Volvo tmd22a (Perkins m50 with turbo)

[VADROUILLE]

Can anybody tell me why there is a "rubber bush" inserted onto the tube stack which slides into the heat exchanger?

Theory is its there to protect the tube stack from rattling on the inside of the heat exchanger, and damaging the tubes. I can't see why it would be a seal as the tube stack has two holes for fresh water flow at each end. Which means fresh water can make its way to each side of this rubber bush.

Any clarification on this would be greatly appreciated

 

[DownWest]

No doubt some one will come and give a more accurate answer,but, If IFIRR, it is to ensure the coolant actually goes through the h/exchanger, rather than just wander past it. It is not a positive seal, but 98% of the coolant will be sent via the h/ex.
DW

More time, so longer answer. The 'box' that the tube stack lives in is divided by a baffle. The stack is the connection between the two spaces. The rubber grommet makes sure that the coolant passes through the stack rather than slip past and not get cooled by the raw water. BTW, it needs to go in first, before the stack. Bit of lube helps to get the stack in after. It is shaped to stay in place and needs to go in from the front end.