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Discussion Starter · #1 ·
Hello everybody

i recently bought 94' 827 coupe, and doing some maintenance work, like replacing fluids and some parts. But i'm confused about the cooling system.
I noticed a little port in the thermostat housing, just above the thermostat, so even if its closed , there should be some little flow through it. The thing is that thermostat's rubber seal covers that little passage completely up, so actually there is no flow, but maybe it should be?

This is the diagram, you can see that thermostat housing has a little port at the top:

The seal looks like its shaped correctly, in reality it blocks that port, at least in my case.

Now, my shiny new Thermostat installed, (without a seal) i added an arrow to point out this bypas port:


and the thermostat cover also is specially shaped to allow the extra flow:



I already replaced all cooling fluid and thermostat. Actually i'm planning to replace that thermostat once again because it came without a seal, so i used a silicone instead, to much silicone, that i blocked that bypass port.

the question is:
What is the purpose of this extra bypass port?
I will be installing a new thermostat with a rubber seal, so should i cut a hole in this seal , to make sure not to block that bypass port above the thermostat? is it that important?

thank you for your input.
 

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Discussion Starter · #2 ·
I got it resolved. This bypass port i was confused about is not for extra fluid flow. this is just a little opening for a little hole which is in the thermostat.

I got a new thermostat, HKT brand (Japanese), and it already includes the seal.

It looks exactly the same like my old thermostat, i guess the stock one.
the seal is specially shaped , so it doesn't cover that little hole at the top of the thermostat.

the seal wraps around thermostat's edges:


this is that little tiny hole i was talking about (on the top), this to balance the pressure between both sides


the seal has two rubber pins help to hold it in place. Actually the thermostat's piston is not in the center, it is a little bit lower , and it must be this way, so when its open, the piston should block the bypass port inside the housing. (that little hole inside).


Thermostat fitted to the cover:


Thermostat installed in it's housing:
 
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