Oil pressure gauge

[reb53]

Had the water temp gauge pack up a few weeks ago.
Local instrument repair place sorted it and I re-fitted it this afternoon.

Now the oil pressure gauge, ( part of the same instrument), is playing up.
Very slow to start, doesn't rise very far, and stays up for a while when engine turned off.
When turned off it doesn't move for a while, slowly drops, and at about 20psi hesitates, then flicks back down to zero in an instant.
I assume you don't need to bleed the oil line to it as it wasn't bled when I pulled it out.
I bled it anyway which made b*gger all difference, so, before I take it back and wait for weeks, does anyone have any ideas of what I should check, or what I could try ?

I rather like the idea of a working oil pressure gauge on a Twink......

Ralph.

[Panda]

Hi Ralph, I would check for partial blockage in the line or at the small orifice on the gauge. simply pull out the gauge and stick the end of the oil line into a container and check for good flow on starting. Be ready to switch off in a hurry! Apply gentle air pressure to the back of the gauge connection and note what is happening to the needle, Increase pressure to check maximum pressure and note that needle should drop quickly when pressure released, unless you do have a block in which case it will be slow.
Good luck. Alan P.

[rgh0]

The needle or its movement can also be jamming on the glass or back plate if it was not replaced correctly when the work was done on the temp guage

cheers
Rohan

[reb53]

I've now taken it back to the repairer so we'll see what he finds.
Suspect I'll get the "we checked it and it's fine".
Yeah right, I've been looking at it for 40 years so I know how it should behave.

The oil flow was fine Alan, I didn't think it'd suddenly got blocked but I double checked.
I can only blow about 2psi so wasn't going to see much there if I blew into it.
And wasn't keen on sticking my air gun on it....

[reb53]

Well, got it back.
"We checked but seemed OK, tightened some screws and made a small adjustment, it is a bit worn you know".

"Worn", yeah right, compared with speedos and tachs it barely moves.

However, it's now working the way it used to, so something was found that they didn't want to fess up to.

[Monster666]

Mine goes up to 20 and stops there / I'm presuming it's the needle that's sticking as it does not fluctuate when i rev the engine

[Craven]

Not exactly a precision instrument. Crude would be polite.

[nmauduit]

Not exactly a precision instrument. Crude would be polite.

I beg to disagree: it can do the job very reliably and for a long time, in addition without the shortcomings of electrical counterparts (corroded contacts etc) - but yes for it to stay accurate it needs a bit of caution (don't drop it, don't bend the small innards springy things etc)...

[Craven]

I don?t disagree but it?s still a low grade and crudely executed gauge.

[StressCraxx]

As mechanical gauges go, it is not bad. The bourdon tube gauge as this one can be accurate and repeatable as long as they are repaired and calibrated correctly and not abused.

[Craven]

By way of illustration, the bent wire link is Smiths the other VDO. Both vehicle oil pressure gauges.

[Chancer]

Those 2 pictures say more than words the difference between the UK and German manufacturers back then, fast forward to today and one country has several global vehicle manufacturers, the other has Morgan no doubt with plenty of bent wires to be found

[StressCraxx]

Those 2 pictures say more than words the difference between the UK and German manufacturers back then, fast forward to today and one country has several global vehicle manufacturers, the other has Morgan no doubt with plenty of bent wires to be found

Of course, if you consider the modern Mini, the brilliant complexity of German engineering combined with the finest English workmanship. They are wonderful until service is required.

[reb53]

Well, got it back.
"We checked but seemed OK, tightened some screws and made a small adjustment, it is a bit worn you know".

"Worn", yeah right, compared with speedos and tachs it barely moves.

However, it's now working the way it used to, so something was found that they didn't want to fess up to.

Well, I spoke too soon.
Reverted to playing up, including either not moving unless tapped, or struggling up to 20 and going no further.
I initially didn't want to fiddle with it as they'd just fixed the temp part, and I was worried that they'd blame me if it also stopped working.
Once I realised how easily it comes apart, and that I could get the oil bit out by merely releasing the gauge from the dashboard and pulling it forward a little, I got it out.
The entire mechanism was covered in a thick, sticky, gloopy type oil that was simply clogging it up.
There was a lot of it and it looked old to me, not something that has recently been squirted in.

My suspicion is that it was the residue of 45 years worth of tiny oil leaks, and oil vapours, mixed with whatever the original lubricant was. Certainly nothing I've ever put in there, and I've had it 40 years.

A trip through the ultrasonic and some top quality clock oil and it now works as it should.
When I'd returned it to the repairer I would guess that, as suspected, it simply went on the shelf for a few weeks.

As an aside, easy for a dodgy seller to give themselves a few more pounds oil pressure by appropriate re-positioning of the needle...........

Ralph.

[billwill]

I don?t disagree but it?s still a low grade and crudely executed gauge.

Not much different than most pressure gauges though. A curved oval cross-section tube which tends to straighten out under internal pressure and the free end is linked to a pointer.

Victorian Steam technology..




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