Radiator cap question; open vs closed system cap?
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Fleet Mechanic
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From: Willamette Valley, Oregon
Radiator cap question; open vs closed system cap?
I have a 302 with a modern radiator, I installed an overflow tank, it never had one before. In order for this to work I need the correct cap. How can I tell if mine is for an open or closed sytem?
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From: Littleton, New Hampshire
Originally Posted by packrat56
I have a 302 with a modern radiator, I installed an overflow tank, it never had one before. In order for this to work I need the correct cap. How can I tell if mine is for an open or closed sytem?
I don't think the cap cares whether the system is closed or not. I have always just used a 13-15 pound cap (or whatever your radiator calls for) with or without a coolant recovery system. When the radiator pressure exceeds the cap pressure the coolant will spill into the recovery tank and then when the system cools back down it will suck it back in to the radiator...
Vern
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The cap does care. I just added a coolant recovery tank to my 52 F3. For my application the Stant number is 10282 for an open system and 10292 for a closed system.
You can use a open system cap on a closed system, but the coolant is taking a one way trip out of the radiator. A closed system cap allows the vacuum formed in the cooling radiator to draw the coolant back into the radiator.
Call Stant customer service or visit their website.
You can use a open system cap on a closed system, but the coolant is taking a one way trip out of the radiator. A closed system cap allows the vacuum formed in the cooling radiator to draw the coolant back into the radiator.
Call Stant customer service or visit their website.
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From: Littleton, New Hampshire
Originally Posted by SteV8e
You can use a open system cap on a closed system, but the coolant is taking a one way trip out of the radiator. A closed system cap allows the vacuum formed in the cooling radiator to draw the coolant back into the radiator.
I guess I've always inadvertently had the right cap. NEVER have I had any radiator cap on a closed system that would not allow the coolant back into the radiator...and I've have converted lot of open systems to closed systems over the years without changing the cap. If what you are saying is true, then using an open cap on a closed system would eventually cause the coolant recovery bottle to overflow. I have never had that happen with any cap I have used, so excuse me for being skeptical...
Vern
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From: Minneapolis
The fact that manufacturers, like Stant, offer two part numbers for an application, one for closed system and one for open, indicates there is a difference.
How do you know that coolant was returning to the radiator? Unless you had a clear tube and were able to watch the flow as the engine cool, you would not know.
A radiator will typically push out enough coolant until it has enough head space and then stop doing it. You would only overflow your tank if you were repeatedly overheaing.
How do you know that coolant was returning to the radiator? Unless you had a clear tube and were able to watch the flow as the engine cool, you would not know.
A radiator will typically push out enough coolant until it has enough head space and then stop doing it. You would only overflow your tank if you were repeatedly overheaing.
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From: Littleton, New Hampshire
Originally Posted by SteV8e
The fact that manufacturers, like Stant, offer two part numbers for an application, one for closed system and one for open, indicates there is a difference.
How do you know that coolant was returning to the radiator? Unless you had a clear tube and were able to watch the flow as the engine cool, you would not know.
A radiator will typically push out enough coolant until it has enough head space and then stop doing it. You would only overflow your tank if you were repeatedly overheaing.
How do you know that coolant was returning to the radiator? Unless you had a clear tube and were able to watch the flow as the engine cool, you would not know.
A radiator will typically push out enough coolant until it has enough head space and then stop doing it. You would only overflow your tank if you were repeatedly overheaing.
You would be surprised what manufacturers do just to sell more stuff.
I know the coolant was returning to the radiator because not only did I use clear plastic tubing for the return, but I also used clear plastic coolant retainers so I could monitor the movement of the coolant and its condition.
After parking the car for a while after a drive the coolant level would always move up in the retainer, but when the system cooled off the coolant level moved back down so I know it was going back into the radiator.
Vern
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From: Minneapolis
Vern:
You can't argue with results, and it sounds like you had success.
I did not, so I contacted Stant, who gave me a different part number for the closed system, which worked for me.
One day when it was hot and I had topped the rad, I had coolant going into the recovery tank and bubbling out of the rad cap too. I don't understand that.
You can't argue with results, and it sounds like you had success.
I did not, so I contacted Stant, who gave me a different part number for the closed system, which worked for me.
One day when it was hot and I had topped the rad, I had coolant going into the recovery tank and bubbling out of the rad cap too. I don't understand that.
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Lead Driver
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From: Littleton, New Hampshire
Originally Posted by SteV8e
Vern:
You can't argue with results, and it sounds like you had success.
I did not, so I contacted Stant, who gave me a different part number for the closed system, which worked for me.
One day when it was hot and I had topped the rad, I had coolant going into the recovery tank and bubbling out of the rad cap too. I don't understand that.
You can't argue with results, and it sounds like you had success.
I did not, so I contacted Stant, who gave me a different part number for the closed system, which worked for me.
One day when it was hot and I had topped the rad, I had coolant going into the recovery tank and bubbling out of the rad cap too. I don't understand that.
I don't understand that either, unless you just happened to get a defective cap. The caps I used were not necessarily made by Stant, but most had the lever you can pull to relieve the pressure if you wanted to remove the cap for some reason. I wonder if Stant's caps are different from other manufacturers...
Vern
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From: Minneapolis
This particular cap is not the lever style. I did buy another one, and it is holding pressure, but the coolant is now coming out of a spot where the top tank of radiator meets the main radiator body. It does leak when I am driving, but about ten minutes after I cut the engine is starts. Is there a repair I can do to the outside, like JB Weld? I know they make a solution for the coolant, but I am leary about adding a stop-leak for fear of it clogging up the works. I can pull the radiator after I put it in storage (Oct or Nov), but I don't want to do it this summer. The driving season is too short!
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From: Littleton, New Hampshire
Steve,
If the leak is near the top tank a radiator shop may be able to patch it for you without removing the radiator. It's worth a trip to see. I've heard good things about JB weld, but I have never used it on a radiator so I can't say if that would work or not. How old is this radiator? I would not hesitate to use a good stop leak in an older radiator, but if the radiator is relatively new, I'd get it repaired.
Vern
If the leak is near the top tank a radiator shop may be able to patch it for you without removing the radiator. It's worth a trip to see. I've heard good things about JB weld, but I have never used it on a radiator so I can't say if that would work or not. How old is this radiator? I would not hesitate to use a good stop leak in an older radiator, but if the radiator is relatively new, I'd get it repaired.
Vern
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From: Minneapolis
The radiator is old. On their website, JB Weld advertises a Perm-O-Seal radiator sealant, and I know there are others. JB claims that their sealant remains in suspension in the coolant and doesn't clog the system. I still don't feel good about having it in my block. I will try your suggestion about taking it to a shop to see if it can be repaired in the truck. It is on the engine facing side, but the radiator sits high enough to give good access. Thanks!
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