Vacuum created in cooling system

[Riley]

Before flushing my cooling system and replacing the PHH , I noticed that when the engine is cold, the larger hoses are a little collasped (i.e. Rad hose). When opening the radiator cap I can hear a whoose of air and then the hoses go back to their normal shape. Obviously there is a slight vacuum building up in the cooling system.

What causes this?

Is this is an issue?

I started thinking about this last night and started to get worried that my HG is starting to fail and pulling coolant into the combustion chamber. But wouldn't I see bubbles in the overflow?

I'm also wondering if I should replace the radiator cap as well. Perhaps this is a fault?

Riley

 

[Eduardo96FZJ80]

How old is the cap?
For the price a new one couldn't hurt ???

 

[Riley]

I'm pretty sure that the cap is the original. I'll replace but I've just forgotten about it.

Not sure it would cause this.

 

[RavenTai]

the cap has 2 valves one to let fluid out as the coolant heats and expands and another to let coolant back in from the reservoir as it cools

I am betting the second is plugged somehow, possibly with a little bit of that gray sludge?

 

[Gauge]

I had this problem on a Ford Ranger. I flushed the radiator and afterward added too much Radiator Sealer and it clogged up the holes on the radiator cap. So, when the system heated up, the pressure would push the coolant into the overflow, but when the system cooled, the vacuum wasn't enough to pull the coolant back and the hoses would collapse. I tried everything to clean the cap, but it was never fixed. I drove it like that for years without problems. I would change the cap and make sure it stays clean.

 

[Riley]

new cap ordered from local stealer. Watch them get the wrong one

Sounds like a reasonable solution and much better than my "stay awake at night, HG is failing cause."

 

[Rookie2]

Did you double check the hoses going to the coolant reservoir, to make sure nothing was clogged there. Seem big and hard to clog, but wouldn't hurt to check this.


Rookie2

 

[Riley]

Just thought I'd close off this thread by saying that this problem was solved by replacing my radiator cap. Expensive little devils when you buy from the local Canadian dealer

Thanks for advice guys. You nailed it!