CDTi using coolant

[Fox3]

I’ve got a little problem on my ZT, it uses about a pint of coolant every 500 miles or so. I’ve got good at topping it up every 500 miles now, but where is it going?

No obvious drips or marks under the car after being parked up, and I can’t see any obvious leaks.

It also starts first turn of the key and runs smoothly, so I presume it’s not seeping out into a cylinder via the head gasket

If left it seems to drop just below minimum and doesn’t seem to go any lower, the previous owner assures me he didn’t ever need to top it up, but did mainly motorway miles so wouldn’t have been affected with the heater not functioning properly at lower driving speeds (That’s my tell-tale I’ve left it too long to top up!)

I’ve ordered a new header tank cap, in the hope it could be that, does anyone else have any ideas?

[Avulon]

Have a look in the water pump area.

[johnnyb44]

Mine was down due to the pressure cap..The rubber seal was the culprit.

[Heddy]

This was the cause of my coolant loss, the case had a hairline split but the square seal had deteriorated too. Not a bad job after the engine cover was removed. The push on attachments were pretty hard to remove though.
http://www.ebay.co.uk/itm/MG-Rover-7...4AAOSwCU1YwwfT

[Darcydog]

Check the O rings in the hoses - there is considerable evidence that OAT antifreeze eats them over time. Mine had a couple that looked like they had melted and were weeping as a result. No leaks to see as what little fluid did come out must have sat on the undertray.

Only when one failed almost completely was I able to track the leak down. So when changing one I did the lot, drained and flushed and now use blue antifreeze. No more issues after nearly two years.

I would suggest that the cdti is such a strong lump that it is best not to jump to the worst case scenario conclusion.

Check out all the above simple inexpensive possibilities first.

Hope this helps.

[Rick-sta]

I've had a couple leaks myself. Check the thermostat for leaks either from the pipe that goes into the top of it as there is a o ring in there that can start causing a leak, or the hose coming out of the bottom of the thermostat, on mine the metal clamp came loose and caused a leak.

Also check the bottom hose on the radiator, mine was leaking.

there is a thin metal hose that goes right around the back of the engine block, I've heard of small pin holes causing leaks from that pipe on a few occasions.

I've also heard of coolant leaking from inside the fuel burning heater.

And as mentioned above, sometimes it's just the coolant expansion tank cap not holding pressure properly and allowing a leak.

[Mickyboy]

In my experience the sealing ring on the pressure cap is a suspect in most cases.

[vilas66]

I recently replaced my thermostat which was leaking. I was unable to find the leak until the weather was cold, here in Italy. With cold weather there were water drips under the car. I changed the water filler cap "O" rings first but, let me say that if the cap holds pressure when the car is warm / hot can't produce coolant loss...

[T-Cut]

Does the diesel get warm enough to lose coolant through pressure cap issues?

TC

[Mickyboy]

Originally Posted by T-Cut

Does the diesel get warm enough to lose coolant through pressure cap issues?

TC

Hi TC
I guess it's possible if an in-line thermostat has been fitted in the top Hose or a specialist component thermostat has been fitted as the thermostat can fail to open correctly at 88 degrees and starts opening very late, I've seen a diesel easily get up to 98° With a inline that was opening to late obviously the cooling fan car in and helped to bring the temperature down , meaning that when the throttle is wide open going uphill it reaches a higher temperature than it should.
Not saying this is particularly common but I have seen it, I noticed it on a Rover 75 by checking IPK diagnostics.