In the process of hooking everything back up after the engine install, Ive located an unknown vacuum line.

I though it went to the cruise - as the car is equipped with cruise, but when I looked under the dash it just end there.....not connected to anything and I cant find any other hose or connection there?!?!

It travels along the D/S fender and enters the firewall on the left side of the brake booster between the booster and the fender.

Can anyone identify it and where it connects??

Heres a pic....

 

I've got a 1971 Cutlass wagon project car with cruise. I'm pretty sure the cruise control has a vacuum line running to the brake pedal. If I remember right, there's a switch on the pedal like the brake light switch, but it will turn off the cruise if you step on the brake pedal. Does your car have something like that? John

 

I'm surfing my photobucket site to see if I have any pictures of the cruise parts. I only found one under hood picture, so I went out and snapped a couple under the dash. There's a swith for the vacuum, but also a different switch with more wires for the brake lights. Let me know if these show what you need. If not, I'll be able to take more pictures tomorrow. John

P1010016-4.jpg

P3240349.jpg

P3240350.jpg

 

There should be a vacuum switch on the brake to release the vacuum when you apply the brake.


The brake light switch has an extra set of wires to release the electrical part of the cruise.

 

Yep, John hit the nail on the head!

 

Thx a lot guys! Yup this should be it.

Gonna pop out to the garage now and see....

Appreciate the pics.

 

Update - John your pics solved it for sure.

I have exactly what you have at the brake pedal - minus the plastic switch at the end of the vac line. I only have a dangling vac line and the empty hole above the brake light switch where the plastic vac switch mounts.

Guess the prev owner removed it...

Any ideas where I might get one? I didnt see one in Fusick catalogue....

 

I have only seen those used - not repopped. I need one of those, too, as mine leaks.
I wonder if one from another make, year, or model of car would work......

 

Yes, GM used the same switches on all the car lines for several years. Has anyone checked a GM dealer parts department?

 

GM did use those vac release valves on several models through the 70's at least.
Part #407347 and they've been discontinued for a while at the GM dealers.
I saw some on the Parts Voice search but those places they link too seem fishy, but who knows.
The other switch cuts the cruise out if you hit the brakes too, not sure if it's the same as a regular brake light switch.


http://www.partsvoice.com/ContentPages/FindParts.aspx

There's an NOS one on evilbay for 25 bucks, I'd jump on it right now if I needed one.

http://www.ebay.com/itm/ws/eBayISAPI...sid=p2992.m753

 

I don't have any personal experience with these switches myself, but if all the switch does is to release vacuum (open) or cut off vacuum (close) when you step on the brake, you can duplicate its function with an electrically controlled vacuum switch (as used in some emission controls) and a relay, in order to get the system running.
The original switch was probably the cheapest solution at the time for GM, but current circumstances may make a different solution more practical for modern owners.

Just a thought...

- Eric

 

The original setup also included an electrical cutout for the cruise system when you'd step on the brake. This vacuum switch was a very simple was to dump the vacuum also. I think the simpler it is, the less of a chance of a failure. Make it too complex and it could fail. I like the concept, but that darn part is just so hard to find...

 

That's my point: The concept is good, but if you can't get the hardware, you might do better with a relay off the brake light switch and a junk emission control valve right next to the cruise control unit on the fender.

- Eric

 

Don't want to add anything electrical into the system; there's enough already. The 80's Cutlii and B bodies used a vacuum release valve that is similar but would take a different mounting method.
I am sure other cars of that era used a similar vacuum dumper but have not had the resources to research it. Need to go junkyard scrounging some time to see what I find.

 

While I understand if a replacement part can't be found a modification might be necessary, I agree with the KISS principal being the best way to go on this. The original setup worked fine when it works.


That switch allowed unfiltered air from under the dash to be pulled in to “dump” the vacuum. I wonder if you might just have a bit of grit caught in the switch? If it isn't cracked or broken, it might be worth a try to flush it with clean water to see if it cleans up.

 

What happens is that the internal O-ring dries up, shrinks, or breaks. It is TINY! Smaller than any O-ring I have ever found in any hardware store. It measures 0.2"OD x 0.1"ID x 0.075" thick.

 

My biggest issue is my switch is missing. So not only do I need the plastic switch that goes on the vac line/brake bracket but prob also a few cruise parts under the hood like the vacuum modulator that mounts on the intake.

Didn't see any of that in Fusicks catalogue or anywhere else.