When you say Cap do you mean the over flow cap?, No that will not cause coolant to disappear. If you are talking radiator cap that will lose coolant and over heat your motor. The main function of the over flow cap is to keep dirt out of the coolant. A rag stuff in it would be almost as good as a cap. Your description is hard to follow but if your hose between the radiator and the over flow tube has issues replace it and get a new clamp. The new clamp will just be a regular hose clamp, don't over tighten the clamp on the plastic over nipple.

 

? did you get your radiator replaced yet confused hear ,over flow not realy it wont would take a long time . years ago i used a cap an foil on the over flow worked ok ,you may want to get another cap it should be fairly tight so it does not allow crap in ,radiator cap allways should be tight


leak replace the hose on res tank,sounds like you got a leak need to take tank out make sure no holes in it, could be res hose leaking from being beat to ,as you hose would be at the bottom of the tank ,so like said replace the hose fist

Again i thought we were just talking about replaceing the radiator,the res tank would need tlc too. sounds like thats it ,it may just be the hose too ,your free lance mech should have the answers to this problem,if he replaced your radiator then he should know what else is going on

 

We're taking about overflow here

I never said radiator cap.

the overflow tube reservoir thingy got it's own half butt plastic cap that don't close tight as if it lost its grip

after only driving it 30 minutes coolant in overflow completely disappears

there thank God is coolant in radiator after driving so my new radiator is perfect

I add coolsnt in intake radiator reservoir overflow an Inch below overflow fill line

when car is parked & not moving it don't disappear from overflow so it only a problem when in use / driving

but after driving for 30 minutes coolant in overflow disappears

ok it is not the overflow cap that is the problem thanks to Gorn we can forget about worrying about the cap.

it is a part O"Reilly autopart store does not have ( the overflow hose) but they cut a piece off after looking at the old one and charge $10

The phone rep from above said store said it may not be a leak in the overflow hose so we re looking at the entire overflow that looks like a 9 inch tall cylinder that has to be replaced?

I see no visible signs of a tear or hole in either the overflow hose or the overflow itself

Above mentioned auto part store said a coolant pressure tester won't help...that this tester to is used to check for leaks in the radiator which ain't my problem- my problem is the coolant overflow aka reservoir tube.

*I will make it easier to understand than what I Thought I did the 1st time around.
Here: "how many different problems account for coolant disappearing in overflow after only 30 minutes of driving?"

1) the overflow hose?
2) the overflow itself?

hopefully it is either those 2 or both of those 2 and not 10 other Damn problems that can explain coolant in overflow disappearing after only 30 minutes of driving?

There does not seem to be a tool by the way, to check for leaks aside from eyeballing or so I would have to take the Damn 2 things out and.just buy aforesaid above 2 autoparts? Hoping that the 2 new parts do not have a manufacturer defect and since they are new-they would finally.end this annoying problem.

I can't make this easier to explain
reason why I'm Often so wordy is I am precise to avoid confusion and repition but my darn laptop is in the pawn shop (it paid for my new radiator) and I'm typing this on a little smartphone keyboard. Ugh!
Thanks

 

Lift the battery out and look at the metal/rubber hose underneath. Very common spot for these to leak from. May have to pull entire overflow and check for cracks too.

Pressure tester would show more than just a radiator leak. It can be used to diagnose a head gasket leak, whether internal or external, as well as hose leaks. It can also be used to determine if a pressure cap is functioning properly.

 

The question is where is the coolant going? Overflow should leak all the time. Think of it like a milk jug with a hose. There is never any pressure on it. It either leaks or it does not leak. Coolant should only move from the overflow to the radiator when there is vacuum in the radiator to pull it. The only time there should be vacuum is when the engine is in the process of cooling down.

Its pretty simple, engine gets hot things start to expand it pushes coolant out. later thing cool down an goo back to original size and the system pull the coolant back in. If you are pulling coolant into the radiator while you are driving, its not good.

Sounds to me like you need a pressure test of your coolant system.

This does fall under a regular mechanic would have found this this issue after installing the radiator. At least I would have. Anytime I worked on a coolant system there was a quick pressure test to prove the repair before returning the car to the customer. Also replacing the degraded over flow hose would have been part of the rad install. Missing a failing part attached to a part I just installed would be considered a come back and I would have had to work on it for free.