Area Representative Nick Bassett Posted April 28, 2019 Area Representative Share Posted April 28, 2019 I had my dry sump gold oil pump refreshed by Titan over the winter and refitted in recently. All seemed well but I now have indicated low oil pressure through my mech oil pressure gauge. At idle it is only 1 bar rising to a max of 1.5 to 2 bar when driving. This doesn’t seem correct to me, but the engine sounds fine.I’ve noticed the clear oil line that goes into the bulkhead and back of gauge has air gaps in it when the engine ( it looks stripey) is off so perhaps it just needs bleeding to give an accurate reading? Sadly I cannot remember how it read before the pump rebuild but the gauge always seemed lazy to me.So should I be worried or what? The oil pump extraction and refitting is fairly straight forward with only 3 main connections all of which are leak free and I primed the pump before fitting, so I pretty sure that part went ok!My car is a 2000 SLR.Thanks... Link to comment Share on other sites More sharing options...
revilla Posted April 28, 2019 Share Posted April 28, 2019 I'm not that familiar with the dry sump setup but the mechanical gauge will still read the correct pressure even when there is air in the line, it just becomes more sluggish to respond. So I would suggest you do have a problem. Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 Thanks Andrew.The odd thing is, I can’t ever remember seeing high oil pressure showing since owning the car for almost 18 months. The pump was refreshed by Titan who built it in the first place so you would assume knew what they were doing. It is a simple enough change/swap so I can’t think why there should be a problem now?I’ve done about 150 miles in the car since the refresh and the engine sounds absolutely fine. If there was a serious oil pressure problem, surely it would have been making expensive noises by now? Link to comment Share on other sites More sharing options...
revilla Posted April 28, 2019 Share Posted April 28, 2019 Could it be a defective gauge? Where is the pressure take off point on your car ... on the filter housing as usual? Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 My God I hope it is Andrew!Yes, starts at the filter housing.Unless anyone on here can suggest something different, my plan is to start by bleeding it and see if that makes a difference. Any advice on how to do that welcome at my end! Run the engine, disconnect the pipe from the back of gauge and let oil run into a jar and then reconnect whilst still running once all air has been bled was my plan... does that sound correct? Link to comment Share on other sites More sharing options...
revilla Posted April 28, 2019 Share Posted April 28, 2019 You don't need to take the pipe right off, just crack the connection loose on the back of the gauge with the engine running and hold a cloth around the joint until it starts to ooze oil, then nip it up again. Best to do it with the engine cold, it won't flow so fast and you won't get hot oil on your hands if it goes wrong. Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 Great advice... thank you.I’m really worried about it now... did I do something wrong when I refitted it etc... it was all fairly straightforward so can’t think what it could be? Link to comment Share on other sites More sharing options...
revilla Posted April 28, 2019 Share Posted April 28, 2019 As somebody pointed out to me the Titan pump is only the scavenge pump tasked with returning the oil from the sump to the tank; unless it isn't keeping up with the pressure pump, it won't be directly driving the oil pressure. The pressure pump in the front of the crank will be providing oil pressure to the engine. Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 Have just bled the pipe to gauge but hasn’t made a difference as suspected... now reading about 0.5 bar at warmish idle. Engine still running OK but afraid to start it now!Oily... I think we need a chat if you’re reading this thread! Link to comment Share on other sites More sharing options...
tangomikeromeo Posted April 28, 2019 Share Posted April 28, 2019 Sorry thread hijack, or at least cul-de-sac. Revilla: how can the air in the gauge line have no effect? Air is compressible and liquids are (for the environment in question) not? I appreciate the evidence has proven you right but I don’t understand why. Education please! Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 Clutching at straws a little but is it at all possible that the Stack gauge is knackered? Do these things go wrong? Link to comment Share on other sites More sharing options...
rj Posted April 28, 2019 Share Posted April 28, 2019 I'll second that air in the line won't affect the reading: You have more or less static oil and the pressure is therefor not affected by flow loss. The air in the line will simply be compressed and get under same pressure as the oil. The gauge will read the same regardless if it's oil or air that applies pressure to it.As for the pump: Have you checked that the oil is scavenged from the sump pan and returned to the tank? Again like Andrew says: The only thing the pump does is to evacuate the sump to the tank; then the ordinary pump pressurises it. Link to comment Share on other sites More sharing options...
