Coolant temperature

[Charles Farran]

Dave,
Here is a photo of my hose from the top of the radiator to the expansion tank . I routed the hose as i believe it was done as it came out of the factory & haven't had any issues, other than using a small fuel line hose clip,rather than the "one use" fold over clip used originally (It was similar to the opening tabs of tins of spam)!
Cheers.Charles

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[Dave Wheatley]

Thanks Charles.

It looks as though the pipe does go over in an arc, and assuming that the highest point of the arc is above or level with the top of the thermostat housing filler, it would then be possible to fill to the 'official' level.

I wish my under bonnet was as clean as that!

[Charles Farran]

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Dave,
Here is a better angled photo of the expansion tank hose.
Cheers, Charles

[Vic Butler]

I've just checked the expansion tank pipe on my 77 BGT and it's the same as Charles'. It's the natural run of the pipe.

[Dave Wheatley]

Charles and Vic.

Can you confirm or not that the highest point on the expansion pipe is higher or as high as the top of the threads on the thermostat housing?

[Vic Butler]

I've just checked mine with a straight edge and as near as makes no difference I reckon the highest point of the expansion pipe is level with the top of the brass plug on the thermostat housing.
I replaced all the cooling hoses a little while ago and the expansion pipe was in the kit so it's the correct length.

[Dave Wheatley]

Thanks Vic.

The high point of the pipe on my car is about 3/4" below that. It's been like that as long as I've had the car and hasn't caused a problem.

However my next job will be to replace the pipe with a longer piece so that I can lift it that extra 3/4"!

[Charles Farran]

Dave,
I reckon mine is similar to yours rather than Vic's.
When i replaced all my hoses i checked that the length of the expansion tank hose was the same length as the original.
As i said in an earlier message i think because of the pressurisation when warm you should,provided there are no leaks, always have the correct amount of coolant in the block. If the expansion tank continues to be half full when cold then i think you have nothing to worry about.
Cheers, Charles

[Vic Butler]

I don't think the height of the pipe to the expansion tank is crucial. The system is pressurized to 15psi which is higher than normal for that era and the pressure alone will ensure the coolant flow will operate as it should. The expansion pipe on my MG just happened to fit in its position, I certainly didn't ensure it ended up that way.

[Dave Wheatley]

Vic and Charles.

I think that the height of the expansion pipe is fairly crucial.
If the high point on the pipe is lower than the radiator/thermostat housing, when topping up coolant at the thermostat housing, the level will only reach the correct level when the expansion tank is filled to the top (water flow = thermostat housing to radiator to expansion tank). If this isn't noticed (which it wouldn't if the expansion tank pressure lid was in place), the coolant will expand and escape through the overflow pipe from the expansion tank on the next trip.

Sorry if this is a bit convoluted - a diagram would be easier but I don't know how to do that on here.

If the expansion pipe high point is higher than the thermostat housing/radiator, the coolant can't escape to the expansion tank when topping up. This does not affect the normal working of the expansion tank in normal running.

All a bit esoteric I know!