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MG Midget and Sprite Technical - Crossflow Radiator Overflow

Anyone have a crossflow radiator out of the car? If so can you look inside of the upper hose connection hole and see if the small overflow tube is visable. Mine came loose so I need to repair it with solder but I don't know if the small tube goes upward or downward inside of the radiator.
Jon Saylor

Pretty sure it just goes straight in. The inside end is going to be submerged and under pressure anyway so it wouldn't make any difference. Other end goes to the expansion tank, so strictly speaking it isn't an overflow. The overflow is the outlet, under pressure, from the expansion tank to free air.
Guy W

The spare that I have in the garage goes upwards.

Dave O'Neill2

That's what I was looking for.
Thank you very much Dave!
Jon Saylor

Thanks to your photo I put it back in the way your photo shows but I wonder why it has to go in the upwards position. As Guy points out, it's submerged and under pressure anyway so it shouldn't matter.
Any thoughts?
Jon Saylor

It looks to be about the same level as the base of the filler plug.

If it was lower, when filling the radiator the coolant would flow out into the expansion tank, if the cap was not on.

Foolproof, I guess!
Dave O'Neill2

If I fill my system with the expansion tank cap off, it does just that, it won't fill to the top and runs straight through to the expansion tank.

The reason I was confident in saying that the pipe just goes straight in is because that is what it does on my rad. And at the time of asking I couldn't think of any explanation why it needed to be more complex. But my rad has been recored, which may explain why it differs from Dave's.

Another reason for it bending upwards that I can think of is that although the rad. should be full (of coolant) there will certainly be occasions when there is air in the system. And one would want the air to be dispelled first as the coolant heats and expands. By having the end of the pipe bent upwards it will automatically dispel any air that does separate out from the water first. Quite a neat solution!
Guy W

Guy,

<<By having the end of the pipe bent upwards it will automatically dispel any air that does separate out from the water first. Quite a neat solution!>>

Not necessarily the case as the water enters the radiator at that point while the engine is running so it'll be constantly in the water stream. I had a slightly weeping head gasket some years back and that resulted in the system being pressurised and pushing the coolant out of the system as a result. I moved the expansion pick-up to the downstream side below the filler and that just vented the gas and expanded water as necessary as air collects at the top of that tank. Ultimately the cause of the leak was tracked to a small rust damaged area on the top surface of the block which I welded in situ and dressed back to solve the problem, this was a 1098 with a 1275 head so the big bore gasket was used with the slightly larger fire ring which sat just on the edge of the damaged area.
David Billington

Ohh! Another of my theories goes down in flames with a direct hit! Bleeding air out of the highest point in the system would have been such a good idea too!
Guy W

David

I had the exact same problem when running a 1275 head on my A35 (948).

Curiously, there is a coolant hole in the small-bore head and a corresponding hole in the small-bore gasket, but no hole in the block. That results in a circle of corrosion, which is in just the wrong place for the big-bore gasket.

Mine blew while on the rolling road, with a flame shooting out of the front of the engine. I wasn't there at the time, but it was quite spectacular, by all accounts.
Dave O'Neill2

Dave,

That sounds the same, at the back of the block IIRC. How did you fix yours? I had some cast iron (high nickel) welding rod and ran a small bead and dressed it back flush to sort the problem in situ.
David Billington

This thread was discussed between 13/07/2013 and 14/07/2013

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