These bubbles normal?

[lotusflasherman]

The cavity is NEVER full. The engine has larger flow areas and a thermostat will not work if it not completely immersed.

A "normal" thermostat would be around 30% out of the flow once the thermostat opened and allowed the coolant to circulate.

There is a lot more science to the cooling system beside running coolant through the engine. It has to flow at a rate where it will "pick up" the heat and carry it to the radiator to exchange it. That is why race engines never run without a thermostat or a blanking sleeve. The coolant never collects the heat and the engine will overheat but the sensor for the gauge won't know it because the coolant never got to do it's job.

Put it together however you want. You could try reading the service manual. Lotus (and Isuzu) apparently wasted the extra sentence to clarify the position and direction of the thermostat fitment.

Totally !

[steve matthews]

You will need your entire cooling system working (properly) this summer in Houston. I suggest
following the prescribed path.

Steve

[Simon_P]

The jiggle pin or notch on a thermostat is primarily to allow coolant to circulate past the bulb, allowing it to work properly and reduce hysteresis. Sure it will bleed some air when the system is filled but mostly that is sorted out when the thermostat opens for the first time and it goes glug glug!

Totally !

? Please point me in the direction of the science.
While extreme flow rate may cause some other phenomenon that reduces heat transfer eg cavitation or a pressure drop. Normally the only time that a road car will over heat is due to to little flow, removing the thermostat creates to much flow and it will run cold.

It has to flow at a rate where it will "pick up" the heat and carry it to the radiator to exchange it.

if the coolant is going round twice as fast it will receive half as much heat from the engine and give up half as much in the radiator, but it is going round twice as fast so it does it twice as often net result 0

A thermostat is simply a valve that varies the flow to maintain a (near) constant temperature. Independently of engine speed and hence pump flow.

[ElanBRG]

From reading the replies, clearly some of you aren't reading mine carefully!

I put the thermostat in with the jiggle pin at the top. I don't have any problem with that. Everyone got that? Good.

My cooling system is working great. Ok?

You won't get me to believe that there should be air in the thermostat housing if everything is working right with the engine and cooling system. Air in the engine block is a very bad thing. If you like to have air in your engine block, that's ok with me as long as you don't try to sell me your car after the engine craters.

So my point is that whether the thermostat is centered or off center is not so the thermostat can stay in the coolant, because it's always in the coolant. That's all, so calm down folks and go back to enjoying convertible driving if you are in warm climates like me, or enjoy freezing you butt off if you're up north.

[lotusflasherman]

The jiggle pin or notch on a thermostat is primarily to allow coolant to circulate past the bulb, allowing it to work properly and reduce hysteresis. Sure it will bleed some air when the system is filled but mostly that is sorted out when the thermostat opens for the first time and it goes glug glug! Please point me in the direction of the science.

Jiggle Valve:
Well, correct term is 'jiggle valve'. Seen it in Lotus M100 documentation somewhere, and theory is the 'pin' hangs down in air but is pushed closed when water tries to flow through it - here's an independent view on the science ...www.motoradusa.com/techtip-purpose-of-a-jiggle-valve-on-a-thermostat

John (BCN) is spot on with "That is why race engines never run without a thermostat or a blanking sleeve. The coolant never collects the heat and the engine will overheat but the sensor for the gauge won't know it because the coolant never got to do it's job."
Mini has a thermostat that drops into the top of the head casting over the water pump and water flows sedately through the head for standard power output. For 998cc that was 38bhp but prepare a race engine giving around 100bhp and there's a lot more heat to get rid of so it was usual to remove the thermostat so flow isn't restricted BUT unrestricted water flowing up through the block and through the holes in the head gasket has a tendency to take an easy bend and flow along the top of the head waterway, so below the rockers, rather than the bottom, where it will remove combustion chamber heat. BL Special Tuning sold blanking sleeve C-AJJ4012 (for 50 pence in the 70's) that forced water to flow across the combustion chamber surface.

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Racers who overlooked spending 50p often had overheating problems and holed pistons that cost an awful lot more.

[CalElan]

Built a race engine for my mini.. had terrible overheating issues until some wise guy asked me if I had a blanking sleeve in..
Live and learn (sometimes).

[Simon_P]

Phil, that's a cheeky edit of my request for the science - I meant the science behind the cooling phenomenon that says increased flow reduces cooling, cos I can't find a word written about it in any text on heat transfer or thermodynamics.

I see that the Mini thermostat blanking sleeve has a big hole in the middle, far bigger than the one in the thermostat, and I read from one of the companies that make them that it is for blanking the bypass - makes sense to put coolant through the radiator.

Some old thermostats used to have the blanking sleeve as part of the thermostat, as it opened the sleeve moves to cover the bypass. The newer wax stat equivalents do away with the sleeve and can cause overheating (eg in Jags) so the correct stats sell for about forty quid.

I stand corrected on the jiggle pin, of course if you have a bypass there is plenty of flow around the thermostat. Looking at patents for jiggle pins - nice simple design that uses small mass and large surface area, the mass is sufficient to let the "valve" fall open in air, but in more viscous coolant the surface area of the pin causes it to close. In the patents the term used is jiggle pin. "so called 'jiggle pin' type check valves"