Radiator cap

1991 DODGE RAM
158,000 MILES • V8 • 4WD • AUTOMATIC
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DIRTYDAN2022
  • MEMBER
  • 3 POSTS
I replaced a bad radiator cap and lost a lot of coolant, but the reservoir appears full. My theory is that the old cap wasn't holding pressure and this one is, so it pushed out excess coolant that the old cap needed due to lack of pressure. You agree?
May 14, 2022 at 12:30 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
Hi,

When the engine is cold, remove the new radiator cap. Check to see if the radiator is full. If you lose a lot of coolant and the reservoir is full, the radiator is likely low.

As far as the old cap is concerned, it's possible that it was allowing coolant to go into the reservoir at a low temperature. The new cap wouldn't allow that to happen.

Let me know what you find. Also, let me know if the vehicle was overheated or if you are experiencing issues now.

Take care,

Joe
May 14, 2022 at 2:49 PM
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DIRTYDAN2022
  • MEMBER
  • 3 POSTS
Everything is full, nothing overheating.
May 14, 2022 at 3:07 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
Okay. If it remains full and not overheating, everything should be fine. Also, yes, I agree with what you mentioned originally. If the cap was not holding, it would allow coolant to bleed into the reservoir.

Let me know if you have other questions.

Take care,

Joe
May 14, 2022 at 3:09 PM
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DIRTYDAN2022
  • MEMBER
  • 3 POSTS
Thank you sir.
May 14, 2022 at 3:40 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
You are very welcome. Please feel free to come back anytime in the future. You are always welcome here.

Take care,

Joe
May 15, 2022 at 11:42 AM
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