Heater core shutoff causing overheating
Melting Slicks
Joined: May 2002
Posts: 2,716
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
I'm with Mike W on this one, unless you have the heater on in the cab its not providing any additional cooling so its just circulating water from the intake to the inlet of the pump.
Could it be possible that the flow through the radiator or T-Stat is marginal and the lower hose is collapsing when the flow from the heater core is stopped. Could the extra flow form the heater core be just enough that it prevents the hose from collapsing.
Just throwing ideas out there
Neal
Could it be possible that the flow through the radiator or T-Stat is marginal and the lower hose is collapsing when the flow from the heater core is stopped. Could the extra flow form the heater core be just enough that it prevents the hose from collapsing.
Just throwing ideas out there
Neal
Team Owner
Joined: Mar 2002
Posts: 24,160
Likes: 78
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I just installed a heater core shutoff valve in my car and like the title says, my car now overheats. I didnt read anyone else saying they had this problem in the big shutoff valve thread. Is it just me?
The valve is a 3/4" pex ball valve (fits perfect BTW) installed in the 5/8 fluid feed line to the heater core. My car used to stay at 180-195* no matter what kind of driving. Now it spikes to 220+* with normal around town driving. If I open the valve to let the antifreeze flow, it drops right back down to 180*
I saw the bypass valve that connects the two lines via a vacuum source, but I do not have any vacuum lines to connect it to anymore. Ideas?
The valve is a 3/4" pex ball valve (fits perfect BTW) installed in the 5/8 fluid feed line to the heater core. My car used to stay at 180-195* no matter what kind of driving. Now it spikes to 220+* with normal around town driving. If I open the valve to let the antifreeze flow, it drops right back down to 180*
I saw the bypass valve that connects the two lines via a vacuum source, but I do not have any vacuum lines to connect it to anymore. Ideas?
Burning Brakes
Joined: May 2003
Posts: 910
Likes: 20
From: Shorewood IL
I had the same thing happen to me with my '80. I had a high flow water pump installed, with the correct high flow thermostat (three holes drilled). I totally got rid of the heater core hoses and put plugs in the manifold and water pump. The car would not stay cool at all.
I couldn't explain it, I'm not sure what it was but I had to put a hose between the water pump and the intake manifold in order for it to cool properly.
It was stewart warner stage two pump and a set of double hump heads, nothing fancy!
I couldn't explain it, I'm not sure what it was but I had to put a hose between the water pump and the intake manifold in order for it to cool properly.
It was stewart warner stage two pump and a set of double hump heads, nothing fancy!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Thread Starter
Burning Brakes
Joined: Oct 2008
Posts: 955
Likes: 50
From: Jersey Shore
Im going to just go ahead and say that this problem has nothing to do with the condition of my cooling system. All of the components work perfectly, and will keep my car between 180* and 195*. No matter what- with the valve open. As soon as I close it, thats when the problem arises. If there was an air pocket in the system it would be overheating all the time.
The temperature gauge works properly and is accurate.
Yeah, just blocking it. Ill have to look into something like this... except I dont have vacuum going to my heater controls anymore.
http://www.ls1tech.com/forums/conver...ter-valve.html
The temperature gauge works properly and is accurate.
http://www.ls1tech.com/forums/conver...ter-valve.html
Last edited by vette427-sbc; Aug 1, 2011 at 05:55 PM.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
I'm with Mike W on this one, unless you have the heater on in the cab its not providing any additional cooling so its just circulating water from the intake to the inlet of the pump.
Could it be possible that the flow through the radiator or T-Stat is marginal and the lower hose is collapsing when the flow from the heater core is stopped. Could the extra flow form the heater core be just enough that it prevents the hose from collapsing.
Just throwing ideas out there
Neal
Could it be possible that the flow through the radiator or T-Stat is marginal and the lower hose is collapsing when the flow from the heater core is stopped. Could the extra flow form the heater core be just enough that it prevents the hose from collapsing.
Just throwing ideas out there
Neal
Scott
Burning Brakes
Joined: Oct 2009
Posts: 1,066
Likes: 57
He means it isnt cooling at top effientcy.
I would first make sure any air pockets are removed. It may not have been clear with the prior post. But to remove any air pockets, with the cutoff(s) open, jack up the front end so the radiator top is the highest point on the car. Then run the radiator without a cap until it gets to operating temperature. This should remI've any air pockets. You an also drill a few 1/8th holes in the thermostat to help.
I would first make sure any air pockets are removed. It may not have been clear with the prior post. But to remove any air pockets, with the cutoff(s) open, jack up the front end so the radiator top is the highest point on the car. Then run the radiator without a cap until it gets to operating temperature. This should remI've any air pockets. You an also drill a few 1/8th holes in the thermostat to help.
