Hello Fellow MGTF owners (and coolant paranoids)

Hi there! New to the forum though I've often browsed looking for shared experiences...
I've just got my 2006 TF 135 back on the road after 4 years as a holiday home for mice.
All major problems have been repaired or replaced, (cambelt, thermostat, alternator, seized brake caliper etc)...
Paranoid about coolant since an overheating issue (due to a faulty bleed I think) I also had a low coolant alarm fitted...peace of mind at last (I thought)
However yesterday on the way back from the garage (a 40 mile drive) panic stations!
After about 20 miles of normal driving the coolant guage suddenly went from normal (a notch below half-way) to over 3/4 in a matter of seconds...
No alarm, nothing.
Cut the ignition, rolled to the pavement, and immediately re-started ignition ...Oh joy, guage straight back to a notch below half where it remained for the 20 remaining miles...
Have noticed the guage is not regular, sometimes also dropping a tad when driving normally...
Any ideas guys (and girls)???
Thanks a million!!!

:welcome2:

Sudden changes in the temp gauge reading are almost always either bubbles(more bleeding needed) around the sensor or dodgy electricals. In normal operation the gauge movement is pretty well damped, so that real temp problems will show as a gradual change of the needle.

Thanks so much for your quick reply David!
As I live in France MG-specialised mechanics are not easy to find...however my guy is an ex-Fiat/Alfa mechanic who I've known for years and I think is pretty thorough..
When bleeding he couldn't unscrew the seized under-windscreen bleed-point for fear of breaking it but seemed happy with the result.
You mention the sensor (I'm pretty hopeless mechanically!)...could this be faulty and give false readings?
You also mention that if problems occur the gauge increase is gradual.
Mine shot up in about five to ten seconds (eyes are always glued on the blood thing!!!)
What I found strange was that immediately i cut the ignition and re-started within seconds and all was back to normal and stayed a notch under halfway for the rest of my trip.
If I had really has an overheating issue due to bubbles or air-lock, wouldn't the gauge have remained high?
Also I didn't hear the ventilator kick in...
One last point - I've just checked the coolant level (cold) and it is much higher (2 or 3 cm) than the level when I picked it up from the garage, and i got some "glugging" when opening the cap.
Sorry to be a pain but expert advice is a godsend!!!

:welcome: :welcome: :welcome:

Hello there Robin!
Thanks!...Nice to feel welcomed by others who enjoy the pleasure (and nightmares) of driving an MG!!!

Sounds very much like an air lock, take off the expansion tank cap and bleed the rad with the heater on full and see if the level goes back to normal ,then run it with the cap off just until warm so as the thermostat opens, hopefully all the air wire escape then Too up as required and run to full temp with heater open and check engine and rad fans turn on as expected, if not repeat bleed process.

Sent from my SM-J500FN using Tapatalk

welcome aboard!

Thanks!!! Nice to "meet" y'all

Being the highest point of the cooling system, the heater matrix is likely to hold air.
You really do need that bleed point opened.
I would suggest using some release spray on the nipple threads for a few days prior to trying to free it again. Sometimes tightening it slightly before trying to loosen it can free it.
Even after that there is often accumulated crud behind the nipple that prevents effective bleeding. A piece of stiff wire pushed into the hole will move it.
However, I would first order/ obtain another bleed screw in case the worst does happen. Rimmer Bros will deliver to Europe,

Hi and :welcome: :welcome: :welcome: from John in Pudsey Yorkshire.

Thanks guys for all your contributions and advice!!! Should have signed in years ago rather than spending a fortune on laundry bills every time I drive the car!!!!
From what you say the heater matrix bleed point is priority number one...my mechanic didn't want to force and possibly break it, so bypassed.
I'll soak it in release spray for a few days (someone mentioned not using WD40?) and see what happens...
I'll be back with (hopefully) some good news!
Take care y'all!!!
Simon (ex pat living in France where MG mechanics are as rare as soap!!!)