RogerH Posted November 5, 2016 Report Share Posted November 5, 2016 Hi Folks, I have an odd one, From cold, when I start the engine, it fires up OK. The engine sounds fine but no oil pressure. After about 10 seconds the pressure starts to build. When running, the gauge rises and falls quite happily. During the initial start up there is no dry bearing sound. Everything is normal - except the gauge reading. The oil and filter were replaced in early October. Next week I'll replace the filter as a start. So, what would cause a sluggish gauge.???? Roger Quote Link to post Share on other sites
RobH Posted November 5, 2016 Report Share Posted November 5, 2016 Have you tried bleeding the pipe at the back of the gauge Roger, in case its an air bubble ? Quote Link to post Share on other sites
RogerH Posted November 5, 2016 Author Report Share Posted November 5, 2016 Hi Rob, I've done nothing yet. But will do everything next week. I can't see it as an air bubble but I will bleed it anyway. Roger Quote Link to post Share on other sites
Don H. Posted November 5, 2016 Report Share Posted November 5, 2016 An obstruction in the line restricting pressure build? Quote Link to post Share on other sites
Guest ntc Posted November 5, 2016 Report Share Posted November 5, 2016 Air will not affect it. Quote Link to post Share on other sites
boxofbits Posted November 5, 2016 Report Share Posted November 5, 2016 Hi Roger I would tend to go for an obstruction or kink in the pipe. I had the same problem on my Mini, except no pressure on the guage at all. It turned out to be an obstruction in the pipe which I cleared with mig wire. I slackened/removed the pipe on the block first it and spurted out with quite a force so I discounted any problem in the engine. Regards Kevin Quote Link to post Share on other sites
Lebro Posted November 5, 2016 Report Share Posted November 5, 2016 semi blocked pipe to gauge would be my guess. can you easily disconnect it in the engine bay somewhere, & use compressed air to see if the gauge responds quickly to that (could also disconnect at gauge, & blow the pipe through. Agree, air bubbles will not make any difference pressure is pressure, air or oil. Bob. Quote Link to post Share on other sites
ChrisR-4A Posted November 5, 2016 Report Share Posted November 5, 2016 Mine stuck at 60 psi after shutdown, I removed the gauge, washed the mechanism out with WD40 gave it a tap and it went back to zero. Relubed with a small amount of 3 in 1 oil applied with a needle and has worked fine ever since, over 10 years so far. Chris Quote Link to post Share on other sites
RogerH Posted November 5, 2016 Author Report Share Posted November 5, 2016 Hi Folks, many thanks for the replies. So Next week I'll remove the gauge/pipe etc and clear the pipe through. I'll check the gauge on the bench. I'll also check the pressure gauge pipe supply for a decent flow on cranking - this could get messy. Roger Quote Link to post Share on other sites
ianc Posted November 5, 2016 Report Share Posted November 5, 2016 Air bubbles in the small bore capillary from filter to gauge will slow the response as each has to be compressed before the next movement can occur down the capillary. And surface tension comes into this, too. I feel sure that Peter Cobbold or my brother (a mechanical Engineer, but no longer a member) would be able to elucidate. Ian Cornish Quote Link to post Share on other sites
Alec Pringle Posted November 5, 2016 Report Share Posted November 5, 2016 Agreed Ian . . . . I've had Roger's problem in the past, it was air leaking into the capillary pipe (presumably as the oil cooled) - even though the pipe was not leaking oil out. Cheers, Alec Quote Link to post Share on other sites
Guest ntc Posted November 5, 2016 Report Share Posted November 5, 2016 Disagree it is not a closed system and the air will be removed over time, I would bet 99% on here have never needed to bleed it. Quote Link to post Share on other sites
Mark69 Posted November 5, 2016 Report Share Posted November 5, 2016 Any way of testing a oil light switch? Quote Link to post Share on other sites
Lebro Posted November 6, 2016 Report Share Posted November 6, 2016 Air bubbles in the small bore capillary from filter to gauge will slow the response as each has to be compressed before the next movement can occur down the capillary. And surface tension comes into this, too. I feel sure that Peter Cobbold or my brother (a mechanical Engineer, but no longer a member) would be able to elucidate. Ian Cornish If there is enough pressure one side of the air bubble to compress it, then the same pressure must instantly exist on the other side !. To test an oil light switch, connect a continuity tester to the terminals, & attach the switch to a variable compressed air source (compressor going through a variable regulator. Bob. Quote Link to post Share on other sites