Drifting
Joined: Oct 2010
Posts: 1,972
Likes: 6
From: Chester Virginia
Every time you cut a coolant line like putting in the valve it's possible to lose some fluid. When your engine is cool, open the radiator cap and see how much fluid is actually in the radiator cool. If it isn't up nearly at the top then you've been running with insufficient fluid in the radiator system. Might be from the line cut but might also be from some other thing. All I know is without a full fluid in the radiator they run hot as heck and i was surprised once when mine had less liquid than I thought after what I thought was a minor leak. Wasn't so minor after all.
Cold engine, check the radiator level below the cap.
I have the same valve inline and it had absolutely no effect on the engine temps when blocking water to the heater core.
Lance
Cold engine, check the radiator level below the cap.
I have the same valve inline and it had absolutely no effect on the engine temps when blocking water to the heater core.
Lance
Last edited by LancePearson; Aug 1, 2011 at 10:17 PM. Reason: add
Drifting
Joined: Oct 2010
Posts: 1,972
Likes: 6
From: Chester Virginia
fluid level
If you lose enough refilling from the reservoir is inadequate.
I don't know if you've checked but you may be losing fluid at high pressure enough that you don't have enough. Double check how tight the new valve hose clamps are so it isn't a small leak from there.
Something's going on assuming the water pump and radiator are working right.
Lance P.
Drifting
Joined: Jul 2007
Posts: 1,889
Likes: 23
From: Kansas
Yes Sir; I have a complete new system, motor, heater core, radiator, hoses & both fans, engine & Auxiliary, Yes when I first take the car out on a cruise, at 35 MPH, the temp. will rise, with the heater shut off, by the pex valve, to around 230, at which time my auxiliary fan will kick in, & cool it right down to approx. 205. With the heater pex valve open, it will not get above the 190 which the thermostat is set at. But the first lesson you learn, is that if the water is not boiling out of the system, the system is not overheating. The auxiliary fan is set to come on at 230 at the factory. You are worrying too much in my opinion. If you don't, like less heat in the cabin, leave the pex valve open, so you won't have to worry. Have a great day, Gene
Burning Brakes
Joined: Jun 2011
Posts: 816
Likes: 11
From: lewisburg wv
I installed the same valve you did a week ago and had an overheating problem also. Ended up had a little air in the system and just needed to burp. Now runs 180. Did you install the valve in the heater hose from the intake manifold?
Melting Slicks
Joined: Jul 2004
Posts: 3,296
Likes: 8
From: Avon, Indiana
Since many of these cars came with the shutoff valve from the factory, then the concept must be ok.Agree that it is very likely air in the system or a loose hose connection or that the radiator cap is not screwed on tight.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Im going to just go ahead and say that this problem has nothing to do with the condition of my cooling system. All of the components work perfectly, and will keep my car between 180* and 195*. No matter what- with the valve open. As soon as I close it, thats when the problem arises. If there was an air pocket in the system it would be overheating all the time.
The temperature gauge works properly and is accurate.
The temperature gauge works properly and is accurate.
Did you check your pump to make sure the bypass was not blocked by the engine builder ?
Burning Brakes
Joined: Feb 2006
Posts: 1,223
Likes: 4
From: Regina Saskatchewan
I had this EXACT problem with my 350 sbc with vortec heads. Got myself a 383 and put the vortec heads back on AND bolted a DeWitts rad on.... SAME PROBLEM. Thought I was going crazy. Changed the thermostat out 3 - 4 times (can't remember now) Always the same thing.
Posted here awhile back and everyone here said , its the rad , its an air pocket , its the thermostat. Then someone posted they were having the same problem with VORTEC heads. And someone else posted that vortec heads don't have an internal bypass , that if you put in a manual shutoff valve you will damage your water pump . I'm not sure but maybe your after market heads are like the vortecs. I don't know. But I do know that I still run the 2 manual shut off valves (have them turned off now) but I had to add a bypass valve ahead of the whole works - and everything runs at 180 deg. If I shut the bypass valve it spikes to 260 then down to 180 then to 260 ........
Posted here awhile back and everyone here said , its the rad , its an air pocket , its the thermostat. Then someone posted they were having the same problem with VORTEC heads. And someone else posted that vortec heads don't have an internal bypass , that if you put in a manual shutoff valve you will damage your water pump . I'm not sure but maybe your after market heads are like the vortecs. I don't know. But I do know that I still run the 2 manual shut off valves (have them turned off now) but I had to add a bypass valve ahead of the whole works - and everything runs at 180 deg. If I shut the bypass valve it spikes to 260 then down to 180 then to 260 ........