[Healeys] Coolant bypass port in the head - 6-cyl

[Mark Donaldson]

Jim,

 

I never experienced overheating in our 997 Austin-Cooper. The sleeve fits many Minis, so I am sure it will fit you’re ‘A’ series engine too.

 

The image below incorrectly says it fits a Hundred.  Clearly it does not.  But it DOES say it fits a Sprite.

 

Cheers

Mark

 



 

 

 

From: Jim Ryan <ryan at jimryan.com> 
Sent: Thursday, 31 March 2022 10:29 AM
To: Mark Donaldson <ardmorebusiness at xtra.co.nz>
Cc: Harold Manifold <manifold at telus.net>; Healey list <Healeys at autox.team.net>
Subject: Re: [Healeys] Coolant bypass port in the head - 6-cyl

 

I've been following this, and just wondered if any of this would apply to a bugeye with the stock 948 in it.

 

On Wed, Mar 30, 2022, 4:33 PM Mark Donaldson via Healeys <healeys at autox.team.net <mailto:healeys at autox.team.net> > wrote:

Gentlemen,

 

I had ongoing mild occasional overheating issues in my 3000 tri-carb for many years  . . .  until I fitted a blanking sleeve two years ago.

Problem instantly solved.  It’ll sometimes climb to 190 on a high-speed hill climb but, otherwise, rock steady where it should be.

 

The sleeve is a stock BMC part.  I got mine from a local Mini supply house here in NZ.  The part number is  11G 176.

Moss sells them: 434-135.     I know other suppliers do also.

 

I fit it with a wax stat, which sits neatly on top.

 

Mark

Ardmore

NZ



 

From: Alan Seigrist <healey.nut at gmail.com <mailto:healey.nut at gmail.com> > 
Sent: Wednesday, 30 March 2022 2:36 PM
To: Harold Manifold <manifold at telus.net <mailto:manifold at telus.net> >
Cc: Michael Salter <michaelsalter at gmail.com <mailto:michaelsalter at gmail.com> >; Healey list <Healeys at autox.team.net <mailto:Healeys at autox.team.net> >
Subject: Re: [Healeys] Coolant bypass port in the head - 6-cyl

 

Harold -

 

Thank you, now I understand how the whole thing is supposed to work.  The sleeve works to cut off the bypass so that hot water is not recycled into the system after it warms up.  FWIW, this only applies to the 6 cyl, the 4 cyl doesn't have any sort of bypass.

Yes, I think it would be great if you could share with us which thermostat to purchase and how to modify it.

Best,

Alan

 

On Wed, Mar 30, 2022 at 1:28 AM Harold Manifold via Healeys <healeys at autox.team.net <mailto:healeys at autox.team.net> > wrote:

The coolant bypass plays an important but problematic role in the Healey’s cooling system. When the thermostat is closed coolant returns to the water pump via the bypass. See the red circle on the attached picture. The bypass is important for three reasons: its allows the coolant in the block to continue to circulate and come to a uniform temperature before the thermostat opens, it prevents hot spots that could develop from stagnant coolant and it prevents the water pump from dead heading.

The problematic part is in the original design the bypass was closed by a sleeve on the bellows type thermostat when the thermostat opened. The original Bellows type thermostat used a volatile liquid and were not reliable and were not suitable for the 7 psi cooling system pressure. Wax type thermostats are much more reliable but they do not have a sleeve to close off the bypass. There may be some expensive wax type replicas of the original bellows type.

After looking at many options the best option for a reasonably priced wax type thermostat with a sleeve to close off the bay pass is the modified Land Rover Series ll thermostat. If anyone would like to know about modifying the Landver thermostat let me know. It can be easily done.

Harold

 

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