Coolant goes to reservoir but doesn't return

[BumpLover]

Good day ,
My problem as stated in the title, is that after using my vehicle I notice that the reservoir is over full but the coolant doesn't return to the radiator after getting cold. When she cools down and I turn her on again I hear a distinctive sound that sounds somewhat like a swooshing, because there is air on the radiator instead of the coolant that should be there. If I turn her on and don't turn AC on or drive her, temperature stays frosty at 192*C. I think that rules out a leak. Now here is some extra info to help dig into this, please advice!

Radiator is a replacement with same specs as original (1 year old)

Thermostat is an OEM one. Changed with the radiator.

Radiator cap is now an original OEM cap. 2 weeks old.(I bought a PepBoys Stant one too but that didn't quite do the job so I got the OEM one.)

Water Pump is a new Bosch one, around 4 months old.

Around last October I had a Water Outlet Gasket fail, added glorious Bar's Leak Copper Stop-Leak and it pretty much made my system go FUBAR.
Like 2 months ago I mounted a by-pass filter with some Wyes and the heater lines (I think using Wyes with I.D. of ½ rules out any restriction.) , also added RMI-25. RMI-25 did it’s job nicely and now I don’t see any bar’s [censored] around and radiator core looks shiny like new. (It had some bars [censored] covering.)
I don’t think I forgot anything of importance, anything else just shoot and I will reply ASAP, THANKS!

 

[Tegger]

If coolant is not being pulled back into the reservoir, these are the most likely possibilities why:
1) the hose between rad and reservoir is pinched or otherwise obstructed;
2) the system is not sealed (leaky), and air can enter more easily than the fluid from the reservoir.

Does the system build pressure when the engine is hot? (upper rad hose will get hard to squeeze)

 

[NHGUY]

Making pressure but not holding suction.Something isnt sealing.Might be a hose,could be something far worse.

 

[quint]

Originally Posted By: BumpLover
...temperature stays frosty at 192*C. I think that rules out a leak.

I hope you mean 192*F, not 192*C, as that translates into 378*F, which is a couple degrees too hot.

Its hard to say without actually being there and checking a few things myself, but I'd bet your engine has a bad head gasket.

 

[SteveSRT8]

Far more likely is a bad cap, or the fit can be bad at the radiator neck. Check both with a tester. Easy and quick, many local stores will do it for free.

The absolute bottom line is that if it does not fill and draw back from the bottle there is a break somewhere in the vacuum that should draw coolant back into the engine as it cools.

 

[BumpLover]

Yes, the system does build up pressure, gets really hard and I have opened it hot and it hisses.
Oh my, that was a typo, yes 192*F not C, it seems chemistry is taking it's toll on me.

I will verify the caps and the neck, will venture out on Sunday to find out where I can do that.

Since RMI-25 has a built in UV Dye ill see what can find, lets hope nothing.

Thanks for now, I'll keep you posted!

 

[bullwinkle]

Not sure if they have free loan-a-tools in PR, but I would be checking for rapid pressure buildup while running & pressure testing the cooling system-something is not right.

 

[Rand]

probably the hose to the overflow isnt sealing so its sucking air back and not coolant.
I'd start with the CAP seal, and the hose to the overflow
and make sure no pinholes etc.

also if the hose goes into the cap not the side.. make sure there is a hose or straw type thing on the inside of the cap going into the liquid.

 

[Eddie]

1 radiator cap. remove and clean selaing surfaces on radiator and cap. check cap gasket.

 

[zrxkawboy]

I'd look at the cap or the hose to the overflow bottle, more likely the hose since you've tried two caps, including an OEM. I don't believe it's anything major.

 

[BumpLover]

As most of you are suggesting, it's a radiator cap/ radiator neck problem. Why? Most of the time I refilled her shortly after turning her off, but today, I refilled after 5+ hours of vehicle off... The system STILL had pressure on it despite being off for that many hours.

I inspected the radiator cap, since it's new it's of course behaving well and looks good BUT i noticed the radiator neck has a black deposit on it (I bet it's some Bar's Leak [censored] leftover).

I think this gunk is the problem causer because everything else looked fine, could it be?

I was able to remove some of it with a Q-tip but not all...
Is there anything in particular I could use to remove that? I don't want to damage the radiator neck with something abrasive.

 

[HerrStig]

The system should be pressure tested for "leakdown". You have have leak (fluid out and/or air IN) potential from the heater core and heater mixing valve to consider as well as the parts you can see under the hood.

 

[ffhdriver]

I had this happen once. Turned out to be a small crack in the reservoir where the hose connected. It didn't leak fluid just air.

 

[demarpaint]

Originally Posted By: SteveSRT8
Far more likely is a bad cap, or the fit can be bad at the radiator neck. Check both with a tester. Easy and quick, many local stores will do it for free.

The absolute bottom line is that if it does not fill and draw back from the bottle there is a break somewhere in the vacuum that should draw coolant back into the engine as it cools.


That's what I was thinking.

 

[BumpLover]

Thanks for the replies, sorry for taking so long!
University and work don't give me much time off.

@Kerrstig, where could I have a leakdown test, a radiator shop right? Cost estimate for the test?

@fhhdriver, sadly my reservoir is not the problem, i looked at it already

The system holds pressure but i haven't been able to test the cap and neck.... I will try to source a good radiator shop and go to it. Thanks!

 

[440Magnum]

Don't neglect the hose from the radiator neck to the overflow reservoir. A pinhole there, or a loose clamp at either end, or a cracked fitting at either end will cause EXACTLY the problem you're seeing. When the radiator is heating up and pushing water out thru that hose, its not really under any pressure so the pinhole won't leak any (or not much). But that hose has to be airtight because when the radiator cools and starts to pull a vacuum, it has to suck coolant back "uphill" through that hose. If there's a hole in that hose its like trying to drink water thru a straw that has an hole in the side. You get more air than water.