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MG MGB Technical - Mk1 coolant loss

Just read the archives.

I noticed a bit of fluid loss following a drive. Drained the radiator (in case any gunk from the block had got into the fluid) and refilled when cold. Apart from overflow as it warmed up , seemed fine.
Just checked level after a couple of weeks in the garage - needed over a litre to fill it up. No hose or pipe leaks

Two questions -
Seems like I might have a radiator neck~radiator cap mismatch as it is a very early Mk1 and a brand new cap. So I should add an extra seal to ensure it is sealing properly?
The engine in my car was overhauled prior to my purchasing it and I don't know if the cylinder head was retorqued after XX miles as required. Is there any problem about doing the retorgue now, as long as I follow the correct procedure?

John
John Minchin

John,
get the correct (7lb) cap, of the correct type, design and length - GRC102

as long as you follow the correct procedure you could retorque the head, have look for a John Twist video on this as you'll need to put the bolts back one turn to retorque

(sorry I don't know if you need antifreeze over there) over here the antifreeze/coolant we use also has corrosion inhibitors for the parts that er, corrode, plus of course the antifreeze part for the odd cool days we get so if coolant is lost and just topped up with water then the coolant mixture is further diluted below correct strength

you're probably going to need to top up your system as a matter of use but don't overfill it, this from Paul Hunt’s excellent - http://www.mgb-stuff.org.uk/hometext.htm
‘The Mk1 radiator with the right-angle filler is the most awkward as you cannot see the tops of the tubes. You must keep coolant just visible from the filler neck or it could have dropped way down, but if you keep it too high in the filler neck it will keep expelling the excess. Probably best to check this when still warm (but not hot!) and if you can see coolant it should be fine, even if it drops out of sight when fully cold.’

I’m a big fan of thorough coolant system cleaning then flush, back and flush again individually on the heater matrix, engine block and radiator individually
Nigel Atkins

John - See the article, Expansion Tanks, Coolant Recovery Systems and How the Cooling System Works in the Other Tech Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/ It sounds like you cooling system is burping out the excess coolant. This will continue until the level reaches the point where the expanding coolant is not high enough to push any more out - the equilibrium point for the system. The problem as Nigel pointed out is that the coolant level at the equilibrium point is difficult to see in the filler of the MKI radiator. I solved the problem by installing a coolant recovery system as described in the above article. Cheers - Dave
David DuBois

just remember you said you had a very early car so more info -

7lb with 1" reach - Unipart GRC102

7lb with 3/4" reach - Unipart GRC112

I hope it's correct, now Q&H have gone down over here its even more difficult to cross reference information
Nigel Atkins

having the wrong cap wont help so check that first as checking costs nothing and replacing the cap if required is very in expensive

the only other worry is if you've 'steam' out of your exhaust, misfires, engine runs hot but you've not mentioned those so ignore my gloom
Nigel Atkins

My water loss over a three plus year period turned out to be a very small and hard to spot leak from the water pump. The car was still drivable for 300 miles or more between water top ups.

When I opened the box I found that my Unipart spare was a pretty useless alloy bodied pump, I'm told that was what they were selling once and I obviously was unlucky when I planned ahead and got a spare in.

John.
1964 car, three bearing engine.
John Prewer

Thanks for that chaps - Well, I thought radiator caps were just radiator caps!

The one (Tridon brand) I have has no markings(part no, pressure) but is about 25mm "deep".

A little googling for local manufacturers catalogues recommendations for Mk1 MGB-
CPC brand - 506-07 is 7psi, long neck
Tridon - CN0430 is only 4psi and seems long (but they do have CN0750 which is 7psi and long (longer than the one I have)
Repco - RC61-07 which is 7psi and long (27mm)

So I will get a new 7psi "long neck" one and see if that solves the problem first

As there are no other worrying symptoms (steam from exhaust, hot engine, misfiring, water in oil, oil in water, etc ) I will leave head retorquing for the moment.

Cheers
John
John Minchin

"pretty useless alloy bodied pump"

I had to replace my pump and ended up with an alloy one, on which I had to modify the bolt holes to get it to fit even though the gasket was correct. After a short time that started to weep when warming up (so minimal coolant loss each time) so I bought another replacement, cast iron this time, ready to replace again when the leak got worse. That was 16 years and 35,000 miles ago and it's never got any worse.
Paul Hunt

Hi John,

I had the same coolant disappearing problem. I realised thatit wasn't an actual loss, but the system reaching it's equilibrium. I didn't like the idea of not being able to see the coolant in the radiator, so I added a recovery system.

See this article on how I did it.

http://www.mgb-stuff.org.uk/saga10.htm

If you're going to buy a new radiator cap you might as well go this route and get the recovery cap.

Herb
Herb Adler

over 3 years ago I fitted a new water pump and silicone hoses with rounded-edge clips on my midget because I was fitting an electric cooling fan (to replace the engine one, and without an override switch - same as modern cars have been for 30 years(?)) and wanted to fit and forget (for at least 10 years)

I checked that the water pumps were well made and reliable before I bought as they only cost 13.45 (inc. VAT) and of course when I took the existing one out it was fine and not old but why chance it at that price, its been fine (Sods Law itll leak tomorrow)

I use 4-LIFE coolant and have done for many years on quite a few classic and modern cars, one reason is that it's very good at showing where weeps and leaks originate and if when hold or cold when I had a 4-LIFE coolant leak on a converted BV8 it looked like the leak was coming from the back of the rad but I could tell CSI style it was from the water pump and not the rear of the rad because of the direction of the increasing size of the dried pink 4-LIFE sprayed droplets and I can tell if its a weep that continues after the coolant system has cooled because it sits as red liquid so easy to notice

your engine and whole coolant system does need to be in good condition to use 4-LIFE as it will find any possible leaks learnt that on the BBS Midget forum
Nigel Atkins

Paul,

My problem with my alloy pump is simply that looking at the impleller (which is plastic instead of metal) the blades that push the water round are triangular which means they will let the water past them very easily.

I'm not commenting on all alloy pumps but my Unipart one obviously won't push water round as well as a cast iron pump.

John.

John Prewer

This thread was discussed between 31/05/2013 and 01/06/2013

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