Radiator Hose Collapse after cool down

[Simplicity-SKO]

I searched before writing this, but couldn't find an answer.

My engine runs fine. Builds up it's coolant temp to between about 200 and 212, the oil and tranny reflect this same range within a few degrees.

After the engine cools, my top radiator hose collapse. I understand that means there's a vacuum in the system.

My research tells me that it's either a bad coolant cap, a clogged line between my expansion tank and radiator, or somewhere else in the cooling system and finally, bad hoses.

What I've done:
I replaced my cap and unlike the old one, the mechanism seems to be functioning, yet there's still a vacuum. It's a 10psi, Dorman (I believe), cap. I screw it on until it clicks.

If I unscrew the cap, the hose immediately expands.

I'm assuming that since the cooling system is keeping everything cool, that it's unlikely that there is a clog somewhere.

Per the hoses, while they will be replaced soon (adding a tranny cooler, running new heater lines and changing coolant and filter), they are functioning with no signs of leaks. So, I'm assuming they are okay.

Since when I unscrew the cap the vacuum releases, I'm assuming that if the cap were working properly, the vacuum should release through the cap (no need to unscrew it).

I'm sure you can get a bad "new" cap, but before I go buying another cap, I wanted to see what all you wonderful people think.

 

[magnakansas]

The collapse....

IF, the radiator vent tube is just below the radiator cap, then the vacuum valve on the cap is - likely - the culprit. I wonder if, you left the cap off what happens. What is supposed to happen- Coolant gets hot, the expansion tank gets more fluid in the tank, as the coolant cools down, expansion tank level drops. The idea is to keep the radiator full at all times. I also think you may be running ten degrees hot.

William

 

[Mr4btTahoe]

First and foremost.. get a quality cap. Dorman isn't known for making quality parts. See if you can find an OEM or Gates/Stant.

Check the overflow tube and make sure it's not soft or kinked. Coolant has to be able to freely flow from the radiator neck to the coolant bottle in both directions when the valve on the cap opens. If the tube is soft or kinked, it will suck flat as the system tries to draw coolant back in from the bottle which would then put the whole system under a vacuum.

Start there.

 

[Danjo-SKO]

Check the expansion tank hose connection nipple on the radiator. Make sure it’s clear