Want to install a mechanical oil pressure gauge in a 12L engine

[Dave64]

Hi All, Been trying to suss out just what is involved in replacing the original oil sending unit on a 200TDI 12L engine.

Don't like idiot lights, don't like electric/electronic gauges. Just want to plumb in an old fashioned mechanical oil pressure gauge. Tried several posts here on this forum, not on faceache and no wish to be, tried several links to other places with not much luck. All I really need to know is just EXACTLY where to plumb into it (top of filter housing looks obvious) but most importantly, EXACTLY what THREAD I can use. Heaps of places will sell you adapters/converters IF you know the one your after. Short of standing on my head, jammed between the chassis and the concrete, don't want to rip the old unit out until I know what parts I'll need.

Going to do the same with the water temperature sender, been told it is 5/8"UNF, at least it is easier to get at.

Thanks for any help

Dave64

[Bowie69]

I think there's some info in here:

 

The adapter used was this: https://www.ebay.co.uk/itm/LAND-ROVER-DEFENDER-DISCOVERY-300TDI-200TDI-OIL-PRESSURE-GAUGE-ADAPTOR-MLR-IE-/401420438140?

[Dave64]

Bowie69,

Thanks for that. As has been written before, only have the TDI 200 engine, not the rest of the vehicle. So I'm assuming that the switch at the top of the oil filter housing is NOT a warning (or what i call an idiot) light, but a sender for an electric/electronic gauge on the vehicle dash?

Still waiting for my workshop manual to arrive so a bit in the dark till it gets here. May have to bite the bullet and remove that sender and try and match the thread, plug it temporarily, just don't start the engine!

Depending which site you go on to, some say that it is 1/8"NPT, others say M10 but don't say what PITCH the actual thread is, 1.0-1.25 or 1.50. So much for metric Land Rovers when general consensus seems to be that the water temp sender on top of the thermostat housing is 5/8"UNF.

Don't really want or need one of those adapters to run both warning/ and mechanical oil senders, too close to chassis rail.

Read varying ideas on what to use, old truck driver who has always lived by my mechanical gauges, whatever their use.

Warning (low oil pressure) lights are OK, but if you sweep your gauges regularly, you should stay on top of any potential trouble.

Just as an aside, set up an 80mm VDO tacho (temporarily) to check alternator output, works fine if I hotwire the "ind" post direct from the ignition, via a diode, but for some reason doesn't like the warning light when it's hooked into the system. Could be something simple like wrong value warning lamp, further investigation needed. WITHOUT the diode in the temporary loom, engine fuel shut off won't work and shut the engine down, put the diode back in, works fine.

Cheers, Dave64

Edited January 3, 2018 by Dave64
correction in text

[western]

the sender at the top is the oil TEMP which operates a electric powered gauge

the factory oil pressure sender operates the red oil can light on the dash warning panel & is next to the bigger oil pressure sender which operates my electric oil pressure gauge, I'm not a fan of having hot oil piped into the cab even if its a very small amount.

 

the 2 oil pressure senders are well clear of the chassis & haven't caused me any concern.

[Dave64]

Thanks, Western,

Will go out and have another look!

Dave64

[Dave64]

OK, after much swearing and gashing of knuckles, got both the oil sender unit and the temperature sender out.

Measured with a digital vernier and a thread gauge, the oil sender is 10 X1.0 mm, got a correct size/thread bolt to screw in easily, so go into the Big Smoke tomorrow and try and find an adapter to 1/8 NPT/BSP.

Now, the temperature sender! I must have drawn the short straw! The fool thing is the odd man out, again measuring with the vernier and thread gauge, it is 16X1.0 mm. NOT 5/8UNF, NOT M16X1.5, but M16X1.0. So what that means it came out of (Disco or Defender) I do not have a clue!

A google search has turned up bookoo amounts of 16X1.5mm to 1/8 NPT/BSP adapters, (also 5/8"UNF),but none of the finer thread. Bloke I buy my bolts off has been in the game for 40 odd years and never even had a request for that size. (He tells me that metric has 4 types of thread, coarse, medium, fine and the hard to get SUPERFINE, which apparently is used in aircraft application as well as some automotive stuff.

If I cant get hold of an adapter, may have to do what a few others on here have done, punch the innards out of the original and drill and tap it to suit the more common threads, 1/8 NPT/BSP.

That means if ever I want to revert back to original, got to then find one.

Whilst I had the thermostat housing off (to get at the sender on the side), drilled and tapped that blind hole in the alloy to 1/2"BSP. Put a bung in it for the time being. Don't like using those ports on top of the thermo housing for gauges or even warning lights, if the thermostat has a failure, at least below the thermo you get a bit of warning of overheating.

Can utilise the new BSP 1/2" outlet for the 16"electric fan that's going to be installed, another idea I don't like is those capillary "balloons" you insert between the top radiator spigot and hose. Did the same deal with a Jeep I repowered with a Ford engine, put a two way switch in the system with a relay, ran manual/auto switching, gave years of trouble free service.

