<Expletive> oil pressure still lacking

[Zaphod]

OK as some may recall I had no oil pressure showing, on either the gauge or the mechanical external gauge and that I had taken the pump apart and fitted new annulus and rotor, along with a new oil relief valve spring, after which I got around 1 bar spinning it up on a cordless drill before the drill stopped. Well today I started the engine, it did make 1 bar cold, but once warm nothing.
Something is no right! My suspicion is that both the sender and the external gauge are faulty (The latter I noticed that oil was visibly leaking form the quick release union that screws in place of the pressure sensor)

According to Mike Taylor the pressure has to be at least 20PSI to reach the cams, if it's not the cams will seize in short order, there is a lot of oil reaching the top of the engine
The engine has now got at least an hours running since it was rebuilt (mostly at idle) with allegedly no oil pressure, and it does not make any untoward noises

I have notices that the service notes state that the oil pressure should be no less than 5 PSI at idle.. not convinced as that would be still in the red on the gauge..

Would anyone in the Oxfordshire area have a mechanical test gauge or known good sender I can try?

[Hawaiis0]

I got as new sender somewhere I'll try and find it.

[Hawaiis0]

Hi Stewart

I have located my new sender if you want to use it.

Hopefully you still have my number.

Stu

[DavidOliver]

Zaphod, I share your comments on Oil Pressure.
You may find it re-assuring if you Search on this Forum for posts under Oil Pressure Question dated around June 2018 and mainly authors Lotus-e-Clan and Esprit2 (Tim Engel)
These posts indicating quite low oil pressures at different oil temperatures and revs.
Worth the read to help insomnia!---if not raising the pressure at higher temperatures.

Dave the cog.

[Zaphod]

Sadly I got my old MG Midget oil pressure gauge connected today, it also says little to no oil pressure, it was only taken off the MG due to the temp side of it failing, as that is now three that say the same thing it looks like it does indeed have little to no oil pressure so its probably already wrecked (even if it does sound really nice with no horrible noises.)
I am wondering what else was screwed up that could cause this. So far I have had to reset every tappet, and found bits of old gasket under new gaskets on what was allegedly a rebuilt engine (given it is very very clean it was defiantly taken apart!) I does have decent compression which is very close across all 4 and does not leak water..
The one thing I have not changed or checked is the pickup olive, I do have a new one but was rather hoping to avoid taking the sump off. I should have examined it when I had the aux housing off but didn't think about using a wheel nut to get the upper section out (seems this will work)

[TAR]

I've no idea if the oil pump on the Esprit Turbo is the same as on an Excel but someone on TLF had an oil pressure issue which turned out to be pressure relief valve in the oil pump housing. It is a piston on a spring. It was stuck open and allowed oil to flow directly from inlet to outlet.

Here is a link to the specific post on his huge thread about his rebuild - https://www.thelotusforums.com/forums/t ... ent-870372

[Zaphod]

Indeed the pressure relieve valve was my first port of call. I fitted it with a new spring while it was apart
The work done so far has improved it, but only so far as the pressure gauge moves (previously is was totally still) but it’s still not moving the needle to the point 0 is uncovered.
Today I took the oil pump off again as a unit with the aux housing and took a look at the pickup pipe olive, I can confirm two things, the olive is intact, present and looks undamaged. The second one it that there is no need to buy any special tools to inspect it, a 19mm ring spanner with a wheel nut works very well!
Is there anything else that can cause the oil pressure to be an issue? One thing that still does not seem right is I can open the oil pressure relief valve open with one finger using a 1/4 extension Mike at lotus bits indicated that it’s not hard to open it but it should be with the palm of one’s hand, I did fit a new spring but it made little difference.
I don’t think I have a crank or big end bearing issue as it’s very quiet, maybe I do just have to get the whole system primed, however it’s defiantly pumping oil round, all the chambers in the aux housing that I cleaned out when I took it apart last time do have a lot of oil in them now.
Is there a resreictor in the block that may have been left out? I have to say I’m looking at my Alfa 166 and wondering is I can fit a Busso v6 in place of the 912.. it would make a lovely sound!

