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Old 17th August 2016, 06:34   #11
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I assume your engine really was totally cold when you removed the filler cap? They retain heat for a ridiculous length of time. Remember that you've got an expansion tank rather than just a simple header so, assuming your cap seals correctly, any warmth in the coolant circuit is going to produce enough pressure to give a little hiss when you unscrew the top. I agree with Kaiser about the fan though: as long as it's spinning it shouldn't contribute to any overheat.

Air locks are very common on the KV6 if it hasn't been re-filled exactly as per the approved MG method, and even when it has it often takes another few days of checking and topping up to get it absolutely right. Otherwise, as I discovered on mine, one or two very small leaks (particularly in difficult-to-see places close to warm items) can give the impression of one big one.
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Old 17th August 2016, 08:32   #12
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Many thanks for replies. For the moment I'll ignore the fan question (basically I have a two speed fan, and the T4 test and the demist test shows that both speeds trigger it to run - but there is no difference in volume between the low speed and the high speed, it sounds like in both cases it's running at the same speed. Does anyone have a link to the difference in sound between the low and high speeds?)

Just on coolant - the system was presumably drained and refilled when the car was serviced and the cambelts and water pump were done a few weeks ago (by a competent Rover trained mechanic who is active on this forum so I assume he used the proper technique for filling up).

Could the cause of my "leak" have been a significant airlock that would now have disappeared on account of my putting in 2 litres of coolant last week? The coolant has to go somewhere. But if there was an airlock, why would it only manifest itself as an overheating engine and dry expansion tank a month after the work was done, rather than on the first drive home? Especially because the first couple of times I used the car after the service, I checked the levels and they were fine.

The alternative is that I do indeed have a leak - but where? It's not the thermostat (no coolant in the "V"), not the oil cooler (normal oil levels and no emulsion), not the head gasket (no mayo in the header tank), not the heater matrix (no coolant stains), not the radiator (new last year, no stains), not the water pump (no stains), not the filler cap (new)....
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Old 17th August 2016, 08:45   #13
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Quote:
Originally Posted by Forestgreen View Post
Many thanks for replies. For the moment I'll ignore the fan question (basically I have a two speed fan, and the T4 test and the demist test shows that both speeds trigger it to run - but there is no difference in volume between the low speed and the high speed, it sounds like in both cases it's running at the same speed. Does anyone have a link to the difference in sound between the low and high speeds?)

Just on coolant - the system was presumably drained and refilled when the car was serviced and the cambelts and water pump were done a few weeks ago (by a competent Rover trained mechanic who is active on this forum so I assume he used the proper technique for filling up).

Could the cause of my "leak" have been a significant airlock that would now have disappeared on account of my putting in 2 litres of coolant last week? The coolant has to go somewhere. But if there was an airlock, why would it only manifest itself as an overheating engine and dry expansion tank a month after the work was done, rather than on the first drive home? Especially because the first couple of times I used the car after the service, I checked the levels and they were fine.

The alternative is that I do indeed have a leak - but where? It's not the thermostat (no coolant in the "V"), not the oil cooler (normal oil levels and no emulsion), not the head gasket (no mayo in the header tank), not the heater matrix (no coolant stains), not the radiator (new last year, no stains), not the water pump (no stains), not the filler cap (new)....
The oil cooler can leak to the outside, that is water dripping out, that would not affect the oil at all.
Get the car looked at on a lift. Don't assume all is well just because it is new! I agree rare, but I have had new items faulty, out of the box.
This is one case where you throw all assumption out, and check each and every item.
Check or substitute each item.
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Old 17th August 2016, 19:04   #14
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... there is no difference in volume between the low speed and the high speed ...
David; the low speed on a resistor system can be extremely loud. The T4 test should be absolutely reliable, unless of course some bodgery has taken place in the control box.

Regarding your coolant problem, I would drain the system completely yourself then refill according to the MGR procedure here. You need only minimal tools to do this and you will then know that it's been done properly.

