how to bleed cooling system ?
Discussion
I need some advice on the following:
- drained coolant and replaced hose
- refilled and ran couple of minutes with swirl tank cap off and heater on
- allowed to cool, topped-up, replaced cap, drove 20mins, allowed reach temp and kept it there
- allowed to cool, topped-up, replaced cap, drove 20 mins, allowed reach temp and kept it there
Despite this, last two drives the needle on temp guage swings up much quicker than usual then drops visibly again - clearly still air in system. At a loss as to how to bleed it further. Should I run it for longer with swirl tank open ? Should I undo the top rad hose (which heads back to swirl tank) and bleed from there ? Should I just carry on driving it and let it bleed itself as the swirl pot is supposed to ?
Also the fans now do not come on automatically. Note that removing th two wires from the fan switch and joining them fires up the fans, so no electrics problems. Measuring the resistance across the fan-switch when temp guage shows 90C tells me it's still an open circuit. Perhaps air in radiator around switch ? On my Sport this is on RHS about 1/3 down from top of rad. But have loosened switch slightly when hot and let water flow out under pressure so that should have bled it. Or fan switch failed ? This at least will be straightforward to replace. Anyone know the donor for Sport rad ? Is there a choice on trigger temperature ?
cheers
Roger.
- drained coolant and replaced hose
- refilled and ran couple of minutes with swirl tank cap off and heater on
- allowed to cool, topped-up, replaced cap, drove 20mins, allowed reach temp and kept it there
- allowed to cool, topped-up, replaced cap, drove 20 mins, allowed reach temp and kept it there
Despite this, last two drives the needle on temp guage swings up much quicker than usual then drops visibly again - clearly still air in system. At a loss as to how to bleed it further. Should I run it for longer with swirl tank open ? Should I undo the top rad hose (which heads back to swirl tank) and bleed from there ? Should I just carry on driving it and let it bleed itself as the swirl pot is supposed to ?
Also the fans now do not come on automatically. Note that removing th two wires from the fan switch and joining them fires up the fans, so no electrics problems. Measuring the resistance across the fan-switch when temp guage shows 90C tells me it's still an open circuit. Perhaps air in radiator around switch ? On my Sport this is on RHS about 1/3 down from top of rad. But have loosened switch slightly when hot and let water flow out under pressure so that should have bled it. Or fan switch failed ? This at least will be straightforward to replace. Anyone know the donor for Sport rad ? Is there a choice on trigger temperature ?
cheers
Roger.
Have never had a problem with air lock.
The bleed pipe from the top of the rad to the swirl is supposed to do the bleeding.
Try jacking up the back of the car or park facing down hill and see if that helps. (getting vague thoughts that this has been mentioned before. Also that the height the build set the swirl pot at may also be a little on the low side).
The water stat will be the standard 22mm thread. Any good motor factors will let you leaf through the catalogue and find the open and close temperature you want. However the stat you choose may have some strange flying leads or unusual termination specific to the make/model it was designed for. Not the end of the world but may be a little more work to adapt.
Steve
The bleed pipe from the top of the rad to the swirl is supposed to do the bleeding.
Try jacking up the back of the car or park facing down hill and see if that helps. (getting vague thoughts that this has been mentioned before. Also that the height the build set the swirl pot at may also be a little on the low side).
The water stat will be the standard 22mm thread. Any good motor factors will let you leaf through the catalogue and find the open and close temperature you want. However the stat you choose may have some strange flying leads or unusual termination specific to the make/model it was designed for. Not the end of the world but may be a little more work to adapt.
Steve
Hi Steve_d
went down Unipart and rummaged along their shelves until I found a 22mm thread 88 degree opening, 85 degree closing switch. Perfect. Took the old one out and rubbed it down to discover it was 100-95. No wonder the fans weren't coming on at my expected temperature of 90 !
Reckon the lower fan trigger temperature should prevent unnecessary temperature rise.
regards
Roger
went down Unipart and rummaged along their shelves until I found a 22mm thread 88 degree opening, 85 degree closing switch. Perfect. Took the old one out and rubbed it down to discover it was 100-95. No wonder the fans weren't coming on at my expected temperature of 90 !
Reckon the lower fan trigger temperature should prevent unnecessary temperature rise.
regards
Roger
Sounds like it could be a cheap fix for some who are worried about cooling (I think mines probably the 95-100 switch judging by my tests yesterday). Getting the fans on earlier and controlling the heat before it gets beyond the capabilities of the system has got to be a good idea.
I know alot of TVR owners who used the same trick to good effect.
I know alot of TVR owners who used the same trick to good effect.
Don't understand why the rad temp switch should be so high. By the time the water has made it through 9' or so of pipe down the length of the car it is going to be a lot cooler than it is in the head/intake where we are measuring/care about it. At idle it's not beyond the realms of possbility that the temperature difference may be as much as 10 degrees. This could certainly explain the runaway temps.
One tip that's not been mentioned in recent threads for bleeding the cooling systems. Drill a couple of 1/8" holes in the flange of the thermostat to allow the aire to bubble out. This might also act as a little bit of a bypass but I doubt the effect would be significant especially with 160F thermostats.
One tip that's not been mentioned in recent threads for bleeding the cooling systems. Drill a couple of 1/8" holes in the flange of the thermostat to allow the aire to bubble out. This might also act as a little bit of a bypass but I doubt the effect would be significant especially with 160F thermostats.
davefiddes said:
Don't understand why the rad temp switch should be so high. By the time the water has made it through 9' or so of pipe down the length of the car it is going to be a lot cooler than it is in the head/intake where we are measuring/care about it. At idle it's not beyond the realms of possbility that the temperature difference may be as much as 10 degrees. This could certainly explain the runaway temps.
One tip that's not been mentioned in recent threads for bleeding the cooling systems. Drill a couple of 1/8" holes in the flange of the thermostat to allow the aire to bubble out. This might also act as a little bit of a bypass but I doubt the effect would be significant especially with 160F thermostats.
One tip that's not been mentioned in recent threads for bleeding the cooling systems. Drill a couple of 1/8" holes in the flange of the thermostat to allow the aire to bubble out. This might also act as a little bit of a bypass but I doubt the effect would be significant especially with 160F thermostats.
Interesting point Dave. I seem to have a 10 degree difference between the Stack reading (taken from a sender in the head) and what I see at the rad (tested with a pyrometer). I guess you could put a rad switch in the manifold instead?
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