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Installing an oil pressure warning light in an Austin Healey
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theopenroad



Joined: 06 Dec 2007
Posts: 19
Location: Warwick

PostPosted: Thu Feb 25, 2010 6:34 pm    Post subject: Installing an oil pressure warning light in an Austin Healey Reply with quote

Most modern cars have an orange oil pressure warning light to let you know if you are losing oil. But by the time it comes on it is probably too late and the damage is done. Many classic cars were fitted with an oil pressure gauge so that the driver could see what was actually happening. Some classics had both a gauge and an oil pressure just to make sure. The Open Road's Austin Healey http://www.theopenroad.co.uk/static_228.htm had just the gauge but after an incident in 2009 I decided to fit a warning light as well.

Modern drivers arenít really in control of their modern cars and know very little about what is happening under the bonnet. You have a temperature gauge so you can see if the car is over heating, other than that everything else is computer controlled with warning lights to let you know if the engine management or ABS fails, or if the oil level is low, or worse if you lose pressure. Most drivers are used to being ensconced in a quiet, comfortable car, listening to loud music and completely ignoring what the car is doing, unless it tells them there is a problem.

This was not the case on classic cars which had gauges to show whether the main systems were all working. A temperature gauge and fuel gauge of course but many of them were also fitted with rev counters and ammeters or battery gauges so the driver would know if the dynamo or alternator is charging properly. Many of them have an oil pressure gauge so the driver can monitor the oil pressure. The key word here is monitor.

Most engines run with oil pressures of anything from 40 to 100 pounds per square inch (psi). When an engine starts up the oil is cold and thick and the pressure will be high Ė maybe near the 100 psi mark. As the engine warms up, the oil thins out a bit and should settle down to around 40 to 60 psi depending on the engine. Oil pressure warning lamps tend to be set at about 5 to 10, so if the light comes on you have virtually no oil pressure left and a major problem.

Most of The Open Road's fleet http://www.theopenroad.co.uk of classic hire cars have pressure gauges fitted as standard and we do explain their function to the drivers when we take them out for a test drive at the start of their day's hire. On the rare occasions I have forgotten to mention this we have occasionally received a phone call later in the day when they have spotted that the pressure was lower than when they set off.

The Open Road had a particular situation develop on our Austin Healey 3000 during 2009. This is fitted with an oil pressure gauge but no warning light. To allow customers of all shapes and sizes to hire the car, we replaced the original 16Ē diameter steering wheel with a 14Ē diameter wheel. This gives the driver more room to enter and exit the cars and it doesnít rub on the tops of their legs.

However with the original steering wheel fitted, all the gauges including oil pressure were visible inside the rim of the steering wheel. The 14Ē wheel meant that the oil pressure gauge was now obscured by the rim and the driverís left hand. When moving, the drivers would have to make a deliberate movement to see the gauge and this assumes they remember they ought to check it, when modern cars donít have such devices.

Our Healey developed a slight oil leak from one of the engine oil seals, as classic cars tend to. Not normally a problem as I check the levels every time the car goes out on hire. Oil leaks by their nature tend to get worse rather than fix themselves so one day on checking the car over after it had been out on hire for a couple of days, I noticed that there was virtually no oil in it and when cornering the oil pressure would drop only to recover on the straight. This happens because the oil surges away from the pump pickup in the sump as the car turns one way, and flows back when it straightens up or turns the other way.

Many years ago in my youth I had a Triumph Spitfire with an oil leak. Being a lazy youngster I waited until the oil pressure gauge moved when going round a roundabout and treated this as a signal to top up the oil level. While that may have been acceptable on a Spitfire worth a few hundred pounds it is not a sensible approach on an Austin Healey worth over £20,000, particularly when the customer probably wonít notice the gauge anyway.

I had the oil seal replaced by my usual garage but asked them to add an oil pressure warning light as well. This is an easy enough procedure. The oil pressure gauge sensor screws into the engine block. This is removed and replace with a threaded brass T piece. The oil pressure gauge sensor is then fitted into one side of the T and the pressure sensor for the warning lamp fitted to the other side of the T. The convention is that oil warning lamps are orange so an orange light was fitted in the centre of the dashboard, next to the indicator warning light and wired to the sensor.

Now when the ignition is turned on, the oil lamp illuminates and goes off as soon as the engine is running. The oil pressure gauge still works as normal but even if it canít be seen behind the driverís left hand, he will know if there is a problem when he gets an orange light right between the eyes.
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Tony Merrygold
The Open Road - Classic Car Hire
www.theopenroad.co.uk
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1254
Location: Nottingham

PostPosted: Thu Feb 25, 2010 9:34 pm    Post subject: Reply with quote

Good advice - older cars are meant to use oil too and 300mpp was not considered unusual but of course sumps held up to 2 gallons.

1950's was when idiot lights became more common and even standard on on top of the range motors like the the Rover 3 and 3.5 Litre saloons. My pre-war Rover 16 (P2) has only the gauge.

Many motoring complained about the loss of the gauges - some did of course have both eg Rover 3 & 3.5 litre Coupes.

As you say it easy to fit one or other as an extra and even both if missing.

There is often an external oil feed pipe to rocker gear or oil filter that can be tapped into where no light or gauge is fitted

BMC models (eg. Mini etc) had a blocked filter light than many thought was an oil warning light
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Fri Feb 26, 2010 1:28 pm    Post subject: Reply with quote

Phil - Nottingham wrote:


There is often an external oil feed pipe to rocker gear or oil filter that can be tapped into where no light or gauge is fitted


Rocker feeds usually have a restrictor in the line to prevent full pressure being fed to the rockers. Often a part of the cylinder head or block. Connecting to the wrong side of the restrictor will give a low reading (if at all). Connections for both gauges and idiot lights need to be directly to the oil gallery which feeds the main and big end bearings. Adding one or the other is best done with a tee piece as mentioned earier.

The converse of this argument, which errs on the side of safety/protection, happened to me on my car which has both. Panic stepped in when the oil light came on, until I remembered to check the pressure gauge. Yes, you've guessed. The oil pressure switch went faulty, but the gauge showed the pressure was OK.
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