mjeff87 Posted August 30, 2005 Share Posted August 30, 2005 Cross-posting this on the Yahoo board as well (seems like a different crowd over here :-D Anyways, second time it's happened, and it's only happened under the same circumstances. Took the MJ on a PA roadtrip over the weekend, and there's one spot on I70 that's a long, gradual uphill grade, like 3 or 4 miles at about 8-10% grade. As soon as I start up it, I lose vac signal to the vac motor for the HVAC and it defaults to the defrost vents. I've checked the blimp under the bumper and all the soft lines under the hood and nothing's leaking (?) Could it be that I just loose manifold vac under load @ part throttle going uphill? It doesn't do it anywhere else but this particular piece of landscape, and as soon as I crest the top I get vaccuum back. (It's I70 westbound, going up Town Hill, for anyone that's familiar with the area....) 700 mile roadtrip and not a single problem other than this weird vaccuum issue <> Jeff Link to comment Share on other sites More sharing options...
Steve Gregory Posted January 19, 2015 Share Posted January 19, 2015 Could it be the motor under a certain type of load? Link to comment Share on other sites More sharing options...
Bobolink Posted January 19, 2015 Share Posted January 19, 2015 When you say you checked the soft lines, are you referring to the rubber lines? Have you checked the black plastic line? It is notorious for developing a leak under the coolant pressure bottle, where it might rub on the heater hose or A/C hose clamps. The area within 6" or so of where it passes through the firewall is where you will often find a hole. And it is not easy to find by visual observation alone. Feel along the line for any roughness. If you find a rough spot, it's almost certainly a hole, and can be fixed by cutting the line and splicing with an appropriately sized piece of vacuum hose. You can lose vacuum on long uphill grades, but it shouldn't happen unless you're on a long grade pulling a heavy load (trailer of whatever). I've climbed long grades in the Rockies at 8000-10000' with 300-400 lb load in the bed at 60 MPH or so without losing enough vacuum to lose the A/C. Link to comment Share on other sites More sharing options...
Dillithium Posted January 19, 2015 Share Posted January 19, 2015 His post is almost 10 years old. Link to comment Share on other sites More sharing options...
nitroxsteve Posted January 19, 2015 Share Posted January 19, 2015 Under load especially if you don't downshift you have low rpm and the throttle open. This gives less manifiod vacuum. I have had a couple different cars do this. If everything is working I wouldnt worry about it. Link to comment Share on other sites More sharing options...
nitroxsteve Posted January 19, 2015 Share Posted January 19, 2015 His post is almost 10 years old. dang! Hope he has it fixed! Lol Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 19, 2015 Share Posted January 19, 2015 Jeff sold his MJ a couple of years ago.................. Link to comment Share on other sites More sharing options...
88mjblue Posted January 20, 2015 Share Posted January 20, 2015 I wouldn't sell my mj just over a small vacuum leak. Link to comment Share on other sites More sharing options...
mjeff87 Posted January 20, 2015 Author Share Posted January 20, 2015 LOL.....yeah, I got it fixed. I just sold it this past fall Don, not a couple of years ago. Now on the hunt for another one to build (a bit differently this time). Jeff Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 20, 2015 Share Posted January 20, 2015 I just sold it this past fall Don, not a couple of years ago. Now on the hunt for another one to build (a bit differently this time). Jeff AARRGG - thought you sold it in 2013 - my bad. Get an HO this time Jeff. :cheers: Link to comment Share on other sites More sharing options...
Bobolink Posted January 20, 2015 Share Posted January 20, 2015 Man, I hate it when that happens........some guy answers a ten year old post, and I don't bother looking at dates beyond his new post.....arrrgh well jeff, I'm glad you got it fixed, though......... Link to comment Share on other sites More sharing options...
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