Engine: T5: Coolant Loss (water pump ?)

[Jon45]

I have a 2000 year (P2) V70 T5, and recently have been experiencing coolant loss. Car has done 110k miles and been regularly serviced.

After long journeys of say 150 miles, once the engine has cooled down, the coolant tank will be empty. (First noted upon starting the engine next time round with the msg "COOLANT LOW STOP ENGINE")

There is no evidence of water in the oil - I changed the oil to double check this - all looked OK. There is a very strong oily smell about the engine after such a journey though.

There is no evidence of coolant leaking when parked up, so if it's leaking during running it must be either evaporating or leaking in such a place as to not be noticed. No sign of dried coolant around hoses etc.

During the journey the temperature gauge will fluctuate from just below half way to just over, depending on the speed / outside temperature.

Engine does not lack power - seems to operate as normal/expected.

I am wondering if this could be the thermostat (will be checking that later), impending water pump failure, or blocked radiator ?

Any ideas please ?

Thanks,
Jon

[rules]

Same car, same problem

I have (not as a result of the current problem but other factors) replaced the radiator, thermostat and water pump, all in the last year, but still loosing water. I did read somewhere something about how it could be that the head gasket has failed in such a way as to allow combustion pressure to escape into the water ways and push out the water and/or suck in water into the cylinder when engine is stopped. I have noticed that sometimes the car would idle roughly for a few seconds when starting up (could be struggling getting rid of the coolant).

Apparently you can do a "sniffer" test to see if there are any CO traces in the coolant.

All I got

[Penguinistics]

Easier way to check this - Have a look at the top of the piston - you can just about do this without taking the engine apart - If the surface looks almost crystaline all is well, if it looks almost smooth / semi-polished this is generally an indication of water getting into the cylinder - just like the momentary rough idle when starting from cold. Another thing to look at is the burn colour on the spark plug electrode. The cylinder that is "different" definitely stands out. If the rough idle clears up after a second or two then the water leak is not very significant (yet).

FYI, whilst this sort of failure eventually erodes the cylinder head sufficiently to cause a head gasket failure and significant coolant loss before that you will find the coolant system being pressurised just like with any head gasket failure. Is there evidence of this?

Incidentally if your water pump is leaking it would be very difficult to see it being driven, as it is, by the cambelt and also being hidden down at the bottom of the engine. Pretty much everything is in the way. A water pump leak coiuld easily loose as much water as you describe, but it is also something you don;t want to fail as it will probably bugger the cambelt and therefore the engine at the same time. Are you due a cambelt soon?

[Penguinistics]

Quick clarification. I ask if you need a new cambelt as you will need a new one anyway if you change the water pump. The labour cost is pretty much the same as for a cambelt change as the mechanic has to do miuch the same job.

[Jon45]

Thanks.. I will make some more checks.. I have arranged for a coolant "sniff" test this weekend.

The cambelt was changed at about 90k, the radiator is new (10 months ago) as are the hoses and cooling fan etc. (accident damage repairs).

My car (unlike rules'), isn't suffering from rough idle though. Engine performs as expected. Maybe it hasn't got to that stage yet !

[rules]

Hey Jon, just thought of something else which I have also been through ... have you checked your heater matrix/core. Some people have problems with the core itself and some, like me, only need to change the o-rings where the coolant pipes connect to the matrix/core.

Have you pressure tested the cooling system? I have found some really small and arb leaks this way in the past. Unfortunately the last time I did it (on Tuesday) I could pick up no leaks, that's why I think it might be leaking into the motor. I have never noticed any bubbling in the coolant reservoir when the engine is running, but I suppose it might be a case where it only does it when driven.

[Jon45]

Update: The coolant loss got worse in the days following my last post.

I decided to change the waterpump and, although recently changed, did the cambelt, tensioner,pulley and aux drive belt too.

Changed the thermostat (which was also faulty) and flushed the system out.

Result is all is OK..the old water pump seemed OK, but there was evidence of leaking through the weep hole.

Thanks for the pointers - hope this info helps.

Now onto an aircon problem....