water temperature sender help

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marsonpee

New Member
Posts
18
Location
Hull
Hello
ive got a 200tdi disco 1 engine fitted into a 1986 chassis which i assume had a 2.5n/a engine in it. The water temperature gauge always shows high after a few minutes an ive been told that its because the sender and the gauge dont match up properly. somebody told me it is simply a case of finding a 2.5 n/a sender and fitting that into the 200tdi or is it a little more tricky than that. Any help would be great, thanks.
 
the 2.5 n/a sender has a different thread and wont fit the hole on the 200 block - you could buy a tap and redo the hole or simply just get a temp guage out of a 200 engine defender

such as ebay item 270201999898 - but ensure it's from a 200 engined vehicle first
 
Although there are some electrical gauges that need their matched sensor, most are made to work with one of two standard sensors these days, Euro and USA. With age, dirty contacts and corrosion, resistances can change. This alters the reading and reliability as the electrical gauge is just recording changes in resistance.
First clean all contacts, including earths, behind the instrument panel.
Second, there may be a cable from the starter motor mount to the chassis and these contacts may also be dirty.
Third, and I would do this anyway, a poor earth from the gauges to the engine can also result in a high reading. Behind the instrument panel you will see the earth wires bolted to the bulkhead. Open the bonnet and look for the bolt on the bulkhead within the engine bay that you can then connect with heavy cable to a good earth on the engine. Ensure you have good clean contacts.
Run the engine and see if this has cured the problem.
Still a problem?
If you know somebody with a remote temperature sensor (looks like a small pistol and uses an IR beam to spot check temp) you can first check that the indicated temperature is wrong. If you have a cooling problem changing the gauge will not help!
Spot check the temp at the thermostat housing as the engine warms up and also along the engine block and bottom and top hoses.
The top hoses will not heat up fully until the thermostat starts to open and it will then settle to the temp of the fitted thermostat.
Anything higher than that and it should be investigated.
If it's all ok, why not just note the true normal on the gauge and relax?
 
maxjones said:
Although there are some electrical gauges that need their matched sensor, most are made to work with one of two standard sensors these days, Euro and USA. With age, dirty contacts and corrosion, resistances can change. This alters the reading and reliability as the electrical gauge is just recording changes in resistance.
First clean all contacts, including earths, behind the instrument panel.
Second, there may be a cable from the starter motor mount to the chassis and these contacts may also be dirty.
Third, and I would do this anyway, a poor earth from the gauges to the engine can also result in a high reading. Behind the instrument panel you will see the earth wires bolted to the bulkhead. Open the bonnet and look for the bolt on the bulkhead within the engine bay that you can then connect with heavy cable to a good earth on the engine. Ensure you have good clean contacts.
Run the engine and see if this has cured the problem.
Still a problem?
If you know somebody with a remote temperature sensor (looks like a small pistol and uses an IR beam to spot check temp) you can first check that the indicated temperature is wrong. If you have a cooling problem changing the gauge will not help!
Spot check the temp at the thermostat housing as the engine warms up and also along the engine block and bottom and top hoses.
The top hoses will not heat up fully until the thermostat starts to open and it will then settle to the temp of the fitted thermostat.
Anything higher than that and it should be investigated.
If it's all ok, why not just note the true normal on the gauge and relax?
Click to expand...

don’t you think you’re over complicating things a tad ? - all he needs is to swap his gauge
 
maxjones said:
Although there are some electrical gauges that need their matched sensor, most are made to work with one of two standard sensors these days, Euro and USA. With age, dirty contacts and corrosion, resistances can change. This alters the reading and reliability as the electrical gauge is just recording changes in resistance.
First clean all contacts, including earths, behind the instrument panel.
Second, there may be a cable from the starter motor mount to the chassis and these contacts may also be dirty.
Third, and I would do this anyway, a poor earth from the gauges to the engine can also result in a high reading. Behind the instrument panel you will see the earth wires bolted to the bulkhead. Open the bonnet and look for the bolt on the bulkhead within the engine bay that you can then connect with heavy cable to a good earth on the engine. Ensure you have good clean contacts.
Run the engine and see if this has cured the problem.
Still a problem?
If you know somebody with a remote temperature sensor (looks like a small pistol and uses an IR beam to spot check temp) you can first check that the indicated temperature is wrong. If you have a cooling problem changing the gauge will not help!
Spot check the temp at the thermostat housing as the engine warms up and also along the engine block and bottom and top hoses.
The top hoses will not heat up fully until the thermostat starts to open and it will then settle to the temp of the fitted thermostat.
Anything higher than that and it should be investigated.
If it's all ok, why not just note the true normal on the gauge and relax?
Click to expand...



