Disco 2 Water loss mystery

i have had my TD5 for nearly a year and apart from needing rear ACE pipes it's been pretty good.

Apart from its thirst for water.

I filled it with fresh antifreeze mix at the start of the year and have topped it up so often its now just filled with plain water.

I've changed the cap for one off eBay which fell apart after a few months so origional one is back, I've changed both main hoses but it still drinks.

No problem with starting or running, its got no smoke from exhaust so I believe head gasket is ok.

Absolutely no water drops under vehicle and carpet is dry in the footwells.

Today I took it to a mates garage to get it pressure tested.

Pumped it to 10psi and it just dropped pretty quickly as you watched it. Probably down to 5 psi in under a minute. Took it up to 17psi and watched as the needle dropped. Looking around for leaks and even listening. Started engine to see if it spluttered due to water in bore but it started perfectly as normal.

Under car as dry as a bone and no water to be seen.

Any clue where to look next.

Plan for now is to service this weekend including all fluids and use 33% mix of antifreeze and just keep a bottle ready mixed to keep it topped up over winter.

Get a proper expansion cap for it

Do you think that's the problem then? Strange the pressure dropped with the kits cap on it though.

Cheap enough to try and also look around drain hole by water pump. They can start dribbling there as a precursor of water pump failure

Brian S said:

Do you think that's the problem then? Strange the pressure dropped with the kits cap on it though.

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was it sealed fully though can be tricky when testing, ive had tp pressurise to 20 psi to find rad pin holes before on d2s

The cap was on tight. The rad was replaced not long before I brought it I believe.

Then i hate to tell you but it seems very like a crack in one of the inlet ports which lets coolant into the combustion chamber and it burns away... before you pressure test the head get one of these kits http://www.ebay.co.uk/itm/UV-Dye-UV...ing-Antifreeze-System-RLD2-Ring-/230723938073 and use it cos it can be some small leak somewhere(most common around the oil cooler) which occurs only when the engine is hot and evaporates then you'll see no signs of it without such thing... if no signs with the UV torch then you might be as unlucky as i was(that crack in the inlet port happened to me and the only symptom was unaxplainable coolant loss nothing else)... usually if there's a leak at the tank's cap that would create overheating and overpressure especially if you have water instead of proper mix... i'll explain that later with scientific arguments if you dont believe me. cos it's a pretty long story(happened to me as well)

what ever you do dont run the engine on water or less than 50% OAT mix cos there will be subsequernt consequences and repercussions which can be expensive

sierrafery said:

Then i hate to tell you but it seems very like a crack in one of the inlet ports which lets coolant into the combustion chamber and it burns away... before you pressure test the head get one of these kits http://www.ebay.co.uk/itm/UV-Dye-UV...ing-Antifreeze-System-RLD2-Ring-/230723938073 and use it cos it can be some small leak somewhere(most common around the oil cooler) which occurs only when the engine is hot and evaporates then you'll see no signs of it without such thing... if no signs with the UV torch then you might be as unlucky as i was(that crack in the inlet port happened to me and the only symptom was unaxplainable coolant loss nothing else)... usually if there's a leak at the tank's cap that would create overheating and overpressure especially if you have water instead of proper mix... i'll explain that later with scientific arguments if you dont believe me. cos it's a pretty long story(happened to me as well)

what ever you do dont run the engine on water or less than 50% OAT mix cos there will be subsequernt consequences and repercussions which can be expensive

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port valve and cylinder will be washed clean,which is a proof

Maybe my mechanic missed that but the leak was very small on mine, from max to min level of the tank in let's say 1000 miles and steady with parked car

sierrafery said:

Maybe my mechanic missed that but the leak was very small on mine, from max to min level of the tank in let's say 1000 miles and steady with parked car

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a leak or pressure drop as op suggested would be very obvious once manifold was removed without any detector

I recommended the dye for the fortunate case when then leak is external though, cos if there will be dye traces somewhere then no need to remove the manifold or other pressure test, as about your other comments i completely trust you i just wanted to share my own experience without having any experience from pure mechanical point of view

Don't sound good then.

It getting a full service tomorrow and antifreeze going in.
Will give that dye a try and report back.

I found that dye very useful tracking down a slight leak (which was from the coolant pump bleed hole as it happened).

Well I have some news.

It possible it was a stupid error by me.

After the service I refilled with coolant and it did not seem to take as much as I thought it should, but filled it properly with tank raised and bleed nipple open, then let engine run while bleed nipple open watching till air bubbles stopped, took a while.

Then closed with fingers as I have been doing, it looks like the type of thing you tighten with your fingers only but as it had a screwdriver slot it took another easy half turn with screwdriver, careful not to overtighten.

After 100 miles I checked and the level was low, not as bad but put a pint of coolant in and put bottle back in boot resigned to needing it regularly.

Well off for MOT this morning thought I would top it up and ask the guy to keep an eye out for leeks but the level was fine, right where it should be.

Was it just a schoolboy error?

Mine used to do similar. I changed the rad cap as it was passing, the radiator as it had a pin hole and the heater matrix was leaking too.

Could try a coolant pressure tester if you think there is still a problem ...

I had similar problem on my TD5
First was a plug in head behind exhaust manifold heat evaporating water
Second was the water pump
I also never had water on floor

Dippypud said:

Could try a coolant pressure tester if you think there is still a problem ...

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i think he has already tried that,
on one i had, a hose clamp/jubilee clip was just weeping, straight onto the exhaust, so when it drippedleaked etc it was burnt straight off so nothing visable, i only found it by accident,