revilla Posted July 28, 2013 Share Posted July 28, 2013 I replaced the oil filter housing on my K-Series VVC today with one with a mount for an oil temperature gauge. In doing so I disconnected the capillary tube for the mechanical oil pressure gauge. Quite a lot of oil drained back from the tube, which was obviously largely full of oil. After reconnecting, I guess it was largely full of air. All appeared to work fine, oil pressure gauge was responsive and pressures readings were just as before, but I was just wondering if you were supposed to do anything to bleed the air from the tube? Or just leave it like it is? Link to comment Share on other sites More sharing options...
Paul Deslandes Posted July 28, 2013 Share Posted July 28, 2013 no need to bleed. The air and oil pressurise just the same as far as the gauge is concerned. Link to comment Share on other sites More sharing options...
revilla Posted July 28, 2013 Author Share Posted July 28, 2013 Thanks Paul, that was what I thought but just had a nagging doubt so nice to have it confirmed. Link to comment Share on other sites More sharing options...
revilla Posted February 15, 2015 Author Share Posted February 15, 2015 I know I'm resurrecting a pretty old thread but I have (what I consider to be) an interesting observation to share ...Today I replaced the capillary tube following my minor mishap described here and when I tested it I noticed that although the pressures were reading about where I expected overall, the response of the gauge was very sluggish compared to how it had been previously. If I revved the engine it took a couple of seconds for the gauge to rise and settle. My first thought was that I had kinked the pipe or pinched it a bit tight with a cable tie, but a thorough check found nothing. There were no kinks and it was free to slide through all of the cable ties, which I had only pulled up tight with fingers. So remembering that the old pipe had certainly contained a good deal of oil rather than air when I removed it, I did what instinct had told me to do in the first place and bled it. With the engine running and up to temperature, I slackened off the union at the back of the gauge a little until oil began to ooze out, then nipped it back up tight. The response was totally transformed and tracked the engine speed immediately.In situations where I may suffer from oil surge I would rather have a rapid gauge response.I've uploaded a video . I'm not sure how this responsiveness compares to others.In equilibrium it is true that the pressure throughout the tube, from the oil filter housing to the gauge, will be the same whether it is filled with oil or air. However when the oil pressure increases suddenly at the filter housing, if there is air in the pipe then a significant quantity of oil must be pumped into the the pipe to compress the air up to equilibrium pressure, which takes time. Similarly when the pressure is reduced suddenly at the filter housing it will take time for the expanding air to drive the oil back out and for the pressure at the gauge to fall.Oil in the tube, being in comparison to air largely incompressible, does not seem to cause this sluggishness. Link to comment Share on other sites More sharing options...
Nigel Riches Posted February 16, 2015 Share Posted February 16, 2015 Well done, full marks for perseverance, and a successful outcome. Quick acting oil pressure indicator is much preferred over a sluggish one. Nigel. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted February 16, 2015 Member Share Posted February 16, 2015 The YouTube video is blocked... please could you bleed it.Jonathan Link to comment Share on other sites More sharing options...
revilla Posted February 16, 2015 Author Share Posted February 16, 2015 @Jonathan - There was a kink in the internet. Try again Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted February 16, 2015 Member Share Posted February 16, 2015 Much snappier.ThanksJonathan Link to comment Share on other sites More sharing options...
Paul Deslandes Posted February 16, 2015 Share Posted February 16, 2015 hehe!Maybe the oil takes time to compress the air as it's pumped through the pipe until it reaches equilibrium (that's a big word for blatchat )I'll try bleeding the MGA gauge as that's very slow to react. Link to comment Share on other sites More sharing options...
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