Hello everybody.

My 2.5td exclusive has been loosing small amounts of water recently. There have been no other symptons of head gasket failure but I had my local garage test the water system for exhaust gasses and it came back positive (fluid turned blue - isnt it suppost to go yellow when there are gasses present).

Anyway, is there any easy way to tell if this is a head gasket or cylinder block issue?

It does not overheat, does not pressurise the header tank and there is no sludge anywhere in the oil system.

I have been test driving lost of other cars and they dont even come near the XM for comfort or power. I would love to keep it but dont wish to start the head gasket job and then find out its the cylinder block.

Any advice would be gratefully recieved.

Thanks
Colin

Hi Colin

Check the rads out first. Life of these is low (4 to 6 years) and manufacture date can often be found on the top of the rad. It might also be worth knowing the car mileage.
The small rad on the 2.5 is a regular item for causing difficult to identify small amounts of water loss. They seem to deteriorate a bit faster than the main rad. They are hidden in between the large rad and the aircon rad and may well evaporate off a continuous dribble without it showing as water under the car. Run the engine on the drive with the bonnet up and see if the rads give off a small cloud of steam as the fans cut in. You can get a look at this little rad by unclipping the main rad and tipping it back towards the engine. A new small rad is around £70 and a large one £100 both on ebay now from the aircon people in Chesterfield. GSF or Eurocar usually match the prices if you push them.

One other thought is that if the rad cap has gone weak the 2.5 usually just dumps a small amount of water back out the overflow each time you drive after a top up.

If the rad side turns out ok then trying a rad sealer like K-seal has worked for some XM owners to get a little more life out of the car without spending on it.

Regards

John

John,

Thanks for the tips. I have had a look at the small radiator as suggested and all seems well. I can see no areas where there are tell-tale signs of a leak.

The car has done 173000 miles but runs very well. One problem I have is that the water loss is minimal - it looses about 1/2 litre over 1500 miles so I dont expect to see steam.

I have added a measure of Forte radiator stop leak and this has reduced the loss significantly.

Do you think it could be my head gasket or has the exhaust gas in the coolant test been wrongly diagnosed?

Regards
Colin

Hi Colin

It has not stopping the car running and it is easy to top up when needed so I suspect it is either a weak rad cap or the gas leak is putting excess pressure on the coolant system which quickly expels your top up water. As the leak progresses it will push out more or you will start to get oil in the water. This might come suddenly tomorrow or it might be another 75k or so, no way of telling. Not familiar with Forte sealer but you will loose nothing with another dose and K-seal seems to me to be the best of those I have tried. With 2.5's the gas leak problems are seldom the cylinder block, may be the head gasket but are often cracks in the alloy cylinder head caused by running a 2.5 with residual air in the coolant. They need a very precise bleeding procedure when the coolant is renewed and this is often overlooked with damage to the head round the valves. Unlike 2.1's you will not be sure you only need a head gasket until the head has been removed, skimmed and successfully pressure tested. Replacement cylinder heads are expensive new, hard to come by second hand and will be of dubious condition anyway unless they are refurbished and tested.

Regards

John

Hi Colin ,
Further to John's comments re coolant cap leak or excess combustion gas pressure further diagnosis and monitoring can be achieved as follows:

There is a plastic tube attached to the filler cap housing that discharges any coolant expelled from the tank below the chassis. Pull the tube up and place the end into a 500ml plastic drinks bottle through a hole drilled in the bottle cap.Place the bottle in a convenient place (between headlamp and ECU box is good) secure the bottle with tape if necessary to stop it moving around.
Any coolant escaping past the cap will collect in the bottle and can be monitored easily. See if coolant collects in the bottle if so try a new cap and see if it makes a difference. If it does not and the seal seat is undamaged then it is likely due to excess pressure through combustion gasses entering the cooling system.
If that is the case is it gasket leak or crack in head? A sealant is, I think, more likely to be effective short term in the case of a gasket leak than a crack in the head. There are products for head cracks but they are expensive and require a more complex procedure. I do not know if they work.
Anyway if it turns out to be combustion gas pressure you have a means of seeing if it getting any worse over time. You could simply carry on and do nothing unless it gets worse and join the AA or RAC in case of sudden failure. You can also recycle the bottle contents when topping up to save the antifreeze.

Let us know how you get on.

Robert.

Hi Colin.

Commiserations with your coolant loss --- I've presently got a 2.5 in suspended animation due to this issue, as I can't decide what to do with it. My symptoms were slightly different in so far as mine would expel water from the header tank if driven beyond around 70 mph for any length of time, but generally not otherwise. Sometimes then it would go for days with no symptoms at all.

As a matter of interest, what is the typical running temperature of yours ? My current one was on the hot side (100 deg) and I found the water pump belt was not tensioned, so circulation not all it might be. Also spotted evidence of a weep from the shaft drain hole on the pump, so this may be another spot for you to check. Don't forget also to check for any sign of dampness on the front carpets, especially on the forward tunnel edge. If present, be suspicious of the heater matrix.
Good luck with it.

Mike.

also worth checking is the pipe behind the head where the bleed screw is, mine has a leak there, just to the left of the vertical pipe , i used Ceelit and it seems to have stopped it

I can state as a fact that the rad caps on these do allow the loss of water from the header tank.
Check the rubber seal. Don't overfill the header tank past the mark. For those who don't know they should NOT be filled to the top.
Make sure you get a replacement to the correct pressure, IIRC 20psi.

DJ