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Jun 14th, 2026
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Joined: Jun 2011
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L - Learner Plates On
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OP
L - Learner Plates On
Joined: Jun 2011
Posts: 106 Likes: 1 |
Last weekend I wanted to make a trip with my Morgan Roadster 3.7 on some passes. Unfortunately, on the very first pass (close to the top) I recognised cooling water to the windshield. I stopped immediately and then I saw that the cooling water splashing out of the pressure relief valve in the cap of the coolant tank. After the cooling water was a little cooler, it has finished to splash out. I had to refill 3 litres of water.
I have discarded my original plan and drove back home. On the way home, the cooling water is not over cooked. Now of course I'm confused why this is happening, and whether it can happen again. My Morgan was last year for repairs in their workshop. Two cooling tubes had leaks. But sins then I drove 2000 kilometers without any problems.
What's also funny. The temperature gauge was at boiling never above the central display area. If the cooling water is leaking from the pressure relief valve, it ought to be hotter than normal, and the cooling water thermal display should get into the red zone. But it didn’t…
Has anybody an idea?
Morgan Roadster 3.7
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Talk Morgan Enthusiast
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Talk Morgan Enthusiast
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Not sure of my physics here, but doesn't water boil at a lower temperature the lower the pressure? How high were the passes you were driving over?  High-altitude cooking is the opposite of pressure cooking in that the boiling point of water is lower at higher altitudes due to the decreased air pressure.
Last edited by Digimap; 23/06/14 01:18 PM.
Graeme: 2011 +4
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Joined: Oct 2011
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Talk Morgan Enthusiast
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Talk Morgan Enthusiast
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Not sure of my physics here, but doesn't water boil at a lower temperature the lower the pressure? How high were the passes you were driving over? High-altitude cooking is the opposite of pressure cooking in that the boiling point of water is lower at higher altitudes due to the decreased air pressure. That's right, high altitude tea is nasty stuff!
1930 Super Sports Aero 'The Elk'
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Member of the Inner Circle
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Member of the Inner Circle
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Not sure of my physics here, but doesn't water boil at a lower temperature the lower the pressure? How high were the passes you were driving over? High-altitude cooking is the opposite of pressure cooking in that the boiling point of water is lower at higher altitudes due to the decreased air pressure. This should make no difference as the system is pressurised and therefore not affected by the atmosphric pressure. Perhaps the cap is faulty releasing the pressure too early and with the slightly lower atmospheric pressure vented. New caps are cheap and an easy fix.
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: Jun 2011
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L - Learner Plates On
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OP
L - Learner Plates On
Joined: Jun 2011
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The cooling system is a closed system. It doesn't matter how high you are. And I drove several times such high passes (2500 meters above sea level)...
Morgan Roadster 3.7
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Joined: May 2011
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Drive on the Wild Side Part of the Furniture
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Drive on the Wild Side Part of the Furniture
Joined: May 2011
Posts: 4,896 |
Had you driven much since the workshop, is it possible they did not properly bleed the system and left an airlock. If you put the heater on as you had not used it in the summer due to being higher up, if the air lock was in the heater matrix this might have been the issue. Just a thought?
Adrian
Buggered Off, to a modern none leaky car, heart's still ticking
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Member of the Inner Circle
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Yes air would do it as it would expand rapidly & push up the pressure
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: Jun 2011
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L - Learner Plates On
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OP
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Joined: Jun 2011
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Thank you for your hints but mentioned points I can exclude.The repair was in October last year. Since then I drove a lot also on cold days with heater on. I never had problems before.
Morgan Roadster 3.7
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Joined: May 2014
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Learner Plates Off!
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Learner Plates Off!
Joined: May 2014
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Buy a new coolant cap and take it from there. A lot of the these plastic coolant caps should be treat as a service item.
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Talk Morgan Addict
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Talk Morgan Addict
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Cap would be my first thoughts.
Mark - No Longer driving Archie the Old English Sheep Mog........... 2010 Roadster 3.0 V6 (S3) 
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