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The mkiv Supra Owners Club

Please help! Water leak from Thermostat


Iky
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Its strange ; I have nevercome across a leaky core plug over the years , but 2 months ago my lads Soarer was leaking water , and lo it was coming from a core plug (it had a tiny hole in the middle), fixed this and then the other side of the engine again core plug started leaking 2 days later !!

The car was parked up for 6 months prior to buying it and wondered if they had rusted due inactivity anyone else had the car parked up before the leak occured ?

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I had two fail on my old na in a 4 year period, the second time it failed I was shocked. My car used to sit around unused for weeks at a time when I work away, but rarely months. Strangest thing is, the second time it happened I popped a couple of other more accessable plugs out with concern that as those at the same age as the first then they too would be close to failing, but they looked like new. I have always been curious why this one fails.

 

Its strange ; I have nevercome across a leaky core plug over the years , but 2 months ago my lads Soarer was leaking water , and lo it was coming from a core plug (it had a tiny hole in the middle), fixed this and then the other side of the engine again core plug started leaking 2 days later !!

The car was parked up for 6 months prior to buying it and wondered if they had rusted due inactivity anyone else had the car parked up before the leak occured ?

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It had red coolant , couldn't tell what was used , it was just purchased cheap as an easy project, but the water was brown , and so system flushed and new pump fitted.

It was a hole in both rather than expansion damage , pinprick hole that released steam !!

About 4 weeks later .

Maybe it pays to turn the engine over regular if parking up

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It had red coolant , couldn't tell what was used , it was just purchased cheap as an easy project, but the water was brown , and so system flushed and new pump fitted.

It was a hole in both rather than expansion damage , pinprick hole that released steam !!

About 4 weeks later .

Maybe it pays to turn the engine over regular if parking up

 

So did it blow the core plug on a new pump?

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always use toyota red coolant mate

 

When it failed the first time on mine it was on 4 life, second time was on someone else's version, probably Comma red as my local factors tends to stock Comma products. Both times mine failed like Jagman's and corroded rather than blown. I see what you are saying re corrosive protection in the 4life maybe being better, but why only this small plug in the back of the stat housing and no others, they are after all made of the same stuff, and also if the other coolant is no good why do other cars that use it not suffer the same fate? I wonder if its because they are such a small plug and when formed in the press the metal in the middle of the disc as it is prior to being formed is stretched and stressed.

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If anyones interested i still have photos of my old plug. It was wierd and bumpy on the inner side. It looked nothing like rust but like its got some sort of grey stonechip on the back of it with a really tiny spot of rust where the pin hole was. (1.5mm)

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  • 6 months later...

Sorry to bump this old thread- but I believe the same has happened to my supra. The O rings on the bypass pipe went first and those were done at a meet by a couple of very helpful members on here (thanks again Craig and Gareth), and now there is a new leak is coming from a behind the stat, I will assume it is this core plug.

 

Is the core plug in the waterpump body or the thermostat cover?

 

Main reason I ask is my car is currently stored away from home so I could do with tooling up and gathering parts before I travel to attack the Job. If the core plug is in the waterpump body itself, and has to be removed to fit the new plug, then i'll just whip a new pump, cambelt and aux belt on as a matter of course- even though the current ones look brand new! I checked the cam timing and set the ignition timing last night.

 

Cheers in advance

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It's part of the rear waterpump housing. Most waterpumps dont come with the housing. You have to remove the whole lot to do it properly. Hope that make sense Dan and that you get it sorted. The gold one that you can see here.

 

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Edited by Iky (see edit history)
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