Wavering Temperature Needle

[Bidz]

I was driving to Leeds last night when I noticed my temperature gauge needle to be wavering slowly between 80 and 85C. I suspected a faulty TIM Gauge but I soon noticed this only happened at high revs - at idle, it settles down.

Thoughts? Seems strange to me!

[Chipper]

Perhaps you have an 80 deg C thermostat fitted, which should normally keep it at around the 80 deg C mark, but at higher speed, combined with chilly winter air, it can't quite make up it's mind on the temperature...

[bmcecosse]

Seems right enough to me !

[gtt1951]

Mine doesn't waver, but does run around 80 to 85 (September 2013 this started going higher, coming back from Gaydon in the Traveller, so I pulled over and turned on the auxillary cooling system).
I'm pleased to hear that 80-85 is OK.

[Bidz]

Perhaps you have an 80 deg C thermostat fitted, which should normally keep it at around the 80 deg C mark, but at higher speed, combined with chilly winter air, it can't quite make up it's mind on the temperature...

I hadn't thought of this but it does seem likely - I was worried that it might be a sign the water pump is failing etc etc

Just never seen it move up and down so quickly before - one cycle around 2 seconds...

[bmcecosse]

Keep your eyes on the road -not on the gauge.... It is possible that it was indicating a low coolant level -you didn't explain the 2 second movement earlier! Is the level ok ??

[Chipper]

Another possibility is that it is down to the electricity supply to the gauge varying, rather than the temperature of the engine - I take it you wired the gauge to the little instruments voltage regulator behind the speedo?

[chesney]

This is a capillary gauge, as far as I am aware, so the regulator should have no part in it.
As long as it's not boiling over, and there are no ill effects, I would let sleeping dogs lie. A TIM instrument is hardly a quality choice, particularly with a delicate (potentially coiled/damaged) capillary wire.
I've had to block off a section of the radiator on my Traveller, as it was overcooling, but then I am on the other side of the channel to you. Even with half the radiator blocked off, with an outside temp of 5 degrees, on a 100km trip to Gorges, the temp never went above 80 degrees (88 degree stat fitted). It could be a sign of breakdown of water pump impeller, you can test this by revving the engine and monitoring the water level, it should 'dip' slightly as the impellers draw the water in. But I think your're possibly thinking too much about a reading which indicates an ideal (well, slightly low but so is the outside temp) temperature.

[Bidz]

A TIM instrument is hardly a quality choice, particularly with a delicate (potentially coiled/damaged) capillary wire.

Well you recommended it at the time, Jack.... ;)

Will check coolant level tomorrow but it should be fine, I only topped it up last week. As long as it's not a known sign of anything serious...

It just seems strange to me that it's fine at idle!

[chesney]

I don't remember recommending it as it happens, I fitted one to a modified blue 2 door I had as, to buy 4 gauges, would be potentially expensive in buying Smiths instruments, and more difficult to get a matching set.
TIM gauges, as I recall, did a tahcometer, oil pressure, water temperature and ammeter for under £50 or so. I had no problems with my water temperature gauge yet I know that they are not particularly quality instruments (one set on fire on here I believe as the bulb holder design is poor). I also took relatively meticulous care in ensuring the capillary pipe was not damaged, which I cannot vouch for in your (home) fitting. I reiterate that a gauge showing the (near enough) correct temperature isn't really cause for concern, it's unlikely to be anything serious at 80 degrees, realistically in my mind it could be something affecting water level to the sensor, ie a blockage, low water level, damaged impellers (loose fan belt?), or possibly an airlock or blowing gasket. If those were the cases I'd imagine you'd have more trouble that you are currently having than a wavering needle. If these give you concern, a compression test (around £20 sterling) will give you peace of mind with your gasket, the impeller test I've written previously.

[Roni]

Both of mine do this and have done for a while, with no problems. Different makes of gauges. Both have around a 2 second cycle. One of the gauges is an early undamped Smiths type which really shows it as it reacts to everything immediately. I put it down to being a bit of a curiosity.
I guessed it was - thermostat closed or mostly closed = higher reading
- thermostat opens = lower reading, due to more water cooling through the radiator.

[Bidz]

I also took relatively meticulous care in ensuring the capillary pipe was not damaged, which I cannot vouch for in your (home) fitting.

Was I not meant to use a hammer? What an idiot I clearly am.