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Wales
by Joske Vermeule, September 1
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Forums39
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Jun 14th, 2026
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Joined: Feb 2009
Posts: 208 Likes: 7
L - Learner Plates On
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L - Learner Plates On
Joined: Feb 2009
Posts: 208 Likes: 7 |
Can someone explain how a swirl pot works?
What are the effects on the radiator?
Do the Z4s have this type of equipment?
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Joined: Dec 2009
Posts: 37,486 Likes: 993
Tricky Dicky Member of the Inner Circle
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Tricky Dicky Member of the Inner Circle
Joined: Dec 2009
Posts: 37,486 Likes: 993 |
Can someone explain how a swirl pot works?
What are the effects on the radiator?
Do the Z4s have this type of equipment? Gaston - Richard explains a little on this post - it was all new to me also.. Swirl pot..Good luck getting your car rectified.
2009 4/4 Sport Henrietta
1999 Indigo Blue +8
2009 4/4 Sport Green prev
1993 Con Green +8 prev
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Joined: Feb 2016
Posts: 8,702 Likes: 416
Needs to Get Out More!
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Needs to Get Out More!
Joined: Feb 2016
Posts: 8,702 Likes: 416 |
Can someone explain how a swirl pot works?
What are the effects on the radiator?
Do the Z4s have this type of equipment? Scroll down this page for general description of swirl pot/tank function.
Richard
2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone
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Joined: Feb 2016
Posts: 8,702 Likes: 416
Needs to Get Out More!
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Needs to Get Out More!
Joined: Feb 2016
Posts: 8,702 Likes: 416 |
My own thoughts which are just that, is that the unique fit, coolant plumbing and components of same on BMW's well proven B48 variant collectively cause the issue. Maybe under sudden load, steam is allowed to form probably in the integral to head exhaust manifold. When the thermostat in the radiator return fully opens, such steam pockets enter top of rad and cause mechanical shock from the thermal shock due to sudden cooling.
Cars driven on the track where stat is open most of the time or at the other extreme when gently driven will likely never experience this issue, explaining why not all rads fail and wasn't noticed in original testing.
Certainly mechanical shock in plumbing is well demonstrated at home when a tap is turned off suddenly and a poorly supported copper pipe rattles or bangs, which can turn to leaks at any adjacent joint over time.
Richard
2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone
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Joined: Jul 2007
Posts: 27,846 Likes: 765
Member of the Inner Circle
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OP
Member of the Inner Circle
Joined: Jul 2007
Posts: 27,846 Likes: 765 |
I too think it is thermal shock / pipe hammer. The earlier fix of lowering both the coolant header tank level and the pressure the cap blows at means there is more air that compresses easily to dampen any hammer & in the worst case vent gas.
In industry pneumatic dampers are quite common to stop pipe hammer caused by say a valve closure on a circuit.
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: Feb 2010
Posts: 1,415
Has a lot to Say!
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Has a lot to Say!
Joined: Feb 2010
Posts: 1,415 |
I dont buy thermal shock cracking welds
My thoughts are that the top 6" of the radiator are completely unsupported- and MMC's fix to date has been to increasingly stiffen the mountings hence the welds cracking...
Also the Header tank is too small to accomodate for coolant expansion. I bet that during testing the cars kept spitting out coolant- hence they were delivered with a 25 odd lb radiator cap to try and keep the coolant in....
Simon @ Sifab.co.uk
Sifabtemporary@gmail.com
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Joined: Feb 2009
Posts: 208 Likes: 7
L - Learner Plates On
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L - Learner Plates On
Joined: Feb 2009
Posts: 208 Likes: 7 |
Thank you for your feedback.
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Joined: Jul 2007
Posts: 27,846 Likes: 765
Member of the Inner Circle
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OP
Member of the Inner Circle
Joined: Jul 2007
Posts: 27,846 Likes: 765 |
I dont buy thermal shock cracking welds
My thoughts are that the top 6" of the radiator are completely unsupported- and MMC's fix to date has been to increasingly stiffen the mountings. Also the Header tank is to small to accomodate for coolant expansion. I bet that during testing the cars kept spitting out coolant- hence they were delivered with a 25 odd lb radiator cap to try and keep the coolant in.... Simon I agree the tanks are very small indeed. Lets hope they find the solution
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: Feb 2010
Posts: 1,415
Has a lot to Say!
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Has a lot to Say!
Joined: Feb 2010
Posts: 1,415 |
I dont buy thermal shock cracking welds
My thoughts are that the top 6" of the radiator are completely unsupported- and MMC's fix to date has been to increasingly stiffen the mountings. Also the Header tank is to small to accomodate for coolant expansion. I bet that during testing the cars kept spitting out coolant- hence they were delivered with a 25 odd lb radiator cap to try and keep the coolant in.... Simon I agree the tanks are very small indeed. Lets hope they find the solution Perhaps they should pay me consultancy.....
Simon @ Sifab.co.uk
Sifabtemporary@gmail.com
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Joined: Feb 2009
Posts: 208 Likes: 7
L - Learner Plates On
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L - Learner Plates On
Joined: Feb 2009
Posts: 208 Likes: 7 |
I dont buy thermal shock cracking welds
My thoughts are that the top 6" of the radiator are completely unsupported- and MMC's fix to date has been to increasingly stiffen the mountings. Also the Header tank is to small to accomodate for coolant expansion. I bet that during testing the cars kept spitting out coolant- hence they were delivered with a 25 odd lb radiator cap to try and keep the coolant in.... Simon I agree the tanks are very small indeed. Lets hope they find the solution Perhaps they should pay me consultancy..... I can perhaps advance them the money to be definitely quiet. 
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