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rover_75
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Discussion Starter · #1 ·
Hello again.

So, after a largely agreeable week in my new 75 I took it up north on Friday and endured an horrendous slog up the M6, lots of stop-start stuff on a warm evening and the temp gauge sat bang slap in the middle, just as it should. The following morning I took a short run, maybe seven miles or so, purring around some country lanes followed by a brief dual carriageway blast and was just trundling along slow, residential-ish streets when suddenly the coolant gauge soared up to the top stop and red light came on. As soon as it did I pulled into a quiet lane and switched the engine off. After a good hour or so of listening to the radio and being a bit cross the engine was cool enough for me to pop the cap off the coolant header to reveal disturbing aridness within. Fed it some water, not much more than half a litre to get it to the max level again, and the car ran fine with the temp gauge showing everything as normal. This morning the header looked a bit dry again, sloshed in some more water and - having taken the precaution of joining the AA - I set off south again. Manchester to London, three hours, roughly averaging a heartening 60mph and just shy of 30mpg with not a single upsetting flicker from the temperature gauge. All very strange.

So ladies and gentlemen, your starter for ten is; what could be up with my car? Small leak, some kind of air lock or the horrible omens of some catastrophic gasket-related malady?

All wisdom greatly received.

Ta.
 

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other_manufacturer
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Couple of options there mate.

1) Leak
2) HGF
3) Broken fan

So, in reverse order, turn the air con to AUTO, does the radiator fan come on?

Any oil in the water or water in the oil?

Any puddles under the car?
 

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rover_75
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Discussion Starter · #3 ·
Good questions, and ones I had myself.

Yep, fan comes on with the climate set to auto.

No sign of water in the oil or vice versa.

No signs of leaks under the car.

This is what makes it all the more strange. Short of finding that Shergar and the Dead Sea Scrolls are jammed in the radiator hoses, I'm stumped for an immediate solution. It's a mystery.
 

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Header tank Cap. Is this allowing the coolant to slowly flash to steam?

Had this problem with my old R8. Coolant disappearing, no oil in coolant (or vv), no leaks etc, didn't get to the overheating stage though.

Cap replaced, no more problems.
 

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I had a similar thing happen to me a few months ago, put the heater on & had no warm air, temp gauge didnt move though, when i checked the radiator i had to top up with about half a litre of water and there were no obvious leaks etc.

I made sure i tightened up the radiator cap up as hard as i could, and have kept an eye on it like a hawk & has only used 50ml or so of water since.
 

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Pressure cap failure? They do fail and are only a few £ to replace

Thermostat-in the 'v' ? If so then should be able to spot orange stains from the coolant

Water pump? Again look for staining

Coolant pipes? Any cracks/are the clips still tight?

Have it pressure tested

Remove the undertray as leaks underneath the car are not that easy to spot with it on

Good luck

Mike :)
 

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Take a torch and look between the inlet manifold into the heart of the V and see if you can spot a trace of orange anti freeze.
 

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There is a bottom pipe which I had changed on mine - it did exactly the same thing, but it only happened under pressure hence no puddles. Not a flexible hose iirc

I'll have to rummage in my file to dig out the invoice to get the description
 

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rover_75
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Discussion Starter · #10 ·
Thanks for all the suggestions chaps. Haven't had a chance to poke around the engine bay as yet but I'll look into all the possible causes.

At the risk of missing the bleeding obvious, could it be something as simple as a duff gauge? Does the 75 suffer from such problems?
 
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