Another update:

BAD news for me. GOOD news for you.

 

But first, the brake booster parts:

 

 

		part number	Description	Remark	ST	Model data
			individual parts for brake servo
2		114595801	diaphragm		1	A
3		114595162	piston		1	A
5		114595784	compensation washer		1	A
6		114595770	disc		1	A
7		114595671	spring 08.76 - 06.82		1	A
(7)		114595672	spring 07.82 - 12.89		1	A
8		114595800	seal		1	A
9		114595761	retaining ring		1	A
10		114595783	spacer		1	A
12		114595222	non-return valve		1	A
18		933201622	seal ring	16X2	1	A
20		114595741	stop buffer		1	A
21		114595785	underlay 08.76 - 12.89		1	A
22		954038107	seal ring	G38X50X7	1	A
23		114595221	valve		1	A
24		114595120	dust cap		1	A
25		114595350	gaiter		1	A
26			no longer available 08.76 - 07.83		1	A
26A		114595311	slide rod 08.83 - 12.89		1	A
28		114595900	seal 08.76 - 07.83		1	A
30		114595710	ring 09.83 - 12.89	50MM	1	A

Inspecting the old brake booster today, I've discovered this: (Output rod seal. No:8 on the list above)

 

 

The most important part is the main diaphragm. In my case, main diaphragm might be intact. I don't know. But this seal is ruptured and it will leak air for sure.

Searching for the parts, I've discovered that, parts stores are selling this seal for $1.5. It's a set with retaining ring. (Codes: 114595800 and 114595761)

They use this same part for Renault 12 and Fiat 131 too. So it's not hard to find.

 

This is one of the cheap fixes that the mechanics could use to charge you $$$ and if you are leaving the old parts with the mechanic. They will repair it with a $1.5 part, and sell it for more $$$.

 

If you have a hissing brake booster, remove the master cylinder, check this part when the engine is running. If this seal is defective. You are lucky. You can replace it in minutes for $1.5. No need to replace the whole brake booster and save lots of $$$.

 

4 hours ago, R_Blue said:

Did you see a another problem than the raised strut?

How old do you think the brake hoses are? Please answer after you bend them looking for cracks.