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Engine overheat
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Rollmop



Joined: 23 Dec 2016
Posts: 14
Location: Market Drayton, Shropshire

PostPosted: Tue Aug 11, 2020 7:24 am    Post subject: Reply with quote

Thanks for all of your constructive replies. I could be a little cautious on the engine heat but, being a non pressurised system, the boiling point is going to be 100C and a contact thermometer has given 93C temperatures on the actual head. I have changed to Prestone coolant because they give a boiling point on their fluid of 129C. The gauge has recently been refurbished so I donít think that is inaccurate. Perhaps I worry too much. Thanks again
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Rollmop



Joined: 23 Dec 2016
Posts: 14
Location: Market Drayton, Shropshire

PostPosted: Tue Aug 11, 2020 7:24 am    Post subject: Reply with quote

Thanks for all of your constructive replies. I could be a little cautious on the engine heat but, being a non pressurised system, the boiling point is going to be 100C and a contact thermometer has given 93C temperatures on the actual head. I have changed to Prestone coolant because they give a boiling point on their fluid of 129C. The gauge has recently been refurbished so I donít think that is inaccurate. Perhaps I worry too much. Thanks again
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alastairq



Joined: 14 Oct 2016
Posts: 1462
Location: East Yorkshire

PostPosted: Tue Aug 11, 2020 7:32 am    Post subject: Reply with quote

Rollmop wrote:
Thanks for all of your constructive replies. I could be a little cautious on the engine heat but, being a non pressurised system, the boiling point is going to be 100C and a contact thermometer has given 93C temperatures on the actual head. I have changed to Prestone coolant because they give a boiling point on their fluid of 129C. The gauge has recently been refurbished so I donít think that is inaccurate. Perhaps I worry too much. Thanks again


Can I draw your attention to the article in the Mayflower club' website?
The one about issues with the thermostat?

http://www.triumphmayflowerclub.com/documents/flowerpowers/articles/
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peter scott



Joined: 18 Dec 2007
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Location: Edinburgh

PostPosted: Tue Aug 11, 2020 9:18 am    Post subject: Reply with quote

When the thermostat opens it is also supposed to shut off the bypass hose. If the bypass is not shut off then much of your water circulation will not be passing through the radiator. You might be able to test this if you can shut off the bypass hose by clamping it.

Peter
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Ray White



Joined: 02 Dec 2014
Posts: 4085
Location: Derby

PostPosted: Tue Aug 11, 2020 10:37 am    Post subject: Reply with quote

peter scott wrote:
When the thermostat opens it is also supposed to shut off the bypass hose. If the bypass is not shut off then much of your water circulation will not be passing through the radiator. You might be able to test this if you can shut off the bypass hose by clamping it.

Peter


I have discovered that this is also a problem with XPAG engines where the original, rather sophisticated, thermostat is no longer available; or if it is, then it will be a reproduction that fails to close the bypass properly.

The answer that has been proven to work reasonably well, is fitting a common wax stat thermostat and adding a restrictor plate to the bypass opening. The small opening also acts as a breather.
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badhuis



Joined: 20 Aug 2008
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Location: Netherlands

PostPosted: Tue Aug 11, 2020 1:43 pm    Post subject: Reply with quote

The same problem also appears with the Triumph TR 4 cylinder engine. After replacing the "modern" type of thermostat with an old type bellows, the engine ran cooler.
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Ray White



Joined: 02 Dec 2014
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Location: Derby

PostPosted: Tue Aug 11, 2020 2:48 pm    Post subject: Reply with quote

badhuis wrote:
The same problem also appears with the Triumph TR 4 cylinder engine. After replacing the "modern" type of thermostat with an old type bellows, the engine ran cooler.


Not wishing to hijack this thread ... but I wonder if the Land Rover thermostat (as above) will work in the XPAG. Only reason is the original design sells for nearly £100. !
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alanb



Joined: 10 Sep 2012
Posts: 508
Location: Berkshire.

PostPosted: Tue Aug 11, 2020 3:52 pm    Post subject: Reply with quote

If it has a water pump and thermostat then surely it is a pressurised system? The cylinder head will be considerably hotter than the water the best place to check the temperature is at the top hose or radiator header tank.
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Ray White



Joined: 02 Dec 2014
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Location: Derby

PostPosted: Tue Aug 11, 2020 4:27 pm    Post subject: Reply with quote

alanb wrote:
If it has a water pump and thermostat then surely it is a pressurised system? The cylinder head will be considerably hotter than the water the best place to check the temperature is at the top hose or radiator header tank.


I agree with that.

Also, non pressurised systems rely entirely on thermo syphon and likely will have a taller radiator probably with a Boyce or Calormeter mounted on the top.

Once pressurised systems could be thermostatically controlled, manufacturers became so confident that they often did away with the water temperature gauge.
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alanb



Joined: 10 Sep 2012
Posts: 508
Location: Berkshire.

PostPosted: Tue Aug 11, 2020 4:44 pm    Post subject: Reply with quote

My Morris 8 is thermo syphon and has a very tall radiator compared to a modern pressurised one, on the cars Iíve had with a temp gauge Normal has been around 80c
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Rollmop



Joined: 23 Dec 2016
Posts: 14
Location: Market Drayton, Shropshire

PostPosted: Fri Aug 14, 2020 10:37 am    Post subject: Reply with quote

The Mayflower is a bit of an oddball regarding the cooling water, yes it has a water pump so it is not thermosyphon but it does not have a pressurised radiator and has a free to atmosphere overflow. Regarding the thermostat, I managed to pick up an NOS early Landrover thermostat which has the bypass cover, I will however try the clamp on the bypass hose.
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alastairq



Joined: 14 Oct 2016
Posts: 1462
Location: East Yorkshire

PostPosted: Fri Aug 14, 2020 10:53 am    Post subject: Reply with quote

Quote:
but it does not have a pressurised radiator and has a free to atmosphere overflow


What kind of filler cap does it have?
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Fiat 126 BIS
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lowdrag



Joined: 10 Apr 2009
Posts: 1413
Location: Le Mans

PostPosted: Fri Aug 14, 2020 11:33 am    Post subject: Reply with quote

My ears pricked up when I saw wax stats mentioned. I had a few for the Jaguar but they are all gone now and the new stats fail closed as opposed to open, which worries me a bit. So, are wax stats still available? The Jaguar ones are found in Zephyrs and many cars so not make or model specific.
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Keith D



Joined: 16 Oct 2008
Posts: 1009
Location: Upper Swan, Western Australia

PostPosted: Fri Aug 14, 2020 12:31 pm    Post subject: Reply with quote

Rollmop,

Many cars of the same vintage as your Mayflower had exactly the same arrangement. All the Austin range had water pumps, thermostats with un-pressurised cooling systems.

Keith
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Penman



Joined: 23 Nov 2007
Posts: 4294
Location: Lancashire

PostPosted: Fri Aug 14, 2020 1:53 pm    Post subject: Reply with quote

Hi
With a vent to air system like that a bottle at the bottom of the vent tube can capture the "lost" coolant and it might even suck it back into the rad when the engine cools down if the vent tube reaches the bottom of the bottle.
Even if it doesn't suck it back at least you have saved that coolant to put back in the rad and reduce the need to keep topping up with fresh coolant.
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