There is a design flaw in the Alfa Romeo 1750 tbi engine and the Lancia 1.8DI engine. The issue is located in the design of the oil pickup tube attachment to the oil pump. A lot of issues are related to this leaky seal (71754365) for example, rattling camshaft phase adjusters, worn out turbo’s and excessive wear on cylindered components.
The issue is caused by the way this pick up tube is sealed to the oil pump. After a period of time the rubber of the seal (71754365 Alfa/Lancia and GM 55589549) hardens out and can start to leak as a result air wil be sucked op instead of oil.
Construction of oil pick up
I do understand the choices of the Alfa / Fiat engineers. As a cost and weight reduction the pick up tube is plastic instead of the more traditional metal ones. Mounting a plastic part in these severe internal engine conditions is a challenge. Mounting it the traditional way directly on the oil pump is a risk because it might snap of thus they choose to mount it very rigid on the oil pan.
An additional advantage is that the plates in the oil pan preventing the oil moving to the side can cover all of the oil pan. When doing sporty curves the plate prevents the oil moving to the opposite side of the pick up tube causing starvation of oil supply. The way the pick-up tube is mounted there is no need for a big cutout for the pick-up tube.
Unfortunately the engineers did not spend much time on the oil seal. An attribute of rubber materials in hot oily conditions is it can harden out. Especially if you try to cover a 4.5 mm distance.
Also issues at GM / Opel / Saab
The same part is used in several GM diesel models. Back in the day the Fiat group worked together with GM sharing platforms and technology, that did not last long. Funny its now the same company; Stellantis. I did even found a petition regarding this issue begging for a warranty repair.
Can i fix it?
The image above is an oil pan and an oil pump of en seized Alfa Romeo Giulietta engine I bought on our local Ebay. Although there is a solution available on Ebay from a guy who makes round aluminium parts with oil seals you mount instead of the original one I was not willing to compromise the internal diameter of the upgraded seal so I made another design. The pump is high volume and a restriction like the round seal replacing solution might influence the performance.
I made one myself as a proof of concept. I will not use it in the Lancia because O-ring tolerances are quite strict and I do not have the proper tools to produce it. Nevertheless, I made it anyway just to see if it wil work out and I like turning on the lathe.
First a mounting tool, than mounting a square piece of aluminium with the outer shapes of the part.
As O-ring material I choose Viton purchased from the company Eriks. Viton has a high resistance to heat and chemicals like engine oil. Eriks provides an O-ring calculator which I commonly use for O-ring calculations.
At this very moment I am having the parts machined, off course one for the Delta but I will get some additional ones. If you need one yourselves send me a message!