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Old 7th August 2019, 23:09   #1
Mr Toad
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Default Coolant leak and slow speed fan not working

Hi All,

When I last posted about the coolant leak it was suggested that I bypass the oil cooler which I have done but there has been no difference still loosing a small quantity of coolant. The thermostat has been replaced the inlet manifold gaskets have been replaced with a coating of Hylomar there is no leak at the water pump or in the V.

I tried a test suggested on here, i.e. take off expansion tank cap run the car cold for about 10 seconds at idle and then accelerate up to the red line, if coolant shoots out of expansion tank this confirms HGF. I did this but no coolant shot out of the expansion tank. Is such a test conclusive or not?

I discovered today that the slow speed of the coolant fan is not working, could this cause coolant loss and do I need a new fan?

Any assistance will be gratefully received. I should mention that the car is a 2003 MG ZTT KV6 with 60,000 approx miles.

Martin
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Old 7th August 2019, 23:16   #2
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I discovered today that the slow speed of the coolant fan is not working, could this cause coolant loss ..
Yes.
Quote:
... and do I need a new fan?
No. You can repair it. Is it a 2 or 3 speed motor?

Simon
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Old 8th August 2019, 11:05   #3
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Thanks Simon. I don't know whether it is a 2 or 3 speed fan. I can't see a resistor therefore I suppose it is 3 speed in that case wouldn't I be better off replacing the whole fan with a new 2 speed one. On the V8 you have to cut the shroud to clear the aircon pipes I know this because I have just fitted one. I assume it is the same for the KV6 or can you just swing the shroud out of the way to get to the fan motor?

Martin
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Old 8th August 2019, 15:51   #4
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... I suppose it is 3 speed in that case wouldn't I be better off replacing the whole fan with a new 2 speed one.
In my view, no you wouldn't. My reasons for saying that are:
  • A new 2 speed system is expensive. A set of brushes for your 3 speed cost £20.
  • You don't have an unreliable resistor to worry about with the 3 speed.
  • The 2 speed is noisier than the 3 speed.
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On the V8 you have to cut the shroud to clear the aircon pipes ... I assume it is the same for the KV6 ...
You will read posts which say that it is, but with a bit of ingenuity and by taking my time I managed to re-brush my 3 speed fan motor without cutting the shroud.

If you do decide to replace rather than repair, perhaps you'd consider offering your removed 3 speed to Arctic.

Simon
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Old 8th August 2019, 20:30   #5
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Hi Simon,

On closer inspection it is in fact a 2 speed fan with a resistor. The high speed is working therefore I suppose it is either the relay or the resistor that is faulty. What do you think please?

You said previously that if the low speed fan is not working this is responsible for the coolant loss. Where do you think the coolant is going?

Martin
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Old 9th August 2019, 08:09   #6
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I suppose it is either the relay or the resistor that is faulty. What do you think please?
Hi Martin. Is it a silver coloured resistor? If so, it will be that.
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You said previously that if the low speed fan is not working this is responsible for the coolant loss. Where do you think the coolant is going?
On a 2 speed system with a failed resistor the fan will not start running until the coolant has reached 112 degrees. Not only is that much too hot, it is only three degrees below the temperature at which the temperature gauge rapidly swings to the red line and you're officially overheating. You also run the risk of the expansion tank cap venting to relieve the pressure with consequent coolant loss which will probably leave little or no trace.

But don't get bogged down in theory Martin. You have identified a fault with the cooling system and it needs to be repaired immediately. You can then reassess the situation.

When the thermostat was replaced, who did the work? If you did it yourself, did you refill and bleed the system afterwards by raising the expansion tank and by following the MGR procedure exactly? If not, this can cause problems with coolant level.

Simon
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Old 11th August 2019, 11:29   #7
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Hi Simon,

I decided for peace of mind and quickness to replace the complete fan after all the fan motors do have a tendency to pack up at between 60 and 80k . MGOC are doing the Chinese ones apparently off the production line for £175 plus postage better than Rimmers for £300 plus postage. They were quick to send me one and I have fitted it, so I will now have to wait and see if it has cured the leak. Personally I am rather pessimistic and I still think it is HGF but will report back in a week or so.

Incidentally I have had the car for 16 years and have changed the coolant on a number of occasions and I always adhere to the procedure set out in the Haynes manual.

Martin
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Old 13th August 2019, 20:11   #8
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I regret to say that my worst fears have been realised. I had to add about 300mls today after travelling only about 20 miles. I have had a good look underneath and there is no sign of any coolant and the v is as dry as a bone. There does not appear to be any coolant on the dipstick and the oil level seems okay in spite of the amount of coolant loss. I would have expected the level on the dipstick to have risen.

I am now at a loss as to where the coolant is going. It is looking increasingly like HGF but I don't know how to prove it. Do you think I should drain the coolant and refill it very carefully? It is very strange because the car is running perfectly.

Martin
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Old 14th August 2019, 09:15   #9
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It is looking increasingly like HGF ...
It isn't Martin. Where's the evidence? What event would have caused the alleged head gasket failure? No, it's a variation in coolant level, the cause of which hasn't been found yet.

300 ml of coolant is not a lot. If it's seeping out of a failing thermostat housing 'O' ring it can evaporate quickly leaving little or no trace. You could leave your engine acoustic cover off for a while and check frequently for coolant with a powerful torch both when the engine is running, hot and cold, and when it's not.

On the straight pipe, are the two plastic clips pushed fully outwards in their channels?

But I'd say that the most likely reason is unintentional errors made during the refilling and bleeding process:
  • The Haynes manual can be misinterpreted. The small bore air bleed hose entering the expansion tank neck should not be disconnected.
  • It is essential that the expansion tank is raised during the refilling process.
  • The bleed screw should be refitted before starting the engine.
  • The engine should not be run with the bleed screw removed under any circumstances.

Another common cause of slight coolant loss is worn seals on the expansion tank cap. They can be obtained separately, there's no need to buy a new cap.

Simon
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Old 14th August 2019, 18:34   #10
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Quote:
Originally Posted by Mr Toad View Post
I regret to say that my worst fears have been realised. I had to add about 300mls today after travelling only about 20 miles. I have had a good look underneath and there is no sign of any coolant and the v is as dry as a bone. There does not appear to be any coolant on the dipstick and the oil level seems okay in spite of the amount of coolant loss. I would have expected the level on the dipstick to have risen.

I am now at a loss as to where the coolant is going. It is looking increasingly like HGF but I don't know how to prove it. Do you think I should drain the coolant and refill it very carefully? It is very strange because the car is running perfectly.

Martin
Hi. I had the same problem last week and the mechanic diagnosed HGF it's easy to proove using a special instrument with inside a blue liquid that need to be putted instead of the water tap.. If the liquid become green that's HGF. Good luck!
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