Erratic temp guage

yeah, I know...

So, for the last three years & 37000 miles, my temp gauge has pointed to the same spot, sat contently one notch below the halfway mark on the scale. Every morning it has risen gently to this point and then stuck there for the duration of the journey.

And then yesterday, the gauge didn't reach that point, it stopped one notch short, then dropped to just below the bottom of the scale, before rising again and dropping again. It fluctuated between these two mark for the rest of the journey (about 20 miles). I stopped to have a look, no steam, no sludge, lovely red OAT in the header bottle, no mayo on the dipstick, just lovely clean 10/40, no funny smells, no loss of power...

haven't driven it today, so will have to check it tonight. Any suggestions? Dodgy gauge or sender? or could it be...

I had exactly the same problem a couple of years ago. I would have put money on my problem being a dirty joint; probably the thread on the sender to the block, it was kacked up with ali' oxide & PTFE tape when it came out, but by the time you’ve got the hatch cover off & given everything a tweak, another few minutes will have a replacement unit fitted. Do make sure you replace the correct one with the appropriate sender.

I would agree with the last comment but would also be looking at the plug and the pesky terminals . MG/ROVER issued a TSB regarding these plugs and terminals and to quote ' can be found to suffer from corrosion fretting ' . This gives poor contact to the thermistor switch . These plugs and terminals are available from a seller on the Bay of E called 3 Way Comp ( 3 Way Components ). They cost about £3 - 4 and in my opinion well worth the effort and cost to fit .
John .

Thanks both. I had arrived at the conclusion it was a minor electrical glitch and not the dreaded you-know-what, but mechanics twitch and all that. I checked all levels last night and they were fine, no sign of a leak/drip anywhere, so I used her to go and see the g/f (40 mile round trip)...and the car ran like a swiss watch (and the gauge was acting normally again!)

I'll add both those items to my shopping list. The car is coming off the road at the end of the month for some long-overdue TLC, so while she is up on ramps having *deep breath*
new rear tyres
oil change & filter
air filter
replacement hood
front wheel bearings
rear brake pipes
fit the carpet properly
new/replacement drivers seat
new ICE
t-cut and polish

so I'll add the sender and connector to the list.

“Fit the carpets properly” if you manage please let us know. The MG rejects carpets like a human rejects transplanted organs, I tucked & tidied mine up before we went on holiday & it was a right mess when I got back, another week & I reckon it would have been on the garage floor.

So, finally got around to this job, actually doing it while I replace my coolant pipes.

Removing the old sensor looked easy enough, and it was although I managed to lose the securing clip. Are these clips available? I couldn't see it on the Rimmer site anywhere.

Hi . The clip is not supposed to be removed from the plug. You have to depress it to release the plug from the sensor . It is not a separate part . You might be able to get one from a breakers yard . If not the plug is available on Flea bay from a company called 3 Way Components. As in my previous post to you . :dry: https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F141054539749
The plugs are available in the correct colour from them as there different aplications .
John

hi. if you have lost the spring you won't be the first to do it, I have as well, got another from a breakers yard 20p

sworkscooper wrote: Hi . The clip is not supposed to be removed from the plug. You have to depress it to release the plug from the sensor . It is not a separate part . You might be able to get one from a breakers yard . If not the plug is available on Flea bay from a company called 3 Way Components. As in my previous post to you . :dry: https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F141054539749
The plugs are available in the correct colour from them as there different aplications .
John

Cheers John.

I had looked for 3 Way Components on eBay after your last post, and couldn't find them, so many thanks for the link. I didn't realise the clip wasn't supposed to come off, a bit worrying that it didn't take much effort.

I actually found it last night, it was resting on the lower edge of the engine block.

edit to add, plug ordered. £3.05, daft not too

No problem , you are not the first to loose the clip and you wont be the last . As I said there are different plugs identified by colour so make sure you get the correct one .

Regards John

thought I ought to update.

While I was fitting the replacement sender and new plug, I also fitted new stainless coolant pipes and changed the coolant, as my original steel ones were badly blistered and swollen.

I followed the guide on here and found the pipe change to be very straightforward. Bleeding the system took a while but was also fairly simple. The car ran up fine, no leaks of drips plus the header tank level remained constant.

On the test drive, the temp guage fluctuated a fair bit, from it's 'normal' spot, then down a couple, back to normal, back down. This went on for about an hours drive (20 miles maybe). I stopped a couple of times to check for leaks, and had none, the level in the header is constant, the heater works fine and there are no funny smells.

What does the panel reckon? Last few pockets of air working their way out? Give it another bleed?