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Old 27th May 2019, 20:19   #11
chillyphil
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Hi Simon,

I haven't done that yet, I will do when I change the fluid, however, I'm sure that was not the issue which caused the overheat.

I've driven it for a few months without any issue?

I just vented the hose when I topped it up, only a few small bubbles then.

Phil
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Old 27th May 2019, 20:25   #12
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Originally Posted by chillyphil View Post
Hi Simon,
I haven't done that yet, I will do when I change the fluid ...
OK thanks.
Quote:
... however, I'm sure that was not the issue which caused the overheat.
I'm not so sure. I recall other members believing that following the correct bleeding procedure couldn't possibly be the cause of their problems, but it was.
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I've driven it for a few months without any issue?
That doesn't prove a thing.
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I just vented the hose when I topped it up, only a few small bubbles then.
You shouldn't remove the bleed screw unless the expansion tank is raised. I've always followed the MGR procedure to the letter and I've never had an air lock. What conclusion do you draw from that?

Cheers,

Simon
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Old 27th May 2019, 20:32   #13
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I'll vent it properly tomorrow and see what transpires.

Any thoughts on why the fan doesn't cut in?

The correct temperature is available to the ECU, does the fan cut in only on the radiator temperature, or is it called by the ECU?

Phil
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Old 28th May 2019, 09:03   #14
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Any thoughts on why the fan doesn't cut in?
Only that if you have air in your cooling system all sorts of strange things can happen. That's why I think it's important that you bleed it properly before speculating on any other faults.

The radiator fan is controlled by the ECM (Engine Control Module) which receives inputs from the coolant temperature sensor and air conditioning system (and automatic gearbox ECU if you have it).

Simon
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Old 28th May 2019, 11:04   #15
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Hello Phil,
Thought I'd jump in here because some important points you made earlier haven't been addressed. So, I'll chuck in my observations.

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Managed to have a look at the fan this afternoon.
There is no resistor visible.
There are the two screw holes on the housing which look like where the resistor should be.
Unless you have a very rare 2-speed setup, you have the earlier 3-speed system. This doesn't have a slow speed resistor and is fixed in a different way. Either a motor brushes replacement or a complete system swap to the later 2-speed is needed. The latter is a plug'n'play swap, though would need a resistor upgrade if not included.

Quote:
Started the engine and left it on idle.
Engine temperature climbed to 96, fan didn't come on.
Temperature climbed to 107, still no response from the fan.
Apart from the aircon demand, your engine cooling stage 1 and 2 systems aren't tripping on at 100C and 106C as they should.

Quote:
I bottled out then and turned the demist on.
The fan came on and the engine temperature quickly dropped to 102 within around 1 minute. Leaving the demist on and fan running, the temperature dropped to 96 within six minutes.
Logically, there was a significant delay before the fan started? Is that so?

The lack of the fan speed 1 and 2 will eventually overheat the aircon sytem and invoke emergency high speed cooling.

So, I think there's a bit more to your predicament than air in the cooling sysem.

TC
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Old 28th May 2019, 15:55   #16
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Thanks for that Cyrano,

How do you think I should proceed?

Simon,

I've now bled the system properly, the cooling system is still reacting the same.
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Old 28th May 2019, 16:08   #17
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Simon, I've now bled the system properly, the cooling system is still reacting the same.
OK Phil. The problem is that your cooling system's behaviour is not consistent with worn motor brushes. It isn't reacting to an increase in coolant temperature but it does trigger as soon as you activate the air conditioning. That's why I wanted to eliminate an air lock.

Can I ask a basic question. Your profile lists two Rover KV6s yet this is a ZT190. Is it a recent purchase?

Simon
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Old 28th May 2019, 20:48   #18
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Hi Simpn

Yes it is, purchased it a few months ago, slowly working through the issues.
The only recent work close to the cooling system is an air con regass, but that was two weeks and 200 miles ago.

Phil
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Old 28th May 2019, 21:24   #19
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Yes it is, purchased it a few months ago, slowly working through the issues.
What were the faults declared by the seller? Were there any linked to the cooling system?

Simon
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Old 28th May 2019, 21:58   #20
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Hi Simon,

Slipping clutch, I replaced a few months ago when I got the car.
Peeling lacquer, still to be done.
Camshaft sensor replaced.
That was the major faults.
Minor issues fixed a few weeks ago.
Bonnet sensor replaced.
Reverse sensor on the gearbox.

Looking at the cars history, a new thermostat and housing was done about three years ago.

Nothing else noteworthy.

Phil
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