13 replies to this topic

[Skam2001]

Hi all
I am in the process of replacing my 998 for a slightly tuned 1275 from an MG, I currently only have a centre speedo but want to fit electrical gauges for water temperature and oil pressure. My question is what exactly do I need? I have a oil sender unit in the block at the moment which wasn't being used, it's about the size of a small spark plug with one make spade connection on it-will this work? Or do I need one of the larger types with the round body?

Any help would really be appreciated

Andy

[dklawson]

I assume you mean a Metro engine?

 

Your center speedometer will need a voltage stabilizer bolted to the back.  It lowers the car's operating voltage from a bit over 14V down to a nominal 10V which the gauges require.  A dark green wire fed from the fuse box supplies the voltage stabilizer's "B" terminal.  Light green wires leave the stabilizer's "I" terminal and go to ONE of the two terminal on the back of each gauge (either terminal).  

 

I don't know if Lucas has specific color codes for electric oil pressure sending unit wires.  The correct color code for electric water temperature is "green/blue".  From the second terminal on the temperature gauge you run the green/blue wire to the sending unit in the cylinder head.

 

What you are calling an oil sending unit is probably just the low oil pressure warning switch.  It will be located on the engine block to the left of the distributor.  Again, it is not a sending unit... but a switch.  You will need to find an electric oil pressure gauge with matching sender and swap it out for the switch in the block.

 

Incidentally... the only car I know of that used a Smiths electric oil pressure gauge was on the MGB (but there probably were a few others).  They are problematic and the sending units are very expensive.  Most MGB owners I know switch from the electric oil pressure gauge back to mechanical once they find a good used one. 

[KernowCooper]

The unit you refer to in the block sounds to me to be a oil pressure switch which warns on low oil pressure, do you not currently have a yellow light in the central speedo not connected to the switch?

 

Smiths oil pressure gauges are normally of the type which displays the oil pressure connected to a T Piece into the Oil Pressure Switch hole, and a small bore pipe then connects to the gauge.

 

The temperature gauge is connected to a sender unit on the thermostat end of the cylinder head and is fed from the 10v voltage regulator normall found on the back  of the central speedo

 

Doug is a faster typer than me lol

Edited by KernowCooper, 25 February 2015 - 09:54 PM.

[Skam2001]

Thanks guys that's a massive help! Doug thanks for the wire colours will give me something to hunt for! Just to clarify would you suggest electrical water temperature and mechanical oil pressure?

And yes it is an MG Metro lump!

[dklawson]

I personally like mechanical gauges for both temperature and oil pressure.  However, there are plenty of electrical water temperature gauges and senders out there and they were used as stock on many Minis.  I do not like electrical oil pressure gauges but to each his own.  The mechanical oil pressure gauges just seem to be more accurate and respond quicker.

[Skam2001]

Ok maybe some food for thought! Thanks very much for your response! I'm always surprised by the speed and conscience nature of everyone's responses on here! This is my first project and hopefully in time I will be able to impart some knowledge back into the forum!!

Thanks again

[Spider]

Sorry to go the other way to what Doug is suggesting here and years ago, that's what I would have done too (in regards to mechanical Oil Pressure Gauge), however twice in recent times that I know of owners have had the feed pipe let go behind the gauge (usually it's at the engine), one just made a horrible mess in the car, however the other actually sprayed the driver while on the move, he did get some on his face, though not serious, it could have been and he did say while it started off 'cool' it quickly got hot as the hotter oil from the engine was coming through. Maybe something to consider when choosing between gauges. Personally, I'd rather have a gauge not working than a failed hose (even in the engine bay).

 

So, if it were me, I'd be fitting an electric gauge. The senders from the Jags and a few other cars are compatible and reliable, though even the new ones from CAI are quite OK.

Edited by Moke Spider, 26 February 2015 - 12:07 AM.

[KernowCooper]

I have a aeroquip stainless braded oil feed pipe on mine far more robust the the aftermarket nylon tubing, should avoid the blow out of the feed pipe.

[cal844]

I use mechanical(pipe fed) guages, far more reliable, the only issue is that if the nut goes loose at the guage end youll end up with oil everywhere

[dklawson]

As Dave, I have a braided oil pressure line on one of my British cars and copper gauge lines on the other two.  I used to run the nylon tubing but after hitting it with a wrench on the Mini (and shearing it off) I no longer use nylon.  

 

Chris, oil pressure lines do fail as you say.  However, it is rare.  The argument could also be made that copper/rubber oil pressure lines and mechanical pressure gauges were selected by BMC for Minis outfitted with the gauge.

[jaydee]

My oil gauge is connected via a copper pipe

Feels a better reliable alternative to nylon pipes

[Skam2001]

Thanks for all the replies! Looks like a flip of the coin! Seems everyone's preference is based on personal experience. I think I'll go down the mechanical gauge to start with and see how that goes!

[dklawson]

Yes indeed.  We each have preferences based on past experiences.

 

Since this will be a trial run for you, invest in the copper gauge installation tubing kit that Jaydee mentioned.  They cost only a tiny bit more than the nylon kits but they are much more robust.  Between the engine block and the car's firewall, coil the excess tubing length to act as a spring.  This will absorb engine vibration and motion which in turn will prolong the tubing life.  If you like the way the gauge works, invest in a braided oil line later as they are a bigger investment.

 

As a footnote to all this oil pressure gauge talk we need to at least mention the connection at the gauge.  IF you install a Smiths oil pressure gauge, it originally would have been connected using a flat-face compression fitting with a little leather flat washer seal.  Those seals and the female fittings are hard to find.  Don't despair.  The copper gauge line kits typically come with a 1/8" NPT female pipe to tubing compression fitting.  Apply Teflon (PTFE) tape to the male gauge threads, install the female fitting securely, and you will have no leaks.  Do not omit the PTFE tape.

[Skam2001]

Thanks for the advice on the pipe work! I would hate to blow a line and have oil everywhere!