Oil Pressure Gauge Problem

[David Stepney]

Ivor and Chris. Thank you for the advice. I have a plastic bowl to catch the oil when I try to bleed the gauge, and, no I will be wearing overalls.

[Greig Smith]

And newspaper, lots and lots of newspaper. over the floor, the seats, the firewall - been there, done this

I run the engine till it's hot, pull the plugs and then bleed it by spinning the starter

Aye
Greig

[David Stepney]

Thank you for that Greig, | was going to get the engine warm, let it idle and just slacken the union at the gauge, hoping that minimal oil pressure would prevent a 'Torrey Canyon' disaster.

[Nick Lettington]

I'm confused by all this talk of bleeding the oil pressure gauge. In 25 years of Austin 7 bodgery, I  have never found it necessary. 

A while ago, I had a gauge that pulsed on low revs and quivered as the revs climbed. It was suggested that the lack of an air bubble was causing the wobble as the air has a damping effect. As the pressure rises, the air will be compressed anyway. 

If it responds to tapping, I'd be more inclined to think it was a little bit of crud on the tiny mechanism that drives the needle.

Just my tuppence worth.

Oh and if anyone has a drip from their gauge, I still have some tiny leather washers for the end of the tube.

[David Stepney]

Nick. I think the theory is that, whilst what you say may be true for oil pressure somewhere between 20 and 50 lbs, I can envisage a situation where, at say 2lbs. the air bubble isn't compressed enough to transmit the pressure. Bleeding the gauge is (hopefully) going to be a 10 minute job. If it doesn't work and the fault lies within the gauge itself, Ruairidh has kindly offered to let me have a replacement. I shall report back later this weekend.

[AustinWood]

I've never experienced any problems with air in the oil pressure guage tube and have never bled the tube. The pressure should reach the guage whatever fluid is in the pipe.
I suspect air would be better than oil because oil is more viscous. Cleaning the pipe out completely might be best.
It seems to me probable that the guage itself is sticking on something. Perhaps the needle is touching the face. It's not difficult to take the front off the guage and see what's happening.

[Reckless Rat]

Mine sticks a bit too at low pressure but if I'm honest I don't look at it. It's just something else to distract you. As long as the little monkey with a lump hammer isn't trying to bash his way out of the crankcase then things are generally OK...

[Dave Mann]

I'm with Nick and Austin on this.

[Parazine]

I'm with Nick and Austin on this.

So am I. In 45 years of Austin Sevens, I've never bled a pressure gauge.

I've had several faulty gauges and several problem pipes/connections but that's all.

[David Stepney]

When I posted this thread, I had no idea that it would engender such an erudite discussion To bowdlerise William Shakespeare: "To bleed or not to bleed? That is the question." There seem to be two sides to this argument, both put forward by forumistas with impressive credentials.

I must admit that my first inclination is to suspect some mechanical derangement of the gauge internals, but, provided I take the required precautions against excessive oil spillage, I think I will try bleeding the pipe first to see if there is any improvement. Given that I shall do this with a warm engine, I shall know immediately whether it has worked or not. I shall perform the operation tomorrow and will report back.

In the meantime, thank you all for your advice and contributions.