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Old 17th August 2016, 22:01   #15
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Quote:
The alternative is that I do indeed have a leak - but where? It's not the thermostat (no coolant in the "V"), not the oil cooler (normal oil levels and no emulsion), not the head gasket (no mayo in the header tank), not the heater matrix (no coolant stains), not the radiator (new last year, no stains), not the water pump (no stains), not the filler cap (new)....
Maybe check the bottom metal coolant pipes for fine perforation as these can corrode over time.

PS if I get time today or Friday I will hook up a 2.5 two wire 2 speed fan with gold resistor to my cars loom and force the two speeds on the T4, take a video of it and post it up for you. Arctic
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Old 18th August 2016, 23:52   #16
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Default Fan Speed Test T4

HI David.
As promised I got round to hooking up a 2.5 fan two wire 2 speed with gold resistor, below are a few photo's of how I set it up and the video to hear the two different speeds.

One refurbished fan new brushes and gold resistor, two wire 2 speed Fig 1
1

One petrol extension loom to aid hooking up the fan to the cars loom Fig 2
2

Cars fan loom/wiring unplugged from the car Fig 3
3

Extension made up loom fitted to the cars loom Fig 4/5
4

5

Fan now set up to be tested and the speeds forced on with the T4 Fig 6
6

T4 plugged in and the fan is forced on in the low speed, in intervals of 3 seconds as per aloud by the T4 Fig 7
7

Fan forced on in 3 second intervals in the high speed Fig 8
8

This was undertaken a few times and the same result you can hear the tow differing speeds quite clearly.

Click the link video for the fan tested off the car.
https://youtu.be/6gDJen2p3-Q

Click this link for the video fan fitted to the car.
https://youtu.be/ZofkZMTmSPw


When the medium was called/forced on it only allows the low speed to run again in 3 second intervals as no medium speed is applicable to the two wire 2 speed fan with gold resistor Fig 9
9

Fan showing the back of the motor and its wiring note the tags have been opened and re-closed due to new brushes being fitted Fig 10
10

SRB2 control box for the 2.5/2.0 petrol engines Fig 11
11
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Old 19th August 2016, 12:41   #17
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Nice work Steve, very easy to see and hear the two different fan speeds!

Tom.
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Old 19th August 2016, 18:42   #18
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Not mentioned yet, and I don't want to muddy the waters, but the inlet manifolds (more specifically the gaskets) can leak, they have coolant flow.

Also not wanting to spread gloom, but when I had a similar issue if turned out to be coolant getting sucked into the centre front cylinder via the head gasket.

Unfortunately a number of possible causes - the bleeding is a good place to start I reckon. I think at some point some folk were using a pela vac kit to do it? (or have I made that up?)
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Old 19th August 2016, 19:54   #19
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Arctic, can't thank you enough. Did you seriously take off your bumper and first remove the fan then refit it and shoot the test just for me, or was it already in your car????

I think (99% sure) that the volume in both "speeds" tested using the T4 is the louder, faster volume. Maybe a resistor problem or a wiring problem? It's a one year old "Jules gold resistor" fitted by Terry so the odds of either happening are pretty remote.

As for the leak, I guess either (i) I just have to keep topping up until I find myself adding such large quantities after short journeys that the source manifests itself, or (ii) I take it to someone who can have the thing stripped right down. Downside is, given it's just been serviced by a Rover mechanic and Terry bless him has also already spent several few hours investigating it without success, so I could end up driving to the other side of the country and still not have the source identified yet still have a leak somewhere.

Is there a definitive sequence of investigations that a garage could pinpoint the leak over the course of a day ie pressure testing, checking each cylinder for HGF, etc etc, so that by the end of the day I know exactly what to fix?
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Old 19th August 2016, 20:15   #20
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Originally Posted by Forestgreen View Post
I think (99% sure) that the volume in both "speeds" tested using the T4 is the louder, faster volume. Maybe a resistor problem or a wiring problem? It's a one year old "Jules gold resistor" fitted by Terry so the odds of either happening are pretty remote.
Was there any work done on the fan system prior to having the resistor upgrade? Did the slow speed ever work correctly during your ownership?

I'm just wondering about quick fixes that are done to make the fan run fast under all situations whether slow or fast is required. Cross wiring the slow and fast speed circuits in the control box will override any change made to the resistor. In other words, fitting a new resistor wouldn't re-establish the slow speed.

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