had my car in the workshop the other day getting the valve springs done when I said to the mechanic that the steering had started shuddering. he took the filler cap off and said the reservoir was under vacuum. he told me to turn the steering lock to lock a couple of times with the cap off and the engine running and what do you know problem fixed. I have heard that it is a common problem with ba's so before you spend any money give it a go it might work for you too.

Dead right same thing happens to mine and this solves it every time