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MG MGB Technical - water loss mgb

I am loosing water but cannot see any obvious leak. Car does not overheat. Any thoughts?
George
G Burrow

Are you trying to keep it too full? You don't mention what year car so this may or may not apply, but radiators on cars without expansion tanks cannot be kept completely full. If you fill it all the way up when cold, it will burp out some water when it heats up. When it cools back down, there will be +/- 1" headspace in the radiator tank. As long as there are no leaks, it will keep that same headspace indefinitely. This is completely normal and is no cause for concern. If you add water, it will burp out the excess and continue to "seek its own level."

Does this help?

Cheers!
Rob Edwards

Rob thank you.

It is a 71 without expanision tank. I will watch if it stabilises or continues to drop.

My other car is a midget with expansion tank so not yet used to the ways of the B.

george
G Burrow

All true. Also, an ancient radiator cap may have lost some of its "spring", influencing the boiling point and the release of pressure too early.

I found an overflow tank at a junkyard to put on my 1970 roadster.

Peace of mind.



Dan Robinson

This is the overflow tank on the 70 roadster I care for. It is a wipes container, with the hose going through, and held by, the orifice where the wipes emerge. The cap comes off easily for inspection, and it is held in place by a tie wrap to the horn, and a tie wrap on the hose. I made a slight angle cut on the hose so as not to bottom flat on the bottom of the container.

As in Dan's roadster, a new cap helped a lot.

warmly,
dave


Dave Braun

George, Might pay you to check the water pump for any leakage. They sometimes leak when the engine is running at temperature with the coolant at pressure and can be a bit deceiving. If it is leaking you should find evidence at the outlet vent under the pump body with a dry finger test.
Roger

Pressurize the cooling system with a leak down tester with the system cold. If the pressure drops you have a leak somewhere. Small leaks can be hard to find as they may only leak under pressure and the heat of the engine boils it away so that you can't see it.
John H

What everyone has said is right on from my experience. The only thing I have to add is the impact of altitude. Here in Denver we use a cap with higher pressure to compensate for the lower boiling temp of water/liquids as coolant tends to overflow and reduce the coolant level. Mine is now 12 lbs and that seems to do it and I am not refilling coolant all the time. Doesn't really effect the cooling otherwise...doesn't make it better or worse. Seems like in Manitoba you are generally in the plains but that doesn't mean you are sea level. East of Denver in the plains is actually 500-1000 feet higher than the 5,280 feet in the city as we are in a creek bed....Cherry Creek where they found gold originally.
J.T. Bamford

I have a 1974 B. Adding an expansion tank was very easy to do. I took a quart plastic bottle drilled a hole in the cap and simply ran the overflow hose into it so it touches the bottom. a bit of closehanger wire attaches it to the left side horn. it has worked great for years. the radiator cap I believe is 7-8 lbs.
Bob Ekstrand

Head gasket?
don g

We had a similar problem ; the heater worked for the first 25 miles then nothing and we were always topping up the radiator. The problem was a hair line crack in the head found after haviong the head pressure tested. Solution - a new stage 2 head from Oselli - £500 plus freight.
bob Marshall

I had a similar problem as Bob... and it was the headgasket. simple job, you might get lucky.
don g

This thread was discussed between 07/07/2007 and 13/07/2007

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