75 V6 overheating problem.

[robinwickens]

Help please?
I have a 2002 2.5 V6 auto Rover 75.
If I drive this for around 15 miles the temp gauge reads normal and then suddenly it will flag up as overheat and the temp gauge goes up to the 12 o/c position.
This seems to persist and there is no evidence of failing gaskets or head leaks.
No evidence of oil in the expansion vessel.
The coolant fan was not working so I replaced with upgraded fan because I want to tow with this vehicle.
If the thermostat was stuck in the closed position then surely I would not have the sudden rise in temperature as I presume that the gauge would advance linearly towards the overheat and not just suddenly jump.
I really need to sort this as the only alternative is scrapping which would be a shame, especially a it cost me £360 to fit the new fan.
Urgent help needed please?

[roverbarmy]

Have you topped up the coolant according to the correct procedure? (Could be airlocked) Is the fan actually working? (Try the demist test to check the speeds) Is the radiator hot from top to bottom? Does the heater get hot?

[minty2]

In my experience, if the car is moving, the car shouldn't overheat even with a bust fan. I ran mine for a couple of weeks without a fan while awaiting a replacement (it was stuck on even when the key wasn't in the ignition so I removed its fuse). I just kept an eye on the dash display and occasionally switched off the engine in stationary traffic if necessary. Your problem sounds like its coming from somewhere else in the cooling system.

Originally Posted by robinwickens

Help please?
I have a 2002 2.5 V6 auto Rover 75.
If I drive this for around 15 miles the temp gauge reads normal and then suddenly it will flag up as overheat and the temp gauge goes up to the 12 o/c position.
This seems to persist and there is no evidence of failing gaskets or head leaks.
No evidence of oil in the expansion vessel.
The coolant fan was not working so I replaced with upgraded fan because I want to tow with this vehicle.
If the thermostat was stuck in the closed position then surely I would not have the sudden rise in temperature as I presume that the gauge would advance linearly towards the overheat and not just suddenly jump.
I really need to sort this as the only alternative is scrapping which would be a shame, especially a it cost me £360 to fit the new fan.
Urgent help needed please?

[SD1too]

Hello Robin and to the club.

The first thing to do is to check that your recently fitted replacement fan is working properly (as roverbarmy has said). Does your Classic have air conditioning? If so, start the engine from cold and press the "A/C" button (for rotary controls) or the windscreen demist button (for digital controls). Now get out of the car and walk to the radiator grille. Can you hear the fan running continuously?

To help with the diagnosis:

• Is the fan MG Rover or aftermarket?
• If MG Rover, does it have a resistor?
• Is it new or second hand?
• If second-hand, was it from a petrol car and not diesel?
• Did you buy from a retailer or eBay?

Before starting, check that the coolant level in the expansion tank is correct. The 'MAX' marker is surprisingly low down and can be seen by looking in through the tank neck.

Originally Posted by robinwickens

... surely I would not have the sudden rise in temperature as I presume that the gauge would advance linearly towards the overheat and not just suddenly jump.

Your presumption is reasonable but incorrect Robin! The temperature gauge reads "normal" when the coolant is anywhere between 75 and 115 degrees. So although the temperature would increase steadily, the gauge appears to "jump".

Please report back a.s.a.p. and we'll have you back on the road swiftly.

Simon