Lebro Posted November 6, 2016 Report Share Posted November 6, 2016 If the sluggish oil gauge is due to a restriction in the gauge or pipe connecting it to the engine, then an improvement would be had by emptying all the oil out of both, & re-connecting. The trapped air will pass through the restriction much quicker than oil will, & so the gauge will be more responsive. Bob. Quote Link to post Share on other sites
RogerH Posted November 18, 2016 Author Report Share Posted November 18, 2016 Hi Folks, I think i have sorted it. The other day I removed the plastic gauge pipe from the filter solid pipe and turned the engine over. The oil was very slow to appear at the end of the copper pipe.. Yesterday I removed the filter housing from the engine. I think I was over enthusiastic with the silicon sealant when I fitted the housing to the block. There was sealant close to the gauge take-off point. There must have been some restricting the flow hence the sluggish movement. I have now fitted a new gasket with Welseal and a new filter and it appears to be working OK. It would have worked better if I had connected the plastic gauge pipe to the solid pipe BEFORE I started the engine. But there wasn't too much of a mess. Roger Quote Link to post Share on other sites
Graham Harris Posted November 19, 2016 Report Share Posted November 19, 2016 HAHA Graham Quote Link to post Share on other sites
mike3739 Posted November 19, 2016 Report Share Posted November 19, 2016 You should know better Roger Schoolboy error Cheers Mike Quote Link to post Share on other sites
Guest ntc Posted November 19, 2016 Report Share Posted November 19, 2016 (edited) You should know better Roger Schoolboy error Cheers Mike Did he have to bleed it? glad you got it sorted Edited November 19, 2016 by ntc Quote Link to post Share on other sites
Lebro Posted November 19, 2016 Report Share Posted November 19, 2016 I started mine once with the pipe disconnected from the gauge - messy. Bob. Quote Link to post Share on other sites
littlejim Posted November 20, 2016 Report Share Posted November 20, 2016 If there is enough pressure one side of the air bubble to compress it, then the same pressure must instantly exist on the other side !. Does this work in brake lines too?? Quote Link to post Share on other sites
RobH Posted November 20, 2016 Report Share Posted November 20, 2016 Yes it does, but the problem is that the air is compressible and acts like a spring. That makes the pedal travel long and the feel is 'spongy' . If the bubble is too big there might not even be enough pedal travel available to get sufficient pressure for the brakes to work. Quote Link to post Share on other sites
Lebro Posted November 20, 2016 Report Share Posted November 20, 2016 (edited) Different scenario. with the oil pressure gauge, there is an infinite supply of oil (well nearly) waiting to be pumped up the pipe to compress the air, & move any oil on the other side of the "bubble". In the case of brakes, you only have what is in the master cylinder bore. With air in the brake lines as you press the pedal it feels spongy because the air is compressing, & you run out of pedal movement before you have generated enough pressure to apply the brakes fully. If you had a very long master cylinder containing lots of fluid, then you would eventually be able to build up enough pressure to fully apply the brakes. You can cheat a bit but "pumping" the pedal, that gets a bit more fluid in the pipes by beating the fluids return into the resevoir. Probably not explained it very well ! but hope you get the gist. Bob. Or, to put it another way, in both cases the pressure at the pump equals the pressure at the end of the pipe run. but in the case of the oil pump, it just keeps on going till air is fully compessed, with the brakes, the "pump" runs out of movement, & so the full pressure cannot be obtained. Edited November 20, 2016 by Lebro Quote Link to post Share on other sites
littlejim Posted November 20, 2016 Report Share Posted November 20, 2016 You bloke's are good!! Quote Link to post Share on other sites
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