Can't truncate Post Preview

I forgot to mention that in the frontpage I resolved it with some workaround. I writed posts just with some introduction and redirected the post to a page where the whole content can be found for that certain post.

BUT the problem is in the car types page. For ex.: Opel Combo B (in the left sidebar). The whole Post is showing instead of excerpt.

At the Edit Post page if I write in the Excerpt block it wont appear. I think the problem is with the Template, but I cannot change it (too much work with it.)

Please give me some advice.
Sorry for the english.
Thanks!