[Zaphod]

I have also noticed three holes, with the aux housing removed I can see some holes, two large ones and one smaller one, the smaller one I am wondering about as it appears to the in the main oil gallery just under the outlet from the oil cooler return, should it be there? It may be a feed to a main bearing (which makes sense). I have seen an oil system diagram for the 912 but can’t seem to locate it, or any photos to confirm this is normal! (I would not expect an oil feed in ‘front’ of the oil pressure sender though?)

[Zaphod]

Worked out the hole I can see in the oil gallery is the feed to number 2 main bearing.. might fill it with oil and see how long it takes to drain..

[Pete Boole]

Not sure if I've mentioned this but I'll be building a rig to test the operating pressure of the oil pressure relief valve. Don't know what your time scale is but it will be a while before it's done. I could bump it up the jobs-to-do list though - I'll need it sooner or later!

Pete

[Lotus-e-Clan]

Have you opened your oil filter (and drained the oil) to look for bearing debris?

At this point (in fact I would have done this a long time a go given the low pressure readings), I would take a tin opener to the oil filter to check. No point in fettling the oil pumping system if you have debris in the filter (and/or sump) suggesting damaged bearings.

[Zaphod]

Not yet, but there are no signs of this elsewhere and the thing runs silent. For the bearings to be bad enough to result in zero oil pressure I’d expect it to be knocking very noticeably, it doesn’t knock at all. The oil in the sump and oil cooler lines is clear, no debris, and I believe they sit in front of the oil filter

Edit to add, I have cut the filter open, and no signs of anything untoward, clean oil, no metal flakes present.

I think I may try adding some packing to the PRV spring to see if that changes anything, my logic is that the new spring is longer than the original and while it did not appear to change the effort required to move the valve after fitting it does make the oil pressure needle visibly move which it did not previously. If they improve then I guess that’s the cause

[Lotus-e-Clan]

Not yet, but there are no signs of this elsewhere and the thing runs silent. For the bearings to be bad enough to result in zero oil pressure I’d expect it to be knocking very noticeably, it doesn’t knock at all. The oil in the sump and oil cooler lines is clear, no debris, and I believe they sit in front of the oil filter

Edit to add, I have cut the filter open, and no signs of anything untoward, clean oil, no metal flakes present.

I think I may try adding some packing to the PRV spring to see if that changes anything, my logic is that the new spring is longer than the original and while it did not appear to change the effort required to move the valve after fitting it does make the oil pressure needle visibly move which it did not previously. If they improve then I guess that’s the cause

This is sounds promising. You can pursue the pressure reading issue without a nagging feeling that the engine might be toast.

The oil filter non-return mechanism should be a simple rubber/plastic/viton membrane covering all the peripheral input holes that prevents back-flow through the input holes.

You should also have a 'blocked filter bypass valve' at the bottom of the filter can that will open only if the filter is blocked, or if the oil is too thick/cold to traverse the filter matrix. Note that modern filter matrices (about 30 microns) are specified for modern thin oils, such that 20/50 will not easily pass the matrix when very cold. Racing filters (like the large K&N Racing filter I use on a remote filter block) have larger pores (closer to 60 microns) so thicker oil passes when cold, and there is less pressure drop across the matrix. If the filter bypass valve opens, then the system pressure will read REALLY high (7+bar) as there is now no pressure drop over the matrix, the UNFILTERED (!) input oil being diverted straight into the centre filter output tube and into the galleries.

[DavidOliver]

Zaphod.
With the auxiliary housing off you can check to see if your cam bearings are shot allowing a lot of oil to go up there, without knocking noises from below.
In the same way we bleed brakes with a pressure bottle you can set up a pressure feed to the cam bearing inlet from the exposed engine block and see what pressure you get. This will be independent of crank oil feed.

There is also a 6mm plug on the front of the block to seal the oil gallery, I doubt you are losing pressure there as you would see oil spirting at the engine front. Worth checking.


Dave the cog.

[Zaphod]

I did something else just now, I filled the main feed to number 2 main bearing (its the one that is visible when the aux housing is removed) and timed how long it took to drain to the top of the oil feed drilling to emerge. (this is the top of the 'pocket' the drilling is in, to the top of the drilling) while not a particularly accurate way to asses it it took 5 minutes for stone cold VR1 20W50 to drain that far via the bearing. Not really sure what to make of that, other than I suspect it would take less time with a real issue? I may try the same later with number 4 main under the oil pressure sender later.