1994 Ranger - Cooling System Question

1994 4.0L Ranger - Purchased 16 lb. radiator cap from AutoZone, was told that what the specification on their computer system. The Mitchell book notes that the radiator cap should be 13 lb. What is the correct pressure
for the system? Will using a 16 lb. cap cause too much pressure in the cooling system and cause leaks that you might not have with a 13 lb. system? Recently changed ou the water pump and already seeing a leak at one of the attachment bolts. Used a torque wrench when I replaced the pump and tightened the bolts down evenly....so I'm wondering if the 16 lb. cap could be the problem. Thank you, Joe
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wrote:

Three extra PSI in the cooling system shouldn't cause a gasket to leak - if the seals and hoses were that sensitive they would pop left and right on people.
The bolt that is weeping might be a "wet" bolt, where the threads have coolant on the other side - check the manual. If so, you should only need to remove and reinstall that one bolt with some sealant on the threads, or (if all else fails) a copper washer under the head.
Mitchell says 13 PSI and Autozone says 16 PSI - One of them is probably right, but which one...? Tie breaker: Go ask Ford. ;-)
--<< Bruce >>--
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Hey Bruce....thanks for the reply. I'll check with Ford regarding the cap pressure as well as reseal the bolt that is leaking. Thanks again, Joe

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"Joe" wrote: (1994 Ranger 4.0L )
AutoZone computer says 16 Lb. radiator cap is specified for my car, but Mitchell book says 13 Lb. Which is right? Will my 16 lb. cap have too much pressure and cause leaks that might not occur with a 13 lb. system?
I recently changed out the water pump. I used a torque wrench and tightened the bolts down evenly but I now see a leak at one of the attachment bolts. Could my 16 Lb. cap be the problem? ______________________________________________
The water pump leak problem has nothing to do with the cap. Assuming that the pump gasket was not damaged at installation, the leak is probably water working its way past the bolt threads. Remove the bolt, coat the threads with sealant and reinstall it.
A pressure radiator cap is used to raise the boiling point of the engine coolant so that it remains liquid instead of turning to steam when heated. If the liquid flowing in the engine block turns to steam, its ability to carry away heat almost vanishes.
The coolant's boiling point is raised about 3 degrees per Lb, so a 13 Lb cap will raise the B.P. of (50/50) coolant from 222 deg F to 261 deg F. A 16 Lb cap would yield 270 deg F.
The 16 Lb cap provides somewhat better protection from hot spots being developed in the head/block casting. The engine and the hoses can easily withstand the pressure.
I can't think of any reason to use the 13 Lb cap, but I don't own any cars with the modern plastic radiators, so I don't know how fragile they may be.
Good luck.
Rodan.
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