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Afternnon all,
Using / losing lots of coolant.
About 1 litre every 100 miles.

Engine temp not overheating
- on motorway temp stays about 90deg
- in town goes up to 100+ (but not into red), fan kicks in temp goes down.

Coolant system holds prssure. (I have to wait a bit before I can top it up!)

No oil in water bottle.
No water in oil sump.
No steam from exhaust.
Took to dealer - pressure tested - no sign of leak.

There is a small drip from the back of the engine - but is from the same area as AC condensor.

My thoughts are that a split heater bypass valve may be the cause...anyone else got any other ideas?

Cheers
Simon
 

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Club Barge
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3,467 Posts
Hello,

Heather Bypass Valve as you have rightly suggested would be my first item to replace. Not a nightmare job and about an hour to replace, how to I wrote in the how to section. I found it best to remove the scuttle and plenum, just for the added access more than anything else. Gave me a chance to clean the breathers as well.

James
 

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172 Posts
Mine's doing the same thing as Bigsi, but the fan is always running after i pull up - not matter what the ambient temperature outside or how hard i've worked the engine. I was thinking about changing the Thermostat, Water Pump and doing a complete system flush - do you think it's related to the HBV aswell or would my measures sort it?

BTW, the car runs around the 95 mark, rising to 100 only when stopped and switched off. Once you switch back on, after a few seconds it drops to 97 ish, then back to 95.

It's almost like it's overheating, but it's not really. And there's a vast amount of heat coming from underneath the bonnet and underneath the car, far more than i've noticed on my Dad's 2.5.

Strange!
 

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Omega Tank Commander
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7,722 Posts
Well the leak isn't near the aircon condenser because thats in front of the rad.....it might be near the condensator as thats in the cabin with condensate exit points either side of the gearbox.

Three favourite water leak points in the following order:

1) Heater bypass valve
2) Thermostat body to block seal.
£) Oil cooler plate to block seal
 

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Heater bypass valve went on mine. Started to drip a little at back of engine. I couldn't find the problem using usual methods so left it until another day to fix it. Unfortunatley, the next day after a long motorway run, came off onto local roads and the HBV dumped all the coolant over the road. Not sure how it works, but presume it is a diaphragm valve operated by vacuum. It seemed like the diaphragm had split and dumped the coolant through the square hole on the lip on the top (Safety valve???). I'm sure someone out there knows a little more about how it actually works and if that is how it fails.
 
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