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Expansion tank overpressure

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fjd

Member
"Engine AQ120B, fresh water ex

"Engine AQ120B, fresh water expansion tank pressure cap releasing small amounts of coolent, cap is 4#s, engine temp is between 160 and 180 F. Engine is not overheating, raw water pipes are cold and heat exchanger is warm. How high can the cap pressure be set? Also no view port on tank, what is proper level? It has never done this with existing cap (about two years old). Any ideas would be great. Thanks,
fjd"
 
Hi Fred my AQ140a is looseing

Hi Fred my AQ140a is looseing coolant after i come of cruise at 4400 rpm back to 1500 rpm then after a few minutes settles ok.Mine isnt overhaeting either infact I can touch the engine block with my hand and the expansinon tank to is not that hot.I have read somewhere you can use a slighter higher pressure cap 7 lbs be interested to see what people think.Cheers for now
 
"Ihave a 15 psi cap on my 120

"Ihave a 15 psi cap on my 120 B. Don't have any problems..... So far
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At 180F the coolant isn't

At 180F the coolant isn't boiling but it does expand when it is heated. Maybe it's overfilled and the excess is being forced out the cap.

I have a 13 psi cap on my AQ120B.
 
Hi all I have just bought a ne

Hi all I have just bought a new cap lowest I could get was 7lb fitted tested and all ok.I did change the coolant for a new antiboil 50/50 mix dunno whetehr that really makes that much differance or not.Volvo mechanic here reconed that the cap is set at 4psi as the seals which join the expansion tank to the heat exchanger on the tube if you know where i mean dont tolerate much pressure thats all...
 
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