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TD5 engine using water but not overheating or overpressurising header


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Hi all,

Sorry if its in the wrong section, i just guess this is a generic TD5 question rather than a specific defender or discovery question. Although the vehicle in question is a 10P discovery

I'm borrowing a discovery off a mate for a while whilst i decide if i want one or not/in order to take the series off the road for some loving. So far i have done ~250 miles in it and ever since i picked it up it has been using water.

Bit of background, the discovery in question has been in my friend circle for a while, i know where its been serviced and i know its been serviced well, it has a couple of niggles, but on the whole a decent car. The head cracked on it about 2 months ago and the owner sold it to another mate as he didn't want to pay for a new cylinder head and the resultant labor. The mate who bought it off him sourced a (supposedly) known good cylinder head, and rebuilt the top end of the engine.

The vehicle is definitely using water at a reasonably rapid rate, the symptoms are as follows:

Engine runs fine, no loss of power etc,

Heaters were blowing cold when i picked it up so topped up and bled system

steady loss of water since i started driving it

Never overheats or gets warmer than usual

no mayonnaise in oil, in fact oil is staying surprisingly clean!

the coolant expansion tank never overpressurises or pukes.

the vehicle runs clean when cold but emits steam when at operating temperature.

I was going to run a cylinder leak off test to determine whether the head gasket was still leaking/the new head isn't as good as thought. but i haven't the right adapter, and can only test 4/5 cylinders due to the lack of a 5th glow plug anyway.

is there any other way water can get into the cylinders i.e. is there a fuel cooler which may have internally failed, although the coolant has stayed clean and doesnt smell of either oil or diesel!

any suggestions welcome.

P.S. there aren't any external coolant leaks before you say :rolleyes:

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The 10p didn't have the fuel-cooler setup that the later 15-series ones have [cylindrical silver thing alongside the intake plenum].

I'd be suspecting head-gasket, cracked head [they sometimes go between the coolant-passages and the intake ports] or possibly a cracked block if the previous head-failure/loss-of-coolant led to significant overheating.

Was the [supposedly good] replacement head hot-pressure-tested before fitting? Cracks won't always show up on a cold pressure-test.

Was the face of the block checked for trueness before the replacement head was fitted? If the engine had been cooked the block-face may no longer be flat . .

Were new head-bolts used? Were they correctly set using an angle-gauge? If the old bolts were reused they will be stretched and even if set using an angle-gauge they may not be providing adequate clamping-force on the head gasket.

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Interestingly, it has a fuel cooler as you described, so maybe it is a 15p engine? as for the head work, i'm not sure of the details, ill find out. Its definately burning it off rather than leaking, and i know its topped up to the cold level now and i'm off out tonight (with a spare water bottle) so ill compare mileage to amount used then.

A cracked block may be the culprit but i'd prefer not! haha

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I think the fuel-cooler's a red herring: it's fitted to cool fuel being returned to the fuel-tank *after* it's been circulated through the head and injector fuel-rails.

If the cooler was leaking to the fuel-side then the 'missing' coolant would end up in the fuel-tank and your engine would die with classic water-in-fuel-system symptoms [or the orange "fuel filter water warning" light on the dash would come on].

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Very similar to what my discovery did. Head was found to be 8 thou out it chuffed like hell if you pulled the breather pipe off the rocker cover but didn't smoke out the exhaust, have mixed coolant or excessively pressurise it, however it used approx 6 litres during ~80 miles or spirited hilly towing with a gator on a 14ft ifor.

For what it's worth I would probably re do the headgasket with new bolts and get it pressure tested, if it is a 10p get the injector galleries pressure tested also.

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Also worth checking the radiator- I've just repaired one that had blown the head gasket and the combustion gases had pressurised the coolant and ruptured the flimsy ally radiator. The leak wasn't obvious especially when hot as it evaporated pretty quickly.

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