Pneumatic parking brake failure

Hello, I need advice, the other day I was passing the ITV (Technical Vehicle Inspection), my vehicle is a truck, two axes, 12000kg, the inspection was unfavorable, the reason was little stopped in the front service brakes and in the parking brake, my truck wears air brakes, I have been since I was a child with trucks and I am 47 years old, I am not mechanical, but I understand the basic.
We go to the problem, I have changed the front pills, since they were spent, but the shoes, according to, looking for the abumers that exist it seems that they are not spent, these shoes have been running for more than ten years and also in the city that is where the brake is most used.
I think the shoes can be crystallized, but I also think the problem can come on the other hand, I appreciate any advice.

Greetings

I forget to say that although the parking brake does not stop well, in the service brake if they stop the shoes well.

Hi Tronh, 10 years the pills may be that as you say, they are crystallized, then this if any air leakage is observed (hose, braking valves, Calderin take or by the compressor), the braking valves sometimes remain seized by oxide or dirt and is not evil disassembling them to clean them and see how they are. Another point that must be taken into account is the hydraulic system and the drive (the pulmon or servo that pushes the pump) that is well regulated, that the pump sends pressure to the brake stirrups, that the hydraulic circuit does not present leaks or have air. You will have to differentiate if the problem is hydraulic, or pneumatic. The shoes would not be bad to give them a sandpaper with a sandpaper enough. Well, let's see if it may not be forced to go to a workshop. Greetings!!

The failure in the parking brake, if the truck is that of the photo, check the springs of the combined cylinders because the parking brake is activated when downloading the air from said cylinders and the spring I mention (it is thick and very powerful) makes the cams operate and the brakes tranca.

Thanks Jorgemf1, in effect it is an Iveco 109-14 Z Series, he is already 25 years old and I hope he lasts for a few years, since the engine is fine, I do about 25 or 30 km per day, a few days ago the ITV passes and they gave it to me favorable, but they told me to fix the parking brake, referring to what you tell me about the springs, something happened to me for at least 15 years. I welcomed me a spring and all the drum was raised, apart from deforming the shoe, I have vague memories because at that time it was my father who was in charge of the camon, we went to a workshop in Illescas and turned the drums, repairing the shoe too, I have tried to disassemble the wheels to see a little better what can happen, but when I arrived at the drum Take them out,
I saw them as with the heads a bit worn, now that I have the ITV after trying to make myself with knowledge and tools to disassemble the drums, since it is the only way of seeing the problem.
all the best