Wrightpayne Posted April 28, 2019 Share Posted April 28, 2019 Gold pump is only a scavenge ie it sucks the oil out of the sump and dumps it back in the tank. The pump in the engine creates the pressure.what sort of tank do you have? I have the easyclean and when running on tickover the oil is level with the top baffle.Could be the gold pump is not scavenging or could be something else? How much oil did you put in?Ian Link to comment Share on other sites More sharing options...
revilla Posted April 28, 2019 Share Posted April 28, 2019 The pressure in a fluid in equilibrium which is not flowing is the same everywhere (well, ignoring the negligible effect of gravity). So once the pressure settles to a steady value, the pressure at the gauge end of the pipe is the same as the pressure at the engine end of the pipe. Oil is largely incompressible so the pressure is transmitted almost immediately. Air is compressible, so when transmitting a higher pressure to the gauge the volume of the air in the pipe is reduced which means oil must flow into the pipe. So when the oil pressure at the engine rises, oil is pumped into the pipe compressing the air ahead of it until the pressure again equalises out and the gauge will then read the correct pressure, but as oil is viscous and the pipe is narrow, it will take some time to settle. So the gauge takes longer to respond. Similarly when the oil pressure at the engine end falls, oil flows out of the pipe allowing the air to expand until the pressure equalises again, again taking some time. So if you bleed the pipe and remove all of the air, there is nothing significantly compressible in the pipe and the pressure is transmitted immediately to the gauge without any oil needing to actually flow. In reality, under pressure the pipe will expand a little so there will still be a little bit of flow required, but a lot less. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted April 28, 2019 Share Posted April 28, 2019 If its the CC DS set up then overhauling the gold pump will have no effect on oil pressure as this is the scavenge pump.Have you checked to see if the oi pressure relief valve is sticking, it can be removed externally and the plunger cleaned etc. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted April 28, 2019 Leadership Team Share Posted April 28, 2019 Nick, as long as your scavenge pump is pumping enough oil to keep the tank filled it has nothing to do with the oil pressure you’re seeing in the engine (at the gauge).The engine pressure showing on the gauge is created by the “pressure pump” on the front of the engine which transfers the oil in the dry sump tank to where it’s needed, ie. pistons and bearings. See if you can borrow another mechanical gauge to determine whether there’s a problem with your existing gauge, otherwise you have an engine problem. In my (limited) experience with the k-series, a reduction in oil pressure can be due to tired big end bearings, although your pressure reading seems rather low for that and still have the engine running okay. Another thought could be the pressure relief valve on the side of the pump, maybe pop out the spring and plunger and clean/check it over. Get the gauge checked first though!Stu. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted April 28, 2019 Leadership Team Share Posted April 28, 2019 Must type faster! Link to comment Share on other sites More sharing options...
7 wonders of the world Posted April 28, 2019 Share Posted April 28, 2019 Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 Ok thanks all.So does anyone near Thatcham / Newbury have a spare mech oil pressure gauge I could borrow please?!Also how easy I it to remove the pressure relief valve and where do I find it? Link to comment Share on other sites More sharing options...
Wrightpayne Posted April 28, 2019 Share Posted April 28, 2019 Could you test the gauge with a foot pump?Ian Link to comment Share on other sites More sharing options...
revilla Posted April 28, 2019 Share Posted April 28, 2019 Nick I have a gauge you can borrow.Not a very good match for the Caterham gauges cosmetically but compatible in terms of fittings and the right size. I won't be fitting it in a car, it's a left over from my testbed contraption, so no hurry to get it back or anything.Let me know if you want me to post it. Link to comment Share on other sites More sharing options...
Area Representative Nick Bassett Posted April 28, 2019 Author Area Representative Share Posted April 28, 2019 Thanks so much Andrew... will pm you my address. Link to comment Share on other sites More sharing options...
tangomikeromeo Posted April 29, 2019 Share Posted April 29, 2019 And thanks from me too for the explanation. Link to comment Share on other sites More sharing options...
revilla Posted April 29, 2019 Share Posted April 29, 2019 I cross-checked the calibration against my leakdown tester this morning. The two gauges on that agree with each other and the compressor so I'm pretty sure it's a reliable reading. Looks pretty good to me.One of the reasons I checked was because I've had three engines in my car and they've never shown particularly good oil pressure, but when one of them was on the testbed with this gauge it showed a very healthy oil pressure indeed. I had thought this gauge might be over-reading, but I'm now pretty sure the one in my car is actually under-reading like yours may be (significantly, but not to the same extent). This one looks spot on.It also provides further evidence for the theory that the gauge should read exactly the same on air as it does on oil.Nick I've got your BM, will get it posted. Link to comment Share on other sites More sharing options...
TomB Posted April 29, 2019 Share Posted April 29, 2019 Have you dropped and changed the oil during the pump removal? Same grade of oil refilled? Link to comment Share on other sites More sharing options...
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