Overheating whilst idling - sometimes

[kennylenny]

Hi Guys
I have been sat in traffic and the temperature gauge starts to rise - hits 12 o'clock - engine overheat warning comes on - I pull away and the temperature gauge returns to the usual 9 o'clock. I finally get home - open the bonnet to make sure I can't see anything untoward with the engine running, waiting for the temperature to go up again and.....nothing. The fan kicks in ok and the temp gauge stays at 9 o'clock. This has happened a couple of times with me getting home and checking and it's never happened when I'm waiting for it to do so. Baffling
I dare say the answer has been covered somewhere and if so could someone please direct me to where to look.
Thanks
Ken

Whoops - should have said - 2.5l V6

[ianfletcher]

Hi Guys
I have been sat in traffic and the temperature gauge starts to rise - hits 12 o'clock - engine overheat warning comes on - I pull away and the temperature gauge returns to the usual 9 o'clock. I finally get home - open the bonnet to make sure I can't see anything untoward with the engine running, waiting for the temperature to go up again and.....nothing. The fan kicks in ok and the temp gauge stays at 9 o'clock. This has happened a couple of times with me getting home and checking and it's never happened when I'm waiting for it to do so. Baffling
I dare say the answer has been covered somewhere and if so could someone please direct me to where to look.
Thanks
Ken
Have you checked the coolant level?

[rrobson]

also what engine, this will help diagnose the propbem

[kennylenny]

I've just had the 2.5 V6 serviced and I've driven 600 miles since without a blip - until now. Coolant topped up.
Cheers

[rrobson]

sounds like air has passed through the emgine then. this means you have an air lock due to the system not being properly bled. this can be really serious and you should have turned the engine off as soon as you saw the rise. keep an eye on the water level as headgasket failure may occur if it keeps overheating

[kennylenny]

Thanks rrobson. I'll keep an eye on it

[kennylenny]

Guys
Could it be a fan relay problem?

[chrissyboy]

doubt it as you say the fan kicks in .more likely air in the system as rrobson says .. was it a winter service you had done ,ie they changed the coolant ready for winter .. if so i would deff say they have not bled the system properly and would advise you to take it back to them to have it bled properly ..could also be the water pump on its way out so coolant not circulating as it should .. re the fan there is lots on here about the fan and how it should work and easy ways to test if the fan is working properly ..

[kennylenny]

Thanks chrissyboy. It was a total coolant change after I'd driven the 600 miles on holiday. They had to redo the coolant as the first time they did it, before my holiday, they'd put the wrong stuff in.

[tezza]

Hi its Tezza!I live in Adelaide in South Australia.I have a 2002 rov 75 con se travelled 106,000 kms and have had some extensive work carried out last week as follows

replace inlet gaskets
head gasket
exhaust gaskets
thermostat and rails
3 x timing belts
water pump
coolant
air filter
engine oil
head repairs
labour

total $3032.00

Then a few days ago noticed the fan was staying on AFTER the turning off the engine.It would take a few minutes to switch itself off took it back to my rover repairer who tried putting in another spare relay box but didn't do the trick today I was sitting at the lights and noticed the temperature gauge was climbing from the 1/2 way mark to the 3/4 mark while is was idling then dropping back to 1/2 way again when its on the move anyone got any ideas as to what might be causing the problem??

Cheers
Tezza

[kaiser]

My guess is you have a leaky thermostat, you have lost about half your water in the cooling system and you will then overheat.
Because the temperature gauge will sit on med. anywhere from 75 ro 115 degrees, you get only warning when almost too late.
Check the water level daily.

[T-Cut]

As above discussion basically. There's insufficient coolant and some air circulating the system. The over-running fan is due to excessive overheat/heat soak after the engine's stopped. It's designed to over-run for several minutes to cool things down. The varying gauge needle indicates the circulating air. When the super-heated coolant again passes over the sensor, the needle rockets. It reqires bleeding or evacuating to get the air out. After spending all that money, maybe you should return it to the garage and tell them what to do.

The repairs listing you quote is very unusaual for a V6. Why did it require a head repairs? Has the engine superheated before? Did the coolant need regular topping up due to a fractured stat housing?

TC

[chrissyboy]

agree with tc and kaiser, when i had the fan running on after i parked the car and it was sounding like a hover craft the top hose split .had new top hose and water pump fitted and had it bleed properly the fan just works as it should an no over heating issues.. would also be worth checking what fan you have and seeing if it needs a uprated resistor ..

[tezza]

As above discussion basically. There's insufficient coolant and some air circulating the system. The over-running fan is due to excessive overheat/heat soak after the engine's stopped. It's designed to over-run for several minutes to cool things down. The varying gauge needle indicates the circulating air. When the super-heated coolant again passes over the sensor, the needle rockets. It reqires bleeding or evacuating to get the air out. After spending all that money, maybe you should return it to the garage and tell them what to do.

The repairs listing you quote is very unusaual for a V6. Why did it require a head repairs? Has the engine superheated before? Did the coolant need regular topping up due to a fractured stat housing?

TC
I originally had the car booked in to change the timing belts as I was unable to confirm from the previous owner wether the belts had been done,a few days before I left the car in I also discovered that the engine had begun to misfire on 1 of the pistons hence the xtra work done on the head!Fortunately it was not the piston but only the valve and plug had excess oil on them and had burned out which the repairer spent time showing me BEFORE commencing the repairs he has asked me to bring the car in this Wed so they can further investigate why the temperature gauge is rising and falling when in idle.I will pass on all the info you have given me and make sure they check the bleed and coolant levels for any leaks.
Cheers
Tezza

[Jules]

Kenny & Tezza
My guess is although you say the fan is coming on, it might be HIGH speed only and you've lost the lower Speed/speeds
(either earlier type 3 speed motor is US or resistor US on later 2 speed)

Go into OBD dash mode and monitor the temp to the nearest degree.
The Gauge reads mid scale from 72 deg all the way to 118 C so you cannot go by that!

OBD link:
Test 19 Log off test no 7 .....Water temp
http://www.the75andztclub.co.uk/forum/showpost.php?p=479038&postcount=1

Let us know your findings.
Kv6 LOW SPEED fan should come on at 99-100 deg and go off at 96 C