if you do a search on this form you find information that contridicks yer bit about only two types. there have bin numerous cases where after fitting a different engine the temp gauge has gone batty. This has always bin overcome by fitting the correct sender to match the gauge or vicky verky
 
Hi Slob. - There are NOW only two STANDARDS of sender. (four if you count single station and dual station units in each basic standard)
That is not to say that you will not find other, non-standard units about.

Hi Sean. - No, I'm not over complicating things.
It costs money to fit a new part, find it's not cured the problem buy another, find the same.
First rule - Test the system to see if that is the fault, not the gauge. The most common fault on instrumentation is faulty wiring, particularly the earth.
The cure could cost nothing more than a good clean and a bit of wire.
There are many modern garage 'fitters' who continue to fit new bits until they stumble across the cure. It all costs the customer money.
Land Rovers, being made of aluminium and steel, are very prone to galvanic corrosion which is a regular cause of electrical faults. In fitting a new part you often clean the contacts as you work and when the fault is cured you think it was the new part that did it!
Save money and frustration by testing first.
 
maxjones said:
Hi Slob. - There are NOW only two STANDARDS of sender. (four if you count single station and dual station units in each basic standard)
That is not to say that you will not find other, non-standard units about.

.
Click to expand...



so is there two types or not? in yer previous post yer made it sound like there was only two types available not yer saying they're are any number of types available... and yer int explained why folk that have fitted the correct matching pair have overcome the problem that shows up with an engine change... it all very well to witter on about steel and ally corrosion causing resistance problems but that int gonna happen over the course of an engine change nor is it gonna uncorode with the fitting of a different part.
 
maxjones said:
Hi Slob. - There are NOW only two STANDARDS of sender. (four if you count single station and dual station units in each basic standard)
That is not to say that you will not find other, non-standard units about.

Hi Sean. - No, I'm not over complicating things.
It costs money to fit a new part, find it's not cured the problem buy another, find the same.
First rule - Test the system to see if that is the fault, not the gauge. The most common fault on instrumentation is faulty wiring, particularly the earth.
The cure could cost nothing more than a good clean and a bit of wire.
There are many modern garage 'fitters' who continue to fit new bits until they stumble across the cure. It all costs the customer money.
Land Rovers, being made of aluminium and steel, are very prone to galvanic corrosion which is a regular cause of electrical faults. In fitting a new part you often clean the contacts as you work and when the fault is cured you think it was the new part that did it!
Save money and frustration by testing first.
Click to expand...

in the good old days i'd have told you to stop talking bollocks but seeing as i can't i'll just have to say that i don't agree with what you say

it's a very well documented fact that when changing engines that the guage has to match the sender - seeing as it's usually not possible to fit the orginal sender to the 200 due to thread sizes the route normally taken is to replace the orginal temp guage with one from a 200Tdi engined defender - this is exactly what i have done at least 5 times now

guages can be found for less than a tenner and takes less than 20 minutes to fit

it also costs money to fanny about "testing" for a fault that clearly isnt there - the OP didnt say that the guage read incorrectly before the engine change
 
yella said:
if the temp sendor is not matched to the temp gauge then it will read either too hot or too cold. if there were only 2 types of temp sendors then why the **** do halfords have a shelf full.
Click to expand...

CORRECT!

And the problem is these things only masure a very narrow band ot temperatures, like from about 70°C to perhaps 110°C. Below and above that sort of span they don't record at all.

The crucial thing to try for is to get a SENDER that matches the CAR, regardless of what engine you decide to fit. Many Landy engines have several drilled and tapped holes for sender units. The 2.5NA engines have at least TWO on the top left rear of the head. If the one fitted is wrong, leave it there to block the hole, undo the other blanking plug and screw in the right sender. It's that easy.

