4.2 Low oil pressure

[simong]

Hello everyone,

I own a 1969 S2 2+2 and are currently experiencing very low oil pressure, at idle it is only about 5lbs and even giving some rev?s the pressure does not change, all of which is somewhat worrying!

Up to this point the engine has been running well with no issues and good oil pressure, it had an oil and filter change 500 miles ago and refilled with 20/50 mineral oil.

The problems started with the oil pressure start going all over the place, one minute at 20lbs at 2000rpm, next 40lbs, at one stage it would not go above 20lb and now 5ibs. As yet I cannot hear any expensive knocks and noises!

So after investigations on the forum far I have so far done the following with no improvements in oil pressure,
1. Replaced the oil pressure gauge and sender with a JEC version.
2. Tested the gauge and sender with an air line, reports the correct readings.
3. Removed oil filter head (this is later XJ6 version), cleaned and replaced the relief valve.
4. Replaced the oil filter.

My only conclusion is the oil pump is the issue so dropping the sump would be my next action unless anyone have any other suggestions. My understanding is the sump can be dropped whilst the engine is in the car and the oil pump replaced.

Your thoughts and comments are most welcome!

Many thanks

[christopher storey]

You do not reportwhat the state of the shuttle was when you cleaned/checked the pressure relief valve. This is a common source of problems if either a. the spring breaks ( not very common ) or more usually b. the shuttle starts to seize in its bore ( very common as a result of gum ) . That is the first thing I would look at again , particularly since the symptoms you describe at the onset of the problem are suggestive of its sticking . If that is all in order, then I should move on to the oil pump, which as you say can be tackled by dropping the sump. The gloomiest picture, of course, is that the low pressure is the result of the bearings being very worn, but this does not sound to be the case when you have been getting inconsistent readings and have seen 40lbs from time to time

PS another thought : make sure that the gasket you used when reassembling the filter head is the correct one ; there are several different types and selecting the wrong one may block off a vital passage

[Heuer]

You can check the operation of the valve by clamping the oil relief pipe closed and running the engine - you should get high pressure as a result.

[tinworm]

Loose oil pickup pipe where it bolts to the block is a common problem.

regards Barrie

[JEP41]

I had a similar problem which was traced to a crack in the brazing on the pump delivery pipe flange where it bolts onto the block. Replaced this pipe and problem solved 8)

[simong]

Many thanks everyone for your advice, it is much appreciated.

The oil filter unit was OK, the previous relief valve appeared OK, the spring was weaker than the new one and was not seized and clean. I will try clamping the relief pipe and see if that makes any difference, if not it?s dropping the sump changing the oil pump and checking the oil pickup and delivery pipes.
I will post an update with the outcome, whether good or bad!

Regards

[simong]

An update to my oil pressure problems.

In the end I dropped the sump and replaced the oil pump and as a precaution the big end bearings, these were in pretty good condition with only some minor scoring on one where it would appear some dirt had got into the bearing. The biggest challenge was removing the sump, once I worked out how high I had to lift the engine it came out relatively easily.

The good news is I now great oil pressure, on tick over with the engine warm I am getting 50lbs and going up to 60lbs. Is this high pressure OK? I would expect the relief valve to open and reduce the pressure, I have replaced the valve during this process.

[PeterCrespin]

I was right there with you until that last comment about the valve...

I have had several of my own and others' E-types that ran fine with no undue noises but showed woefully low pressures on the electric gauge. They all turned out to be fine when checked with a master gauge, although I did drop the sump and change all shells on one.

Since you changed both leading culprits at once (reaction valve and oil pump, we'll never know which was dud, assuming the shells were truly OK. Unless you measured them, it's possible the shells were just worn very evenly. Of course I don't blame you for doing all three at once, and the important thing is the car runs fine, but you'll never know whether the issuewas pump, valve or shells. You can check clearances and scoring or other pump damage easily enough of course.

Pete