Cooling Fan constantly running

[JRE]

I have recently aquired a 1.8 petrol saloon, 2004. 48000 on the clock. Appears to be in very good condition, but after driving for about 5/6 miles the cooling fan comes on, and stays on. It seems to be unaffected by whatever setting I put the climate control/aircon on, other than when the heater is on a very high setting (presumably when its drawing hot air away from the engine), the fan will then go off. Once the temperature guage on the dashboard reaches the 'normal' level, it remains there with no variation. The cooling fan sometimes 'runs on' for about 20/30 secs after I switch off the ignition. I Have had the car seen by a Rover specialist. He firstly replaced 'E/M Temperature Sensor', and then realised that many of the 'veins' in much of the radiator were clogged, so he replaced this also. There was some evidence of the water in the cooling system being greasy prior to the radiator change, so I could be heading for a head gasket change (this hasn't been done). Should I be worried, and should I have the head gasket done at this stage to pr-empt any further problems?
All advice welcome.

[jcwatrichmond]

Clearly it's overheating. Is it losing coolant externally? You must check this and repair any leaks. When cold there should be about 1cm in the top section of the header tank under the cap. If this engine loses coolant it overheats quite quickly and then the head gasket gets destroyed, or worse.

JCW

[JRE]

Many thanks. I have checked the coolant level since yesterday (24 hours/approx 50 miles). It remains at the same level. No signs of leakage to be seen anywhere, yet the cooling fan continues to kick in and remain running once temperature guage achieves 'normal'. Could it be a circulatory/water pump problem?

[T-Cut]

I'd suggest you use the OBD trip screen procedure to display the coolant temperature while noting fan activity. It has a 2-speed fan, which should start at around 105-107C and stop at 96-98C. The running on at high speed after shutdown suggests the coolant is reaching at least 112C during a typical run. None of these variations will be seen on the dash gauge itself, since they are regarded (by MGR at least) as 'normal'. If the temperature readout is realistic and the fan trips on/off at the scheduled temperatures, then the reason for the overheating should be explored.

My first suggestion would be that it could be a sticking thermostat. I suspect your 2004 model will have the external PRT. This can be confirmed by looking underneath or whether there's a plastic T-piece in the upper coolant hose from the head to radiator. Maybe it needs replacing.

TC

[JRE]

Dear T-Cut,
Many thanks. O.B.D. is a new world to me. Is it something I can do myself? I've tried to find out about the process online, but am struggling somewhat. Can you point me in the direction of a simple guide for my particular problem?

[jcwatrichmond]

How to access 75/ZT diagnostics and car data via the Instrument Pack (IPK)
Rover 75/MG ZT - Diagnostics access via the Instrument Pack


Have the engine running before you start.
Hold down the trip button till the diagnostics mode appears then just press repeatedly till you see number 19. Stop pressing and watch the screen toggle between XXX-off and xxx-on. When it's in the xxx-off screen, start pressing the button exactly as before. The screen will look similar to before, but stop pressing at number 7. The coolant temperature will display as 3 digit number, eg: 012 is 12 degrees Centigrade.
The screen will stay in this mode until you stop the engine or hold down the button again.

To enable the OBD diagnostics:

a) Press and hold the trip reset button.
b) Put key into ignition switch and turn to KLR (Ignition switch position #1)
c) Your LCD display will show something like this "test 1.-"
d) Press the reset button till you get to "test 19.-". (19.0 unlocks all the features)
e) Wait for display to show "Log I -off" and press the reset button
f) With no delay press Trip Reset several times to select one of the following functions:

1 Car, Engine and cluster data

1.0 VIN serial number
1.1 K-number
1.2 Cluster Part #
1.3 Coding (04)/diagnosis (52)/bus index (10)
1.4 1200 Week (12)/year of manufacture (2000)
1.5 09_160 Hardware (09) and software # (16.0) of cluster
1.6 Injection Status-number of cylinders-motor number

