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Discussion Starter · #21 ·
Regardless, this thread is a prime example of the of the way most things unfold. There is some smoke out of the exhaust, must be a head gasket, tear it all apart. It's a good thing MR2 spyders and 2zzs are dirt cheap and easy to work on. If this was Porsche motor shoehorned above a subframe, I hope there would be a different approach.
I've gotten pretty fast dropping the engine. I've contemplated keeping a spare engine. Then it would just be an inconvenient weekend.
 

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Discussion Starter · #22 ·
If an aluminum cylinder head is severely overheated, part of the head can be annealed (softened) and this can hurt its ability to seal.

Dave
Noticed the engine got hot pulled off the interstate 2 miles later at the next exit. So hard to say?
 

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2 miles is an incredibly long time to drive on an overheated engine. Temps shoot up in seconds to minutes when the cooling system isn't functioning properly. 2 additional miles after already overheating sounds like you really did a number on it.
 

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Once you get to boiling, things happen fast. The coolant will blow out of the head, and then you get hot spots over the cylinders. Also, none of this will show on your gauge, because there is no longer coolant flowing past the sensor.
 

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IMHO the cluster water temp gauge is nothing more than a fancy red light warning, when the gauge needle raises above normal the temp is very hot (problem time). I have a after market gauge can indicate a temp rise of 5 degrees.
 

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Toyota seems to always put a deadband in the temp gauge that covers the normal operating range. I suppose that the idea is that the customer will not be alarmed by the normal fluctuations in temperature.
 

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Once you get to boiling, things happen fast. The coolant will blow out of the head, and then you get hot spots over the cylinders. Also, none of this will show on your gauge, because there is no longer coolant flowing past the sensor.
This is very true...if you miss the high temp needle at some point you may never see it in the red again until catastrophic engine failure. If there's ever any doubt put the heat on...if you have no heat, you have no engine cooling.

I use the dash gauge as a marker then use the PFC for an exact temp if needed. Even just above normal on the dash gauge is already an instant 10+ degree jump in coolant temp.
 
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