XM Mk2 Electrovalve Cycling ("Click-Clonk")

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rg
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XM Mk2 Electrovalve Cycling ("Click-Clonk")

Post by rg »

Folks,

The 3-second "click-clunk" under the passenger seat returned for around 40 miles this morning, at all speeds up to motorway, and even when stationary with the engine off.

I take it that this is the electrovalve. It sounds uncannily like the electric fuel pump on my dad's old Morris Minor Traveller. There was a distinct current "pull" when it cycled, as the cabin lights dimmed very slightly, and the alternator came under load, changing the engine tickover note.

After a time parked, and a restart, the noise has disappeared.

Of course, I guess that this may be a sign of a duff sensor, and I'll need the ECU read, but has anyone experienced this before, and what caused it?

Rg

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Post by Peter.N. »

I doubt if it was the valve as the current required to operate it would hardly be noticeable, its more likely to be your radiator fans cutting in and out, it happens occaisionally on my XM, I think its an intermittent fault in the fan control system, but it wont stay there long enough for me to find it.
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Post by rg »

Thanks, but it was certainly not the rad. fans. The "drop" is only very slight, but I could notice it in time with the "clunk"

r
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Post by Peter.N. »

Strange! It takes a lot of current to slow the alternator, I cant think of anything else that would draw that much. Will it do it while the car is stationary? if so, you could try bouncing the suspension between clicks and see if it stiffens. I have just thought of something else that could take that much current, if its a diesel, and thats the glow plugs, the light isnt coming on is it?
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Post by rg »

Not exactly "slowing" as when you switch the screen heat/high speed fans on, just a discernable change in note. Another sign is the temperature sensor fan in the roof module, which changes in note.

I understand that when the electrovalve is powered, the H2 suspension is in soft mode.

r
Peter.N.
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Post by Peter.N. »

OK you are obviously more discerning electrical load wise than most people, not a TV engineer are you? Well, I can only suggest the suspension test as previous mail. I cant hear the valves inside my car, but can hear them operate from outside when I open the door!
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Post by rg »

Hmm... I work in telecommunications recycling, so I am used to strange noises in comms. rooms when taking things out.

I also drive my Cit. Indie mad, as I can hear bearing noises he can't...!

As time goes on, I'm usually proved right (smug grin).

It's definitely "dipping". Re the suspension test, I'd need to be pretty quick, as it only engerises for a second or so.

And now it's stopped....arrggh! Don't you just love intermittent faults?!

r
Peter.N.
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Post by Peter.N. »

...Bain of my life, I am or was a TV engineer, now retired. Without dry joints, the primary cause of intermittent faults on TVs, we wouldn't have had any work for the last five years or so, anyway, happy hunting.
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Post by dnsey »

Since you know what you're doing, why not temporarily connect a lamp across the valve, and mount it where you can see it easily. That way, you can be sure whether it's the valve (or at least its supply) or not.
As I understand it, the valve receives an energise pulse, followed by a 'hold' supply, so you'll probably only notice a flash, but that would do!
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