Perkins 4-108

[Rbrucek]

Thanks everyone I'm going to clean the heat exchanger now

[1affiah]

If you have a HW heater in the coolant line, check the plumbing. There is a reduction in hose sizes. On my boat, all the cooling water passed thru the HW heater, and the PO had a PVC reducer installed. When it leaked, he just kept tightening the hose clamps, and the ID of this fitting was down to pencil size.
Brass fittings solved the problem.

[skipperpete]

Originally Posted by Rbrucek

Thanks everyone I'm going to clean the heat exchanger now

I'm sure this has been raised before on other 4-108 overheating posts but I'll mention it again. The cylindrical core stacks used on many engines are enclosed in a bronze/ brass tube with a hole through it at each end to allow the flow of coolant through and over the tube bundle. Raw water goes through the small tubes longitudinally. If the coolant flow is able to just travel down the outside of the bronze tube the heat transfer is greatly diminished and you get a slow coolant temp increase and eventually an overheat. To direct the coolant flow there was a flange inside the heat exchanger housing to stop the coolant from taking the shortcut outside rather than through the more restrictive tube stack. Perkins used several different methods to direct this flow including simply aligning the hole to the tubes with the circulating pump inlet or , on the perkins Prima , the inclusion of a plastic sealing ring around the core outer tube that had to be pushed into a casting sealing face in the housing.
The trick is to get a good flow of coolant through and around the tubes, not straight past em.
Hope this might help if you're having the slow overheat.
Pete

[BigAl.NZ]

Originally Posted by skipperpete

I'm sure this has been raised before on other 4-108 overheating posts but I'll mention it again. The cylindrical core stacks used on many engines are enclosed in a bronze/ brass tube with a hole through it at each end to allow the flow of coolant through and over the tube bundle. Raw water goes through the small tubes longitudinally. If the coolant flow is able to just travel down the outside of the bronze tube the heat transfer is greatly diminished and you get a slow coolant temp increase and eventually an overheat. To direct the coolant flow there was a flange inside the heat exchanger housing to stop the coolant from taking the shortcut outside rather than through the more restrictive tube stack. Perkins used several different methods to direct this flow including simply aligning the hole to the tubes with the circulating pump inlet or , on the perkins Prima , the inclusion of a plastic sealing ring around the core outer tube that had to be pushed into a casting sealing face in the housing.
The trick is to get a good flow of coolant through and around the tubes, not straight past em.
Hope this might help if you're having the slow overheat.
Pete

Ok with the benefit of reading this post and your pics, I understand what the ring does and the point your making.

Is this sealing ring not a Perkins part?

Cheers

Al