Coolant flow control valve plugged
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 21
Likes: 1
Coolant flow control valve plugged
The heater in Debbi's '94 - C4 has been blowing cold air and my son found that the hoses leading to & from the heater core were cold when warmed up.
We pulled out the coolant flow control valve and found it was plugged with crud, but the rest of the cooling system is clean. Has anyone had a similar problem that can give us advice? Is it possible to flush only the heater core of any crud in there? We ordered a new valve and will compare the existing one with a new one. Right now it is sitting in the garage partially dismantled as a "work in progress"
Debbi is the second owner of this low mileage C4 Arizona car (60K) - now in BC, Canada. I doubt the heater was ever used in Az.
We pulled out the coolant flow control valve and found it was plugged with crud, but the rest of the cooling system is clean. Has anyone had a similar problem that can give us advice? Is it possible to flush only the heater core of any crud in there? We ordered a new valve and will compare the existing one with a new one. Right now it is sitting in the garage partially dismantled as a "work in progress"
Debbi is the second owner of this low mileage C4 Arizona car (60K) - now in BC, Canada. I doubt the heater was ever used in Az.
Melting Slicks
Joined: Mar 2008
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From: Delta B.C. Canada
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You should be able to flush the crud out of the control valve with regular water pressure. However, I'd do a whole cooling system flush anyway.
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 21
Likes: 1
flushed the heater core
Hey ragtop,We couldn't find a new coolant control valve locally, but we solved the problem and will do a complete flush next.
We flushed and back-flushed the heater core by disconnecting the inlet hose at the control valve and disconnecting the outlet hose from the radiator surge tank. We temporarily attached garden hose quick coupler hardware and were able to easily connect a charged hose and a drain hose. We flushed, then back flushed a dozen times using low pressure H2O. The quick couplers made the process easier.
We flushed a lot of crud from the heater core. Also cleaned out the control valve with some "iron out" and then tested it. The heater works like new now.
This has been a frustration that qualified professionals couldn't fix. Sometimes it just takes determination to git'er done right.
PS - the coolant control valve restricts flow to a 1/4 inch opening inside. I need to learn more about it's purpose and where to find a new one.
Thanks for your interest.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
Just something to consider....... when you flush the cooling system, you should remove the 2 knock sensors from the bottom of the block. The bottom of the block acts like a sump for contaminants, and once the sensors are removed, a stream of water should be sprayed in the sensor holes several times to remove all the 'gunk' that has probably been there for nearly 20 years. Replace the sensors with new sensors.
Here is a link for the valve:
http://www.rockauto.com/catalog/x,ca...,parttype,6860
Here is a link for the valve:
http://www.rockauto.com/catalog/x,ca...,parttype,6860
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 28
From: South Riding VA
I thought I read somewhere that the control valve was there to reduce the pressure to the heater core for longevity.. dunno if that is true though. I think I have one sitting around the garage that I swapped out when I changed my hoses if you need one...
Instructor
Joined: Sep 2003
Posts: 179
Likes: 0
From: Las VEgas NV
The heater in Debbi's '94 - C4 has been blowing cold air and my son found that the hoses leading to & from the heater core were cold when warmed up.
We pulled out the coolant flow control valve and found it was plugged with crud, but the rest of the cooling system is clean. Has anyone had a similar problem that can give us advice? Is it possible to flush only the heater core of any crud in there? We ordered a new valve and will compare the existing one with a new one. Right now it is sitting in the garage partially dismantled as a "work in progress"
Debbi is the second owner of this low mileage C4 Arizona car (60K) - now in BC, Canada. I doubt the heater was ever used in Az.
We pulled out the coolant flow control valve and found it was plugged with crud, but the rest of the cooling system is clean. Has anyone had a similar problem that can give us advice? Is it possible to flush only the heater core of any crud in there? We ordered a new valve and will compare the existing one with a new one. Right now it is sitting in the garage partially dismantled as a "work in progress"
Debbi is the second owner of this low mileage C4 Arizona car (60K) - now in BC, Canada. I doubt the heater was ever used in Az.
The FSM says for INSUFFICENT HEATING to:
Get car to operating temp. Check both upper and lower hose. Upper hose should be cooler. If both hot, check for restrictions in heater core and related hoses and pipes.
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 21
Likes: 1
I should tell you that I have both the GM shop manuals for the 94, and there is no mention or diagram of the coolant flow control valve. My son is a much better mechanic than I am and he figured big on this one. Nothing in the shop manual was of help on this one.
The hoses to/from the heater core run under the coolant surge tank that is mounted on the passenger side. You should see what looks like a black plastic "hose coupler" secured with two hose clamps on the heater core inlet hose. THIS IS actually the control valve. We loosened the surge tank from it's mount so we could get better access and see what we were doing. We also remove a cover behind/below the surge tank so we could see if blend-door was working. (the blend-door opens/closes when you operate the heater with dash controls). The heater core outlet hose runs from the core to the BOTTOM of the surge tank.
Note that the control valve has an arrow to show the direction of flow.
You can block the flow just BEFORE the valve by crimping the hose with padded needle-nose vise grip if you don't have a hose crimp tool.
