Falling Oil Pressure

[GuyO]

My 97 4.2 has developed falling oil pressure. On start up it's fine. The longer the distance driven and/or the harder its driven, the further it falls. Diagnostics don't appear to show anything, whilst the engine has shown hesitation (see previous topics)during cruising which may be linked? The car is now off the road pending a strip down of the engine.

Anybody had a similar experience?

[dannylt]

Well, oil pressure will drop as it warms up due to the reduced viscosity. i.e. 60 cold idle could well become 30 for a very hot idle. But it should still show 50+ at revs & load. What did it fall to?

danny

[GuyO]

Down to about 10 to 20 psi, from 40. Have had guage checked and it is reading (relatively) accurately.

[madasahatter]

Could this just be the Oil Pressure Relief spring? replacement may be all that is needed, and it is not dear to do so?

Does this sound feasible?

Steve

[ianfirmstone]

Andy at APN did some thing to my 97 4.2 which improved the pressure it involved a new spring? I don't think mine was too bad but Andy said straight away when he looked at the car he could improve it and he wasn't wrong.
well worth checking with Andy first before stripping the motor! 07740723673 he's a really nice guy give him a bell!

[GuyO]

Thanks chaps. car is at Castle at the moment. Will put the spring theory to them. Anybody suggest anything else?

[paulk]

get them to pressure test the pots a lot cheaper than a strip down. It may be a glazed engine like min was. A quick pressure test should tell you the state of the rings.
Team Proactive did mine and come highly reccommended.

PS does it use a lot of oil?

[james]

I used to frequently replace oil pressure relief valve springs in my 4.5. There was a design flaw in the oil pipes that set up a resonance, which could snap them. I think mine was the worst. A couple of oil pipe mods, and it never happened again.

Symptoms are:

Tickover - low (or no) oil pressure.
As revs rise - oil pressure rises proportional to engine speed.
Above 3,500-4,000 RPM - normal oil pressure.

Depending on where along its length the spring snaps, you get a greater or lesser effect.

It's a 5 minute job to check. Well worth looking at before you start stripping engines.

Another option can be the woodruff key on the oil pump shaft. I know that it was a problem on early 4.2's.

[GuyO]

Not especially. About 5 litres in 2 years and 15,000 miles.

[GuyO]

James. Thanks. My problem goes one step further in that the symptoms are the same except prolonged running sees oil pressure gradually drop.

[gazzab]

wouldnt change a spring yourself as you can cause engine damage. A snapped spring with a new one on top of it doesnt do an engine any good.
The spring design has been changed recently and they are less likely to snap now.