moteur qui compresse dans sa base

[sebsmods]

J'ai constaté un reflu d'huile par le gauge a huile. Premier diagnostique possible, la tête perd de la compression dans la base... Ca semble logique!

Quelqu'un a déjà eu ce trouble?

Je crois que c'est le début de la fin pour mon moteur...

Savez-vous si ca se soigne??

Merci de vos conseils!

[Cinqops]

Un test de fuite interne t'en dirais plus! avant de dire que cest les rings de tes pistons je te le conseil fortement.. cest p-e un PCV ( ou l'équivalent volvo ) qui fait mal la circulation des vapeurs de la panne. Ce qui causerais ton surplus de pression. Et aussi test de compression combine tres bien le tout pour etre sur que ton moteur est tjrs en forme!

[sebsmods]

Oki, j'ai fait changé le breather box déjà et des seals qui fuillaient... La moteur semble encore très performant! C'est quoi ca le PCV?

[Cinqops]

C'est une valve connecté au vacuum de l'intake, situé sur le couvert de valves, qui sert a controlé la pression et recirculer les vapeurs dhuiles qui se forment dans le bloc, et aussi les fuite de gas par les segments de pistons (rings) qui s'y perdent. Ces gas/vapeurs sont rediriger dans l'entrée d'air pour etre brulé dans les cylindres. C'est un moyen de sauver les joints d'étanchéité. PCV est le terme commun mais volvo peut avoir une autre appellation pour cette piece mais je ne la connais pas.

Wikipedia :

As an engine runs, high-pressure gases are contained within the combustion chamber and prevented from passing into the crankcase (containing the crankshaft and other parts) between the side of the piston and the cylinder bore by piston rings which seal against the cylinder. However, some amount of gas always leaks past the piston rings into the crankcase. This amount is very small in a new or properly rebuilt engine, provided that the piston rings and cylinder walls are correctly "broken in", and increases as the engine wears. Scratches on the cylinder walls or piston rings, such as those caused by foreign objects entering the engine, can cause large amounts of leakage. This leaked gas is known as blow-by because the pressure within the cylinders blows it by the piston rings. If this blow-by gas could not escape then pressure would build up within the crankcase.

Before the invention of Crankcase Ventilation in 1928 the engine oil seals were designed to withstand this pressure, oil leaking to the ground was accepted and the dipstick was screwed in. The hydrocarbon rich gas would then diffuse through the oil in the seals into the atmosphere. It is therefore an emissions requirement as well as a functional necessity that the crankcase has a ventilation system. This must maintain the crankcase at slightly less than atmospheric pressure and recycle the blow-by gas back into the engine intake. However, due to the constant circulation of the oil within the engine, along with the high speed movement of the crankshaft, an oil mist is also passed through the PCV system and into the intake. The oil is then either burnt during combustion or settles along the intake tract, causing a gradual build-up of residue inside the inlet path. For this reason many engine tuners choose to replace the PCV system with an oil catch can and breather filter which vents the blow-by gases directly to atmosphere and retains the oil in a small tank (or returns it to the sump), although this technically fails to meet most engine emission legislation

http://en.wikipedia.org/wiki/PCV_valve