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MG MGF Technical - TF 160 overheat

Got stuck in a massive traffic jam on the A3 yesterday and, worryingly, my TF 160 started to overheat. I've noticed it before in traffic jams but never this bad - was basically stationary for 2 1/2 hours, but crawling occasionally so I couldn't stop the engine.

It may have been something of an extreme test, but still... After around 45 minutes stationary following a 15 minute 70mph run the temperature gauge reached about 3/4. I then had to have the heater on max for the next 2 hours to keep the gauge on half (it's normally slightly below half) and the oil temparature was up to 120. I didn't particularly appreciate having a soaking wet arm from the open window and driving rain along with a cooked leg due to the baking hot transmission tunnel!

During all this time I couldn't hear the engine bay fan kick in (I know I wouldn't be able to hear the rad fan) - I'll check the fuses when I get a minute, but is it normal for a TF to behave like that in "extreme" conditions? Mine's a very early 04 model (PRT and newer alarm system but no coolant level indicator) - most of the stuff in the archive is about earlier cars, and I know the electrical system changed a lot.

Cheers,
Tim
T Jenner

The engine bay fan isn't critical but the radiator fan is. You need to check it is coming in by disconnecting the temp sensor which should cause the fan to come on.

See http://www.apttony.co.uk/ radiator fan not working
Jon Baker

Thanks, Jon. Just popped out to the car park and all three fuses look OK (visually) - one 20A under the bonnet and another under the dash for the rad fan and one 10A under the dash for the engine bay fan.

Is the temp sender in the same location on all cars? I don't have any other issues such as poor idle or dodgy temperature gauge, does everything run of the same sensor?

Cheers,
Tim
T Jenner

OK, so I spent some time with the workshop manual last night. It only goes up to 2003 and mine's a 2004 model so I hope everything works in the same way - things like the fuse box is totally different! I now understand how the thing is supposed to work and have trawled the archive. Sounds like it's not unusual for the connectors to get corroded, given that it's a pain to get to is it worth replacing the sensor as a matter of course or is it much more likely that the connector just needs cleaning? The sensor seems to be MEK000030 and costs about £25 - not a massive amount of money but I'd rather replace now if it's likely to have failed than have to take the thing apart twice!

Cheers,
Tim
T Jenner

For the benefit of the archives, I spent Saturday morning with the car hooked up to my EOBD reader. Looks like the old sensor was under-reading by about 20 degrees - hence the ECU never thought the engine was hot enough to need the fan. Even with the temperature gauge at about 3/4 (mid-way between normal and the red section) the coolant was still only showing 95 degrees (fan doesn't come on until 102). As expected there was a fair bit of corrosion on the sensor contacts, which would show an artificially high resistance to the ECU and therefore cause it to read a lower temperature. It wasn't bad enough for the ECU to register it as faulty, so no fault codes were stored.

As it's a pain to get to the engine I replaced the sensor anyway - first impressions are that it seems to have worked. As it's a warm day today I'll see if I can get the fan to trigger when I get home after a long run. The car seems to run better especially when cold - presumably as the ECU now actually knows how cold the engine is and is adjusting the fueling and timing properly. I'm hoping this may actually also fix a different long-standing fault with my car - will start another thread if it proves to be the case!

A couple of things to add as the archive doesn't have much info about the late TF's with their different wiring. The sensor now has a black body instead of brown and is a BMW part (must be why it fails and costs twice as much! :) ). Disconnecting the sensor forces the engine bay fan to always on when the ignition is at position 2, and both the engine bay and rad fans to always on when the engine is running. Unlike the brown sensor shown in Dieter's photos there is no gasket fitted.

Cheers,
Tim
T Jenner

Last time I bought a brown old-school sensor it was under £13, so yes you're absolutely right ex BMW it costs twice as much... Replacing the sensor was a good precautionary measure, their failure rate is significant and when you consider what an important job it has to do on an engine that is already quite exposed to cooling issues, it's good insurance to have.

Good info for the archive, thank you for sharing your pain ;o)

bandit

This thread was discussed between 30/04/2008 and 10/05/2008

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