The hoses to/from the heater core run under the coolant surge tank that is mounted on the passenger side. You should see what looks like a black plastic "hose coupler" secured with two hose clamps on the heater core inlet hose. THIS IS actually the control valve. We loosened the surge tank from it's mount so we could get better access and see what we were doing. We also remove a cover behind/below the surge tank so we could see if blend-door was working. (the blend-door opens/closes when you operate the heater with dash controls). The heater core outlet hose runs from the core to the BOTTOM of the surge tank.
Note that the control valve has an arrow to show the direction of flow.
You can block the flow just BEFORE the valve by crimping the hose with padded needle-nose vise grip if you don't have a hose crimp tool.
Last edited by canadabob123; Oct 26, 2013 at 10:06 AM.
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Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 21
Likes: 1
I also should mention that you'll want to have some absorbent rags, small containers and an extra set of hands to minimize making a mess and getting frustrated.
FYI - the control valve is GM part #10157988. Google the part # and you should be able to find out what it looks like before you start.
I hope this is of help to others here.
Cheers,
FYI - the control valve is GM part #10157988. Google the part # and you should be able to find out what it looks like before you start.
I hope this is of help to others here.
Cheers,
Last edited by canadabob123; Oct 26, 2013 at 10:15 AM.
Instructor
Joined: Sep 2003
Posts: 179
Likes: 0
From: Las VEgas NV
I should tell you that I have both the GM shop manuals for the 94, and there is no mention or diagram of the coolant flow control valve. My son is a much better mechanic than I am and he figured big on this one. Nothing in the shop manual was of help on this one.
The hoses to/from the heater core run under the coolant surge tank that is mounted on the passenger side. You should see what looks like a black plastic "hose coupler" secured with two hose clamps on the heater core inlet hose. THIS IS actually the control valve. We loosened the surge tank from it's mount so we could get better access and see what we were doing. We also remove a cover behind/below the surge tank so we could see if blend-door was working. (the blend-door opens/closes when you operate the heater with dash controls). The heater core outlet hose runs from the core to the BOTTOM of the surge tank.
Note that the control valve has an arrow to show the direction of flow.
You can block the flow just BEFORE the valve by crimping the hose with padded needle-nose vise grip if you don't have a hose crimp tool.
The hoses to/from the heater core run under the coolant surge tank that is mounted on the passenger side. You should see what looks like a black plastic "hose coupler" secured with two hose clamps on the heater core inlet hose. THIS IS actually the control valve. We loosened the surge tank from it's mount so we could get better access and see what we were doing. We also remove a cover behind/below the surge tank so we could see if blend-door was working. (the blend-door opens/closes when you operate the heater with dash controls). The heater core outlet hose runs from the core to the BOTTOM of the surge tank.
Note that the control valve has an arrow to show the direction of flow.
You can block the flow just BEFORE the valve by crimping the hose with padded needle-nose vise grip if you don't have a hose crimp tool.
I was also looking at the diagram in the FSM. Do the in/out heater hoses from the water pump both go to the coolant surge tank. I thought one actually went to the firewall, but after looking close at the book it seems both interact with the coolant tank. I am currently in Saudi and do not have access to my Vette in Vegas. The FSM is not as good as I expected, but after spending hours with it, it will probably get better
Thread Starter
Heel & Toe
Joined: Oct 2008
Posts: 21
Likes: 1
The inlet hose beyond the control valve runs beneath the surge tank and through the firewall. Your diagram is very poor and doesn't match. No it is not at the 90 degree bend. It is on the hose that comes from lower on the water pump and you should be able to see the control valve clamped in the hose (below and slightly in front of tank)without loosening the surge tank.
When we loosened the surge tank we also temporarily unplugged a wire to a sensor on the surge tank. This is necessary to move the tank enough to get access to the core outlet hose and the blend-door cover and fan motor to check that. The core outlet hose has a 180 degree bend (horse shoe) at the bottom of the surge tank.
I was the extra set of hands and my son actually did the work. We fitted misc. garden hose fittings we had on hand to rig the garden house quick couplers when we did the flush. We were careful not to use full pressure. Only open the valve on the garden hose 1/2 to 1 turn so you use low water pressure and it'll work fine.
On your diagram it is in the hose that starts low on the WP and is the higher hose on the left. The valve is approx. where the two vertical lines are on that hose
Good luck
When we loosened the surge tank we also temporarily unplugged a wire to a sensor on the surge tank. This is necessary to move the tank enough to get access to the core outlet hose and the blend-door cover and fan motor to check that. The core outlet hose has a 180 degree bend (horse shoe) at the bottom of the surge tank.
I was the extra set of hands and my son actually did the work. We fitted misc. garden hose fittings we had on hand to rig the garden house quick couplers when we did the flush. We were careful not to use full pressure. Only open the valve on the garden hose 1/2 to 1 turn so you use low water pressure and it'll work fine.
On your diagram it is in the hose that starts low on the WP and is the higher hose on the left. The valve is approx. where the two vertical lines are on that hose
Good luck
Last edited by canadabob123; Oct 26, 2013 at 12:11 PM.
