Oil pressure relief valve adjustments

Hi

it's a long time since i have been posting on this forum, however my 1950 TEA has had some oil pressure issues for some time now.

Im running straight sae 40w, the pressure gauge is an
aftermarket one with uncertain accuracy

I followed John UK's advice from a post back in 2004, that i copied in below.

I turned the relief valve
screw in two turns, that resulted in 100 psi at full
throttle, backed out half a turn, and got 80 psi at
full throttle on half warmed engine.

After 18 km driving in 4th gear and full throttle the
engine was thuroughly warm, and now I have 60 psi at
half, to full throttle, and 0 psi at idle. At 5-600 rpm
i have around 10 psi.

So what do you guys think? Is it time for an engine
rebuild soon?

Regards Jone

Here is the post from John back in 2004.

John (UK)
08-11-2004 13:09:48

Re: 1951 TEA20 oil pressure gauge reading in reply to Patrick Wa, 08-10-2004 14:41:20

The oil pressure on a good engine should be 40 - 60 psi at anything over half throttle. The oil should be 20W/50 unless you are in a very cold climate then you should change to a slightly lower grade. Have you changed the oil filter, that can affect the oil pressure reading and there is an adjustment on the top side of the oil filter, try screwing in in a couple of turns to see if it puts the pressure up, if that doesnt work Have a look at the filter in the oil pan (the oval plate on the right side of the oil pan)make sure its clean. If that fails you could drop the oil pan and check the bearings, if they are down to the copper backing they need replacing if the C/Shaft is worn it needs a regrind. If it just needs bearings I would change the oil pump Rotor too, they are available from Sparex Part number S61996, it should also be available from this site too (top left of this page and click on H.Ferguson)Any good tractor dealer should be able to get this for you. You can get bearings too and gaskets. If you have any problems post again.

Seems all the standard petrols suffer low pressure when warm, both my 87mm do. Cranked one so high it sprung the gauge. Don't believe it's my bearings but if the pump is capable of 80 lbs.
its hard to believe its that either. If the filter was changed something could be missing or in the wrong place. Study the parts breakdown of the filter. Let us know what fixes it.

I dont think there is anything wrong with the filter assy, but i will defenetly check it out.
I have altso wandered about plumbing in a test pressure gauge that i know is good in to the oil gallery in the back end of the head, so i know what pressure i have furthest away from the pump.
But i find the whole thing puzzeling that the pump can give 60-80 psi at half throttle, and hardly any at idle. And when the oil is warm and thin it still gives good pressure at higher rpm
Can it be the pump that is worn out, and the bearings are ok?
Have any of you guys changed the pump only with good result?

I dont have the tractor at home, so any work that needs other tools than a adjustable spanner is a bit difficult, so i had to test Johns trick first.

If you get 10 PSI at 500 RPM, and there are no unusual knocks or rattles, I would not be too concerned.

I don't know of any way to determine if low oil pressure is due to a worn pump or loose bearings. On an engine with a lot of hours, it is a combination of both. Sometimes replacing the oil pump will help, but generally the result will be minimal. As you have found, adjusting the relief valve spring has no effect on idle pressure. In rare cases, a relief valve that is not fully closing will cause low idle pressure, but that is not likely happening.

Things that should cause concern are a sudden drop in oil pressure, knocking under load, top end noises which can be caused by loss of oil to the rockers, rear main seal leaking more than usual which can indicate main bearing failure, or metal flakes in the bottom of the pan or inside the oil filter.

My first inclination would be to check the oil pressure directly from the block using an oil pressure test gauge .
Recent gauges , especially those originating from India , whilst looking the part are very inconsistent in accuracy .
The tube leading to the gauge can often be restricted and should be cleaned with wire rather than just air and solvent . This goes for the banjo bolt holes as well .

Yes i have to get hold of an accurate test gauge, to verify the pressure.
The oil pressure issue is only a problem when i have been running the tractor hard, running a wood chipper for a few hours, or pulling a trailer with load on it, i dont use this tractor on flat roads too much... she is a worker
Theres no unusual knocking or valve gear noises, it's running smooth
But im starting to think the gauge is a bit pessimistic, it might be indian...[/img]

(quoted from post at 03:51:45 04/14/17) Yes i have to get hold of an accurate test gauge, to verify the pressure.
The oil pressure issue is only a problem when i have been running the tractor hard, running a wood chipper for a few hours, or pulling a trailer with load on it, i dont use this tractor on flat roads too much... she is a worker
Theres no unusual knocking or valve gear noises, it's running smooth
But im starting to think the gauge is a bit pessimistic, it might be indian...[/img]

Click to expand...

Had the same issue, just kept the engine speed just above idle until I found time to rebuild the engine. TEA 20s only suffer from low oil pressure because the crankshaft bearing clearance is excessive and the oil pump rotors have too much backlash, rarely from other issues, except of course when the wrong oil has been used or the engine oil is way past its change point, or is suffering from fuel dilution.
Don't be tempted to check the oil pressure at the fitting in the back of the head. The oil at this point is regulated down by a slot in the camshaft journal, which only aligns with the oil galleries every 2nd engine revolution.
If the oil strainer is blocked in the sump, then the bearings would be suffering anyway.
If the oil filter is installed incorrectly, or blocked, then the filter bypass valve will be directing oil past the filter, and again, the bearings will be suffering.
At 10 PSI, and no filters or strainers blocked, the bearings will still last quite a while, as they are generous in their size.
I installed a new crank, bearings to suit, replaced the rotors in the oil pump and refaced the end plate of the oil pump, and have around 20 PSI at idle after many hours of hard work in the Australian summer using 20w/50 oil.