Topic

Please can anyone help i have just brought a 1998 mgf vvc with the car ticking over the temperature gauge will go up to just under half way in 20-30 mins i have left it for longer until fan comes on,with no over heating.But when i drive it the gauge drops to zero & if i pull over for a few minutes it goes up again.The heater will only come on when i turn it to position 3.Has anyone had these problems before,If anyone can help i would be very grateful thank you everyone.Chris.

Hi Chris, the gauges on these cars are notorious for causing mayhem and alarm. Your problem is a curious one that I hope someone will be able to answer better than I could. Good luck and I'm sure we'll find out what's wrong between us here.

I would suspect one of two things on the gauge problem. 1. Electrical fault 2. Air in the cooling system.

Does the heater give good heat even when the temp gauge reads zero?

Try bleeding the cooling system, especially at the engine bay bleed point. Air at the temp sensor can cause rapid alterations in the gauge readings.


The heater only working on 3 and 4 is a fault with the resistor pack in the heater and is easily fixed by replacing the blown resistor.

Just under the halfway mark is typically where the guage should read when things are going well.
I wonder if the sender is on it's way out?
You may want to borrow an infrared thermometer and check the engine compartment hoses for temp when the odd reading occurs.
If nothing else that will be good for peace oif mind if it shows that the temp stays steady when the guage drops.

Hi thanks for your reply, what is the sender, is it a very big job to do.

Thank you for your reply,the heater does blow warm when the gauge reads zero.But when its half way it still is not what you would call hot.It isn`t as hot as the mgf that i had before i think it may be air in the system.Tomorrow i will give it a thorough bleed from all 3 points & go from there ,do you think it could be the cold air flowing onto the rad cos it is fine until the car is moving & the faster i go the quicker the temperature drops. Thanks.

This photo of Clive's shows the location of the sender for the temp gauge.


Try bleeding first. From your description air in the system is likely. Also check the thermostat is operating correctly.

hate to say it but it could be some thing else
my old f had hgf and was fixed but on tick over it warmed up then started to go to 3/4 front fan kiked in ok
rev the car and the temp droped and fan stoped had heat all the time on the heater

replaced parts so far
temp gauge
3 thermostats 3 at 88 and 1 at 82 deg c
both temp sensors
new watre pump
new radiator
new under floor pipes
5 new pressure caps used and tested

new owner has fitted new ecu to solve the tick over problem
but it still has the cooling issue
so next job hes doing is striping the entire pipe system off and cleaning every part
its almost if the enine on tick over is not pushing the coolant round
but on reving the car the water is being pushed round

so you could have the oposite problem heating up rev engine coolant moves so cools down thermostat closes

good luck with this one as i gave up with mine after £600 spent trying to fix

Hi is there a easy way of testing the thermostat as i think it is a bit of a job to remove and test in hot water. If it was not opening at all would you still get hot air from heater.Thanks.

chrisd300 wrote: wrote:

Hi is there a easy way of testing the thermostat as i think it is a bit of a job to remove and test in hot water. If it was not opening at all would you still get hot air from heater.Thanks.

the heater is on a seperate system from the thermostat
the thermostat allows heated water to the radiator

as for changing / testing iv got so good at it it takes me 30 mins but you have to rebleed the system:)

how old is the water pump as some are known to rot away or the pump becomes lose on the shaft

but from what your saying it sounds like it could be thermostat but check the easy bits first

just noticed your down ramsgate way give DUSY MGF a shout he might be able to help

Hi thanks for that, the car had been standing for over a year, its only done 23,000 thats why he sold it to me i bet.

how do i get in touch with DUSTY MGF thanks.