What does the top injector seal actually do?

[Mervyn44]

Hope this doesn't sound too stupid, but... what is the top plastic/rubber seal on the diesel injectors actually for?

I know the lower copper seal maintains compression in the cylinder so why is another top one needed?

[StuY]

Late reply, sorry, but here goes anyway. The 1.6 HDi head is made in two parts, and the injectors sit inside steel tubes that are pressed into the lower part of the light alloy head casting. The rubber seal is an oil seal between the injector tube and the top part of the head, preventing the oil splash that is goes on inside the cam case from getting out, and dirt from getting in. If fitted correctly, the rubber seals don't actually touch the injectors.

[Hell Razor5543]

Hope this doesn't sound too stupid, but...

I (and most of the forum) have a simple attitude to questions; they are not stupid, as the person asking the questions does not know the answers, and needs to know. One of my many sayings is "There are no such things as stupid questions, but stupid avoidable mistakes do exist".

[Mervyn44]

Many thanks for the replies fellas, much appreciated - Merv.

[Michel]

Hope this doesn't sound too stupid, but... what is the top plastic/rubber seal on the diesel injectors actually for?

It appears to be there solely to leak and create havoc, going off some of the 1.6HDi engines I've seen today...