Panel voltage stabiliser?

Technical MGB discussion
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Charles Farran
Posts: 210
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Panel voltage stabiliser?

Post by Charles Farran » Fri Apr 05, 2019 4:40 pm

Dave,

If i understand you, you said the tank cap held good pressure overnight. Once the coolant has gone cold, i think you should just be able to turn the cap against the spring & rubber grip. Isn't the coolant (when the engine is/has been running) supposed to to be able to syphon back from the tank in to the block? If you have a dodgy cap this may affect this; might this be the cause of your small coolant leak which you might not spot when driving etc. (I may have a total misunderstanding of how the cooling system works, but i thought it worth mentioning as we are all here to learn from others aren't we)?
I am also aware from the BBS forum that there are plenty of miss-fitting caps around due to poor manufacturing / divergence in dimensions of the cap spring length , circumference of rubber washer at base of spring which do not fit the neck of the expansion tank very well.

Cheers,
Charles
1980 Roadster

Dave Wheatley
Posts: 122
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Panel voltage stabiliser?

Post by Dave Wheatley » Fri Apr 05, 2019 6:55 pm

Charles you wicked man. Finding me more problems to solve!! When you think about it you are correct - the pressure should push the coolant back from whence it came when it cools. My pressure cap is 15lb - not sure if this is correct.

So, any more thoughts on this?

Charles Farran wrote:
> Dave,
>
> If i understand you, you said the tank cap held good pressure overnight.
> Once the coolant has gone cold, i think you should just be able to turn the
> cap against the spring & rubber grip. Isn't the coolant (when the
> engine is/has been running) supposed to to be able to syphon back from the
> tank in to the block? If you have a dodgy cap this may affect this; might
> this be the cause of your small coolant leak which you might not spot when
> driving etc. (I may have a total misunderstanding of how the cooling system
> works, but i thought it worth mentioning as we are all here to learn from
> others aren't we)?
> I am also aware from the BBS forum that there are plenty of miss-fitting
> caps around due to poor manufacturing / divergence in dimensions of the cap
> spring length , circumference of rubber washer at base of spring which do
> not fit the neck of the expansion tank very well.
>
> Cheers,
> Charles
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

User avatar
Charles Farran
Posts: 210
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Panel voltage stabiliser?

Post by Charles Farran » Fri Apr 05, 2019 8:18 pm

Hi Dave,
The stated pressure on your cap is correct at 15lb . Whether it is fuctioning correctly at that pressure is another matter!
Cheers, Charles
1980 Roadster

Vic Butler
Posts: 514
Joined: Wed Dec 21, 2016 6:07 pm
Forename: Vic
Surname: Butler
Location: North West Hampshire

Re: Panel voltage stabiliser?

Post by Vic Butler » Fri Apr 05, 2019 9:06 pm

Charles, I agree with you about the poor quality of some of the radiator caps around.
Dave, many years ago some time last century shortly after I bought my B, I replaced the plastic plug in the thermostat housing with a brass one. I don't know if they are still available though.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine

User avatar
Charles Farran
Posts: 210
Joined: Fri Oct 31, 2014 11:08 am
Forename: Charles
Surname: Farran
Location: Warwickshire

Re: Panel voltage stabiliser?

Post by Charles Farran » Fri Apr 05, 2019 11:39 pm

The brass ones are & sold ( i think by Moss,MGOC & DAavid Manners) as an alternative to the plastic plug which very easily gets butched on removal. The brass one is used with a cork gasket as opposed to a rubber o ring type seal . I bought & changed mine last year and it has been leak proof with no tell tail drips over the thermostat housing. I always carry a spare cork gasket in the boot never mind a plastic plug & rubber seal in the boot as tiny & weightless.
Cheers, Charles
1980 Roadster

Dave Wheatley
Posts: 122
Joined: Fri Sep 28, 2018 4:55 pm
Forename: Dave
Surname: Wheatley
Location: SW Scotland

Re: Panel voltage stabiliser?

Post by Dave Wheatley » Sat Apr 06, 2019 8:32 am

Vic Butler wrote:
> Charles, I agree with you about the poor quality of some of the radiator
> caps around.
> Dave, many years ago some time last century shortly after I bought my B, I
> replaced the plastic plug in the thermostat housing with a brass one. I
> don't know if they are still available though.

Mine has a brass plug Vic and Charles.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

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