tracing vacuum leaks..
Team Owner
Joined: Sep 2006
Posts: 31,316
Likes: 4,422
From: Westminster Maryland
Hi j,
Remember, the vacuum tends to suck the hose connections tighter; it doesn't try to blow them off like air pump will.
Often vacuum hose connections can be improved by cutting about 1/2" off each end of each hose.
Regards,
Alan
Remember, the vacuum tends to suck the hose connections tighter; it doesn't try to blow them off like air pump will.
Often vacuum hose connections can be improved by cutting about 1/2" off each end of each hose.
Regards,
Alan
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Keep in mind, maximum vacuum possible is 30" hg, or minus 15 psi. Start going anywhere close to this positive, and you'll be finding plenty of HVAC system vacuum motor diaphram leaks, as you'll be making them. I normally just take the time diagnosing individual components with a small hand Mity-Vac tool.
Thread Starter
Le Mans Master
Joined: Jul 2003
Posts: 7,501
Likes: 1
From: Maine
i found one online... i traced all the hoses and there is one hard plastic tube broken running along the firewall towards the drivers side... there is no where to plug it in to.... still stumped why there is no vacuum at all in any of the 4 lines that attach to the heater control..
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
http://forums.corvetteforum.com/c3-t...wer-works.html
Sounds like 1 from above, source tube to intake vacuum.
Sounds like 1 from above, source tube to intake vacuum.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Bad idea for air pressure...unless the air is very low pressure. Vacuum in the system is less than 20" Hg [about 8psi], so anything much over that in 'positive' pressure might damage some components.
It would be much simpler to buy a vacuum gauge and "T" it into the main vacuum feed line. Start the engine, let it idle, then take a vacuum gauge reading. Now, clamp off the vacuum line just past the T for the gauge. If the reading is significantly higher, there is a leak somewhere downstream of the gauge. Just keep moving the "cut off" clamp farther down the line until you see that the result is lower than before. Between the last two 'clamping' points, there is a vacuum leak.
Continue that process until you've found and fixed all the leaks.
It would be much simpler to buy a vacuum gauge and "T" it into the main vacuum feed line. Start the engine, let it idle, then take a vacuum gauge reading. Now, clamp off the vacuum line just past the T for the gauge. If the reading is significantly higher, there is a leak somewhere downstream of the gauge. Just keep moving the "cut off" clamp farther down the line until you see that the result is lower than before. Between the last two 'clamping' points, there is a vacuum leak.
Continue that process until you've found and fixed all the leaks.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
i found one online... i traced all the hoses and there is one hard plastic tube broken running along the firewall towards the drivers side... there is no where to plug it in to.... still stumped why there is no vacuum at all in any of the 4 lines that attach to the heater control..
Scott
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
While really not much to do with the original question, a little primer on vacuum.The atmosphere around us at sea level is about 14.7 psi of gasses weighing down on us. 80% nitrogen/20% oxygen to be close. 350 cu in engines cruising around with the carb plates mostly closed pull lost's of negitave pressure in the intake system, and manufactures take advantage of this energy for driving other components. Another note. Water boils at 212° Fahrenheit at sea level, and about 0° Fahrenheit at zero atmosphere/30” hg vacuum. Water’s an enemy to HVAC systems, so why a vacuums pulled to evacuate/boil out moisture on these systems during service.
Thread Starter
Le Mans Master
Joined: Jul 2003
Posts: 7,501
Likes: 1
From: Maine
http://forums.corvetteforum.com/c3-t...wer-works.html
Sounds like 1 from above, source tube to intake vacuum.
Sounds like 1 from above, source tube to intake vacuum.
Thread Starter
Le Mans Master
Joined: Jul 2003
Posts: 7,501
Likes: 1
From: Maine
thanks... i ordered a whole new hose kit.... i took the connector off the heater controls and tested all 4 lines... not 1 will hold vacuum.... seems like if just that 1 line was broken the others would still hold vacuum...
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
This might sound weird, but........are you testing the lines from inside the car? If so, you are doing it backwards.
Scott
on to the next project... carpet....
