coolant warning light on

[80ESTATE]

hi,help needed Please
i was having overheating problems when engine under pressure,slow traffic,over hills etc.
i noticed the expansion tank was leaking at the seam,so i got a new one(europarts£26+vat),fitted new tank, drained old stuff off while running hose through till water ran clear,refilled with correct coolant mix.
Ok at first,after first few journeys coolant turned dark colour so i replaced coolant again.a 20mile run later the coolant warning light was flashing,next morn checked level +topped up.
drove 55 miles today,up few long hills ok till near home, light flashes on again,started car again later and coolant light flashes on immediately.
the coolant is not dark.
is it temp sensor or what have i not done.
thanks for any help.

[murphyv310]

Hello.
The coolant sensor haas three connections, one common, one to the gauge and the remaining one to the warning lamp. the normal running temperature is around 90 degrees but if it is high over 105 degrees the light should come on. The sensor will be faulty it the temp gauge reads 90 and the light is on.
If both are high I would check the thermostat, but what is worrying is the colour of the coolant, it really should be changed every 2 years but there could be contamination from engine oil usually caused by a faulty head gasket and far more common on diesels.
If the head gasket is the problem use a genuine one not a pattern part as they don't last.
good luck.
Trevor

Also check the fans are working

[80ESTATE]

thanks Trevor,
I should have mentioned that the engine temp stayed about 90 after i changed the tank+coolant,no more overheating,the coolant light flashes from cold.
I`ve never heard my fans on.The oil filler cap is clean,no white stuff. think i`ll replace the sensor,do you know exactly where it is?
regards.

[murphyv310]

Hi.
It usually lives high up on the engine in a plastic housing attatched to the coolant hoses, its grey in colour and has 3 pins the sensor is held in with a horseshoe clip.
Make sure the cap is off the expansion bottle before removing it as pressure in the system will blow coolant everywhere.
Good Luck
Trevor

[80ESTATE]

thanks Trevor, am taking a few short runs today to see what happens,starting from cold the light stayed off.I`ve located the sensor it`s good thing you told me about the cap.
will let you know what happens,
cheers,Liz.

[micheal balbrig]

thanks Trevor, am taking a few short runs today to see what happens,starting from cold the light stayed off.I`ve located the sensor it`s good thing you told me about the cap.
will let you know what happens,
cheers,Liz.

Not sure if this 100% correct but I think when the red
light flashes it signifies low level in header tank so if it is flashing
when level is correct it may be a problem with sensor in header tank. As far as I know the red light stays on continuous if engine is overheating

[murphyv310]

Not sure if this 100% correct but I think when the red
light flashes it signifies low level in header tank so if it is flashing
when level is correct it may be a problem with sensor in header tank. As far as I know the red light stays on continuous if engine is overheating

Yes.
I have misread the first post, the level sensor is a little float and may be stuck or sticking possibly a little clean up will help.
A solid warning lamp indication is the coolant temprature sensor though.
Cheers
Trevor

[80ESTATE]

thanks guys, I went all saturday and Sunday no light. Today Monday light came on and later when going out again the light flashed from cold.
Is the sensor the coolant sensor and/or is the header tank different to the expansion tank. prob basic stuff but i need all the help i can get,I just hd to fork out £78 for a new tailgate lock.

[murphyv310]

Hi.
The header tank is the same as the Expansion tank.The senor can get choked up with dirt and often shows up when its been disturbed, possibly happened when you changed your header tank.
Taking it out again and giving it a good wash may be the cure, also check the plug is OK.
Cheers
Trevor
PS Did your new tank come with the sensor fitted if so send it back under guarantee.

[80ESTATE]

thanks Trevor, I will wash out tank and change coolant again & check connections.
If this doesn`t cure it I`ll take the tank back and change it.
After a couple of 20mile runs the dreaded light usually starts to flash,then if I leave her for an hour or so the light will flash straight away,but never 1st thing. The engine temp has not went above 90, even under strain she only slightly moved. Before I changed the tank and coolant she frequently went to 100 110 when pushed.The only time the light flashed with old tank is when the seam started leaking, so I think my engine temp gauge is ok.
Thanks for all your help,will keep u posted.
all the best,Liz.