2.0 2 Cluster System Test - Activates the gauge drivers, indicators and LEDs to confirm function

3 Service Inspection (SI) Data
3.0 Used fuel in liters since last SI
3.1 Periodic inspection days; elapsed days (since last SI)

4 Momentary Consumption
4.0 Instant fuel consumption - 0145=14.5 liters/100km
4.1 Instant fuel consumption - 0018=1.8 l/Hour

5 Distance Gone Consumption
5.0 Average mileage; 082=8.2 liters/100km
5.1 Calc. km to refuel (momentary distance to go)

6 Fuel Level sensor inputs in liters
6.0 Fuel level averaged; 109330 - Left half sensor input=10.9 liters; Right sensor input=33.0 liters
6.1 Total tank level averaged; 0439 - vlgs 6.0: 10.9+33.0=43.9 liters
6.2 Indicated value and diagnostics:
last digit: 1 - both sensors ok; 2 - sensor error; 3 - signal error - no display

7 Temperature and Speed
7.0 021+ Coolant/Engine temperature (21C)
7.1 130 Ambient/Outside temperature - chg met 5 pts. 125/130/135
7.2 Engine speed / Current RPMs 1/min
7.3 Vehicle speed / Current Speed in km/hour

8 Values of 7.0 bis 7.3 in HEX form

9 Battery
9.0 140 Battery Voltage - 140 = UB 14.0v

10.0 Country code

11.0 Unit code

12.0 Not used

13.0 Gong test

14.0-14.4 Error memory: if 000000 no error in memory

15.0 - 18.0 not used

19 Lock Status; unlocks functions in range 3-18
19.0 L-On/L-Off Unlock: press button when "L-Off"

20.0 Correction Factor for OBC Fuel Consumption
Formula for the Correction Factor:
Indicated Consumption X 1000 / Measured Consumption = Factor (4321)
Press Reset button to begin setting the of the first (1) digit - press
reset when the right digit appears
20.1 Setting of the second (2) digit
20.2 Setting of the hundred (3) and thousand (4) digit
20.3 Store and Display the Correction Factor

21.0 Software Reset; reset OBC settings
----------------------------------------------------------------------------------------------

Print this off and keep it to the car as it's hard to remember.

[JRE]

Many thanks. I've done the O.B.D. trip meter procedure, and here's what happened: I drove on both occassions for about 6 miles. First time in a quiet rural area with no congestion, second time in town so slow moving. On both ocassions the fan did kick in at 104/105 and continued running. The temperature did NOT fall back, in fact on the second journey it rose to 108 and stayed there until I turned off the engine. On stopping the engine the fan changed into fast mode, and ran on for about forty seconds. I did the procedure again immediately with the engine off. The reading was then 101. The only way I reduced the temperature reading (on the first journey) whilst driving was again to put the heating onto 'Hi'. When the reading had dropped to 96 the fan stopped. The temperature in the cab does feel unnaturally high when moving, even with the heating switched off. There has definately been NO loss of coolant since the radiator was changed, and the system flushed just over a week ago, and no signs of outward leakage (see earlier posting). The temp guage on the dashboard rises to the 'quarter to' position when warmed up, and does not waver from this at all. I can't understand however why the temperature reading using OBD doesn't fall when the fan is on. Is it advisable to carry on driving? Any further suggestions welcome.

[T-Cut]

See paragraph 2 in Post 4.
Do you have the PRT?

TC

[JRE]

Many thanks. Yes I do have the PRT. Will get this checked out.

[chrissyboy]

if the rad was changed and the car has started doing this since then i would say there is air in the system blocking the coolant from circulating. when you stop you say the fan runs on. from the test you did re the temps and fan coming on at 104 and going off at 98 would suggust that all is well with the fan . do you hear any gurgling noise rush of water, when you turn on ignition? if so, it is deff air in the system