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Running cool or wonky temperature gauge?

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As the weather starts to turn up here in the frozen north i'm noticing my TD5 is taking longer to get up to temperature. It's always run a little cool but the needle is barely moving on a 20 minute commute through town. On a longer run i can get it up to temp but if i'm on the motorway then i can only get about 1/5 up the temp scale. The strange thing is that whenever i press the accelerator the needle dips slightly so i'm wondering if the gauge might be the issue. I've checked for the usual head gasket failure signs and there's nothing to note and i've also changed the thermostat about 6 months ago so i'm ruling those two out. No obvious leaks in the system and it holds coolant just fine. Is it time for a radiator muff or should i be looking at that gauge a bit more?

 

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Get yourself an IR gun, very handy for this sort of thing, just point it at the temperature sender on the engine to confirm whether it is reading properly.

Unless the stat was a good make/genuine I would be suspecting that, as cheap copies are very poor, and can fail in 6 months very often, and the symptoms you state are classic thermostat.

No affiliation, but there are thousands of these on ebay: 

https://www.ebay.co.uk/itm/LASER-INFRARED-IR-NON-CONTACT-GUN-DIGITAL-TEMPERATURE-TEST-METER-THERMOMETER/122512014040?hash=item1c8648fad8:g:~MwAAOSwAPVZFC4U:rk:1:pf:0

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Cheers Bowie. What sort of running temps should i be seeing? The gauge is an original from what i can tell and can't see any fiddling with any of the wiring behind it either. It's all very strange!

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Modern turbo-Diesels run hot - it improves efficiency, prolongs engine life and reduces emissions. Temperatures in excess of 100C in the head are quite common (thats also one of the reasons why you need to have the right coolant concentration - the Glycol raises the boiling-point significantly). I'd be aiming for 100C as a 'good' exit-temperature of coolant from the head.

My TD5 does take ages to warm-up though: starting up after an overnight 'cold soak' in frosty weather the needle doesn't move off the stop for the first 3 or 4 miles - it's been like that from new. And in similarly-cold weather if you hit stop-start traffic when the outside-temperature's zero and you've got the heater going full-blast the needle soon sags back into the blue because the heater's sucking more heat out of the coolant than the engine generates at idle.

If I were you I'd be checking your thermostat, and also the condition of the engine-to-earth/battery cable, as corrosion here could generate 'odd' readings. But also remember that the TD5 temperature-gauge is actually driven from the ECU, using data from the injection's Coolant Temperature Sensor - so it could be worth getting a code-reading done in case you have an undrlying issue with the CTS or its wiring.

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its also worth noting that the td5 temp gauge is controlled by the ecu, not the sender, if you have a bad earth at the ecu this can effect the gauges accuracy in regards to the temperature,

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but a td5 temp gauge will work if the wire from sender goes direct to the gauge, thats how mine is connected.

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Cheers guys. I've suffered from a bad earth from the ECU in the past so i'll start there. Is it worth getting a radiator muff for it anyway as we move into winter?

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Depends where you live, but in the UK, no.

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its also worth noting that you can use a thermostat from a k series freelander that's available in 3 flavours which allows you to alter the warm up characteristics, I currently have a black thermostat fitted which is fully opened at 82c rather than the standard 88c

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Surely opening at 82c instead of 88c would make warm up of the cab even worse, since coolant circulates through the heater whether the t'stat is open or closed?  Or have I got it backwards?

Mike

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The gauge problem is probably an earth.

The Td5 thermostat opens about 82 and is fully open about 96, so 88-89 would probably be an average running temperature.

2 hours ago, Troll Hunter said:

Surely opening at 82c instead of 88c would make warm up of the cab even worse, since coolant circulates through the heater whether the t'stat is open or closed?  Or have I got it backwards? 

Mike 

Yes coolant flows through the heater matrix all the time and when the RPM is above 1500 the bypass valve opens to prevent pressurising it too much. So driving at RPMs below this will force all the coolant through the heater, though wouldn't create as much heat, so who knows how you heat it up the quickest.

This thread is relevant:

 

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On 11/28/2018 at 3:27 PM, Troll Hunter said:

Surely opening at 82c instead of 88c would make warm up of the cab even worse, since coolant circulates through the heater whether the t'stat is open or closed?  Or have I got it backwards?

I'd think so - and the 88deg stat only fully opens at 92deg according to the RAVE manual :ph34r:

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Hi 

There are lots of potential problems with the earthing behind the instruments. One day climbing to the top of Rannoch Moor from Glen Coe the temp went into the red, I pulled off in panic and turned off the headights... and the needle went back to normal.  Lights on needle up. the TD5 110 was not obviously hot.  Problem went away after a general clean up of earthing points on the bulkhead.

 

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I'm going to give the earth a good going over this weekend and hope that it helps. Interestingly enough my brother's TD5 has also been struggling to come up to temp recently so i'm wondering if it's just the weather. It's been -5C these past couple of days and this morning it was a balmy +6C and she heated up no bother. Also planning on giving my heater matrix a bit of TLC so we'll see how that goes. I found a couple of guides on here and nobody has been particularly enthusiastic about the task!

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The heater matrix is not a difficult job to do paime, 2 spanners out of 5. Being methodical and stopping air getting around the matrix is the key.

Mo

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43 minutes ago, Mo Murphy said:

The heater matrix is not a difficult job to do paime, 2 spanners out of 5. Being methodical and stopping air getting around the matrix is the key.

Mo

It seems like a therapeutic job once the matrix is out so hopefully it won't take too long and i won't lose any knuckles in the process.

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Can't guarantee the knuckles 😉😁

Mo

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