??? My radiator hose flattened out?

[TurboChris]

Hmmmm haven't see this one before. I recently changed over my radiator reservoir to a new one on my 66 Fairlane (see photo)....I had a vent hose on it but it was expelling a little fluid after a drive so I plugged it up making it a closed system. I popped the hood open the other day....3 days after driving it and this is what greeted me. (see photo)

No cooling issues when driving what so ever. And of course, as expected when I crack the reservoir cap it regains its shape.

What do you guys think?

Something is creating a vacuum but dammed if I can't figure out the solution.

[jayb]

Can't tell from your pictures, but do you have a bypass from the intake to the water pump?  That little tube that goes between them?  If not, and if your thermostat is closed, I can see how this might happen, with the water pump sucking on the inlet hose and the radiator, and no way for coolant to enter the upper radiator hose.

[TurboChris]

No it's there. You can see it in this one.

My first thought was thermostat but I drove in 90 degree stop and go right before it and never saw over 210 on the gauge. But I never had it happen (noticed it) until I plugged the reservoir overflow.  So while it seems like a clue, not sure how they could relate to each other. My next thought is replace the radiator cap.

[70tp]

The overflow tank has to be vented to atmosphere.  The radiator has to be able to vent    When a liquid is heated, it expands and has to go somewhere.     If the catch can vent is plugged, it will do the same as plugging the radiator overflow.   The cap can’t do its job and pressure will build until something fails.   If you have a rad cap made for a catch can then you can vent the catch can and the rad will pull the fluid back in and not collapse the hoses.  The catch can doesn’t have to be full to be effective.    Maybe 1/4 full when cold , possibly a little less.   But should not be full when at temp.   A rad cap made for a catch can is different than one made to not use a catch can.  A catch can cap has a little valve thingie in the center to let water be drawn back into the rad when it cools and pressure drop to a vacuum

[70tp]

The catch can hose also has to draw from the bottom of the can back to the rad.    Not just catch the overflow

[galaxiex]

The system cannot/must not, be completely closed.
It must be able to "breathe", or vent somehow.

If the system is sealed tight, no vent of any kind,
when it cools off, everything contracts, and creates a vacuum in the system.
That causes the hose(s) to collapse.

[TurboChris]

The catch can hose also has to draw from the bottom of the can back to the rad.    Not just catch the overflow

Interesting, so I should reroute the hose to the radiator so it's coming off the bottom of the can AND keep a vent hose on it as well? I only plugged it as it was leaking a couple oz's of fluid after a drive.

[TurboChris]

The system cannot/must not, be completely closed.
It must be able to "breathe", or vent somehow.

If the system is sealed tight, no vent of any kind,
when it cools off, everything contracts, and creates a vacuum in the system.
That causes the hose(s) to collapse.

Ok makes sense. Easy enough to change back.

[Stangman]

Make sure coolant is full also. If it’s low it could do that when thermostat opens. At that point I would have shut it off let it cool down and I bet it would be low. Just a feeling.

[Riderjeff]

At least you know the rest of your cooling system is tightly and properly sealed! Catch can should be a simple fix.

[gregb]

nm

[TurboChris]

Ok what I ended up doing is I cut a new hose and ran from the bottom of the reservoir to the radiator filler neck. Then I was thinking I'd get another can for the overflow. But then I had an idea. I have a couple of the reservoir caps, maybe if I just drilled a tiny hole in the cap for venting?

So I tried it and drove yesterday to the Long Beach hot rod swapmeet and car show.  About 30 min in each direction. Warm day. Mix of stop and go and freeway driving. Performed perfectly. I think my problem is solved.

[mygasser]

when you have a recovery tank/reservoir like that the cap on the radiator should have 2 rubber seals. the normal one on the sprung bit that holds the engine coolant pressure and a second where the cap tightens to the top of the radiator's filler neck. if the second is not present the system can't pull coolant back from the recovery tank/reservoir into the radiator when cooling down.
neil.