We keep failing water pumps as well. Currently on no 3. The gasket seal just blows but it’s pumping round ok.
There is something wrong with the cooling system if that keeps happening. It might be clogged, coolant doesn't run freely inside radiator therefore improper cooling and blown seal. A system cleaning would do great probably, you can do it with citric acid. Can read abot the process
here, I did it mainly for the heater but that actually cleans the entire system and very efficient, too. You'll be amazed by what comes out.
1.5 litres in how much time, how many kilometers?
If you can't spot leaks there could be a leak on the camshaft pulley seal. If there is, it's under the belt cover so you can't see it and the oil leaks down the hot engine and burns so it won't be dripping on the floor. So it worth a check.
So, your cylinder head gasket is OK between the lubrication system channels and the cooling channels. The gasket could also be burned between the oil channels and the cylinders and then the oil can enter the combustion chamber through that path. In this situation, compression in the cylinders is lost and you will have increased pressure in the engine block. Probably bluish smoke would also be visible at the exhaust and a decrease in engine power would be felt. A compression test helps here.
Of course, oil can also enter the combustion chambers if the piston rings are worn, but then it is quite obvious, you can feel a loss of engine power and you can see bluish smoke at the exhaust. The compression test is conclusive for this case.
Even if you do not see bluish smoke on the exhaust, it does not mean that the engine is not burning oil in the combustion chambers. If the valve seals are worn, the oil enters the combustion chambers there and is burned. It enters in small quantities, which means that there is no obvious bluish smoke, but it is a constant consumption and it accumulates with every kilometer traveled.
Then, it often happens that the lubrication system channel inside rocker cover gets clogged, which causes insufficient lubrication in the upper part of the engine, excessive heating in the upper part and premature burning of the valve seals. Also, lots of oil gets burned there if so and excessive oil vapors goes to intake manifold via the breather.
Also, a serious problem with the lubrication system is the clogging of the oil pump pickup pipe strainer with the effect of inefficient lubrication. Also with the oil pump, the seal between the pickup pipe and the pump wears out and the pump draws air there and sends a smaller amount of oil to the channels. This problem is usually not noticed, the oil warning light only lights up when the pressure is very, very low. The engine overheats on certain parts and burns the oil that comes into contact with the overheated parts, and oil vapors reach the intake manifold and combustion chambers through the breather, again.
My Punto engine used to consume a lot of oil, and I fixed the problem. You can read about it
here and
here.
Basically, the work I did was related to the mandatory maintenance of the lubrication system, and it took me some time and it consumed quite a lot of oil in the meantime until I fixed it, because I did not find details and recommendations about maintaining the lubrication system, as I did. And besides, repairs require access to the engine, getting inside and I've seen that the general perception is to avoid that as much as possible. People freak out when they hear that the cylinder head gasket needs to be replaced. The lubrication system is usually ignored because the engine is running and there are no clear signs that it needs to be serviced.
