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MG Midget and Sprite General - How to test a Smiths oil gauge?

Hi,

I've looked through the archives but I haven't found anything of use. I've got a 1500 midget and thus only a water temp gauge. I have finally purchased a dual gauge second hand and at a good price too!

Now the question, I have dipped the bulb in boiling water to establish whether the water temp works (which it does) but how can I test the oil pressure? I've blown down the line with all my might but I can't get the needle to move. I haven't got a compressor in my garage so what can I do?

Thanks in advance,

Steve
Steve H K-ser

foot pump?
garage tyre compressor?
Mick struggling with the wiring

Cheers Mick,

It's getting a solid connection between the two to create the pressure though!
Steve H K-ser

just fit it and see what happens, the oil part of the dual gauge is pretty reliable, I've never had a duff one.
David Smith

I agree, just connect the oil line and fire up the engine. You don't even need to fit it in the dashboard.
Lawrence Slater

This may sound a bit like a circular logic. But if your engine is currently known to be in reasonably good condition with normal oil pressure, then fit the gauge and run the engine up to normal operating temperature. Then if necessary adjust the needle to what the pressure should be. (This would be 60psi @ 3500rpm if it were a 1275, but the 1500 may be different).

That at least will give you a consistent start point. If in future the needle varies from this then you are alerted that something has caused this change and can investigate or act accordingly.
Guy

Cheers guys, I have a K series engine now which is mid conversion so I can't run the engine up just yet :(
Steve H K-ser

Ah then you have to improvise.

Do you have the oil line with the gauge?

The end of the oil line is connected via a flexible rubber hose to the output on the block of the engine.

So you can do the same thing with an airline or foot pump.

Get a length of small bore rubber hose, and use that and small jubilee clips, to make an air/oil tight seal. Then apply pressure.

However, air compresses, whilst oil does not, so I don't know if this will work.

If not then you can try a grease/oil gun to do the same thing.
Lawrence Slater

Hi Lawrence

Pressure is pressure whether gas or liquid...

A
Anthony Cutler

Lawrence, I'll give that a go, I've got a remote filter head with plenty of line off of it, I'll try and get the foot pump on it to create a bit of pressure.

Cheers all :)
Steve H K-ser

Hi Anthony,

but won't it take quite a bit of effort to compress the air before the needle moves?

I just figured that oil would be easier than air, although maybe a bit messy. I'm only guessing. :)
Lawrence Slater

Hi Lawrence and Steve

It takes exactly the same pressure using air as it does liquid to move the gauge.
Therefore 50 psi oil pressure believe it or not is just the same as 50 psi air pressure (Scotty) :)

Steve I had a bit of a gigle when I imagined you blowing into the gauge. It is impossible almost for a human to blow anywhere near 1 psi let alone 10 or 20 to significantly display on the gauge.

In fact just a couple of psi pressure in the human body would rip your internal organs apart.

As David suggests the oil pressure gauge is a very reliable piece of kit due mainly to the fact that damage to these items would only occur with over pressurization, not sure any engine has the capacity to achieve that.
Robert (Bob) Midget Turbo

You'll need to do more pumping if you want to build the pressure using gas... but that's only because you need to do work to compress the gas (some of which is given off as heat). However, 15psi at one end of a pipe filled with gas is the same as 15 psi when filled with oil (assumes no net flow).

I always have a bike inner tube, which has been sliced and one end closed off, is very useful in the garage for all sorts of things, incl bleeding clutch, brakes... and maybe testing gauges.

A
Anthony Cutler

Bob, glad it made you smile Lol. I'll try and get something rigged up this weekend possibly as AC mentioned.

I'll keep you posted!

Steve
Steve H K-ser

Hi Anthony/bob,

Yup DOH, my brain must have disengaged when I wrote that cobblers about air. Thanks for re-engaging it again without calling me an idiot. :).

Anthony, I'm intrigued by the bikke inner tube. Can you explain more detail about how to use it for bleeding brakes? Sounds like a very useful bit of kit, and I have a spare car and bike tube in the garage.

Cheers.



Lawrence Slater

Yes; cut the tube about 6" from the valve, so you have a long section and short section either side of it. Then close up the short side by rolling it tightly and secure it eg. with jubilee clip.

Fill the master cylinder with fluid. Attach the open end of the tube to the mouth of the reservoir with a jubilee clip.

Pump a little pressure into the tube. Then release the nipple on the slave cylinder and fluid will emerge. Don't let more than half the capacity of the reservoir out - you'll be draining into a jar... could make it similar size to the reservoir to judge more easily.

Every now and again, release the tube from the reservoir and refill.

There is no easier and cheaper way to do this, esp. if your person operating the clutch/brake pedal is not always sensitive to instruction or easily bored...(!)

Our garages are full of tools we didn't realise. I'm always pleased to hear/read about a job made more easy by things lying around, instead of looking to buy a tool for a purpose and finding:

a) it can't be used for similar jobs as it's too purpose-specific
b) it doesn't work particularly well
c) part of it becomes lost since it's rarely used
d) you can't get to a shop as it's closed, too far away without the use of the car that's being repaired
e) etc

A
Anthony Cutler

<<Our garages are full of tools we didn't realise. I'm always pleased to hear/read about a job made more easy by things lying around, instead of looking to buy a tool for a purpose>>

A bit like using an acro prop for removing a tyre ;o)
Dave O'Neill 2

Yup exactly Dave, my acro prop came in very handy.

Anthony thanks, that's so brilliantly simple it's ingenious.

Up until now my self bleed kit employed a device called a bullworker, as pictured.

You compress it, and place one end on the drivers seat, and the other on the pedal.

Then you open the valve, the bullworker pushes the pedal to the floor, and you close the nipple whilst it's still squirting fluid into the jar.

I've used this method for years, but now I'm going to convert to the rubber tube. I'm getting to old to excercise anyway. LOL.



Lawrence Slater

Steve - surely there is SOMEBODY in Lincolnshire who would be willing to help you out?

I have the dual gauge in Primerose and Bitsa so was a bit confused when you said you only had a water one, but then remember that there were a few years that they did just the one - silly proceedure if you ask me, but, since you didn't .... :)

Sorry I can't help out, unless you were totally desparate - and then you'd probably have to come down here as I can't get time away at the moment with winter coming up alarmingly quickly.
rachmacb

I thought that is what you were using the tube for Ant!

My method for bleeding brakes is very similar. I cut the hose off a bu99ered foot pump (mini compressor) and attached this to a secondhand Master Cylinder cap I then fill the master cylinder and with the cap tightly in place I put the tyre end of the hose onto my front wheel and bleed as you describe. As you say a simple way of pressurizing the system.

When I have finished I pump up my front tyre to make up for the air loss. In fact before I start I generally drop the pressure in the front tyre to avoid too much pressure being applied to the master cylinder.

I do like to little get arounds!! LOL

Could have sworn I lived in Lincolnshire but maybe I was mistaken LOL.
Bob Turbo Midget England

This thread was discussed between 16/10/2011 and 18/10/2011

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