I have noticed that the oil pressure gauge reduces to near zero while idling but is in the 40 ranch while running at normal speeds. Any thoughts. Thanks
Skeets
Hi.
If it drops to maybe 10 or 20 thatâs completely normal. If it went to zero it wouldnât be good. If itâs at least 40 at 3000 rpm itâs supposedly all right; and if used to be way better your relief valve might be stuck open. But that would mean very low pressure at speed as well.
Oil pressure is more or less a function of oil viscosity (what grade do you use?) and resistance to flow from the motor. As long as all bearings get enough flow for cooling and the oil reaches the cams there is no more additional pressure needed, especially not at idle. I think youâre alright.
If you are still worried check your oil gauge accuracy with a proper gauge and switch to heavier, thicker oil as in 20W50.
Regards, David
Hi David, thank you very much for the direction. I use Castrol 20 W 50. I will check out your specs and suggestions and go from there. Appreciate the prompt response.
Skeets
If you are anywhere near Washington DC you can try out my old sender and gauge which I just replaced with a 0-100 PSI
Thanks for the offer Michael, I am in Florida.
If you run into trouble I could ship them
I had the same issues with my 190k miles engine and started to think it might be time. for an overhaul. Before I pulled the engine I plumbed in a mechanical oil pressure gauge. The issue was the old sending unit.oil pressure gauge in the car. The mechanical gauge shows an idle pressure about 20psig and a running pressure of almost 50psig. This is with Mobile 1 15/50 fluid. I suggest you verify the pressure reading with a classic mechanical gauge before you go any further with work on the engine or oil viscosity changes. The sending units, including new replacement units, are not as accurate, or reliable, as I believe they should be. I found a helpful tech at a local store to help me find the pieces needed to install a âTâ assembly where the original sending unit is installed so I now have two oil pressure gauges.
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David, thanks for the information. The forum has given some great feedback.
Thanks
Skeets
Skeets, I had the same fluctuations with my oil pressure senders. In fact I tried ones from various suppliers and some read high and some read low. I was down to 10psi at hot idle with one sender. I eventually installed a mechanical Smiths gauge and now I have 50psi at most running speeds and around 30psi at idle.
I bought all the stuff you need from Merlin Motorsports in the UK and it came within a week.
Photo show brass T connection, fittings and new gauge. The sender screws into the top of the brass T into the 1/4"BSP female thread.
I installed the new mechanical gauge on the RHS of the radio console so I can check it all the time.
Andy 69FHC
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Thank you very much for the information and details. I am diving into the problem.
Thanks again
Skeets
Irving C. Lunsford, III
904-466-1080
I have the same T Piece from Merlin Motorsports but when I chatted with them on line they told me to use their p/n M-COP-4 copper crush washers to use with it to seal at the sending unit and oil filter block. Total price including shipping to Houston from the UK was $23.
I have not tried to put it in my car yet but I am going to try just directly installing my mechanical gauge into the T to check and keep tabs on the accuracy of my stock gauge in the cockpit.
David
68 E-type FHC
If your car is a six, then everything suggested is fine. If your car is a V12, then not so much. So you see why including info on your car is important.
V12 gauges often drop down to heart attack readings at hot idle. The first thing would be to check if itâs a genuine pressure. If not, youâre golden. If so, then you mebbe silver⌠This is a common finding on V12s.
The V12 oil pump is designed to move a LOT of oil to keep so many bearings lubed. Flow and pressure are related, so it is likely your pump is flowing well even if part worn shells are causing low pressure in the oil gallery at idle. Since the pressure jumps up with the revs you can relax a bit.
Iâd check the relief valve isnât stuck open, but assuming it isnât at the moment Iâd carry on driving with a wet gauge for company. The chances are high that youâll be able to drive many, many, miles before having to re-shell the bottom end.
Skeets
Irving C. Lunsford, III
904-466-1080
Thank you again.
Skeets
Irving C. Lunsford, III
904-466-1080
My new oil pressure sender has been fluctuating like crazy. Had ZERO pressure at idle after a 10 mile run. Plenty of oil flowing to the cam shaft gallery and engine sounds fine. Next morning, pressures back to normal. Replace oil pressure relief valve just to be safe. No indication of anything keeping it open like debris or something stuck. Still fluctuating depending on, seemingly, itâs mood.
Gave up. Ordered this unit and will see if that solves the issue. Will also check pressure with a mechanical gauge, but I think itâs the sender unit failing.
Curious how you were verifying flow to the cam galleys? Dud you just pull the covers?
If you havenât yet opened your new gauge there another popular option that was written up in the UK forum, the mechanical gauge kit from Wilkerson. More expensive likely, but it removes the troublesome sender from the equation. It also gives some headroom since true pressure often exceeds 60.
http://www.mandcwilkinson.com/2014/01/m-c-wilkinson-sayer-oil-pressure-capillary-gauge-conversion/
Another (low buck) alternative is a TR6 mechanical gauge. Also ranges to 100 psi and although not identical to an original it does not look too out of place.
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Oh that does look fine. How did you plumb it?
I took off the oil filler capâŚif the pump was supplying zero pressure the oil gallery would look like it does after shutting off the engineâŚvery low level of oil in the gallery well below the bottom of the cam shaft. With oil pressure, the bottom of the cams are sitting in oil. And the fact that if I turn off the car and let it sit, pressure goes back to normal. If there was a problem with the bearings or the pump, it wouldnât self-repair each night. Thatâs my theory anyway. I could be way off base. Iâm far from anything resembling an expert on much of anything, let alone this topic.
I have no desire to have a wet oil gauge in my dash. I may put in a backup under the bonnet if I still see a lot of fluctuation, but I donât need oi in the cabin. Thatâs just meâŚI prefer to keep liquids under the bonnet vs in the cabin, although if it dripped, it would be a nice rust-proofing agent. And while I know they are designed not to leak, and a lot of folks use them, itâs just my personal preference to not plumb an oil fitting into the dash.
Besides, I want to try an air core instrument anyway, so itâs a good excuse to try one.
I realize the most accurate way to go would be a wet gauge in the cabin. Just no my cup of tea.
Adapter on oil filter head:
Braided line to cockpit (uses same hole as reverse lamp wires):
The on to the gauge:
I later learned there is a right-angle connection available to fit the gauge, this would probably be a better choice.
Plastic loom wrap is just there as a back-up in case the braided line should contact a live 12V (it does not). View with panel up (and dash top off):
PS - 50 years of driving Triumphs has probably left me sanguine about engine oil plumbed into the dash. I do carry a brass plug for the filter head if I ever need to address a leak or failure.
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