If your engine doesn' t have spare tapped holes, you'll need a little imagination, but they are all standard threads, and there are plenty suitable locations where you can drill and tap for it.

Rocket science it is not, but the sender MUST match the car, meaning the gauge itself.

CharlesY
 
CharlesY said:
CORRECT!

And the problem is these things only masure a very narrow band ot temperatures, like from about 70°C to perhaps 110°C. Below and above that sort of span they don't record at all.

The crucial thing to try for is to get a SENDER that matches the CAR, regardless of what engine you decide to fit. Many Landy engines have several drilled and tapped holes for sender units. The 2.5NA engines have at least TWO on the top left rear of the head. If the one fitted is wrong, leave it there to block the hole, undo the other blanking plug and screw in the right sender. It's that easy.

If your engine doesn' t have spare tapped holes, you'll need a little imagination, but they are all standard threads, and there are plenty suitable locations where you can drill and tap for it.

Rocket science it is not, but the sender MUST match the car, meaning the gauge itself.

CharlesY
Click to expand...

there's an echo in here

the n/a may well have more than one tapped hole but this question tends to be asked when a 200Tdi has been used to replace either the TD or the n/a etc - people simply expect to be able to use their orginal guage and the sender that came with the new 200 engine - as has been mentioned a zillions times this will result in the guage giving a falsely high reading

putting a temp guage from a 200Tdi engined defender will result in the correct indication

however - the senders used in the n/a and TD have a different thread to the 200Tdi - plus the fact that there isnt a suitable place to drill and tap a new hole (on the 200 block) for the orginal sender means that the ONLY way to acheive a correctly reading guage is to use the 200 guage
 
The two types (standards) work by, in the one case, measuring an increase in electrical resistance of the sensor as engine temperature increases, the other measures a reduction in resistance of the sensor as temperature increases. This change in resistance registers on the gauge as a change in voltage, which the dial marks as temperature.
Manufacturers like to make you spend money on their products, so many of them change the threads, resistances and so on to their own advantage.
As for an engine change, I have known a well respected Land Rover specialist complete a full rebuild, including engine, and still not notice the lack of a proper engine to chassis/body earth strap. This was the cause of the instrumentation fault. Yes, it might be necessary to change the gauge to get a 'normal' reading in the middle of the dial BUT;
My point remains the same. First make sure the electrical continuity is good before spending money.
 
yes we all know about NTC and PTC senders

why are you answering a question that hasnt been asked ?

if the OP asked something like "my temp guage keeps going up and down" then yes i'd have said check yer connections - but he asked a question directly in relation to changing an engine, for which the answer was simply to match the guage and sender
 
So we agree there are two standards then. ( I would only say that NOT all people know about NTC / PTC )
And we agree that it is manufacturers who cloud the issue with their own minor changes in resistance, thread etc.
We only differ on opinion of what to do.
Having seen examples of engine changes where the earth strap was left off, causing lots of problems, I wanted to ensure this was checked. Perhaps my lack of confidence in others, particularly 'specialists', caused me to overcomplicate things.
I would always test first anyway as I've had experience of resistance faults that did not show a fluctuating reading.
Where the needle points is less important than knowing it's 'normal' and being able to identify changes. Knowing that the wiring is fine you can then chose to live with the gauge or change it.
 
you ever think about joining a circus? you go down a treat as the clown that travels backwards on his bike. dunt think i've ever seen anyone backpedal as much as wot you do
 
Backpedal? Me?
Always happy to admit I'm wrong, but as the OP did not state that he was the person who did the engine swop, or even that it was done during his ownership, I did not wish to assume anything.
As I said, test things first before spending money.
Oh well, back to the lion taming. It's safer!
 
i STILL don’t agree with there being 2 "standards" at all, have you included senders that have a linear or exponential characteristics ?

what you may like to call "manufacturers who cloud the issue" is in this case simply the fact that the engines in questions probably have in excess of a decade in age difference between them so it's not unexpected for items to be incompatible
 
And if it was a earth deficiency between the engine and the chassis/body, the engine wouldn't start anyway.

It would also probably fry the throttle cable when you tried to start it.

Crapola. (can I say that without being banned?)

CharlesY
 
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