v6 2.5 kv6 engine overheat

[fabian]

Hi there,

Can anyone tell me where I can get the cooling system chart showing how the water flow? My problem is the engine fan turn on at the high speed often. It sounds like the cooling system doesn't work as it should be. What I have done and found so far:

1. check the expansion tank that the water level is ok.
2. then check the heater matrix next to the footbed and found the inlet pipe was hot but the outlet was cool when the heater is not on.
3. remove the heater matrix and flush. (you can't believe it how much stuff inside)
4. refit the matrix, got both inlet and outlet pipes hot again.

However, it still the same. My understanding is this car only has one water circulation and the heater matrix is located at the end of the system (correct me if I'm wrong). I guess the water flow from the engine to the matrix is ok since I got both pipes hot, but after the matrix is still blocked somewhere.

I question is where the water goes after the matrix?? back directly to the radiator?

Can anyone suggest what I should check and try next? Some people say I can do a pressure test to flush the entire system using garden pipes but I don't know where I should connect the pipe to.

[SD1too]

Originally Posted by fabian

My problem is the engine fan turn on at the high speed often.

Hi yu chang li,

You need to do the 'demist test' to check that your fan is operating at the all-important slow speed.

My understanding is this car only has one water circulation and the heater matrix is located at the end of the system (correct me if I'm wrong).

No, that's not correct I'm afraid. The heater circuit is in parallel with the engine so even if there was no water flow through it, the engine would still run at normal temperature.

Simon

[fabian]

Originally Posted by SD1too

Hi yu chang li,

You need to do the 'demist test' to check that your fan is operating at the all-important slow speed.

No, that's not correct I'm afraid. The heater circuit is in parallel with the engine so even if there was no water flow through it, the engine would still run at normal temperature.

Simon

Thanks for the reply, can u tell me how to "demist test"??

[SD1too]

1. Start the engine from cold.
2. Press the windscreen demist button (next to the HRW button).
3. Get out of the car and walk to the radiator grille.
4. Is the radiator fan running continuously?

Simon

[fabian]

Originally Posted by SD1too

1. Start the engine from cold.
2. Press the windscreen demist button (next to the HRW button).
3. Get out of the car and walk to the radiator grille.
4. Is the radiator fan running continuously?

Simon

Hi Simon,

yes, the fan is running continuously. I don't think I lost the low-speed as I can always hear the low speed first before the fan turn in high speed. I don't think it's normal since now is winter here. I have also tried:

1. start the engine from cold with nothing on.
2. after 10 mins the fan start running at low speed.
3. after 2~3 mins the fan turn high speed and never stop until engine off.

I also found that the engine temp rises faster than before. When the engine starts from stone cold in the morning, it often needed to be driven for at least 700m to get a normal temp (level pointer), but now only take 200m.

[SD1too]

Thanks for your informative reply. Your fan appears to be in good order.

Next I'm going to ask you to start the engine with the heating/air con in 'Econ' mode. Leave it running until the radiator fan starts on slow speed. We now need to check the temperature of the bottom radiator hose. It's the large diameter one containing the bleed screw and The best access is alongside the air cleaner. Does it feel hot, almost the same as the top radiator hose, or is it luke warm or cold?

Simon

[fabian]

Originally Posted by SD1too

Thanks for your informative reply. Your fan appears to be in good order.

Next I'm going to ask you to start the engine with the heating/air con in 'Econ' mode. Leave it running until the radiator fan starts on slow speed. We now need to check the temperature of the bottom radiator hose. It's the large diameter one containing the bleed screw and The best access is alongside the air cleaner. Does it feel hot, almost the same as the top radiator hose, or is it luke warm or cold?

Simon

Hi Simon,

Today I have checked the radiator hoses. The top one was hot (not sure what level of hot it should be, but it feels hot for me). However, the one next to the air cleaner with a bleed screw was not that hot (warm or even less). I also found air inside as when loosening the bleed screw right after turn off the engine, the coolant didn't come out instantly, I can hear air release for few second. Does it mean I got airlock?

[SD1too]

Originally Posted by fabian

I also found air inside as when loosening the bleed screw right after turn off the engine, the coolant didn't come out instantly, I can hear air release for few second. Does it mean I got airlock?

Quite possibly and it's definitely worth sorting that out before going any further. Here is the official MG Rover procedure for refilling and bleeding the KV6 cooling system. So that you have to do it only once and aren't left in any doubt, I would recommend draining it fully first not forgetting the LH bank drain plug. Note that the expansion tank must be raised and that the bleed port is never open when the engine is running. If you follow those instructions exactly you'll be ok.

Let us know whether the bottom radiator hose becomes hot, which is as it should be, after you've completed the official bleeding procedure.

Simon