Morris Minor Owners Club

I had fitted a lower 74degree thermostat as advised due to the hot weather here.

Drove it for 2weeks with no issue. But a week back, after city driving for 15-20mins i heard some spooling metal sound and engine sound weird so i stopped.

After letting it cool down i checked and i found out that the radiator tank emptied out. Needs around 4.5liters of water to fill to brim.

After checking, it seems that when the thermostat is activated, pressure builds up and all water escapes through the rad overflow pipe.


Now i have removed the thermostat and drove it for 30mins for the past 3 days and have no problems.

Any idea what cooking?

It is a recon rad, using a 4psi rad cap.

Is th cap correct one - long enough to seal on the lower internal rim ? Some are too short - fit on just fine - but do absolutely nothing!

i have measured, the cap has a length of 26mm and the rad top rim to the bottom rim is 25mm. Therefore there is 1mm extra. is that enough?

Yes!

One thing to note is that there is no point in filling the rad to the brim (unless someone has fitted a separate header tank).
Water expands when it gets hot so some will always be pushed out of the system if there is too much.
Before you topped it up were the tops of the tubes visible?
If they aren't covered then there definately wasn't enough water.
4.5 litres is a gallon which is a lot but I recall your header tank was quite large to start with then had been 'ballooned' which made it larger.

The 'spooling metal sound' sounds nasty and needs investigating but I can't think how being low on water would cause it.
But then I can't really envisage a 'spooling metal sound' but I assume metal will be involved somewhere.

yup i understand that some water will be pushed out when expand.

currently tops of the tubes are covered so no problems now.
my header tank has been repaired and it is not balloon anymore.

the thing is i find it odd that when the 74deg thermostat is fitted, i have those problems like rad needs a gallon of water which is crazy..


Problems is now solved after removing the thermostat :?
Not sure if its due to the hot weather in Singapore?

You really should not run without stat - I sent you the link to the competition sleeve that should be fitted. But -if it's working for you - I suppose no great harm !

its not really a good idea not running a stat. news i've heard from old timers that minors exported to Singapore all came without a stat. not too sure about that fact.

bmc-i understand how not having a stat will affect the cooling of 3 and 4 cylinder due to water short circuiting in the front. I was thinking of getting one sleeve but i do not see how this blanking sleeve works. could you enlighten me?

It just acts like a 'stuck-open' thermostat (but with rather less restriction to flow) - and ensures the water circulates correctly. But since yours is hardly a 'competition' engine, and you presumably don't need the heater(!) - no great harm if you just continue as you are doing. I seriously doubt engines were ever sent out by BMC without stats!

rite i doubt so too but cant really say if its true also.

no worries. appreciate your help Thanks