Thanks, Dave64

[Dave64]

Spent the best part of the day looking for an adapter or even a blank solid plug (has been confirmed by two different workshops as DEFINITELY M16X1 mm), plenty of 1.5 around, even get 1.25 at a pinch on special order), so ended up buying a 1/8 NPT tap, drilled the centre out on a lathe and screwed a hex headed plug into that for the time being. So, left with a 1/8 NPT female fitting that should take an electrical gauge, as long as the correct seat can be bought. Seen several 1/8 NPT male fittings that will screw into my new adapter, available, with seats, for 1/8-1/4-3/8 up to 1/2 NPT to take both electrical as well as capillary type senders. Hope I never have to reinstall the original, or even get hold of one for that matter. May be different overseas, but here they just look at you blankly and tell you there is no such sender size, and to stop smoking that stuff in the garage!

Dave64

[Ex Member]

The oil temperature sender is M16x1.5.  I installed one last year, so I can guarantee it....

The oil pressure port is M10x1.0.  Very common.  Buy a Tee extension.  https://www.merlinmotorsport.co.uk/s/instruments-gauges/oil-t-pieces-line/page:2

[Dave64]

Red90,

                     Got the oil pressure port adapter no problems.

I can only go on what I have been shown and told, when it comes to the water temperature port thread. Yours was, as you say, 1.5 pitch, this one is definitely 1.0, watched the bolt man check it against a metric thread gauge in front of me. Yesterday, took the sender unit to two different hydraulic fitting specialists, both confirmed it as 16X1.0. Bit of a moot point now, as can be seen from accompanying photos, already drilled and re-tapped to 1/8NPT.

A Land Rover specialist told me that , and again it has been confirmed here on other parts of this forum, that depending if the 12L engine came out of either a Defender or a Discovery, COULD account for the disparity. He also added that a lot of L/R owners are under the impression that the port thread is 5/8"UNF. Not so, it is a lot coarser than mine.

No wish to get into any sort of argument about it, yours is 1.5 pitch, mine is 1.0 pitch. Just as to WHY they are different is anybody's guess. Maybe simply that if you need a replacement sender unit you have to go back to L/R for original O.E.?

Just as an aside, the L/R specialist said that when they (L/R) went metric, they would not have mixed up a combination of metric/BSF/NPT/BSP on the same unit.

Well, I had a GM product quite some time ago, was a model in between major model changes and they used every conceivable old component they could find,made it very tricky when trying to identify correct replacement parts.

Cheers, Dave64

[Retroanaconda]

Plenty of mixed threads on a Land Rover. My 200Tdi engine definitely has UNF and metric threads, not sure about BSF but wouldn’t surprise me given it's traceable heritage back to the older engines. Rest of the vehicle is a mixture too. Even had some 2BA screws on the fuel filler though that might not have been original!

Glad you got it sorted anyhow.

[western]

200Tdi 12L prefix engines are Discovery or RR units,

the Defender 200TDi is 11L prefix & is definitely a 5/8 unf thread for the coolant temp sender, 

[Ex Member]

5/8 UNF and M16x1.5 are basically the same, so it may have been 5/8".

[Dave64]

Well, all I can say is that very little surprises me anymore when it comes to what some manufacturers throw at you. Already been drilled and tapped to 1/8 NPT, which would seem to be pretty common thread. Bought an el-cheapo water temp gauge and installed it after checking the thermostat in a saucepan of water bringing it to the boil. Gauge shows opening between 175* and 190* so I'm in the ball park.

Had an old Stewart Warner oil pressure gauge squirreled away in the shed, removed the M10X1 oil sender unit, screwed in the 1/8NPT adapter and 90* elbow, cold idle comes up around the 45lb/in, drops back to bit above 35lb/in when engine hot idle. Under no-load 2000rpm going by pulse tacho, engine oil pressure running 60-65 lb/in. Still waiting for the Haynes workshop manual but rang a bloke up who had the engine originally, said the figures sound about normal for an engine that has roughly 250k on it. He had the injector pump done not long before he pulled the engine out, but not the injectors themselves.

Doesn't seem to matter if engine is hot or cold, upon initial start gives one puff of smoke, then runs clean, although to me it smells like it may be over-fuelling just a bit, even with the garage door wide open.

Middle of summer here, 44 celsius outside, so would expect the engine to maintain heat, even under no load, no engine fan fitted and original R/Rover x-flow radiator, no shroud. Minor oil leaks around sump gasket, rocker box gasket, but all in all, engine seems to tick over quite well, only revved it out to about 2500 RPM very briefly as tacho has to be calibrated correctly.

Think it will make a nice little engine, can only compare it with my 2004 Toyota Prado 3.0L TDI or the optional Perkins 4/203 that the project vehicle came out with back in the mid fifties, so not really an accurate guide. Old Perkins 4/203 were just that, good reliable engine, but way outdated today. Even the 3.0L Toyota, although a high torque engine for their size have been surpassed with modern CRD engines given the same capacities.

But, been a bit of fun getting it up and running, learned a bit along the way, including new swear words when things weren't going as well as I thought they should, educated the neighbour's kids along with it.

