Low oil pressure

[championdungspreader]

I've had an oil pressure issue for a while with my 1098. When hot, the green oil light flickers on at tick over. I fitted a pressure gauge to establish exactly what it was.
So...when cold it rises to 40lbs but when warm, it ticks over at around 4-5 lbs and on the motorway will only get to 18 or 20 lbs pressure.
I put in a litre of gear oil but this made no difference once warm.

My mind is thinking either oil pump or worn bottom end. Both require a major job.
Any tips on establishing what the cause is before I start taking things apart???

It is my daily car so whatever I do, I have to get it back on the road for a Monday morning!

Thanks

[philthehill]

I suspect that your problem is the mains and big ends - I doubt very much that the pump is worn.
The oil pressure figures quoted are terrible and the engine should not be run hard with the engine condition as it is.
You could remove the sump and big end caps and see what you find - you may be able to get away with just replacing the big end bearings.
If you know the size of the bearings i.e. standard or undersize get a set just in case it is only the big ends.
The mains are a different matter as the front main cap cannot be removed as the front engine plate is attached to the front main bearing cap by the two 1/4" UNF screws.
You could take the centre main cap off and see what you find.
If you get your self prepared with shells and gaskets replacing the big end bearings can easily be completed in a weekend.
You should always have in the back of your mind though that you may find the bearings and crankshaft worse than you would have liked.
If when running a finger nail over the journal it feels rough - that is a sufficient indicator to say that the crankshaft needs re-grinding.
But of course always better if the crank journals are measured with a micrometre.
You could always get a good S/H engine and change over the engine which could be completed over a weekend with a bit of effort and then overhaul your original engine in slow time.
When was the last time the engine oil filter was changed? whilst not a primary cause of your problems it would do no harm to change the oil filter.

[championdungspreader]

Thanks...I feared that may well be the issue!

[dalebrignall]

put some stp or wynns oil charge just to help you along , but sounds like you need new big ends etc