C4 Cooling System Leak Checker
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
C4 Cooling System Leak Checker
I have developed a mystery coolant leak in the front lower right area of the engine. I am looking for a test cap to pressurize the system. I recall I rented one from a local parts store a few years ago but none on the caps in the kit would fit. My car is a 1996 collectors addition. Thanks!
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
You know that the cap in the pressure test kit hooks up to the surge tank, up by the firewall....right?
Short of working that out, why not just wash the general area of the leak, then start the car and let it warm and build it's own pressure.....watch for the leak?
Short of working that out, why not just wash the general area of the leak, then start the car and let it warm and build it's own pressure.....watch for the leak?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
You know that the cap in the pressure test kit hooks up to the surge tank, up by the firewall....right?
Yes. I hope I know that much.
Short of working that out, why not just wash the general area of the leak, then start the car and let it warm and build it's own pressure.....watch for the leak?
Yes. I hope I know that much.
Short of working that out, why not just wash the general area of the leak, then start the car and let it warm and build it's own pressure.....watch for the leak?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
The hose and barb deff rule out that is being the culprit. Leaking gaskets likely won’t impact the Optispark. Those connections are on either side of the Opti spark unit and against the block….. not directly over the top of the unit like the weep hole.
Last edited by KJL; Oct 25, 2021 at 05:28 PM.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
While pressurizing the system is the "best" option, I would suggest that some fluorescent dye in the coolant may work. They sell dye for this purpose, and a couple of Oz. added to the cooling system, will do the trick. Add they dye, then drive the car a bit. Bring the car home, let it cool off, and when it's dark out look for the flourescent dye with a blacklight. Itshould lead you to the leak.
BTW - OTC makes a cooling system pressure tester with an inflatable diaphragm - that WILL work on a C4 cooling system.
BTW - OTC makes a cooling system pressure tester with an inflatable diaphragm - that WILL work on a C4 cooling system.
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
Burning Brakes
Joined: Jan 2019
Posts: 1,225
Likes: 682
From: Park City, TN
2024 C6 of the Year Finalist - Unmodified
2023 C6 of the Year Finalist - Unmodified
2022 C4 of the Year Finalist - Unmodified
2021 C4 of the Year - Unmodified Finalist
2020 C4 of the Year Finalist - Unmodified
2019 C4 of Year Finalist (stock)
This one is compatible.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
Most of us who turn wrenches have made similar mistakes. No one got hurt and your car is fine. Could have been a LOT WORSE !!!!
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
At some point I will probably remove a bunch of stuff and retorque all the water bolts. the one on the passenger side is buried under spark plug wires compliments of the Opti Spark unit.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Ah....that's not right. Opti (and it's associated wires) should be well below the water pump. You should be able to remove the air bridge (two hose clamps and the IAT sensor plug) and then reach all 6 water pump bolts with a typical 3/8 ratchet, wobble extension and socket.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
Ah....that's not right. Opti (and it's associated wires) should be well below the water pump. You should be able to remove the air bridge (two hose clamps and the IAT sensor plug) and then reach all 6 water pump bolts with a typical 3/8 ratchet, wobble extension and socket.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA