Bearings, oil pump ?

[reb53]

In all the time I've owned my Sprint the oil pressure, at normal open road speeds, has hovered around the just under the 40psi mark. Maybe 38.

Over the last several months, of not much mileage, it's come down to 33/34.
There are no death rattles from the engine, which is something I'm quite keen to avoid....!
Possibly the bearings, with about 80K miles on them, are a bit tired.
Or, I'm hoping, the oil pump with about 240K miles is the more likely prospect. Mainly 'cos it's easier to change.
I'm religious about oil/filter changes so I'm thinking maybe not the bearings.

Any thoughts, or reassurances...?
Current thinking is that a pump change is not expensive, and wouldn't go amiss regardless.

Ralph.

[promotor]

In all the time I've owned my Sprint the oil pressure, at normal open road speeds, has hovered around the just under the 40psi mark. Maybe 38.

Over the last several months, of not much mileage, it's come down to 33/34.
There are no death rattles from the engine, which is something I'm quite keen to avoid....!
Possibly the bearings, with about 80K miles on them, are a bit tired.
Or, I'm hoping, the oil pump with about 240K miles is the more likely prospect. Mainly 'cos it's easier to change.
I'm religious about oil/filter changes so I'm thinking maybe not the bearings.

Any thoughts, or reassurances...?
Current thinking is that a pump change is not expensive, and wouldn't go amiss regardless.

Ralph.

Perhaps it's time to drop the oil and check it, and also remove the pump and check its tolerances: inner to outer rotor clearance, outer rotor to body clearance, and end-float.
Check that the oil pressure relief valve is moving freely and is returning to its seat - it may be sitting / stuck very slightly open due to dirt or wear, or even a weak / broken spring.

[2cams70]

Validate the reading first by using a separate oil pressure test guage.

[512BB]

I would not rush to do anything Ralph, other than change the oil filter at this stage. A twin cam will run quite happily at your stated pressures, although not ideal.

A few years ago I was driving one of my cars at a steady speed and I noticed the oil pressure wavering, going from say 40 to 30 and back again. It did that on a few drives, but I let it carry on until the next oil change. Haven't noticed it since. Who knows what it was........filter?

I built a twin cam a few years ago that ran with low oil pressure from the start. Was right miffed. Changed the Paul Matty supplied no name oil pump for a quality pump and good pressure was resumed.

Leslie

[ericbushby]

Hi Ralph,
I would say, change the filter even though it is not due yet. I say this because it is quick, cheap and eliminates one thing. I once had a steady reduction in oil pressure over a short period. It turned out to be a recently fitted filter which was probably collapsing inside.
Next, if you have had the pump a long time then change it for the same reasons as above.
Good luck.
Eric in Burnley
1967 S3SE DHC

[smo17003]

Another option would be to purchase an oil analysis kit. They can give a good indication to the health of an engine, and any potential problems. They cost £40/£50 in the UK, probably similar in NZ.

[promotor]

Validate the reading first by using a separate oil pressure test guage.

Very good point.

[reb53]

Validate the reading first by using a separate oil pressure test guage.

Thanks for all the quick, and informed responses.
Having just finished breakfast I'm heading off to get a filter. I have one on hand but it's the same brand as fitted, so I'm being cautious and will get the brand I always used in the past.

I forgot to mention that I'd checked the accuracy of the gauge with a test rig I cobbled up using an old acetylene regulator. The rig was tested with a couple of decent tire gauges and was pretty much on the money, the green tape making it spot on.
Having spent the last 25 years repairing old clocks and barometers the internal mechanism of the gauge "bent" to my will relatively easily !
With the rig sitting on the bench I could dial in whatever pressure I wanted, and make sure it was accurately reflected on the gauge which I could then tweak as required.
I'll let you know the outcome of the filter change.

Ralph.

[reb53]

So I removed the Fram filter, ( 3K miles old), and replaced it with a Ryco.
When I started, ( on cold oil), pressure was instantly 60, and I hadn't seen that for a while.
Going for a drive, and as the oil warmed, it slowly came down and settled at 41/42, ( ).
Trundling along gently at 2000 revs it refused to go lower, until I went down to 1000 revs where it dropped to 35.
This has to be the cheapest engine "overhaul" I've ever done !
Thanks for all the quick, and good, advice.

I've added a pic of the unused, identical, filter I had on standby.
It's highly unlikely to get used now.
I may open up the old one to see if there's anything obvious but I don't have the knowledge to make a sensible assessment.

Cheers,
Ralph.
N.Z.