[Healeys] Radiator cap with expansion tank.

[JSARCH]

All you really need to do is to not top off the radiator coolant. Keep the coolant level 1” to 1-1/2” or possible a little more below the point where the radiator cap seals the top of the radiator chamber will allow enough space for the coolant to expand and contract without sending coolant through the overflow tube.

 

Best - John 

 

From: Healeys <healeys-bounces at autox.team.net> On Behalf Of Michael Oritt via Healeys
Sent: Saturday, October 11, 2025 4:02 PM
To: sbyers at ec.rr.com
Cc: Healeys <healeys at autox.team.net>
Subject: Re: [Healeys] Radiator cap with expansion tank.

 

By running the hose from the radiator neck to the bottom of the "expansion" tank you will have created a coolant recovery system--the slight vacuum created in the radiator by the engine's cooling down pulls open and unseals the pressure plate on the radiator cap, thus "recovering" the overflow back into the radiator.  Probable result:  no more coolant on the garage floor and no need to top things off. 

 

Best--Michael Oritt

 

On Sat, Oct 11, 2025 at 2:24 PM sbyers--- via Healeys <healeys at autox.team.net <mailto:healeys at autox.team.net> > wrote:

Simon, I have an expansion tank in my BJ8 using the original metal tank from an MG Midget.  I also have the stock 7 psi cap on both the radiator and the overflow tank and a clear “overflow” hose on the radiator neck to the tank.  The tank captures any overflow from the radiator and I can see the system operate with the clear tubing.  When hot, the flow is out to the tank and back into the radiator as it cools.  Excess coolant in the overflow tank can flow out to the ground through the tank overflow connection.

 

Steve Byers

BJ8 Registry

AHCA Delegate at Large

 

From: Healeys <healeys-bounces at autox.team.net <mailto:healeys-bounces at autox.team.net> > On Behalf Of Simon Lachlan via Healeys
Sent: Saturday, October 11, 2025 11:32 AM
To: 'Healeys' <healeys at autox.team.net <mailto:healeys at autox.team.net> >
Subject: [Healeys] Radiator cap with expansion tank.

 

Forgive another stupid question but it’s sensible to be sure……….

Am I right in assuming(!) that, if one fits an expansion tank, the standard cap is moved from the radiator to the expansion tank and is replaced by a blanking(?) cap ie one which has no spring, no means of relief etcetc? Seem logical to me but logic has let me down before.

Simon

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