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Discussion Starter #1
Does anyone know what this thing is? I found it in the passenger side wheel well "under" the fender of my '68. It seems to have two spouts sticking out into the passenger side engine bay with nothing connected.




Bonus question: My heater control valve (the valve bolted to the passenger side firewall with a vacuum line, I think this switches the heater core coolant loop off when you turn the AC on). This thing leaks a little bit and I haven't had time to replace it yet but, is it possible for that to leak while I drive and for it to somehow get coolant to the top of the fender (where the fenders bolt to the front clip) and for the coolant to run down the bolt and drip where the red circle is in my pic? Not sure if what I said made any sense, I'm just weirded out there is coolant there.

Thanks all in advance!
 

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That's a vacuum canister. It's designed to let your manifold create a 'reserve' of vacuum, so you can run your vacuum-operated heater/air conditioner stuff consistently, regardless of what the engine's doing. It's possible that the previous owner just didn't understand or care about any of those vacuum lines, so he plugged them off, or perhaps has the climate control accessories running directly to the manifold. The Mustangs don't have a lot of vacuum-operated equipment anyway.



And for the bonus question: Yes, definitely. Liquids really get flung around in your engine compartment when you're driving around. There's a lot of vibration and rapidly-moving air in your wheel wells and engine bay, so it can get everywhere.
 

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That's a vacuum canister. It's designed to let your manifold create a 'reserve' of vacuum, so you can run your vacuum-operated heater/air conditioner stuff consistently, regardless of what the engine's doing. It's possible that the previous owner just didn't understand or care about any of those vacuum lines, so he plugged them off, or perhaps has the climate control accessories running directly to the manifold. The Mustangs don't have a lot of vacuum-operated equipment anyway.



And for the bonus question: Yes, definitely. Liquids really get flung around in your engine compartment when you're driving around. There's a lot of vibration and rapidly-moving air in your wheel wells and engine bay, so it can get everywhere.
Grimbrand is on 100%, that's for the A/C system. If it's not hooked, the various doors and motors would be in constant movement as the vacuum signal from the engine changes.
 

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It looks like they have you covered.

As for the water control valve, it’s pretty easy to test, fix or replace. Show a picture to see if you have the original.
 

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Yup typical Ford Vacuum canister. Ford was so cheap that they were scrounging the trash cans of the local neighborhoods for materials and found a use for old soup cans. Yes it is an actual tin can for food. They were using them into the late 80s and possibly early 90s.

Course Ford has nothing on Piper. If you look at some of the stuff on their old planes you will see the brake master cyl reservoir is a can of cox .049 fuel. The elevator trim crank is a GM window crank mechanism and the parking brake lever is a GM brake lever and so on.
 

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The vacuum canister is for the A/C. The tilt steering used a similar canister mounted under the battery. They have a built in check valve. Most likely the check valve failed or the canister leaks and the PO disconnected it. There is always the possibility the PO just didn’t know to connect it when replacing old hoses.. it’s not critical for the A/C but ensures the vacuum driven doors don’t move in a low vacuum situation.

Yes they are seemingly expensive to replace. NO don’t go cheap and buy a Chinese knock off.

I bought a “cheap” $75 unit for my 68. Ended up buying a $90 replacement a week later. The cheap one didn’t have the ridges to stiffen the sides. Amazing what 20” of vacuum can do.



Not all original Ford canisters had te ridges either. The OP’s doesn’t appear to, but they were made out of much stronger and thicker metal in the 60’s. Also test the check valve when you get it. I had a bad one right from the factory. The good ones are made by Classic Auto Air and sold by NPD and others.
 

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Discussion Starter #10
Thanks everyone, super helpful as always. Looks like I'll have to reroute the vacuum lines sometime in the future.

It looks like they have you covered.

As for the water control valve, it’s pretty easy to test, fix or replace. Show a picture to see if you have the original.
I'm pretty sure I have an original, it has a ford part number. I don't know if it works but it leaks...

 

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The control valve is held to the bracket with 3 screws. There is an inset gasket that you will need to clean out...it was originally some type of fiber paper that is probably hardened and brittle. I went to the local hardware store (not big box) and got an appropriate O ring and put a little RTV on it, then fastened it up.

While it is apart, you might want to make sure the plunger moves up while applying vacuum. You could also run water through the inlet at the same time to make sure it seals.
 

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Discussion Starter #12
The control valve is held to the bracket with 3 screws. There is an inset gasket that you will need to clean out...it was originally some type of fiber paper that is probably hardened and brittle. I went to the local hardware store (not big box) and got an appropriate O ring and put a little RTV on it, then fastened it up.

While it is apart, you might want to make sure the plunger moves up while applying vacuum. You could also run water through the inlet at the same time to make sure it seals.
Thanks for the tip, I will give that a try before I order a replacement!
 
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