I have fitted a few of the hydro mounts & have never heard any sloshing sounds from them failed or new, the worst i seen was the one below V6 had leaked a rusty colour substance from it due to failing over time.
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I would presume to water intake
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3
This diesel one was changed due to the owner noticing a little degradation in the rubber but no knocking.
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I was informed that the car felt a lot better to drive after the change over.
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This is the hydro mount from that car above, and it still seems fine to me, no sloshing sounds come from it.
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Also the thread can not be pushed over to 3/4 either way.
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Lets remember that most these hydro mounts being purchased as OEM for (SAIC Motor) will not be for the diesel engine but for the petrol engines
Shaking Stevens.
https://youtu.be/cxe-5oaDdfQ
Diesel
https://rimmerbros.com/Item--i-GRID001744
https://rimmerbros.com/Item--i-KKB101923
1800 petrol engine.
https://rimmerbros.com/Item--i-KKB101903
V6 petrol engines
https://rimmerbros.com/Item--i-KKB101914