My Perkins 4.108 has been fitted with a 7 lb cap forever. Operating temps are stable at 185' unless I accellerate over 2000 rpm. I have read that the proper pressure cap s/b 10 psi. I'm not looking for trouble but I wonder what the proper psi should be. What affect will a 10 lb cap have on general operation. Bob
Expansion tank cap psi
- Thread starter bobtigar
- Start date
Bob,
I am not sure if this helps but - I struggled with overheating problems with our 4-108 for several years. I spoke with Westerbeke and they suggested the following fix...
http://www.sailingseadragon.com/Engine%20Cooling%20Mod.htm
The pressure cap on Sea Dragon's overflow tank is 7 psi as well.
Garner
I am not sure if this helps but - I struggled with overheating problems with our 4-108 for several years. I spoke with Westerbeke and they suggested the following fix...
http://www.sailingseadragon.com/Engine%20Cooling%20Mod.htm
The pressure cap on Sea Dragon's overflow tank is 7 psi as well.
Garner
Higher pressure raises the boiling point of the coolant a few degrees. That would allow operation at higher temperature without boiling. Does not change the temp alarm set point.. . Boil point with 7 pound cap is about 234F with 10 psi cap, that goes up to 240F Not much difference.. What it might prevent is localized boiling in places of low pressure related to flow.. like the inlet to the circulating pump.. or places of higher local temperature like the cylinder head around the exhaust valve and port. These areas of local boiling can restrict flow enough to be a problem.. in this case, probably not.. but worth a look/see if Garner's post does not apply.. A 10 pound cap is cheap.