Technical Drilling sump for oil temperature guage

[ClassicFiat500]

Hi everyone i am about to remove my alloy 4 litre sump to fit an oil temperature sensor as there is a flat 30 mm blank on one side obviously there to accommodate a sensor & hopefully re seal the very slight drip. I am taking the advise from the forum to not use a gasket obviously checking the flatness of the alloy, I will use a gasket sealant. However one question is with the sensor most seem to come with a 1/8th thread, what size hole should I drill and what side Tap should I order & do most sensors tap straight into the sump or do they have a nut on them to fit on the inside of the sump with a sealing washer Therefore eliminating having to Tap the alloy sump (drilling it doesn't bother me) it's just Tapping it,of which i am a little apprehensive of doing but if I have to i will do. Also are digital temperature gauges any good or are analogue more accurate ?
Any comments would be welcome

 

[Toshi 975]

Never heard of a nut on the inside. Most sensors I know of screw in against some sort of sealing washer be it fibre or copper. You need to know for sure what thread you have on the sensor. Going to show a picture of the Zeus table (no engineer would be without one back in the day) and a Starrett table for BSP threads. Shows a tapping size of 8.75mm which is pretty much 11/32".

 

[jackwhoo]

Don't drill till you have the sensor you are going to fit in your hand.

 

[ClassicFiat500]

Many thanks Toshi looks as if I am going to drill & Tapp the hole. Just got to find the right temp guage!

 

[jackwhoo]

Many thanks Toshi looks as if I am going to drill & Tapp the hole. Just got to find the right temp guage!

Find a decent instruction video of how to cut an internal thread. It is very important to turn the tap quarter turn anti clockwise for each half turn clock wise. If you don't the tap will bind in the hole and possibly snap.
You will need a taper tap to start cutting and a second cut tap as well.

 

[Bleeding Knuckles]

Many thanks Toshi looks as if I am going to drill & Tapp the hole. Just got to find the right temp guage!

Hi, As has been said don't drill or tap anything until you have the sender unit. Make sure that you have a matched set of sender and gauge (they work together) that work on a negative earth return. You will find that most fittings will probably have metric threads. it's not a difficult job.
Ian.

 

[phoenix1]

Just a question WHY . Yes why do you need one they have run fine in Italy which is a much hotter country for years without a problem.

 

[fiat500]

Just a question WHY . Yes why do you need one they have run fine in Italy which is a much hotter country for years without a problem.

I suppose it's interesting to see the range of temperature changes your engine experiences in much the same way that knowing the RPM or even the speed of your car maybe enhances the experience of driving; it also obviously serves as advance warning of potential problems.

But I fully agree with the sentiment implied. On this forum there has been a noticeable fixation on the subject of overheating over the last couple of years. Maybe it's the easy accessibilty of the engine that leads owners to be very aware of the temperature. It might be that the fact that an air-cooled engine doesn't dissipate its heat content via a water-jacket and radiator and has much more localised radiant heat spots which gives a more direct sense of the heat?

More frequently I think it's down to bigger engines and carburettors than designed using greater quantities of fuel creating more heat whilst the cooling system is only marginally improved.

Like you Bryan phoenix1, I've been fortunate with the heat situation, but that's in the north of Scotland where it's usually winter, where I rarely go faster than 70mph and with a standard (650) engine and impeller.

 

[jackwhoo]

Hi everyone i am about to remove my alloy 4 litre sump to fit an oil temperature sensor as there is a flat 30 mm blank on one side obviously there to accommodate a sensor & hopefully re seal the very slight drip. I am taking the advise from the forum to not use a gasket obviously checking the flatness of the alloy, I will use a gasket sealant. However one question is with the sensor most seem to come with a 1/8th thread, what size hole should I drill and what side Tap should I order & do most sensors tap straight into the sump or do they have a nut on them to fit on the inside of the sump with a sealing washer Therefore eliminating having to Tap the alloy sump (drilling it doesn't bother me) it's just Tapping it,of which i am a little apprehensive of doing but if I have to i will do. Also are digital temperature gauges any good or are analogue more accurate ?
Any comments would be welcome

As an alternative to drilling sump, how about bonding a thermocouple to the exterior of sump in an area out of the air flow but below the surface of the oil level and reading the temperature for that?
Much less invasive and the temperate of the sump will be very close to the temp of the oil.

You could insulate over thermocouple if you were concerned about accuracy.

If sump plug is in the side of the sump pan(rather than the bottom and hence vulnerable to damage) could you fit a temp sensor in a spare sump plug?

Jack

 

[ClassicFiat500]

Sump now drilled & tapped with new oil temp sender fitted, I have used cap head as it's much easier to tighten with a long Alen key rather than 10 mms socket then heat resistant gasket seal to refit the sump.
Just have to wire it in now to the guage. & refill with new oil & new filter. I was a little concerned on where the cable comes out from the sender out of the r/h corner of the sump, it's very close to the silencer about 2" so I will fit a small heat shield to guard the wires. Once again thanks for the invaluable help from everyone. Should anyone need an 1/8 NPT i will stick it on eBay tomorrow ,can't see me ever using it again (one carefully owner! 5 turns into aluminium).

 

[jackwhoo]

Sump now drilled & tapped with new oil temp sender fitted, I have used cap head as it's much easier to tighten with a long Alen key rather than 10 mms socket then heat resistant gasket seal to refit the sump.
Just have to wire it in now to the guage. & refill with new oil & new filter. I was a little concerned on where the cable comes out from the sender out of the r/h corner of the sump, it's very close to the silencer about 2" so I will fit a small heat shield to guard the wires. Once again thanks for the invaluable help from everyone. Should anyone need an 1/8 NPT i will stick it on eBay tomorrow ,can't see me ever using it again (one carefully owner! 5 turns into aluminium).

Sounds a good job any chance of a picture?
Jack

 

[ClassicFiat500]

Will post tomorrow

 

[gordinir8]

I am using aviation type wire which is made of Teflon, made it spiral and it's just fine. You can find such wire at eBay, and it can stand any heat or chemicals a car engine can produce.

 

[ClassicFiat500]

Hi interesting how many versions of Abarth labelled 3 or 4 litre sumps there are, on mine the oil sensor taps into the front r/h corner near the flywheel and emits close to be silencer. I have made up a narrow heat resistant flexible pipe to take the cable that comes up by the distributor (123) then drilled into the back of rear seat panel, then along the sill and up to the dash board. I am waiting or some more heat shield to place between the silencer and the sump, hopefully it will arrive today.. When fitted i will post some pics.