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Chat Area => General Car Chat => Topic started by: Shackeng on 16 October 2011, 18:04:32

Title: MG TF temp gauge
Post by: Shackeng on 16 October 2011, 18:04:32
...is underreading, only gets to 1/3rd warm, even though fan kicks in OK. I suspect it is a poorly earthed gauge sensor, (which is a b****r to get at) but has anyone had a similar problem, possibly on a K series engine? Or is it likely to be the gauge?...(I don't think so). :y
Title: Re: MG TF temp gauge
Post by: TheBoy on 16 October 2011, 18:08:11
Shame you're not a bit closer, as I have a T4 Mobile.
Title: Re: MG TF temp gauge
Post by: Shackeng on 16 October 2011, 18:23:29
Shame you're not a bit closer, as I have a T4 Mobile.

Who he?
Title: Re: MG TF temp gauge
Post by: TheBoy on 16 October 2011, 18:26:25
Shame you're not a bit closer, as I have a T4 Mobile.

Who he?
Testbook. Rover version of Tech2.
Title: Re: MG TF temp gauge
Post by: Shackeng on 16 October 2011, 18:46:56
Got you. I'm fairly certain it is the earth, looking at the MG forums. Thanks anyway Jaime. :y
Title: Re: MG TF temp gauge
Post by: Andy B on 16 October 2011, 18:52:10
Got you. I'm fairly certain it is the earth, looking at the MG forums. Thanks anyway Jaime. :y
Isn't it just the sender that'll be fubar'd?  :-\ Temp gauge senders usually become less resistive as they get hotter, earthing the wire to the sender will make the gauge show HOT. As the sender is screwed into the block/head it'll use a main earth lead, and if that's not earthing properly you'd have a whole load of other problems.
Either that or your fans are switching in early.  ::) ;)
Title: Re: MG TF temp gauge
Post by: Shackeng on 25 October 2011, 19:58:11
Belated update, I've changed both sensors, and checked by earthing that the gauge works OK. After much bleeding of system, (its supposed to be vacuum bled) which is a b*****r of a job, as the air hides everywhere in this badly designed coolant system, I have got the gauge up to 3/4 once only. Cooling fan still works OK but the gauge stays stubbornly at 1/3 hot, even though I've checked the temp at the sensor positions (both adjacent) and the temp is 102 when the fan comes on. I can only assume the new sensor is Donald. :-\
Title: Re: MG TF temp gauge
Post by: 2woody on 26 October 2011, 09:17:14
it's bound to be the head gasket ...... :y
Title: Re: MG TF temp gauge
Post by: Shackeng on 27 October 2011, 11:48:15
Strange if so, as no oil in coolant, no mayo, and not losing coolant. Very puzzling. :-\
Title: Re: MG TF temp gauge
Post by: Shackeng on 27 October 2011, 11:49:33
And why would the dash temp gauge stay low?
Title: Re: MG TF temp gauge
Post by: henryd on 27 October 2011, 12:13:15
Its possible someone has fitted a lower temperature thermostat to it,I wouldn't worry about it,better reading low than high :y
Title: Re: MG TF temp gauge
Post by: Kevin Wood on 27 October 2011, 12:17:30
I wonder if the sensor is not fully immersed in coolant due to an airlock or similar? Can't remember where it is on a K, though. :-\
Title: Re: MG TF temp gauge
Post by: henryd on 27 October 2011, 12:27:20
I wonder if the sensor is not fully immersed in coolant due to an airlock or similar? Can't remember where it is on a K, though. :-\

K's don't take kindly to airlocks,I would have thought the HG would have popped by now if that was the problem.
Title: Re: MG TF temp gauge
Post by: Shackeng on 27 October 2011, 13:31:47
I'm pretty certain that there are no air locks, as very little expansion of coolant level while running. However, I've got to drain it all again soon to upgrade the thermostat to a PRT, also to fit stainless pipes on the underside which are badly corroded.  Stupidly designed system, no block drain, thermo is on the inlet side instead of the outlet, thus allowing regular thermal shocks to the engine, and encouraging HGF's:y
Title: Re: MG TF temp gauge
Post by: henryd on 27 October 2011, 14:15:05
I wonder if it's possible to remove the stat behind the pump and fit one of the old renault 5 type stat that fits in the top hose and is held in place with a jubilee clip ???
Title: Re: MG TF temp gauge
Post by: Kevin Wood on 27 October 2011, 14:31:03
I'm pretty certain that there are no air locks, as very little expansion of coolant level while running. However, I've got to drain it all again soon to upgrade the thermostat to a PRT, also to fit stainless pipes on the underside which are badly corroded.  Stupidly designed system, no block drain, thermo is on the inlet side instead of the outlet, thus allowing regular thermal shocks to the engine, and encouraging HGF's:y

Yep, that arrangement works fine in a shopping cart where there is a small radiator and very little coolant plumbing but when you have gallons of stone cold water sitting in the system, as you say, every time the thermostat opens it shock cools the engine until the thermostat closes, whereby the  engine then heats up again, and the cycle repeats. Eventually it'll reach a stable operating point but not ideal with an engine that's prone to HGFs anyway.

IIRC there is a modification that relocates the thermostat to the "top" hose, popular with elise owners.
Title: Re: MG TF temp gauge
Post by: Shackeng on 27 October 2011, 18:44:05
Correct Kevin, I am already planning to do this mod when I fit the stainless pipes. http://www.mgfcar.de/thermostat/Water_System_Mods.htm :y :y :y