced.
Theotherotter
Posts: 13
Joined: Mon May 15, 2023 6:16 pm

Re: Water control valve replacement - HVAC removal?

Post by Theotherotter »

I found it at LaJolla Independent. They were filed in my mind as a place that carried old parts so I thought maybe they'd have one. Called, they went and got their old-car guy (or one of them), he said sure, got a new one in a bag and I said I'll take it. I probably wouldn't worry if yours doesn't even leak, but I understand having a spare!

In my case, I was replacing the broken U-joint (I'd picked up a couple of used replacements locally) and I was having trouble getting the broken half out of the green bit on the valve - I couldn't get the best angle with a screwdriver to depress the tab enough to pull it out - and suddenly I pulled just *that* much too hard and the green thing came out of the valve. It was odd, because there was no fracture surface or any other witness mark to suggest anything had broken, and there was no obvious form of retention - yet retained it had been, until it wasn't. Nothing I tried worked to stanch the eventual faucet of coolant that would empty onto my shoe and the carpet when I ran the car. So it sits in my garage until I fix it.
dutch
Posts: 27
Joined: Sat Apr 15, 2023 8:22 am

Re: Water control valve replacement - HVAC removal?

Post by dutch »

ok, thanks.
I `ve had one fail in a hurry while doing 80mph... That indoor coolant and outdoor winter weather resulted in zero visibility within a second. That was kinda scary to say the least. :shock:
Theotherotter
Posts: 13
Joined: Mon May 15, 2023 6:16 pm

Re: Water control valve replacement - HVAC removal?

Post by Theotherotter »

Eek! That must have been exciting. Fortunately, I discovered that mine was not going to be in any way usable when I was driving it around the block as a test.

So my questions come down to two, really: 1)Can I remove the air conditioning and heater assemblies without removing the upper dash? And 2) about how long can one reasonably expect this to take? E.g. a few hours or all day?
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