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Old 21st August 2020, 22:35   #1
racing green rover
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Default Fan struggling to reduce temperature unless revved kv6

Hi further to my cooling system problems the fan is taking a long time to reduce the temperature from 100 to 95 when this temperature is reached sometimes the bottom hose will go Luke warm and the top hose warm but you can squeeze it easy enough here's the thing when I rev the engine the top will go harder and the bottom hose will get hot again with the temperature dropping down to about 90. Also sometimes when I undo the coolant tank cap when it's cold a couple of big air bubbles come through the bleed hose hole whilst sometimes the level is higher than what it was the previous day if I leave the cap off a minute the level will drop in the tank. Also when the fan comes on you can smell like hot coolant odour been wafted around I have checked the radiator which is not leaking and I have recently renewed the lower coolant rail. When I start the car from cold with the cap off and rev it the coolant will rise to the top within about 30 seconds. Me and my friend think exhaust gases are going in the cooling system even though there is no bubbles in the coolant when it rises and no pressure release when I undo the cap.
Thanks.
Forgot to mention the coolant backing up in the expansion tank has only happened since I replaced the oil cooler.

Last edited by racing green rover; 21st August 2020 at 22:44.. Reason: More info
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Old 21st August 2020, 22:47   #2
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The most likely issue is an air lock in the cooling system. Revving the engine encourages it to move and a partial coolant circulation occurs. This explains the temperature variation in the hoses. The first thing to do is to bleed and top up the system using the 'official' procedure. You can easily locate it using the forum search system, or read the Haynes manual which contains the same info. When all the air's been eliminated, any further problem diagnosis will be a lot easier.

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Old 21st August 2020, 22:54   #3
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Thanks I already used the correct bleeding method provided by the forum however when I was in process of doing it one of the rubber coolant hose clips which connects to the lower coolant rail was leaking which I have now fixed so could be that? I'll try re bleeding it
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Old 22nd August 2020, 14:15   #4
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Yes, coolant leaks out and is replaced with air. The air may become locked if you simply keep topping it up.


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Old 23rd August 2020, 00:16   #5
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Had exact issue on a 2.5 v6 auto, turned out the plastic impeller on water pump had shattered and wasn't working effectively.
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Old 23rd August 2020, 08:50   #6
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Quote:
Originally Posted by racing green rover View Post
... the coolant backing up in the expansion tank has only happened since I replaced the oil cooler.
Hi Pete,

Did you follow the MG Rover refilling and bleeding procedure afterwards?

KV6 cooling system: filling and bleeding.

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Old 23rd August 2020, 13:10   #7
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Hi Simon yes I did although one of the quick release connectors from the rubber pipe to the lower coolant rail wasn't gripping enough so water was leaking as I was in the process of bleeding it I'm going to rebleed it tomorrow and report back on results. I checked the top hose earlier and you could easily squeeze it there was no flow through it even though it was hot
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Old 23rd August 2020, 17:52   #8
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Quote:
Originally Posted by racing green rover View Post
Also when the fan comes on you can smell like hot coolant odour been wafted around ...
Remove the engine acoustic cover (two 8mm screws) and shine a powerful torch into the 'V' to look for evidence of a coolant leak.
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I checked the top hose earlier and you could easily squeeze it there was no flow through it even though it was hot
That's normal. There is flow through it, that's why it's hot.

Has this engine ever had K-seal (or similar) added to the cooling system?

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Old 23rd August 2020, 20:10   #9
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No the thermostat isn't leaking I've checked it and also replaced it last year, as for the top and bottom hoses I was being vague with the temperature they was just warm you could easily hold them for ages you can easily squish them when the engine is hot it's as if it's lost pressure and the maximum temperature was 103 when the fan was on slightly dropping to 102 and dropping all way to 87 when I hold revs at 3000 rpm. The engine had k seal in it when I bought it 18 month ago but I've flushed it countless of times and used a few bottles of flush if you look at the thread 'looking at buying a contemporary se v6' that's the same vehicle.
Cheers

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Old 23rd August 2020, 21:32   #10
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Angry K-seal

Quote:
Originally Posted by racing green rover View Post
The engine had k seal in it when I bought it 18 month ago but I've flushed it countless of times ...
We've come across this before Pete. Once K-seal has been administered all sorts of cooling system oddities occur which defy logical diagnosis and full recovery can be impossible.

As for your radiator hoses, they both should feel too hot to hold. I remember one member found that his oil cooler was blocked with K-seal. Maybe you have this too or perhaps your radiator channels are similarly affected. I'm afraid the only way to find out is to physically check suspect components. Have you disconnected the top and bottom radiator hoses and tested flow with a hosepipe?

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