Overheating

2004 BMW 525I
102,000 MILES • 2.5L • 6 CYL • 2WD • AUTOMATIC
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SUNSARO67
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Engine overheats and the expansion tank cap got melted. Replaced the cap but engine stops after over heating.

Did the bench test for thermostat. It looks okay.

Compression test results in psi
1st 200
2nd 180
3rd 170
4th 190
5th 190
6th 190

Leak down test : 3rd and 5th have little exhaust valve leak

Is it the gasket or what else could be wrong?

I shall thank you to answer.
Jan 24, 2020 at 4:34 AM
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KASEKENNY
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Let's do two things. First, let's test the cooling system for hydro carbons. You do this with a chemical test shown below.

Then we need to find out if the cooling fans are coming on. However, we need to clarify if the engine will keep running or does it shut off after it overheats or once it starts?

https://www.2carpros.com/articles/engine-overheating-or-running-hot

https://www.2carpros.com/articles/head-gasket-blown-test
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Jan 24, 2020 at 5:32 PM
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SUNSARO67
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Thank you for your reply.
The engine starts without any problem but shuts off after it overheats.
Jan 24, 2020 at 6:33 PM
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KASEKENNY
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Okay. Let's check fan operation when it gets hot. As it approaches 200 degrees the fan should be on. As it increases the fan should kick to high. I suspect this is our issue and the ECM is shutting the engine down to protect it.
Jan 24, 2020 at 7:29 PM
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SUNSARO67
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It's a long weekend here in Australia. I am going to do the other tests by next week and let you know the results.
Thanks once more.
Jan 25, 2020 at 3:44 AM
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KASEKENNY
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Thanks for the update. Please take care. We hear about all the issues over there so our prayers are with you guys. Hopefully you are not anywhere near the fires.
Jan 25, 2020 at 4:29 PM