additional air slide valve - checking off car?

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wattsmonkey
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additional air slide valve - checking off car?

Post by wattsmonkey »

It turns out this valve was not working, adding to start-up problems. Not seized, but not moving. using spare from an M635 results in starting straight up, but (as you'd expect) idle is high. Still stumbling until throat clears.

Possibly a stupid question, but once it's established the disc isn't seized, can they be checked by applying 12v off the car?

Thank you,

Rob

Under "cooling system" on realoem!
additinal air slide valve 13631284414.JPG
additinal air slide valve 13631284414.JPG (40.14 KiB) Viewed 951 times
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86_6series
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Re: additional air slide valve - checking off car?

Post by 86_6series »

I would read the voltage going to the valve first.
If it's 12v proceed on the bench.
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wattsmonkey
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Re: additional air slide valve - checking off car?

Post by wattsmonkey »

Of course!

Many thanks,

Rob
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
wattsmonkey
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Re: additional air slide valve - checking off car?

Post by wattsmonkey »

Well, every day is a school day.

Here's a new valve.
152 valve july 84 635.jpg
152 valve july 84 635.jpg (27.99 KiB) Viewed 867 times
This is what the additional air valve should look like.

Here's one of four broken valves, all of them look exactly like this:
broken E12 valve.jpg
broken E12 valve.jpg (31.38 KiB) Viewed 867 times
This is the wrong one for the car, but the aperture visible is the same on all four, including the broken one on the car (hence the confusion).
All four discs move freely.

Now I know what a good'un looks like, diagnosis is super-easy - if it's pretty much closed when it's cold (like the above pic), then it's broken. The voltage to the valve is constant when the car is running, heating up the element inside the valve and closing it. If it's already closed then there's no additional air getting in on start up, so cold starts require the application of throttle to compensate. This much is obvious to all you learned people, no doubt, but because I didn't know how much of a gap there should be, I was thinking the small gap was normal! Every single spare being broken does seem a little unfortunate, in my defence.

For reference, here's the M valve - the shape of the disc doesn't look much different, but common sense dictates that its closed position still lets a lot more air through than the cooking 635 one does, hence I was running rich with the M valve.
M635 valve.jpg
M635 valve.jpg (30.77 KiB) Viewed 867 times
The difference in driving the car is remarkable, as you might imagine.

Also, I learned that I've been misspelling "aperture"!
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'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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Re: additional air slide valve - checking off car?

Post by Jubilados »

I’ve done a bunch of work/experimentation with that valve. Some things I’ve learned.

There’s a million different part numbers for that piece, but they’re all basically the same and other than maybe some very odd applications, they are interchangeable. As long as it’ll bolt to the car (and they seem to all have the same bolt pattern).

They can be “fixed” sometimes.

The first fix try is to put it in the fridge or freezer for 10 minutes and see if it’s opening all the way. (It doesn’t open completely. The one in the pic attached is open all the way). Then apply 12 v and see if it’s closing all the way.

If not, you can shoot some carb cleaner in and work the disc back and forth with a small screwdriver to see if it’ll loosen.

If it isn’t closing all the way when cold, the spring is broken or damaged (the spring holds it closed when 12v isn’t being applied). That’s a tough fix, you’d have to open the unit (not an easy task) and substitute the correct length and strength spring. Not sure how you’d figure that out.

Mine was closing all the way, but not opening quite enough. So my car when cold would sometimes need some throttle to start.

I took a Dremel with the long pointy grinder attachment, and ground off part of the disc to let more air in. I was careful to take material off an area that allowed it to still be fully closed when the car is giving it 12v. See picture.

It worked perfectly. I started small, then kept taking off material until the car started up properly when cold. Worked great.
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wattsmonkey
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Re: additional air slide valve - checking off car?

Post by wattsmonkey »

Thank you, Jubilados, that's really helpful.

I know what you mean about the apparent interchangeability, but I was running like a bag of nails at idle with the M valve (in full working order) - a rich-running bag of nails that smelled of petrol, too!

I'll try the freezer trick, would be nice to have a working spare again.

Thanks again,

Rob
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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Re: additional air slide valve - checking off car?

Post by Jubilados »

wattsmonkey wrote: Tue Jun 20, 2023 12:37 pm Thank you, Jubilados, that's really helpful.

I know what you mean about the apparent interchangeability, but I was running like a bag of nails at idle with the M valve (in full working order) - a rich-running bag of nails that smelled of petrol, too!

I'll try the freezer trick, would be nice to have a working spare again.

Thanks again,

Rob
As far as interchangeability, it seems like the only difference in running would be initial startup and the first 2 minutes or so while the car is warming up and the valve is closing.

Because after 2 minutes the valves all function exactly the same - they are fully closed.

(This of course assumes functioning valves).
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Re: additional air slide valve - checking off car?

Post by Stoffie »

Interesting topic, didn't know there were M6 specific ones.

Always found cold idle to be quite low on my M635 so maybe it has the wrong type in there :-k
The M88/3 was all about power, no cats. At idle the raw fuel from the exhaust will make your eyes water like an old V-8 powered muscle car's exhaust did.
wattsmonkey
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Re: additional air slide valve - checking off car?

Post by wattsmonkey »

I didn't realise that they should close completely. Yes, that makes sense - I used the bypass adjustment to bring the idle down to a sensible level on startup with the M valve - that's why it wouldn't run right when warm.

Thanks again.

Stoffie - if your M is a Euro, it should have the same number as the valve in my picture above.
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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