The problem that wasn’t

Warning, long post.

In my Introduction post I alluded to a cooling issue I was having.
Ok, so here is the background : while I was on a 2000 km trip with the caravan from Melbourne to Brisbane, I passed through that well known Australian town of Sydney to visit my son, whilst there I knew of an MGF for sale at what was a good price in Australia and had been owned by the same owner for 22 years. So after a quick inspection and test drive I was now the owner of a1998 MGF to replace my MGB. 
Now the PO drove the car regularly for 10 years, then occasionally for the next 12 years, and hadn’t done the timing belts for over 10 years, and it was still on its original Head Gasket. So I loaded it the F onto a trailer, and took it to one of the few remaining MG specialists an hours drive north.
I booked it in for the works, new Head Gasket, water pump, timing belts, tensioner, coolant flush, and an oil change whilst it was there. Said I will be back in a month to pick it up. Well, the month passed, the work was done, the car was collected.
We drove the 980 km back home over 3 uneventful days, well almost. I double parked the F in our street and left her running while I parked the Jeep my wife had driven back, as I returned to the F it decided the time was right to dump over a litre of coolant from the expansion tank.

Discussions ensued with the workshop that did the head gasket, we run it without the cap on the expansion tank up to temp a few times, and again with the cap on, bled the system twice from all 3 points and all seemed good with a few drives around town.
Then we became adventurous and took her on a 3 day car club run. After a few days of highway driving, winding mountain roads all was well until I drove 10km of unsealed roads at a neck breaking 20km/h ( dust is a problem in Oz, especially for the following cars), as I pulled into the winery car park she again decided that there was too much coolant and ejected another litre of green fluid. I consoled myself with a wine or two.

So it appeared that the car was happy on long highway drives where the airflow kept things cool, but didn’t like slow driving or peak hour stop start traffic in the city. This lead us to rebleed the system just in case ( all was ok ) and then investigate the cooling fans, Disconnecting the ecu temperature sensor engaged the fans as it should have, so the fans were not seized and worked accordingly. Next I had the Aircon fixed, cut out the front air box to access the  blower motor resistors and relocated them to the aircon evaporator housing and fitted a TF front air snorkel.
Now the aircon and blower fans were working, both radiator fans came on as they should and the coolant level in the expansion tank didn’t move after idling the car up to temperature and letting it run for 45 minutes, previously it would overflow after 20 mins stationary idling.

Without the aircon engaging the cooling fans the coolant would rise and expel from the expansion tank, with the fans running all was ok.
We changed the expansion tank cap to a new one that came with the car, unfortunately this did not change anything, she still overheated and expelled coolant without the fans kicking in unless the aircon was on.
OK, so maybe the temp sensor was faulty and not telling the ecu to engage the fans. 
Replaced the brown temp sensor with a new one to no avail, still overheated before the fans engaged.

About this time I discovered through this forum that Cobber lived literally 10 minutes away, after a lengthy discussion we ruled out the fans as aircon fan circuit worked as it should. it came down to possible wrong wiring on the two sensor plugs, ie swapped around or the expansion tank cap.
The sensor wiring was correct, and luckily I had ordered 3 new caps when I purchased the snorkel. Even though I had previously changed the cap for a new one supplied by the PO, I changed it again for one purchased through B and G and voila, coolant loss problem resolved.

So far so good, a few hours of city driving combined with idling in the car park and checking the coolant level and I am much relieved that everything is behaving as it should and I can now get out and enjoy the car.

Moral of the tale is, go back to basics, never trust something supplied as new by a po, and not all expansion tank caps are created equal 🙂

Now the fun begins, I’ll be installing a warning light so I can check the cooling fans are coming on and doing their job (essential in an Australian summer), and fitting an aftermarket head unit with android auto and reverse camera in the coming weeks to bring the ICE and navigation up to spec.



 

If only all our problems were so simple to fix!

Thanks for the chat and advice on the cooling issue. Without a second opinion and going back to basics as you suggested, I’d probably still be chasing the problem.

As I have always advised..........always suspect the "new" part

The boiling up problem can only be exacerbated by your supercharged summers. I commented on Cobber’s superheated steam the other day whilst talking about his beloved alarm & now he’s rebuilding his car & I can almost hear the hissing of escaping steam once everything is up to temperature.
Whether the hissing is from the car or Cobber is a matter for conjecture. At least he now has a pal around the corner to hiss at.
Emgee you couldn’t be in a better place for an MGf owner!
Others in a less accommodating climate have changed the header tanks for ones from the VW stable
& although the blow off value is different, I for one have never experienced a problem, even in some of the hottest days I can remember.
You, of course, might consider those temperatures as a balmy evening chill, but us Poms char easier than you chaps.
M

You really have bought the right car in the right town there! What Cobber doesnt know about these cars, isnt worth knowing.

Notanumber post=209727 userid=17316You really have bought the right car in the right town there! What Cobber doesnt know about these cars, isnt worth knowing.

Thanks for the compliments and vote of confidence, but I still think I've got more to learn......only an arrogant fool thinks they know it all, whist I'm definitely arrogant, and probably an old fool, I try not to be both simultaneously!

And while you’re at it, what about fitting a Bruce low-level-coolant sensor?

https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/99262-unashamed-thumbs-up-for-bruce-tf135-low-water-alarm-kit?start=12#209663

Martinr wrote:

And while you’re at it, what about fitting a Bruce low-level-coolant sensor?

https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/99262-unashamed-thumbs-up-for-bruce-tf135-low-water-alarm-kit?start=12#209663

Seconded and highly recommended!