Upper rad hose being sucked closed when engine is warm, motor revs?

Guys, any ideas why this is happening when engine is running, warm. If you rev it when temp is 200, the upper hose starts to collapse. I have a new TA performance 180 t stat. New 5 blade water pump, running a/c pulleys....I put a spring in lower rad hose, it seems fine. Thanks, Brad

 

Check radiator cap.

 

X 2

 

[Edited]
Rad cap first, but the second thing is a plugged hose for the overflow. Third would be an aged/degraded upper hose. Fourth would be a suspect thermostat.

Any problems with overheating?

 

New acdelco rc27 being picked up Friday. Since installing a temp gauge, I’ve noticed temps in the 215 range at times. I have a new TA 180 t stat, 7 blade clutch fan and shroud. What I witnessed yesterday, upper hose sucked closed when I rev the engine when the t stat should be open (gauge at 200) is a first for me. Once the hose relaxes, you can see temp drop.
I hope new rad cap is cure. If not, I’m buying a good quality upper hose next.

 

If the problem with the hose collapsing began after you installed the t-stat then I would start with the t-stat.

 

It’s a weird one for me.......I use a system called “air lift” when filling. The tool creates a vacuum of the system, refills itself by sucking the coolant into the system by the vacuum created.

After I try the rad cap, if it solves issue....great.....if not, new rad hose, will check position of t stat when changing rad hose.

Never seen an upper hose suck shut while engine is operating.

 

Edited my prior post to include a plugged overflow hose. The radiator hose can't "suck" shut without low pressure in the system, and the overflow hose has to flow in order for the vacuum-relief valve in the cap to relieve vacuum.

How do you create vacuum? Engine is hot, coolant pressure gets relieved via the rad cap. Then engine RPM increases, air flow increases, and the temp drops a little. Lower temp...lower pressure.

 

I just took the overflow hose off....perfectly clear. Heading down to GM to get the ACdelco RC27 cap......the other cap was a 13 lb “S” ....made in Mexico cap.....

 

Put the new acdelco rc27 cap on, a new hose from rad to overflow tank, drove it Friday afternoon.
- could not duplicate collapsing upper rad hose....so that was good.
- coolant temps for the most part stayed between 175-190 once warmed up (180 t stat)

I may be watching the gauge too much.....it seems very responsive to fluctuations as the system cools the car. I have the transducer mounted in the intake where the vacuum tcs used to be.

See pics of old cap versus new.

For sure big improvement

 

Great news. Glad it was an easy one.