Vacuum Leak on Intake????
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,713
Likes: 31
From: Shreveport LA
LA Events Coordinator
Vacuum Leak on Intake????
First let me state that the Vette is running perfectly. BUT this morning, while she was idling (purring like a kitten), I noticed some dirt/grease on the intake 
(heaven forbid!!) Anyway, I got some Gumout Carb Spray and sprayed the area to clean it (while it was running). WHEN I sprayed it, the engine speed increased from 700RPM to about 900-1000RPM....but here is the kicker....where I sprayed it, there's no openings, connections or anything!!!! (see the picture of below)
Now I have read to find a vacuum leak, spray carb cleaner around the base of the carb, intake and anywhere you feel may leak and if the engine increases in RPMs, that's where the leak is. Problem with this situation....there's nothing there to "leak". I searched real careful for a possible crack....but nope....nothing! After the RPM's dropped back to normal, I sprayed around the base of the carb, the base of the intake...she did not increase in speed once....only when I spray in the indicated area.....What would cause it to react that way? As soon as the carb cleaner dried, the engine went back to the normal RPM's (700 in Park).
P.S. The engine was at operating temp when I did this.....
(heaven forbid!!) Anyway, I got some Gumout Carb Spray and sprayed the area to clean it (while it was running). WHEN I sprayed it, the engine speed increased from 700RPM to about 900-1000RPM....but here is the kicker....where I sprayed it, there's no openings, connections or anything!!!! (see the picture of below)Now I have read to find a vacuum leak, spray carb cleaner around the base of the carb, intake and anywhere you feel may leak and if the engine increases in RPMs, that's where the leak is. Problem with this situation....there's nothing there to "leak". I searched real careful for a possible crack....but nope....nothing! After the RPM's dropped back to normal, I sprayed around the base of the carb, the base of the intake...she did not increase in speed once....only when I spray in the indicated area.....What would cause it to react that way? As soon as the carb cleaner dried, the engine went back to the normal RPM's (700 in Park).
P.S. The engine was at operating temp when I did this.....
Le Mans Master
Joined: Jan 2007
Posts: 8,007
Likes: 3,340
From: Omaha NE
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2022 C3 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
Hairline crack? Loose intake bolt?
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,713
Likes: 31
From: Shreveport LA
LA Events Coordinator
Hairline crack....I keep thinking that...but I don't see one....and I have looked and looked and looked...under a realy bright light etc....Can you see a hairline crack?
I checked the bolts to the intake....all tight...Plus when I sprayed around the base of the intake, the engine did not speed up or react in any strange way.....
I checked the bolts to the intake....all tight...Plus when I sprayed around the base of the intake, the engine did not speed up or react in any strange way.....
Le Mans Master
Joined: Jan 2007
Posts: 8,007
Likes: 3,340
From: Omaha NE
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2022 C3 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
Hairline cracks can be to small to see. A job I had when I worked for the railroad was to magnaflux different things for cracks. And more then once I found cracks under the black light that were impossible to see.
Pro
Joined: Aug 2005
Posts: 503
Likes: 0
From: Ozark MO
I was told to try using smoke to find a vaccuum leak. Other then a big cigar, I don't know how you'd do that. But I was told the smoke would be drawn into the leak and be easier to see that way. Let me know if it works. 
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,713
Likes: 31
From: Shreveport LA
LA Events Coordinator
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,713
Likes: 31
From: Shreveport LA
LA Events Coordinator
