Topic: STILL RUNNING HOT
in Forum: C3 Cooling and Heating Systems
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Canada
Joined: 3/9/2008
Posts: 164
Vette(s): 70 VETTE 350/300HP, AUTOMATIC, ALL STOCK EXCEPT FOR MILD CAM,LAGUNA GREY, 3:55 POSI GEARS
I HAD MY RADIATOR RECORED, FLUSHED ENGINE BLOCK, 160 F THERMOSTATE, NEW STAGE 2 Q-JET CARB, NEW NGK PLUGS AND WATER PUMP WAS REBUILT 2 YEARS AGO. THE CAR IS RUNNING GREAT EXCEPT FOR THE WATER TEMP FLACTUATION. AFTER DRIVING FOR MORE THAN 15 MIN THE TEMP GAUGE STARTS TO CREEP UP, IF I REALLY HAMMER THE CAR OR RUN AT HIGH SPEEDS THE TEMP JUMPS TO 220-240, IF I GET TO A STOP OR AFTER A WHILE THE TEMP GAUGE DROPS DOWN TO 180-190 WITHIN 10-20 SECONDS OR IF THE CAR RUNS IN IDLE FOR A LONG PERIOD OF TIME THE TEMP STAYS AT 190. I INSTALLED A MECHANICAL TEMP GAUGE( I BELIEVE THATS WHAT ITS CALLED) I REMOVED THE SREW ON TOP OF THE INTAKE MANIFOLD AND PUT IN THE SENSOR AND RAN IT TO THE FRONT OF THE WINDSHIELD SO I CAN SEE THE GAUGE, JUST TO CHECK AND SEE IF MY SENDER OR GAUGE WAS INCORRECT. I TOOK THE CAR OUT FOR A RIDE AND THE GAUGE WAS DOING THE SAME THING, IT WOULD REACH UP TO 245 AND WITHIN SECONDS GO BACK DOWN TO 190. COULD IT BE AIR IN THE SYSTEM, MY MECHANIC WHO DID THE WORK IS VERY WELL KNOWN ALL HE DOES IS RESTORES CLASSICS, HE WANTS ME TO BRING IT BACK TO HIM FOR A CLOSER LOOK. COULD IT BE THE WATER PUMP NOT WORKING WELL AT HIGH SPEEDS, HOW COULD A ENGINE COOL DOWN THAT FAST. ANY IDEAS!
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Lifetime MemberModerator
Moses Lake, WA - USA
Joined: 4/16/2005
Posts: 2134
Vette(s): 1976 L48 4-spd, Mahogany Metalic exterior, Buckskin interior 350ci/350hp, 3rd owner, fiberglass spring, 255/50-16's Torq-Thrust II
Do you have the foam seals installed around the radiator? If not you will have air bypass the radiator. Do you have the plastic spoiler installed to help direct air up to the radiator. I had overheat issues while at freeway speeds but ok when driving around town. Installed the seals around the radiator and no longer had overheat issue.
Former Member
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Canada
Joined: 3/9/2008
Posts: 164
Vette(s): 70 VETTE 350/300HP, AUTOMATIC, ALL STOCK EXCEPT FOR MILD CAM,LAGUNA GREY, 3:55 POSI GEARS
ALL THE SEALS AND BOTTOM SPOILER ARE THERE. THANKS
Lifetime MemberOceanside, CA - USA
Joined: 11/19/2003
Posts: 191
Vette(s): 1978 Silver Anniversary model. Original L82 engine, 700r4 trans, edelbrock intake, thorly headers, rack&pinion steering, mono rear and front spring, MSD 6A box
My 78 does the same thing that you have decribed. I have a new Edelbrock water pump, front spoiler and new seals. Maybe they are suppose to run at those temp. No boil over so guess will just live with it, unless you come up with a solution, if you do pls let me know.
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I think with that severe of a temp change you may well have air in the cooling system. 245 is TOO hot for the engine!!!
