vacuum hose thru the firewall

[tdr1919]

Quick question - while I was mesing around with the wiring to the clutch pedal switch, I knocked loose a vaccum hose coming through the firewall ( drivers side, up by the brake & clutch) where does it go to the dash cluster?

Thanks,
Tom

 

[gmjunkie]

Quick question - while I was mesing around with the wiring to the clutch pedal switch, I knocked loose a vaccum hose coming through the firewall ( drivers side, up by the brake & clutch) where does it go to the dash cluster?

Thanks,
Tom

It probly gos to a t or y fitting that splits and gos to the Clutch and Brake switch's for the Vacuum Dump to shut down the Cruse Control when the clutch or brake is depressed!!

 

[surfer93]

It is!

Just replaced mine, if yours is in as bad a shape as mine. Go ahead and replace it while your in there.
I think GM thought only midgets would have to work under the dash, doing anything under there is a real pain.

 

[Brian Smith]

gmjunkie,

I had the same hose and looking at the FSM it looked like there was NOT supposed to be a vacuum connction to the brake switch even though there was a hose barb on the switch. My hose only went to the clutch switch. A few weeks ago I was halfheartedly troubleshooting the inoperative cruise control and my neighbor came over and him being twenty years younger than me and aparently predisposed to helping by laying on his back to adjust the switch position (that was out by about 3/8") he noticed that open barb on the brake switch. He demanded in the kindest terms to put a tee on the line feeding the clutch barb and branch over to the brake as well. No change in operation as expected.

My next step is to get to the cruise CPU below the glove box and use the troubleshooting flow charts to drill into the problem. Maybe this weekend but what are your thoughts on a 93 with LT1 needing that branch vacuum line going to the brake switch as well.

Logically it makes sense that you can kill cruise with the either/or logic set up with either brake or clutch pressure.Your thoughts?

Regards,

Brian

 

[gmjunkie]

It is!

Just replaced mine, if yours is in as bad a shape as mine. Go ahead and replace it while your in there.
I think GM thought only midgets would have to work under the dash, doing anything under there is a real pain.

Just remove the seat and the lower dash panel and lay on your back in the floor!!It only takes about 10 minutes to do it,and it will save you 2 hours in time!Not to mention save your back!

 

[gmjunkie]

gmjunkie,

I had the same hose and looking at the FSM it looked like there was NOT supposed to be a vacuum connction to the brake switch even though there was a hose barb on the switch. My hose only went to the clutch switch. A few weeks ago I was halfheartedly troubleshooting the inoperative cruise control and my neighbor came over and him being twenty years younger than me and aparently predisposed to helping by laying on his back to adjust the switch position (that was out by about 3/8") he noticed that open barb on the brake switch. He demanded in the kindest terms to put a tee on the line feeding the clutch barb and branch over to the brake as well. No change in operation as expected.

My next step is to get to the cruise CPU below the glove box and use the troubleshooting flow charts to drill into the problem. Maybe this weekend but what are your thoughts on a 93 with LT1 needing that branch vacuum line going to the brake switch as well.

Logically it makes sense that you can kill cruise with the either/or logic set up with either brake or clutch pressure.Your thoughts?

Regards,

Brian

Make sure that the vacuum side of the switches are not leaking,thats a problem I find on the cruse not working allot!!

As far as not having both switches hooked up,I've never seen a standard shift just going to just 1 switch!! I'd think it would be kinda crazy,If it was just going to the clutch,in a quick panic brake the cruse would not shut down!! If it was just run to the the Brake,if you went to down shift,your engine I'd think would rev up to red line!! Never tried it!!

 

[surfer93]

Check both the vacuum line coming into the cruise control and the one out.
Mine had a small crack in the incoming line and a hole right where it went into the firewall on the one going out.

It should have 2 hoses inside the car, atleast my friends 92 does.

 

[tdr1919]

my 86 has only one hose coming thru, and I cant see anyting in the FSM, and I felt around for a nipple ! but couldnt find one.

 

[Brian Smith]

It tested the vacuum switches by using my MytyVac pump. Removed the hose, at the servo, from thru the firewall. Pulled 23" and tested the release function for both switches. Released perfectly. Then I pulled another 23" and left it for 20 minutes and when I came back the same 23" was there. Good switches and good adjustment!

Then I pulled the glove box to be able to backprobe the Cruise CPU connector and lo and behold there is a ton of ductwork stuff in there! I decided that, in spite of the FSM troubleshooting tree and the above directions from our esteemed member, I would just test the most likely point of failure. The turn signal stalk. Looked at the schematics and ohmed them and a great deal of variability resulted. 1/2 of the switches appeared open while the other half's resistance wandered (150 to >1K Ohms). Shot tuner cleaner/contact lube into the end of the stalk around the pushbutton and the open switch "healed" itself and the other half settled down with .1 Ohm readings. Test drive still no go.

Alright, I saw some fastners that would start to get the passenger side ductwork out. There must be an easier way than that. C'mon give me the trick fellers! It looks like a couple hours to get it apart and I don't want to take more apart than needed. Seems like an opportunity for failure waiting for a time to happen!

 

[John Robinson]

Been there done that

I spent over 8 months this year chasing my cruise problems on my 93. First do as Junk suggests take out the seat and remove the top if you have a coupe. It makes it a whole lot easier to get under the dash. I also found that putting a stool next to the car that I could slide onto when I came out from under the dash made it easier. Before you go any further reset the brake and clutch switch check to see if they are working by pulling vacuum on the dump hose and seeing if it holds the vacuum. I used a long hose and simply sucked on it so I could press the brake in and see if it would dump. If that works then get into the car and press the brake and clutch down hard several times and repeat the vacuum test. If yours is like mine was the plastic that held the adjustment became brittle and when I used the pedal with my foot the switches slipped out of adjustment. Buy all new clutch and brake switches and put them in and I will bet that your cruise will work again. Like you I tried to get to the CCu and I ran the diagnostics from the FSM so many times I could do it in my sleep and I got to the point that I did not have to crawl under the dash any more because I could feel and disconnect things without seeing them. I also made up a set of switches that simulated the function of the stalk so I could check out the circuit to the servo and CCU