Coolant leak - but where?
Thread Starter
Instructor
Joined: Jun 2003
Posts: 176
Likes: 0
From: Columbia SC
Coolant leak - but where?
1986 stock coupe. Radiator, water pump, hoses, thermostat all less than a year old (can see good flow with cap off and engine running). Car has been getting warmer and losing a little coolant. The past few days this has increased and today lost almost 3 liters on 80 mile trip. Problem is: there is no obvious place that the coolant is going. No puddles under the car, oil is not milky or low and there is no water in passenger floorboard from the heater core. Had slight leak at rear intake from the EGR switch pipe - tightened, leak gone. Slight leak at heater control valve - removed and have temporary straight hose in it's place to insure there is no leak there for now. Any clues as to what I am overlooking? Could it only leak at higher rpm when pressure increases from the pump? Do I need to pressure test? If you have a thought, pass it on. Thanks in advance.
Safety Car
Joined: Nov 2004
Posts: 4,991
Likes: 5
From: The Pines South Jersey
Originally Posted by loflyin
1986 stock coupe. Radiator, water pump, hoses, thermostat all less than a year old (can see good flow with cap off and engine running). Car has been getting warmer and losing a little coolant. The past few days this has increased and today lost almost 3 liters on 80 mile trip. Problem is: there is no obvious place that the coolant is going. No puddles under the car, oil is not milky or low and there is no water in passenger floorboard from the heater core. Had slight leak at rear intake from the EGR switch pipe - tightened, leak gone. Slight leak at heater control valve - removed and have temporary straight hose in it's place to insure there is no leak there for now. Any clues as to what I am overlooking? Could it only leak at higher rpm when pressure increases from the pump? Do I need to pressure test? If you have a thought, pass it on. Thanks in advance.
Thread Starter
Instructor
Joined: Jun 2003
Posts: 176
Likes: 0
From: Columbia SC
Overflow tank has been getting low also, but once again, no puddles...? Could the thermostat stick closed, coolant heats up, pushes through to the overflow and leaves as steam, taking some of the overflow water as vapor with it? Sorry, but I'm forced to be creative at this point.
Burning Brakes
Joined: Oct 2004
Posts: 1,094
Likes: 0
From: West Palm Beach Florida
Originally Posted by loflyin
Overflow tank has been getting low also, but once again, no puddles...? Could the thermostat stick closed, coolant heats up, pushes through to the overflow and leaves as steam, taking some of the overflow water as vapor with it? Sorry, but I'm forced to be creative at this point.
You need to fabricate a long cotton swab and go into your heater box anally through the drain and see if you need a core. Mine was seeping slightly and never dripped but I did have a slight hint of coolant smell in the car. The drain on my 92 was inside the car on the pass side.
Thread Starter
Instructor
Joined: Jun 2003
Posts: 176
Likes: 0
From: Columbia SC
Thanks, I'll give it a try. I have noticed slight coolant smell and saw an oily residue on the vents today (heater), after heavy fluid loss. I believe tomorrow I will pressure check the system - hopefully will make leak noticeable.
Burning Brakes
Joined: Oct 2004
Posts: 1,094
Likes: 0
From: West Palm Beach Florida
Originally Posted by loflyin
Thanks, I'll give it a try. I have noticed slight coolant smell and saw an oily residue on the vents today (heater), after heavy fluid loss. I believe tomorrow I will pressure check the system - hopefully will make leak noticeable.
It will do more than that... it will create a larger leak... I hope you are ready to do a repair. If this is your only vehicle you may want to wait till you do.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Radiator side tank gaskets,
Oil cooler
Oil cooler lines
heater lines
leaking intake base
bad head gasket
radiator drain ****
cracked overflow tank
There's lots of less obvious places to lose coolant.
Oil cooler
Oil cooler lines
heater lines
leaking intake base
bad head gasket
radiator drain ****
cracked overflow tank
There's lots of less obvious places to lose coolant.
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
Racer
Joined: Mar 2004
Posts: 311
Likes: 0
From: Oakley Ca
Had a Chevy pickup that did the same thing. Turned out to be the water pump. Only leaked at above idle RPMs. Go figure? Check below the shaft for water/coolant stains running down the front of the engine.
