Hello all just purchased a 1988 grand marquis LS in mint condition with 82000 miles this car is perfect except for one problem the heat and ac both work great at idle but as you accelerate the v ents switch to defrost no matter what you have them set to. Also if u turn all the controls off u get heat out of the fllor vent while driving down the road. This car does the auto climate control and I have already replaced the coffee can vacuum canister under the hood and also the one way check valve but am still having the same problem, and I am stumped as to where to look next for a vacuum leak. It also seems that there may be a problem with my ac compressor as when u let off the gas and are just cruising it will switch back to the dash vents but only blow cool air not the cold air u get at idle almost as if the compressor is weak. Any help in this matter would be greatly appreciated thanks.
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does it exhibit any other signs of vacuum issues? hunting at idle, rough idle, poor fuel consumption, etc? have you put a vacuum gauge on it? these cars tend to be in the 18-22"HG range at idle.
a couple specific places I'd check would be the line to the MAP sensor (under the upper intake, big line) and the lines going to the firewall right behind the engine.
85 4 door 351 Civi Crown Victoria - Summer daily driver, sleeper in the making, and wildly inappropriate autocross machine
160KMs 600cfm holley, shorty headers, 2.5" catted exhaust, 255/295 tires, cop shocks, cop swaybars, underdrive pulley, 2.73L gears.
waiting for install: 3.27's, Poly bushings, boxed rear arms, 2500 stall converter, ported e7's, etc
06 Mazda 3 hatch 2.3L 5AT (winter beater that cost more than my summer car) -
check the thermal blower lockout in the heater hose. They frequently leak vacuum. I unplugged mine and simply sealed off those lines. The problem you describe is definitely a vacuum issue though. ATC defaults to hot defrost when it loses suction.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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You definately have a vacuum problem with the air coming out different places. Theres also a plastic vacuum tree bolted to the firewall behind the intake, could be cracked, or other damaged hoses.
Alex.Comment
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I do believe the problem is located in the thermal blower lockout being as that i had absolutely no fan when using floor vents since ive gotten the car. A few mins ago i jumped the the wires on the lockout and immediately my floor vents started working right now i am looking for something to use to plug the two vacuum lines and i will check then to see if the problem has gone away.Originally posted by gadget73 View PostComment
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my 88 had this issue as well. the check valve on the center of the firewall, engine side, likes to crap out. It's the one with 2 lines in one end and the fat line to the vacuum tree. I replaced that and my AC was cool again at all load levels. Looks like I need to replace it again too. Been 2 years of hot summers.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
Originally posted by gadget73
... and it should all work like magic and unicorns and stuff.
Originally posted by dmccaig
Overhead, some poor bastards are flying in airplanes.Comment
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ok i seem to have finally found my problem ever since i got the car ive noticed if you shut the engine off and then stand anywhere near the front of the car u can hear air wooshing at high speed. But before this i never thought of it much now i believe that it is my vacuum leak and it sounds as if it is coming from the passenger side rear corner of the upper intake manifold or maybe under the upper manifold itself. It seems to be rushing very fast and lasts about 10-15 seconds before stopping.Comment
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that's basically where the vacuum lines going to the firewall that I mentioned are. they're hard to see because they're pretty well hidden behind the intake, but they're there and on mine at least two were leaking.
85 4 door 351 Civi Crown Victoria - Summer daily driver, sleeper in the making, and wildly inappropriate autocross machine
160KMs 600cfm holley, shorty headers, 2.5" catted exhaust, 255/295 tires, cop shocks, cop swaybars, underdrive pulley, 2.73L gears.
waiting for install: 3.27's, Poly bushings, boxed rear arms, 2500 stall converter, ported e7's, etc
06 Mazda 3 hatch 2.3L 5AT (winter beater that cost more than my summer car)Comment
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ill have to check that out i got a guy who fixes everything i cant fix gonna look at it next tuesday afternoon so ill point him in that direction, and hopefully that will get me somewhere in the meantime i might mess around a lil working ten hours a day first shifty by the time i get home i dont feel like doing much btw i did get a gallery uploaded on my profile with some picsOriginally posted by johnunit View PostComment
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what I've used to plug the TBL stuff is small ball bearings from the hardware store. Most good ones that have the bins of random misc BS have a selection for very small money.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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well at this point im just gonna wait till tuesday and have my mechanic take a look tuesday as i have no desire to go mess with it in 100 degree heat hopefully he can find the leak if not ill have to find someone else because money is not the object with this car it is in mint condition otherwise and i will not stop till i have everything working sounds kinda crazy i know but i get attached to my cars and im very particular about every little detail so i got this prob to fix then power window and light under hood and i should be done finally.Originally posted by gadget73 View PostLast edited by mercurygm88; 07-20-2011, 05:04 PM.Comment
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Ok update my local mechanic can't work on the car until sometime next month and I'm having no luck finding this leak I've replaced the vacuum canister under the good and the check valve near the firewall but I still have a bit of a leak somewhere but can't tell where by listening to it so I'm at a loss as to where to look next also thermal blower lockout is shot cuz I have to jump it for floor vents to work but I dunno if its the leak or notComment
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probably is the leak. Its on the main vacuum line to the control head, so a leak there will cause big problems. Replace or bypass it completely and see what you have.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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is the best way just to bypass it just to jump the plug and and plug the lines if so ill have to get to the hardware store tomoro after work and pick up some small ball bearings then ill see what ive gotOriginally posted by gadget73 View PostComment
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Ok car goes to mechanic at 5pm but in the meantime I believe I found my leak and I think its in the line going from the soup can to the check valve. The reason being that when the car is running and you remove the line from the soup can you can hear air rushing into it. But if you shut off the engine and wait more than a couple of seconds and then pull the line off there is no vacuum at all on the can and I just replaced the check valve yet air is returning to the also new soup can which to me means the leak is in that little plastic vacuum line.Comment
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