mikeyb Posted January 18, 2012 Share Posted January 18, 2012 Catching up with jobs on the Sprint today, I removed the oil pump with the intention of fitting an o-ring set to cure the oil leak that I had from the Pressure Relief Valve bung. On removing the pump it became obvious that the PRV had been chattering - another broken retaining split pin and a mark on the bung where it had been rubbing/banging.So the question - what causes oil pressure relief valve chatter? :-/ Link to comment Share on other sites More sharing options...
That Man Posted January 18, 2012 Share Posted January 18, 2012 mikeyb wrote:So the question - what causes oil pressure relief valve chatter?I've been told (by my uncle who used to design hydraulic systems for aircraft ) that using too hard a spring can be one cause, use a softer spring with more pre-load to achieve the same fitted load. Gordon Link to comment Share on other sites More sharing options...
mikeyb Posted January 18, 2012 Author Share Posted January 18, 2012 possibly logical, but I have had the car 25 years, from 30k miles - and am sure that this is the original oil pump/relief valve and has never been apart until today! Link to comment Share on other sites More sharing options...
Nick Jones Posted January 18, 2012 Share Posted January 18, 2012 Might simply be related to the bung being a rather loose fit and not being sufficiently well damped by a healthy O-ring. So a nice new fat and squashy O-ring might well help!Otherwise most likely cause of "hammer" in a system with a PD pump is entrained gas. Could be trapped air from oil surge or just from foamy oil. Could also be cavitation on the inlet side of the pump due to water or fuel contamination in the oil "boiling" in the low pressure areas on the pump inlet side and forming bubbles which then collapse as the pressure rises on the way through the pump. Fresh oil greatly reduces the probability of that. I suppose air leaks in the suction pipe or possibly a partially clogged strainer on the pickup leading to lower pressures in the inlet pipe (increased risk of cavitation) are possible too but not very likely.Nick Link to comment Share on other sites More sharing options...
thescrapman Posted January 18, 2012 Share Posted January 18, 2012 My thought was too low pressure coming out of the pump, so it was only just actuating the valve, making it chatter. :-/ Link to comment Share on other sites More sharing options...
Nick Jones Posted January 18, 2012 Share Posted January 18, 2012 thescrapman wrote:My thought was too low pressure coming out of the pump, so it was only just actuating the valve, making it chatter. :-/That's a low energy event as far as the bung is concerned - pressures and thus forces are low and it's isolated from the plunger by the largely uncompressed spring. I'm thinking of something that occurs at higher rpm when the pump volume is way up, the relief valve is fully open (Triumph always seem to undersize their relief valves) and the plunger is pushing against the cap.Don't think we'll ever know for sure though, unless you happen to have a pressure transducer and high speed datalogger handy....Nick Link to comment Share on other sites More sharing options...
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