03 plate (2.4) xc90 gearbox and leaking radiator fault

[Turnipstar]

Having a problem with our 03 plate xc90 (2.4) we had a whole new gear box fitted about 10 months ago, it is still under warranty.... Driving along last week and gear box makes noise then stays in 3rd gear. We were able to drive home through 30 zone and get to garage who fitted it, who initially said it was a fault in the hydraulics in the gear box (meaning they would cover it) - this is what they said was showing through their diagnostics when they rigged it up. I'm sure you can see by this point I am not remotely car savvy so please bare with me!!!
Anyway husband calls today for update and they are now saying the radiator has leaked into the gear box and caused the damage therefore we need another new gear box. Our car is quickly becoming like trigger's broom (5 new heads and 15 new handles!!!) our car has had in excess of £6k spent on it (I had a crash and settled out of court) and is worth 3k max now we can't justify spending anymore but we have 4 kids so need the extra seats and feel better the devil you know! What is the likelihood the garage are trying their luck? We had no visible water leaking at all and it suddenly went with no warning and the heating gauge stayed same- would it do that if radiator was leaking? We honestly feel they are trying their luck - is it a common fault on this model of car?

[kdst5]

There are some reports on the XC90 and V70/S60/S80 P2 forums of this as a problem but they seem few and far between.

From what I remember the most likely explanation is the antifreeze has been replaced with the wrong type or not kept at the correct concentration. As the radiator cools both the engine and the gearbox (two radiators in one package) if the antifreeze is not working correctly then the radiator can rust internally and allow the oil from the gearbox to mix with the water from the engine. This will then lead to a gearbox failure.

I also think I remember Clan on here saying that if you keep to using the Volvo antifreeze in the correct concentration it's not a problem. So do you know the history of the car and any work done on the cooling system? have you had to top up the cooling system?

Also what was the cause of the first gearbox failure? Could it have been coolant in the gearbox that time as well? If it was then the radiator should have been replaced then.

[Tannaton]

Oh dear it sounds like you have had a really rough ride...

It can happen as the gearbox oil is pumped through part of the radiator to cool it (and heat it when cold).

It should be obvious when this happens though, the gearbox oil should be a milky emulsion if water has mixed with it. 3rd gear is the "emergency gear" which the gearbox will sit in if there are no hydraulics.

I would walk in to the garage un-announced and ask to see what evidence they have found to lead them to that conclusion - I would also try flushing the fluid and see if this improves things? It can't have mixed that much water with the oil as you don't need to lose too much from the cooling system before you have overheating problems.