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Rebuild 12a questions: Crud in coolent passages and heat marks on crank

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Old Apr 2, 2016 | 08:41 PM
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From: McPherson Ks
Rebuild 12a questions: Crud in coolent passages and heat marks on crank

Hello,
So I have a 79 rx7 that I pulled the motor and trans to put into a 72 Mgb GT and I just pulled apart the engine because it was locked up. I found all the coolent passages were plugged with this yellow/orange mucus. Also the crank has heat marks on the side of the lobes. My questions are: what could have caused all the yellow/orange crud? Is heat marks on the crank, is that normal or do I need a new one? Finally what's a good source for a rebuild kit? What's a good source for a carb rebuild kit?

(using the original Nikki carb) Thank you

Gross crud in the coolant passages





Heat marks





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Old Apr 3, 2016 | 10:12 AM
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From: https://www2.mazda.com/en/100th/
the E shaft is normal, they all have those marks from new.

the crud comes from having iron and aluminum in water for a long time, ie rust. looks like the coolant seals failed too.
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Old Apr 3, 2016 | 10:38 AM
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From: bristol,pa
I agree with j9 ,the entire shafts looks normal, and the housing looks like it had a bad coolant seal. You can clean it out with it pick, brushes , brakleen, and degreaser to see how bad the damage is
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Old Apr 3, 2016 | 12:28 PM
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From: McPherson Ks
good to hear

Originally Posted by j9fd3s
the E shaft is normal, they all have those marks from new.

the crud comes from having iron and aluminum in water for a long time, ie rust. looks like the coolant seals failed too.
Thats good to hear! And yea I have cleaned out everything and it seems to be in good condition, now I just need a rebuilt kit, do you have any suggestions on where to find a good reliable one?
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Old Apr 3, 2016 | 12:31 PM
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From: bristol,pa
It all depends on what you need,it used Atkins rotary and had no problems, it all depends on what seals you want to use or need
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Old May 2, 2016 | 11:57 AM
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yea the e shaft is good, if anything its getting stronger from the heat releasing carbon. which is good. if you haven't put it back together yet i would try to clean the housing as clean as possible.
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Old Jul 1, 2016 | 12:44 AM
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From: CA
Interesting info

Last edited by kkev.7788; Jul 1, 2016 at 12:48 AM.
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