Dead or dying cruise control servo?

[Paul_]

The Mercury doesn't like to maintain the speed I set the cruise control at going up the slighest grade. Could the cruise control servo be heading south, or is it something else?

[turbo2256b]

Check for vacuum leaks. Heater controls, vacuum can, emergency brake release vacuum switch.

[Archangel]

My cruise control doesn't like the car going uphill with the A/C on, it will turn off randomly on some trips, on others it hauls ass and acts as if the A/C isn't there - dunno what causes that, but I hope overriding the automatic A/C compressor activation with a manual switch will take care of that as it will be a completely separate electrical circuit.

[mrltd]

check the vacuum canister and that crap ass parking brake release.

[turbo2256b]

Could very well be the speed sensor were it goes into the traany have replaced a few. also check the electrical connection there for croading

[88crwnvc]

the so called "crap ass emergency brake release" deal is messed up on my 88 vic, everytime i put it in gear it hisses under the dash.. what do i do to fix the problem? also my cruise quit about the time this noise started to occur, so this is the problem?

[86GmLsCoupe]

My 86 Grand Marquis does the same thing as your 88 Vic. Hissing under the dash when put into gear (sometimes can stop by wiggling the shifter), no emergency brake release when driven foward, and no cruise control. The ATC vacuum controls are working fine though.

1986 Grand Marquis LS coupe [/url] http://photos.yahoo.com/leo76830

[Archangel]

The cruise control servo is vacuum operated, so if the E-brake auto-release is leaking (hissing sound) the cruise is very likely to not work. To fis it get under the dash and either replace the vacuum switch at the base of the column (looks like a half-moon with two ubber lines going into it), or just take it out and plug the lines. I kinda did the second thing, but went even further by completely removing the e-brake vacuum solenoid and its linkage.

[86GmLsCoupe]

MeLikeyStripperChicks was right, pulled the vacuum switch and bypassed it and sure enough the parking brake released as soon as the car was started. From what I can tell the switch allows vacuum to pass through depending on what gear the car is in (Tab from selector column connects to the back of the switch). This would explain the hissing/leaking noise when selecting gears. Posted pics of the switch are below. Thanks again for the help. Next thing to repair is cruise control.

1986 Grand Marquis LS coupe [/url] http://photos.yahoo.com/leo76830

[turbo2256b]

Check for vacuum leaks emergency brake release vacuum switch.

Hummmmmmmmm

[86GmLsCoupe]

Sorry bout that. I do have an update. Switch is in and brake releases when put in any foward gear. One word of caution. The part comes with a red tab which keeps the sliding part in the correct place (and was told to leave it in until part was installed. However, I could not get the part in (onto gear selector tab) and lined up with the screws without taking it out before the install. As for the cruise control not working, I ran all the tests listed in the EVTM and everything passed. Next I checked to see if the cruise servo would hold any vaccuum and it does not, so the diaphragm inside the servo is shot. Going to look for a replacement and will let you all know what happens.


1986 Grand Marquis LS coupe [/url] http://photos.yahoo.com/leo76830

[turbo2256b]

There are some one way check valves in the vacuum lines check those for proper opperation. One bleed off line goes to the carbon canester I usally disconetet it and cut the line short near the servo itself.

[gadget73]

I think the line turbo is referring to is the one fitted to the T check valve near the wiper motor. One side goes to engine vacuum, one to the servo, and the third leg goes down to the smog pump. There is a wierdo venturi thingy on the smog pump bleed-off tit that is supposed to generate vacuum when the engine is under a low vacuum condition. What it actually does is make annoying whistling noises and cause stupid vacuum leaks. I yanked the T off and fitted a regular connector in there instead, cruise works fine.

[turbo2256b]

Thats it. The connection at the smog pump then to the carbon canester is just used when the vacuum servo needs to vent when the cruse control needs to dump vacuum when slowing down or shutting it off. It is connected to the carbon canister for vapor recovery. Shorting it seens to quicken speed changes reacts faster. I will take some pics.

[86GmLsCoupe]

What I did was just pull all the hoses off the servo, capped them except one which was tested with a vacuum pressure tester. Did that test for both sides (of the diaphragm) and neither held vacuum, plus it's 21 yrs old so I really think it's shot. The vacuum line from the tree was capped temporarily and all seems well. The car feels much smoother and stronger since the "crap ass brake release" was fixed and servo vacuum feed was capped (smog stuff is gone). I'm guessing those are two vacuum leaks gone? One question I have though is I know there is a cruise control servo which I need to replace, but what is the cruise control actuator (saw it listed, runs around $25-40)?

1986 Grand Marquis LS coupe [/url] http://photos.yahoo.com/leo76830