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Topic: Replaced water pump, can't get air out of the cooling system

in Forum: C3 Cooling and Heating Systems


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Replaced water pump, can't get air out of the cooling system (1/12)
 3/1/19 10:59am
Cliffs_81_Vette
Former Member

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McKinney, TX - USA

Vette(s):
1981 Yellow Corvette, 4 spd 295/50-15 Magnum XLs on the rear!


Joined: 8/24/2016
Posts: 7

Hello. 

I recently replaced the water pump, hoses and coolant in my 1981 Corvette. I cannot seem to get all the air out of the cooling system. I've run the car with the nose on jacks, and have tried various other methods I've read about in other forums and on youtube. 

The car appears to warm up normally and I can see the temp gauge move when the thermostat open. The top hose gets hot and it all seems good to go. Then I'll got out on the highway and the temp soars up to about 230F.....this never happened in the past. The air temp outside was in the 60s so that isn't a reason for the car to get that hot. 

Any tips on how you've burped your C3 in the past? 

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Re: Replaced water pump, can't get air out of the cooling system (2/12)
 3/1/19 11:58am
nosal1
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.


Joined: 3/21/2006
Posts: 261

Good Afternoon, I suggest you jack up car on the side the radiator cap is and after you get ONLY that side up with cap off leave cap off..Be sure the engine is cool when doing this.You will leave front end off ground on JACK  Stand on the side of cap,you will leave the car this way for 24 hrs. and check level in radiator after this time period.Fill radiator and allow to stay that way for another 12 -24 hrs...I know it sounds crazy but I have done this every time I have built engines and installed them and followed this procedure.. Assure you it works,if not then you have another problem like a bottom side of radiator loaded with organic solids like Calcium carbonate,Magnesium carbonate and radiator needs cleaning..

Good Luck..                nosal 1
Re: Replaced water pump, can't get air out of the cooling system (3/12)
 3/1/19 12:39pm
73shark
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Overland Park, KS - USA

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1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


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If that doesn't work, remove the thermostat and put it in boiling water and see if it opens. I've had bad thermostats when they were new before.

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Re: Replaced water pump, can't get air out of the cooling system (4/12)
 3/1/19 12:58pm
F4Gary
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.


Joined: 8/26/2006
Posts: 1028

With the cap off, can you see coolant flow out of the cross tubes in the radiator?



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Re: Replaced water pump, can't get air out of the cooling system (5/12)
 3/1/19 1:36pm
Cliffs_81_Vette
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McKinney, TX - USA

Vette(s):
1981 Yellow Corvette, 4 spd 295/50-15 Magnum XLs on the rear!


Joined: 8/24/2016
Posts: 7

Thank you, I'll try that techniques. 

The radiator is less than five months old..... I replaced it in September. 

I don't see coolant flow through the radiator fins as the fluid comes pouring out after the motor warms up. 




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Re: Replaced water pump, can't get air out of the cooling system (6/12)
 3/1/19 1:37pm
Cliffs_81_Vette
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McKinney, TX - USA

Vette(s):
1981 Yellow Corvette, 4 spd 295/50-15 Magnum XLs on the rear!


Joined: 8/24/2016
Posts: 7

73shark said: If that doesn't work, remove the thermostat and put it in boiling water and see if it opens. I've had bad thermostats when they were new before.


The thermostat is brand new. I didn't have this issue prior to replacing the water pump. 

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Re: Replaced water pump, can't get air out of the cooling system (7/12)
 3/1/19 1:38pm
Cliffs_81_Vette
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McKinney, TX - USA

Vette(s):
1981 Yellow Corvette, 4 spd 295/50-15 Magnum XLs on the rear!


Joined: 8/24/2016
Posts: 7

F4Gary said:
With the cap off, can you see coolant flow out of the cross tubes in the radiator?



You're just up the road from me! 

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Re: Replaced water pump, can't get air out of the cooling system (8/12)
 3/1/19 1:45pm
nosal1
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.


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Posts: 261

You can test thermostat on the stove and a meat thermometer.Put a sauce pan on a burner as water approches boiling you can visually see thermostat opening and if you have meat thermometer you can identify at what temp thermostat opens.

Also someone suggested to watch water move through radiator with cap off as well,however will not tell you if middle to bottom rows or free and clear.Also for the future do not use house water even if softened water in house as it also has organic solids..

Always use DISTILLED water when adding to reclaim jug etc.or 50/50 antifreeze.   Sal C       nosal1

Re: Replaced water pump, can't get air out of the cooling system (9/12)
 3/1/19 7:06pm
F4Gary
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Grapevine, TX - USA

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1972 LT-1 convertible with factory air.


Joined: 8/26/2006
Posts: 1028

I've never had to burp a gen I small block chevy.  Once the thermostat opens, it pretty much shoves all the air to the radiator and then out to the expansion tank. Not sure why you don't get flow through the top tubes unless.  Maybe the water pump gasket moved or something.  Maybe take the thermostat out and see what kind of flow you get when you rev the engine.Beer

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Re: Replaced water pump, can't get air out of the cooling system (10/12)
 3/2/19 9:26pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#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


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I would make absolute certain that you have a water pump that is designed to turn in the correct rotation. Wouldn't be the first time a parts place has sold the wrong pump, or a pump was mis-boxed, for the application. Cars with serpentine belts have pumps that spin in the opposite direction from ones with V belt setups.....the pumps will bolt right up, and look the same, but the impeller is different on the two styles. 
 I don't think you have an air in the coolant issue...I think you have a water pump issue. A normal, working cooling system on these cars will burp the air out on it's own after heating up and cooling down.  
as others have suggested, I would also remove the thermostat(cold engine, of course), start the car, and see if you have full coolant flow instantly. If you do not, or if the coolant surges out of the radiator instantly, I'd have to bet on it being the incorrect water pump. If however, you DO see proper coolant flow with the t-stat out, it's probably a bad t-stat...new or not. hth  Thumbs Up


|UPDATED|3/2/2019 7:26:38 PM (AZT)|/UPDATED|


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Re: Replaced water pump, can't get air out of the cooling system (11/12)
 3/2/19 10:32am
knotacare
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Newark, DE - USA

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1968 Conv, 454HO,500HP-600TQ, TKO-600,3:70 HD rear,hotrod air, custom paint & suspension,1973 Ruby Red,T-top, 383 Stroker, TK)-500,frame off restro,


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Years ago I had a parts house sell me the wrong water pump & when you got on the highway it would heat up at idle it would go to the normal temp. Finally took the pump off & found it was trying pushing the water the wrong way. So I have to believe Adam is correct on this problem. 

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Re: Replaced water pump, can't get air out of the cooling system (12/12)
 3/8/19 12:07pm
danascar
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Germansville, PA - USA

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Did you replace lower rad hose? If not there is a possibility that if the hose does not have internal spring in it, it could be collapsing under running conditions...just a thought.

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