The temp sender has to have water touching it to read correctly, so if there is air in the cooling system, it can cause the gauge to read like that, and fluctuate quicky....and run hot!
You may have a hose that is collapsing too...
I'd say take it to the guy and let him check it out before it turns nasty, and damages the engine.
The temp sender has to have water touching it to read correctly, so if there is air in the cooling system, it can cause the gauge to read like that, and fluctuate quicky....and run hot!
You may have a hose that is collapsing too...
I'd say take it to the guy and let him check it out before it turns nasty, and damages the engine.
Joel Adams
C3VR Lifetime Member #56 
My Link 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Like Joel said, check your radiator hoses. Make sure they are firm, and especially make sure the bottom one has a spring and it's in good shape.
Hate to say Ditto - But Joel has the right idea - air in the system and collapsing & John's mentioned especially the bottom one -with a spring. Check it out before 245 fries something
Big Al
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Canada
Joined: 3/9/2008
Posts: 164
Vette(s): 70 VETTE 350/300HP, AUTOMATIC, ALL STOCK EXCEPT FOR MILD CAM,LAGUNA GREY, 3:55 POSI GEARS
THE BOTTOM HOSE SEEMED FINE WHEN THE RAD WAS PULLED OUT, THE SPRING LOOKED FINE. HOW WOULD I KNOW IF IT NEEDS REPLACING? MY RAD HAS NO RAD CAP ON IT JUST THE EXPANSION TANK. I STARTED IT UP TODAY AND RAN IT WITH THE CAP OFF OF THE EXPANSION TANK, WHILE STILL COLD AND RUNNING I DID SEE ALOT OF AIR BUBBLES COMING UP, I RAN IT FOR A LITTLE LONGER AND REPLACED THE CAP. TOOK IT OUT FOR A RIDE AND DID SEEM TO BE BETTER, STILL GOT UP TO 230 FOR A SHORT PERIOD AND WENT BACK DOWN TO 190-210. GOING TO TRY A COUPLE OF MORE TIMES TAKING THE CAP OFF. ANY OTHER IDEAS HOW I CAN GET THE AIR POCKETS OUT. THANKS
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Your thermostat may be sticking.
One thing I always do when installing one is drill a small, 1/8" hole in the flat area around the center of the 'stat. This allows all of the air to get out when you first fill the system. Most new 'stats these days have a hole with a little restrictor in it for the same reason. I will remove the restrictor on those.
Also, when filling the radiator with a cooling system that is empty, always turn the heater control to "Hot", so the coolant will circulate thru the heater core too(if your heater core is still connected, that is). This keeps the air in the system moving, and easier to find it's way out.
Make sure your coolant expansion tank is mounted in the right location too, and the hose is not loose where it attaches to the tank and the radiator. A loose hose connection at either or both ends will allow air to be sucked into the system as the engine cools back down.
btw...air bubbles in the tank could mean air in the system, or...a leaking head gasket/cracked head...
Did you have this same temp issue before flushing the engine?Adams' Apple 2008-05-29 19:15:10
One thing I always do when installing one is drill a small, 1/8" hole in the flat area around the center of the 'stat. This allows all of the air to get out when you first fill the system. Most new 'stats these days have a hole with a little restrictor in it for the same reason. I will remove the restrictor on those.
Also, when filling the radiator with a cooling system that is empty, always turn the heater control to "Hot", so the coolant will circulate thru the heater core too(if your heater core is still connected, that is). This keeps the air in the system moving, and easier to find it's way out.
Make sure your coolant expansion tank is mounted in the right location too, and the hose is not loose where it attaches to the tank and the radiator. A loose hose connection at either or both ends will allow air to be sucked into the system as the engine cools back down.
btw...air bubbles in the tank could mean air in the system, or...a leaking head gasket/cracked head...
Did you have this same temp issue before flushing the engine?
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
in Forum: C3 Cooling and Heating Systems
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