Expect that you've already found answers to your enquiry. If not, then suggest that you use the CF Search
facility and look for the thread Perkins Prima-50 HeatExchanger
started June,2012. Read the full thread and the replies. Your questions are answered there.
In your question, you say that you saw two(2) rubber sleeve pieces (inside the heat exchanger bundle housing) after removing the tube stack. This seems odd! To my knowledge, there is only one (1) sleeve piece on the heat exchanger tube bundle. The sleeve material could be either rubber or plastic (dependent on engine number/date of factory assembly). If you see two rubber pieces, then its possible that the single
rubber sleeve has at some time in its life, divided into two halves. Either way, inspection
is suggested to determine the origin of the pieces.
Suggest that you install a replacement sleeve. See below.
The sleeve performs an important role. A baffle wall is cast to the inside of the heat exchanger cavity. The baffle is factory drilled oversize to enable the tube bundle to slide the full length of the HX cavity. To install the sleeve, It is necessary for the sleeve to be first installed on the end of the tube bundle, and then slid forward (attached to the stack). Thereafter the sleeve will engage with the baffle and also retain a friction fit on the tube stack. At this point, two sealed chambers are created inside the exchanger cavity. A serviceable sleeve is necessary to ensue that the heat exchanger functions correctly in that the raw water
flow is directed from the first inlet chamber, through the tube stack (only). The raw water
flow then exits the tube stack in the second chamber. Expect a new genuine replacement sleeve to be costly (+/- US$50). Regards.