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Joined: Jan 15 2016
Posts: 378

Coolant temperature sensor - falling temperature fault

It's intermittent, well it would be wouldn't it! When I've got all the kit ready, it wont replicate.

Sensor replacement or anywhere else to look?

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Joined: Dec 30 2015
Posts: 3773

Might just be an iffy connection. Try running with the Nano connected and recording the temperature. If it falls nice and smoothly, it'll be the sensor, if it leaps up and down it'll be a connection.

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Joined: Jan 15 2016
Posts: 378

Cheers Richard.

Had the nano on it and it ran up temperature smoothly but stopped at 90. The engine didn't cut but the fault showed up again.

Rang a pal who has a garage (and a P38) and he fired me a new sensor over. It's a bit late for a test run, but it ran up to 97 at idle before stabilising. I'm assuming the other one was causing the "falling temperature" fault as the engine management wasn't seeing the rise it expected?

Anyway it looks like a BMW part, No. VNE39090 iif that's of any use. I'll report back after a test run tomorrow morning.

Also fitted a new brake accumulator today, so that's the last link in the brake chain complete.

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Joined: Jan 15 2016
Posts: 378

New sensor fitted, three hour test run, no repetition of the fault.

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Joined: Jan 15 2016
Posts: 378

Had an SMS from a pal today who has a '95 4.0L. Same problem and fault code.

Like buses, nothing, then two come at once!

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Joined: Nov 16 2016
Posts: 890

Not on Rangerovers but on other marques I've known quite a few people fit coolant temp sensors bought from Ebay... then wonder why their radiator cooling fan runs flat out as soon as the engine warms up a bit. It's because the sensors they bought are incorrect spec, so the ECU reads much higher engine temp than is actual. Seems a particular problem on V6 Nissan Skyline's, the proper part is a few times more expensive than a part with same thread, same electrical connector and listed on Ebay as compatible with V6 Skyline's. With the wrong sensor on them the ECU can easily read 100+C when actual is 80C (with the 80C confirmed by me via LPG reducer temp readings). The consensus of many owners clubs is 'they do run hot these engines... fan running nearly all the time is normal'! I found the consensus and problem when I converted a Nissan Maxima (I think they call them a Maxima... anyway it's a model of car only in the UK by grey import) which more or less has Skyline running gear but in a big estate car... the owner who hadn't had the car long before bringing it to me for LPG conversion reckoned the fan didn't used to run before LPG conversion yet it had a shiny new coolant temp sensor. I'd seen the fan run fast before I even touched the car but agreed I'd have a look to make sure I hadn't for example fitted the reducer close to an aircon line temp sensor (which could also trigger the fan). Soon found the real problem though, told him to fit a proper compatible sensor and that fixed the problem.