I did a leak check and found a massive air leak behind the thermal wax deal. I'm talking about the thermal wax system on the throttle body that has the dreaded 90 deg. coolant hose attached to it. The engine is an 88 T2.

Now I look at the gasket and there appears to be a thin long cut-out causing this leak.

Here's a pic of the gasket.



Is that cut-out supposed to be there causing this leak--wtf? Why would the end of the shaft need to be vented?

Thanks in advance for your help.

Scott

 

NM, the o-ring sits on the other end... I'm cluless. Sorry.

 

Okay, I did a little thinking for you.

The turbo's have this little bleed in the gasket... I have no idea why.

HOWEVER... the N/A's do not have this little bleed in the gasket... so you could purchase an N/A thermowax gasket to replace it with.

BUT (there's always a but, isn't there) you would have to modify the N/A gasket slightly. The N/A thermowax does not actually pass coolant through the throttle body, so there is no need for the coolant feed hole through the gasket. So, for modification, you would need to drill the N/A gasket with the coolant feed hole. It wouldn't be very hard.

The N/A thermowax gasket is under $10 from the dealer, and is part number N326-13-W89
(turbo gasket would be N330-13-W89).

 

OH! Just had a thought...

Mazda was designing against failure modes... so see if this seems logical:
Let's say, under boost, pressure leaks past the secondary plate shaft. This would push against the thermowax assembly. Now, if the gasket decided to break anywhere, it would cause the air pressure to possibly A) feed into the cooling system, giving a next to impossible to find feed of pressure into the cooling system, causing air pockets and overheating or B) cause an external coolant leak. Both of these could potentially lead to a overheated, and thus, a blown motor.

So why not simply install a controlled leak? this leak would be so remotely tiny as air would have to leak through a 1mm x 1mm square and then around a tightly fitted shaft before entering and exiting the throttle body. Such a minute quantity surely could have no effect on driving...


That's about the only logic I can come up with. I would replace it with the N/A gasket if it makes you happy.

 

Thanks scathcart,

yea I was just thinking of making a new one and not cutting the vent into the gasket.

 

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