Radiator Cap???
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Senior User
Joined: Apr 2006
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From: Everywhere, USA
Radiator Cap???
Some time ago I went to Advance to buy a new radiator cap. The one that was one the truck appeared to be origanal 212,000 miles. It said 16LBS. Motorcraft RS-90. The truck was not running hot or anything, just pushing coolant into the resivor more than I thought it should. Well the guy at Advance said this one is the one I show for your truck... It was a 13 LBS, cap. I said well this is what was on there. He said well if you want a 16LBS they are all the same, so I bought the 16LBS he had. I thought the interal spring and seat was a little short. Anyway, it still pushes coolant more than I think it should. The truck never runs over 210, maybe 215 with the A/C @70mph.
So the question is... Is this the right cap?? Are they all the same?? What is the right Cap?? I just don't want to be in the desert pulling a load and have the wrong cap.
So the question is... Is this the right cap?? Are they all the same?? What is the right Cap?? I just don't want to be in the desert pulling a load and have the wrong cap.
Senior User
Joined: Dec 2006
Posts: 344
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From: Byron New York
If it is moving radiator fluid around do you have to add because it is low? The pressure really only keeps the water from boiling much like a pressure cooker works. But if your temperature stays the same and your not losing any coolant I would just keep an eye on it.
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
Total cooling system capacity is almost 7 gallons.
That much fluid going from say 70 degrees to over 200 degrees does expand a good bit.
Several quarts being pushed into the reservoir on a hot engine is normal.
As long as the radiator is full when you check the fluid level on a cold engine you should be fine.
When you start finding the coolant low in the radiator and there is coolant in the recovery tank you have a problem.
Several things that could cause this are,
A small leak that is sucking in air as the engine cools.
Cavitation just starting to show.
A leaking head gasket.
A bad upper seal on the radiator cap leaking air into the radiator.
That much fluid going from say 70 degrees to over 200 degrees does expand a good bit.
Several quarts being pushed into the reservoir on a hot engine is normal.
As long as the radiator is full when you check the fluid level on a cold engine you should be fine.
When you start finding the coolant low in the radiator and there is coolant in the recovery tank you have a problem.
Several things that could cause this are,
A small leak that is sucking in air as the engine cools.
Cavitation just starting to show.
A leaking head gasket.
A bad upper seal on the radiator cap leaking air into the radiator.
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From: Everywhere, USA
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Hello.......the pressure rating on the radiator cap is very important on cooling systems (specially 7.3 diesels).......OEM speck is 13 lbs........not only does it help in controlling boil over, but it is a major factor in stopping cavitation in the block......................as well as the cap, the coolant system should be pressure tested at least every two years....................the coolant system must be air tight in order for the recovery system to work properly....................99% of all vehicles the radiator cap is bad and the system is not air tight..............as well, you should add a "air bleed tee" in the heater hose if it is at or higher than than the radiator cap.....................
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