radiator bleed screw
Discussion
markbigears said:
Any idea how I can get air out the the system?
The engine will expel air into the swirl tank so make sure that is filled up, and bleed the radiator using that screw. It's a big of a faff if you have trouble getting it to seal afterwards but just a matter of tightening it until it seals.
Mark,
I filled up my system several times without bleeding the radiator, so I would not risk breaking the plug:
- open heater control!
- fill up cold as far as possible through the swanneck. I add first the proper amount of glycol, then add water.
- start the engine with open swan neck, let the engine warm up on idle whille keeping the swanneck nearly full
- as soon as the top radiator hose becomes hot (i.e. the thermostat opened) stop engine
- let the engine cool completely down keeping the swanneck filled 90%.
- fill up to 100% and close the swanneck, I am of the bloodgroup that uses the pressurecap here.
- fill up the overflow tank to 30% level, leave the blank cap open for now.
- heatup the engine again untill either the overflowtank fills up > 60% or the bottom radiator hose gets to 40 C
- cool down completely keeping the overflowtank from emptying and sucking in new air. Add to 30% when cold.
- repeat heating/cooling/filling while increasing the max bottom hose temp if the overflowtank changed more than 50% level per cycle
- place blind cap and drive the car at first gently untill hot and check/fill overflow tank after each drive to 60%.
- when cooled check/fill overflow tank before your next trip if the level to 30% minimum.
Remember, a properly filled system will swing the overflowtank between about 60% hot and 30% cold.
Any air in the system will make the this swing much bigger, because air expands so much more then water with temperature.
mvg Boudewijn
I filled up my system several times without bleeding the radiator, so I would not risk breaking the plug:
- open heater control!
- fill up cold as far as possible through the swanneck. I add first the proper amount of glycol, then add water.
- start the engine with open swan neck, let the engine warm up on idle whille keeping the swanneck nearly full
- as soon as the top radiator hose becomes hot (i.e. the thermostat opened) stop engine
- let the engine cool completely down keeping the swanneck filled 90%.
- fill up to 100% and close the swanneck, I am of the bloodgroup that uses the pressurecap here.
- fill up the overflow tank to 30% level, leave the blank cap open for now.
- heatup the engine again untill either the overflowtank fills up > 60% or the bottom radiator hose gets to 40 C
- cool down completely keeping the overflowtank from emptying and sucking in new air. Add to 30% when cold.
- repeat heating/cooling/filling while increasing the max bottom hose temp if the overflowtank changed more than 50% level per cycle
- place blind cap and drive the car at first gently untill hot and check/fill overflow tank after each drive to 60%.
- when cooled check/fill overflow tank before your next trip if the level to 30% minimum.
Remember, a properly filled system will swing the overflowtank between about 60% hot and 30% cold.
Any air in the system will make the this swing much bigger, because air expands so much more then water with temperature.
mvg Boudewijn
you must do the radiator.
My Butterfly is anticlockwise to loosen and Clockwise to tighten, which seems normal.
Use pliers across the butterfly to loosen and pinch tight again only when all air expelled.
Run with pressure cap off to remove any more air.
(When I say run, I mean the engine with the car stationary of course!)
My Butterfly is anticlockwise to loosen and Clockwise to tighten, which seems normal.
Use pliers across the butterfly to loosen and pinch tight again only when all air expelled.
Run with pressure cap off to remove any more air.
(When I say run, I mean the engine with the car stationary of course!)
not fair Well,
my experience was that without bleeding, most air came out during the first thermostatopening after initial fill and engine start.
Originally my radiator did not even have a vent, since a recore a few years back it has.
Because the radiator flow is horizontal, the air will easily move left (port if you like) and will largely be entrained downwards inside the 50x50 mm channel towards engine/waterpump/swirltank. As soon as the local watervelocity is 0.5 m/s or so.
The swirltank will intercept this air and sends coolant to the radiator and expansion as preferentially air through open hole or pressure cap.
This separation is simply what the swirltank is for!
Residual air will dissolve in the cool coolant at the left side of the radiator. Because the engine circulation is hotter then the cold side of the radiator (and the swirltank is elevated relative to the radiator) dissolved air comes out there, which again is intercepted and removed by the swirltank.
This will take a period of topping up the overflowtank after each drive.
mvg Boudewijn
my experience was that without bleeding, most air came out during the first thermostatopening after initial fill and engine start.
Originally my radiator did not even have a vent, since a recore a few years back it has.
Because the radiator flow is horizontal, the air will easily move left (port if you like) and will largely be entrained downwards inside the 50x50 mm channel towards engine/waterpump/swirltank. As soon as the local watervelocity is 0.5 m/s or so.
The swirltank will intercept this air and sends coolant to the radiator and expansion as preferentially air through open hole or pressure cap.
This separation is simply what the swirltank is for!
Residual air will dissolve in the cool coolant at the left side of the radiator. Because the engine circulation is hotter then the cold side of the radiator (and the swirltank is elevated relative to the radiator) dissolved air comes out there, which again is intercepted and removed by the swirltank.
This will take a period of topping up the overflowtank after each drive.
mvg Boudewijn
The air never does get carried down out of the rad though. It gradually collects there and needs to be vented from time to time. If you don't have a vent on top of the rad then the only way you have to do this is to ease the clamp on the top hose and make sure water comes out, not air.
Greenv8s,
if you have to bleed regularly, air must be leaking in, probably at one of the 2 radiator connections.
Perhaps because your pressurecap does not break vacuum (while letting in overflow water) when the system cools down.
The system is not uniquely TVR, many cars have it, including the (old) mini.
mvg Boudewijn
if you have to bleed regularly, air must be leaking in, probably at one of the 2 radiator connections.
Perhaps because your pressurecap does not break vacuum (while letting in overflow water) when the system cools down.
The system is not uniquely TVR, many cars have it, including the (old) mini.
mvg Boudewijn
No, the problem is that gases naturally accumulate in the coolant and eventually come out of solution and form bubbles somewhere in the system, the degas system is designed to coninually remove these from the coolant but it only holds the gas content down to a low level, it never completely eliminates it. Then you have coolant with a small amount of gas in it pumped into the radiator and left for a few hours, so the gas has time to settle to the top of the tank. Unfortunately due to the layout of radiator the air would have to be carried downwards some distance before it leaves the radiator, which it will do happily while it's in the form of fine bubbles bit not once it has settled out. The result is that every time you run the engine, small quantities of gas are left in the top of the radiator. If you leave this to accumulate over months then the quantity of gas can be enough to affect the performance of the cooling system.
Most production cars have far better designed cooling systems which statically bleed the gas up to the header tank instead of letting it collect in an air pocket in the radiator.
Most production cars have far better designed cooling systems which statically bleed the gas up to the header tank instead of letting it collect in an air pocket in the radiator.
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