knowledge thread: final resolution of thermostats conundrum for stock M30B30 engine, testimony with pictures

deQuincey

deQuincey

Quousque tandem...?
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It is well known the feeling of anguish caused by hidden things whose pernicious effects bring us closer to anxiety, despair, and finally melancholy.

The case of the engine cooling system is not immune to these feelings; the closed thermostat box sometimes hides a puzzle whose resolution requires wading through smelly coolant, possibly getting hurt, and finally facing a pile of parts whose unknown nature threatens our happiness.

Sometimes, as children, we were told to distrust our certainties, those built by conventions, the flow of habits, and the ignorance of science. In the case at hand, it is better to muster courage and investigate the situation.

It is essential to know that there are two thermostat boxes, that these boxes must mount different thermostats, and that for some dark reason, Hans decided to forget about 'poka-yoke' and made this matrix of four elements combinable and mountable despite its functionality being called into question. The images will comfort the 'connoisseurs'; only they will understand the essence. For the rest, it is enough to know that 'news' should not be mixed with 'olds'; just as we do not pour new wine into old wineskins, as the Old Testament says, we must not fall into this error.


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we will start with the OLD

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the thermostat is able to displace the back plate 6/7 mm so it can close the back hole properly




and now the NEW

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again also in this case the 26+7= 33mm so the hole will be covered

as a proof of this capacity the following pic shows displacement of new thsat when hot

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I know that you are not seeing 33mm in the picture, this is because when out of the boiling pan the plate returns to its position very quickly




i hope this solves your doubts by means of a collection of pics easy to understand and identify

you can give a like if you like it, or stay silent if disturbed by the view of naked parts
 
Thanks @deQuincey for posting this small chapter on the intricacies into E9's.
And to @sfdon for providing a summary of the effect when new and old are combined. I didn't quite get it at first when reading Deq's poetry...

Would you know what the benefit would be to use the new style housing? I still have the old housing, and as long as my Thermostats fits and works (which i can now check), what reason could there be to change to the newer style?
 
eriknetherlands said:
Thanks @deQuincey for posting this small chapter on the intricacies into E9's.
And to @sfdon for providing a summary of the effect when new and old are combined. I didn't quite get it at first when reading Deq's poetry...

Would you know what the benefit would be to use the new style housing? I still have the old housing, and as long as my Thermostats fits and works (which i can now check), what reason could there be to change to the newer style?
Click to expand...

IMHO the benefit of the old version is only aesthetic

me thinks once in function and properly fitted both will work exactly well,

some consideration on dimensions: the opening at the back is the same 5mm, but some consideration could be made for a different diameter between the old and the new
 
So many differences…
count the sensor holes. 1 hole becomes 5.
No paper gasket needed on late housing.
Better internal water flow.
Better thermostat design.
From memory- there were 8-9 functional differences in the later housing and thermostat.
 
sfdon said:
So many differences…
count the sensor holes. 1 hole becomes 5.
No paper gasket needed on late housing.
Better internal water flow.
Better thermostat design.
From memory- there were 8-9 functional differences in the later housing and thermostat.
Click to expand...

so really better flow ? i have not checked in detail and i wonder if i can tell from a visual inspection, but i appreciate your knowledge in great extent
 
1744657978877.png


This is the general layout of the cooling system.

The thermostat is dual-action, which means it operates at both points 1 and 2.

When the engine is cold, point 1 is closed, and point 2 is open.

With point 1 closed, it prevents flow from the radiator, so all the flow moved by the pump passes from the cylinder head through point 2, enters the pump, and it introduces it into the block. This causes the engine to reach temperature quickly.

This temperature produces two effects: on one hand, point 1 starts to open and point 2 closes. This way, the return flow from the lower part of the radiator allows the flow coming from the cylinder head to enter the upper part of the radiator, which causes the entire flow to be regulated.

now think what will happen if you use a different tstat, i.e. one that permanently block point 2, or one that permanently leaves point2 open
 
It would be great to instrument the thermostat to see if it is constantly opening and closing as a way of doing this negative feedback control loop or it operates around a stable equilibrium where both point 1 and 2 are partially open.
Also how does one know that 1 and 2 operate exactly at the same displacement point?
 
Thank you all for the very informative and well-documented write-up.
In my research the part number for the "new" housing is 11531710959.
The corresponding and fitting thermostat is 11531713040.

Both are available new at this time.
 
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