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I understand many of the B230's suffer from piston slap. To start, here's what this chap has to say about it:
In simple terms, piston slap occurs when the piston is forced rapidly against the side of the engine cylinder wall. The more clearance between the piston and cylinder wall, the louder the knock. Controlling piston slap is a complex process. Too little clearance between the piston and the cylinder wall and the parts will score and fail. Too much clearance and you get a knock. It doesn't help that usually the piston and cylinder are made of different materials and have different expansion rates.
CanadianDriver: Auto Tech - Noisy engine? It might be "piston slap"
The key here is it happens when the engine is cold and is from the piston hitting the side of the cylinder wall. But what about the "clacking" sound when the engine is fully warmed up? I posted this on another forum and could use expertise:
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My Volvo (B230FT) sounds a bit like a diesel Jetta when warm: "clack clack clack" sound. I'm not really worried about it but I wonder what is physically causing this noise.
I've checked for rod knock by removing each injector. The clacking sounds heavier than valves (I have that too, more of a ticking sound). And I thought piston slap mostly went away when warm once alun piston expanded..?
I've ran both 10W30 and 15W40 Castrol with no difference in sound. Car has 125K miles on it.
A bit of history. It was overheated a few yrs ago (enough to warp head) but oil consumption and power are not adversely affected.
Thoughts? I know it's hard to isolate and explain without hearing but anyone have any ideas of what causes a gas engine to emit the clack clack clack of a diesel?
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Norm Cook; Vancouver BC; 1989 745T 210,000KM
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