Hello and thanks for choosing Just Answer,
When your mechanic says "slack adjuster" , I beleive he is refering to the timing chain tensioner. You do have to remove the timing chain to get the waterpump off this particular vehicle. And yes sometimes the tensioners will have to be replaced when doing this. If the tensioner would happen to go bad and the timing chain became loose it could cause engine damage, so replacing the tensioner is not at all a bad idea either.
As far as replacing the bolts, I can not answer if it true that they need to be replaced because I have ot seen, but in some occasions bolts can deteriorate and become weak. reusing them may cause them to break in the future. So having new bolts installed is not a bad idea either if they are in bad condition. If they are in good shape upon an inspection they can be re-used.
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