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Water expansion stuff


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Hi

 

 

The water in my 4A heats up, expands and overflows into the overflow bottle as you would expect.

When it cools down, the water gets sucked back up into the radiator. Excellent. The car does not overheat, and is steady at the mid-point on the dial.

 

BUTas it cools down it sucks up all it can until the water is level with the expansion pipe. I've put the water level back several times to an inch or so between the filler neck, but it still just fills right up again from the bottle after a run.

 

Any good theories as to why this is?

 

 

Dave

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It sounds like you have a net loss of coolant going on. Does your nylon pipe go to the bottom of the expansion bottle with a slash cut at the end?

 

Rereading your post I'm not clear about which water level you're describing. When you remove the rad cap it should be full right to the top and the expansion bottle should be half full.

Edited by peejay4A
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Hi Dave,

is the engine running hot. It should not dump fluid too often.

Radicle thinking !!! - One way to stop the rad sucking back too much is to have no water in the bottle to start with. and the tube sitting on the bottom of the bottle.

That way it will put in x amount and suck back x amount.

 

Roger

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Hi Pete.

The tube does indeed go to the bottom of the bottle, with a v-cut in it.. I always understood though, that you fill the rad to an inch or so below the filler neck, it expands and then finally refills to the same level you started with - i.e. an inch below the neck. I'm pretty sure RogerH has mentioned this before?

 

But my rad fills right up to the top as you say. With some water left in the bottle.

 

Roger, I don't believe the engine is running hot (well not according to the water temp gauge). Electric fan too. I cleaned it all out, and put all new hoses and rad in last year.

 

I'm not sure if anything is wrong, as it doesn't overheat, other than this thing about being an inch below the rad filler neck.

 

 

Dave

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Hi Dave,

I've had another thought.

If the rad was filled to the top, as it expands the excess will go into the bottle.

The rad, upon cooling, will suck back that fluid.

It will only ever be full. Not sure how the hydrodynamics works with combined temperature.

 

A modern rad with expansion tank does exactly this .

Roger

 

PS - I'm sure I did mention that the level should be about an 1" below the top. I'm sure that is right but your question is now making me doubt my sanity.

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Dave, mine is exactly the same as yours, I start with 20/30 mm in bottle and on a run it fills to about 3/4 full then when cool it's back to 20/30mm. Level in rad is flush with neck where cap seals. Only on long continental trips when air temp is 27-33 deg is there a small loss of coolant which I put down to evaporation. Usually about a cup full in 1000 miles. My rad had been re cored slightly thicker than standard and holds about a pint more.

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My radiator runs full to the brim and the level changes in the overflow bottle. This is perfectly normal. The partial vacuum in the radiator tanks will draw until it's at atmospheric and it doesn't know how to suck some coolant and then some air from the bottom of the bottle. Leave it as it is -- it's fine -- and monitor the level in the overflow bottle.

 

As long as it cycles between the same high and low, all of which are above the suction tube, then all's good. If it's disappearing from the botlle, then you have problems.

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Right then. I have now officially stopped worrying about it. Thanks for your advice everybody.

 

 

Now I have to find something else to worry about. Like why my ammeter always reads about +2. Even without the engine running. Or, why don't the seats sit on the runners, but rather just off near the transmission tunnel, and wear a hole in the carpet? I could go on.

 

Cheers everyone.

Dave

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Re the ammeter, get yourself a small magnet and stick it to the back of the metal instrument panel. Move it about to zero the needle. Job done.

 

As you've realised, your cooling system is behaving correctly.

Edited by peejay4A
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Magnet thing works, but I can't get my hand behind the dash. (its temporarily on the front of the dash).

 

Seats - I have rubber things on the bottom of the seat, but the actual sides of the frame sit lower than the rubber bit - thus they are on the carpet, Need to make the rubber sit lower then. Although I must say the seats are comfy as they are, even over long distances.

 

 

Thanks

Dave

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I've changed my new radiator's cap to a TR6 item with a much stronger Spring. My header tank was spewing coolant at higher revs as the water pump displaces more at speed. The higher pressure retention increases the collant's boiling point too. Engine always kept a good temperature despite being stuck in traffic at >30 degrees on several occasions.

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You would if you kept losing your header tank over your engine bay!!

 

Allowing the engine to run hotter doesn't really seem to be a solution to an overheating problem.

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I've an efficient water pump, nothing is over heating nor problematic now the pressure is being retained with a stronger rad' cap.

 

So the top tank of your radiator is overflowing because the suction side of the pump is too strong? I'm having a tough time visualizing this.

 

It sounds like there's a restriction in the system someplace, given that you're reporting no overheating. But I'll admit I don't get this.

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Mark, My rebuilt slightly modified engine filled the bottle up and overflowed every time I drove over 75 for very long. I had flushed the rad but have never found this helps much so had it rebuilt with a thicker core and slightly larger capacity. Problem cured, 75 all day long if req and electric fan only cutting in when slowing right down . Standard rad cap.

How olds your rad?

Edited by potts4a
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