See comment on radiator cap below.
Play4aBuck said:
Hi All,
What is the most common reason for coolant to leak out of the reservoir Cap?
The car does not over heat yet, but looses coolant from time to time. I'm
not sure but I think it may leak the most when cooling off.
Do the caps go bad? (It's a 15lb plastic pressure cap).
I've often seen radiator caps that go bad over time. The symptom would be
what you have described: loss of coolant. If the cap no longer holds the
full 15 pounds per its original design, then the coolant will fill the
recovery tank sooner and be pushed out the overflow while the vehicle is
running (or when it has just been shut down since the engine is very hot and
the coolant is no longer circulating.) Once the engine cools, the recovery
tank fluid gets sucked back into the radiator resulting in the low fluid
level when you check it when cool.
The simplest thing here is to replace the cap with a new one (they are
fairly cheap and easy to replace) and then refill the radiator to the full
cool line. With any luck this will solve your problem. If not, then you
will need to look for the real source of the problem (plugged radiator or
leaking heater core, failed cooling fan, bad coolant temperature sensor,
defective fan relay, leaking/defective hoses or water pump) keeping in mind
it could be a blown head gasket and you might be buring the coolant.
Good luck!
Bob
Could I have a blockage in the hose that runs from top of the the reservoir
tank to the top of the engine?
You could, but not likely given that you said the vehicle is not
overheating. Try squeezing the top radiator hose when the engine is cool
and see if you can see result in the overflow reservoir. This should verify
there is no blockage.