Cheers, Dave64

[Ex Member]

You need to wait until the oil is properly hot to know what the real oil pressure will be.  You have to run the engine hard for a long period to get the oil hot.

Do not waste any time or money on a Haynes manual.  Use a genuine one.  They are free to download or not expensive to purchase.

[Dave64]

Thanks, Red90,

Moved on from oil pressure issues, seems to be within the ball park on figures quoted here and elsewhere.

Only to discover charging system hiccups. 

Only way I can get the alternator to charge as expected, was to put a 12volt 5watt NON-DIRECTIONAL festoon in series with the IGN to IND post. Anything of higher value, fuel shut off won't work, anything lesser value and the alternator won't show charge.

Seems like part of the problem may have been that both warning lamps I tried were ONE-DIRECTIONAL, pulled them out of the system and hooked directly to the battery, will light up one way with leads, reverse them and nothing.

The only load I have on the system at the moment is the fuel shut off, an electric water temperature gauge, an old 0-16 volt test voltmeter and the 5 watt globe for the indicator lamp.

With a multimeter, once engine started and running, main alternator output post is showing between 11.5 and around 12.8 volts, fluctuating. Yet tested at the battery terminals, a steady 14.4 volts.

Original wiring diagram I gleaned from this forum shows the charging system for the 200 TDI 12L engine as having both a diode and a small value resistor in the system, tried both, didn't seem to achieve anything, maybe the values weren't compatible with the warning lamps I was using.

Asked an auto electrician in closest town, reckons you shouldn't need either if you have the correct value warning lamp, didn't ask about the fluctuating voltage as only became aware of it later today.

Cheers, Dave64

[western]

Quote

a diode and a small value resistor in the system, 

same item its within the dash loom in what looks like a in line fuse holder, if you need to gain access to it most of the dash has to come off, as it lives behind the raised edge between instrument pack & centre of the dash, just to left of the heater blower slider, 

[Dave64]

Western,

Ah, problem. Only using the 12L 200 engine in another project. So, don't even have a dash, let alone the rest of the vehicle.

Engine sitting in another bare chassis, just sorting out some plumbing as well as wiring. Want to sort it out before working on cabin.

Thanks, Dave64

[Ex Member]

I gave you the correct wiring in the other thread.  Follow it.  If you are using an LED for the indicator, the ground side needs to be towards the alternator.

[Dave64]

Yes, you did. And I copied it.

But all I come up with is a G101 Resistor and a G126 Diode, what I'm trying to determine is the value of each of those components.I put them into a google search and it just leads me back to these topics on this forum or one similar.

Alright for some of you blokes who have ready access to replacement shops on every second corner, some of us live miles from anywhere, the only way to get reasonable info is to ask on these forums.

[Dave64]

OK, followed instructions and wiring diagram explicitly, seems to be working fine with the 12v 2w non-directional lamp and diode in place. Tried 2w-3w-4w bulbs, didn't seem to matter much.

I will have to get the alternator sussed out as the voltage is still fluctuating wildly at idle 10.9v to 13.5v, bring engine up to 2000 RPM, voltage drops below 12v.

May have smoked something inside the alternator, was tested OK before I got my hands on it!

Thanks, Dave64

[Ex Member]

100 ohm, 5 watt resistor.

2 amp diode should be fine.

[Bowie69]

I've seen a relay coil used for this purpose...

[Dave64]

Thanks for the heads up, Guys.

Will take the alternator to the sparky's, few blokes reckon I may have cooked a diode or something inside.

Dave64

[Dave64]

Alternator checked out OK, reinstalled, started from scratch again and whatever I've done, seems to have cured it. Half the problem may have been a brand new dodgy ammeter.

Now reads, ign off, engine stopped----12.3v

ign on with fuel shut off, tacho and temp gauge--eng stopped---12.0v

eng idling, --13.5--12.9v

engine RPM, 1500-2000,---13.4-13.8v

battery with everything off--12.4v

battery with engine running--14.4v

So that's going to do me for a while.

Dave64

BTW, read either on here or maybe another L/R forum, how some bloke was using the temp sensor in the top of the thermo housing (12L engine) for a thermoswitch to operate the electric radiator fan he replaced the conventional fan with. switch PRC 3505. 

[Ex Member]

You could.  But...  It is meant as a high temperature switch to turn on the A/C fan(s).  It turns on at 100 C, which is a bit high, IMO.  In addition, it is normally closed, so you need a relay to get the fan to work.  You are better off buying a switch meant for normal engine fan control.  Lots of those around.

The important thing is getting a real fan with proper air flow rates.  I'm not sure what this engine is being fit into and what you are using for a radiator and intercooler...but with the normal Defender 200TDI setup, the "Taurus" two speed fan fits really well and has a huge air flow.  I seem to recall they were on some Ford or another in your part of the world.

Here are some photos of one installed on my 90.  http://red90.ca/photos/land-rovers/taurus-fan/  The same fan has been going strong for 10 years with no issues.

Edited January 9, 2018 by Red90