1994 Ranger - Cooling System Question

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Joe - 28 Apr 2008 03:30 GMT

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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Bruce L. Bergman - 28 Apr 2008 07:39 GMT

>1994 4.0L Ranger - Purchased 16 lb. radiator cap from AutoZone, was told
>that what the specification on their computer system. The Mitchell book
[quoted text clipped - 5 lines]
>tightened the bolts down evenly....so I'm wondering if the 16 lb. cap could
>be the problem. Thank you, Joe

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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Joe - 28 Apr 2008 11:45 GMT

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

>>1994 4.0L Ranger - Purchased 16 lb. radiator cap from AutoZone, was told
>>that what the specification on their computer system. The Mitchell book
[quoted text clipped - 21 lines]
>
> --<< Bruce >>--

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Rodan - 29 Apr 2008 00:40 GMT

"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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