Frothy oil

[Nick Salmon]

I am in the process of recommissioning an RP that has stood for 30+ years.

About a year ago the previous owner filled the rad with water in order to run the engine. Unfortunately he didn't remember that the cylinder head was not screwed down and so ended up with water in the bore/sump. He says he drained the rad and the sump.

When I acquired the car it was a non-starter but it is now running well. It has a new head gasket. The rad level stays constant.

However...

On starting from cold and at fairly high revs there is about 7lbs max indicated oil pressure. On any other 7 I'd expect to see it 'off the scale' on a 10lbs gauge or 20lbs+ on a longer scale gauge.

After a few minutes running, when I pull the dipstick I find the oil is 'frothy', as show in the photo. It returns to a non-frothy state not long after switch off.

Is this caused by a worn oil pump cavitating the oil?

   

[Derek Sheldon]

Nick,
I would suggest that there is still water in the oil. Has this engine run hot for any time since changing the oil, one would expect a certain amount of evaporation of the remaining water thus clearing the oil. Could the oil pressure thing be down to water compressing easier than oil ? Or perhaps one of the vanes be stuck

[Nick Salmon]

Thanks Derek. I wondered if it was water that had been in the galleries - but I have changed the oil twice since I have had it running so I really don't think it can be.

[Chris KC]

Sticking my neck out a bit here as I haven't driven a splash fed engine in years - but in my memory that pressure's about right for a standard A7...

The water episode will have done no lasting damage IF it was thoroughly drained at the time. If water was still in there somewhere you'd see 'mayonnaise' floating inside the rad cap.

[Nick Salmon]

Sticking my neck out a bit here as I haven't driven a splash fed engine in years - but in my memory that pressure's about right for a standard A7...

The water episode will have done no lasting damage IF it was thoroughly drained at the time. If water was still in there somewhere you'd see 'mayonnaise' floating inside the rad cap.

Thanks Chris. 5-7lbs is fine for a warmed up engine but not at start up from cold. This lack of higher pressure when cold made me think maybe the pump is at fault. There's no mayo in the rad and there's no obvious grey emulsion in the oil. Only the frothing, which subsides after the engine is turned off and left for a while.

[Chris KC]

Sticking my neck out a bit here as I haven't driven a splash fed engine in years - but in my memory that pressure's about right for a standard A7...

The water episode will have done no lasting damage IF it was thoroughly drained at the time. If water was still in there somewhere you'd see 'mayonnaise' floating inside the rad cap.

Thanks Chris. 5-7lbs is fine for a warmed up engine but not at start up from cold. This lack of higher pressure when cold made me think maybe the pump is at fault. There's no mayo in the rad and there's no obvious grey emulsion in the oil. Only the frothing, which subsides after the engine is turned off and left for a while.

I see. Yes I note the oil looks clean. I can't comment on the froth I'm afraid, but I guess a worn pump is the obvious culprit if pressure is low. (What happens if you let it warm up?) A cautionary note about oil pressure loss - I trailered my car ignominiously back from Southampton docks once when oil pressure suddenly dropped to zero; it turned out to be a bit of red hermetite which had somehow found its way up to block the oil  pressure gauge pipe. The engine was running fine!

[Austin Carr]

This article gives a few more possible causes of foaming oil:-

http://www.machinerylubrication.com/Read...ing-in-oil

[Robert Leigh]

I am in the process of recommissioning an RP that has stood for 30+ years.

About a year ago the previous owner filled the rad with water in order to run the engine. Unfortunately he didn't remember that the cylinder head was not screwed down and so ended up with water in the bore/sump. He says he drained the rad and the sump.

When I acquired the car it was a non-starter but it is now running well. It has a new head gasket. The rad level stays constant.

However...

On starting from cold and at fairly high revs there is about 7lbs max indicated oil pressure. On any other 7 I'd expect to see it 'off the scale' on a 10lbs gauge or 20lbs+ on a longer scale gauge.

After a few minutes running, when I pull the dipstick I find the oil is 'frothy', as show in the photo. It returns to a non-frothy state not long after switch off.

Is this caused by a worn oil pump cavitating the oil?

I have found some remarkably rusty vanes in old oil pumps that haven't been disturbed for years. Do you know how long the engine stood after the oil and water mix was drained out? The other thing that can suffer in this situation is the vane springs which rust quite easily. I think it is worth checking the pump. It can be done with the engine in place; if you find anything amiss with vanes or springs change them. I do agree that a higher reading cold would be normal.

[Ian Williams]

I my experience would suggest it is never wise start an engine that has stood for years without first removing the head to inspect bore's and grind in valves, removing the sump, cleaning and checking the oil pump, etc. I have found a surprising amount of corrosion in some engines, it is also worth removing the two water manifolds as these are often clogged as well. I know that some will say, oh we simply changed the oils started the engine and it has been fine ever since, well you may have done so, but you may also have been lucky. The pictures attached are of an engine that has been through my workshop recently, it was apparently completely rebuilt not many miles before being laid up 20 odd years ago......would you want to have started it??

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[Hedd Jones]

Ian. It boils down to what floats your boat.

That engine would probably needed the valves sorting but beyond that would probably have run fine with an initial early oil change after start up.

If your 'bag' is driving the car it would have probably done thousands of miles and many years in some peoples use before needing overhaul. 

If your 'bag' is taking engines to pieces and rebuilding them great, but the fact it 40% of the people who take vintage cars to pieces never finish them, 10% probably wouldnt know how to put it back together.

Better get the enjoyment out of what you actually have rather than what you might have I say.