Oil pump leak, only when oil is cold.

[Richard Kaye]

I am having some issues with my oil pump leaking when the car is cold. Once warmed up it doesn’t leak at all. It will leak even with it idling. It has the old type of oil pump driven by the distributor shaft. I have 20w-60 oil in it.

The car is a RRC with a 4.6, new bearings, pistons and rings, done around 1000km, it has done this ever since it was rebuilt.

When the car is hot and I turn off the ignition, then turn it back so I can see the oil light the light comes on pretty much instantly. When it is cold, I turn it off and check the oil light it stays off for 3-4 seconds before it lights up.

I can’t tell exactly where from the oil pump its leaking but as I said it only leaks when the oil is cold. I don’t have an oil pressure gauge to see the difference in pressure from cold to hot.

[V8Ian]

Was any work done to the oil pump, when the bearings were refreshed? If the pump is worn and performing below optimal, it could struggle when the oil is thicker.

[Richard Kaye]

The oil pump is the same one I had on the 3.5, no changes.

Only opened the pump to pack it with Vaseline so I could prime the oil system.

[Old Farang]

Arh, not sure that you can blame the pump. Really need to have an accurate pressure gauge before condemning the pump or looking for a leak.

The Rover V8 system is a low pressure high volume system, so it may just be that the original pump is not quite up to the bigger engine at low RPM. Also, the system may just be draining back more than previously, as there is probably a difference in oil gallery size and supply arrangement.

Originally these engines ran about 10psi / 1,000rpm, increasing up to around 40 psi depending on the relief valve setting. Too much pressure is not a good thing either, as it can scour out cam shaft bearings.

It could also be the oil that you are using. I would be inclined to try a something around 10w30 or 40.

[Richard Kaye]

I think I will get an oil pressure gauge and have a look what it's doing. At least this may give an indication of what's going on.

Will also try a lighter oil, with the pressure gauge.

[Mercguy]

If it's not delivering pressure cold, you'll hear rod knock at idle. Clear as day.

Check the spring and plunger and make sure there is no galling or scoring in the housing.

pump should have no issues pushing a 20-60 - that's got a pouring viscosity of about 30wt.

Guessing you're using penrite or similar, and there is no issue with running a 10w30 when it's really cold (alpine) but pretty much anywhere else in the country below 1200mASL you're not going to have temperature related issues with a 20w-60 viscosity oil.

I heard the rod knock in the d2v8 I bought. bit of a post-purchase letdown and it ended up being the pump and pressure relief spring
Replaced with a new high volume pump unit from rimmer bros.
didn't want the hassle of a partial fix potentially coming back to bite me in the rear end, since the timing cover had to come off to do the job - and all the other junk in front of the cover...

There are service kits to do the spring with uprated units.
I wanted a complete new pump.

[DoubleChevron]

I think you might have it backwards. When cold, with such thick oil you have so much oil pressure it's pushing past the dizzie seal. A slightly thinner oil may reduce the cold running oil pressure enough that it doesn't leak ?

[Richard Kaye]

I bought an oil pressure gauge yesterday and hooked it up this morning. I have here the results from both a cold engine and a warm engine.

Revs Idle 2500rpm
Cold 40psi 65psi
Hot 30psi 40psi

I didn’t rev it past 2500rpm when cold as I thought 65psi was pretty high. When warm the maximum oil pressure was 45psi at around 3000rpm, it didn’t increase any higher than this even with more revs.

I had a close look at the oil pressure switch I removed to fit the pressure gauge on the oil pump. It looks like its leaking between the centre, where the terminal is, and crimped edge of the switch.

[DoubleChevron]

I bought an oil pressure gauge yesterday and hooked it up this morning. I have here the results from both a cold engine and a warm engine.

Revs Idle 2500rpm
Cold 40psi 65psi
Hot 30psi 40psi

I didn’t rev it past 2500rpm when cold as I thought 65psi was pretty high. When warm the maximum oil pressure was 45psi at around 3000rpm, it didn’t increase any higher than this even with more revs.

I had a close look at the oil pressure switch I removed to fit the pressure gauge on the oil pump. It looks like its leaking between the centre, where the terminal is, and crimped edge of the switch.

replace the oil pressure switch before you drive the car again. I've had them fail and dump an entire sump of oil on the ground in mere seconds in the past! if there is every anything ever slightly suspect about an oil pressure switch, replace (or even cap it off if you can) immediately.

[Mercguy]

I will second that - had same issue in the RRC about 12 months ago, wondered why the oil pressure light was coming on... sure enough...
it certainly doesn't take long as Shane said.
and it's a very quick loss even when driving around the paddocks in low range.