Venturi Vacuum Problem On Cooling System - Need Help

[Fitz98]

2003 Suburban 1500 with rear AC.
I touched base on this in another discussion, but now I am down to actually performing the task and am having a problem.
Not sure if it a problem on the cooling system or the Venturi is not working with my partially drained system.

First off, I have drained the radiator and hoses, but have only recovered less than 8 quarts of a 15.8 quart system. I imagine the rest is mostly in the engine and maybe the front heater core?
There was some debate about whether the venturi would work or not on a partially drained system.

When I apply the venturi vacuum, it vacuums well up until about 18-20HG, then I hear what sounds like bubbling and that is all the vacuum I can get, when I close the valves, I lose vacuum quickly down to about 10 HG. The hoses stay collapsed.
I can't find any signs of a leak, so not sure if this is related to still having 50% of the coolant in the system and the venturi is not working, of if this is something else.
If it is about coolant still in the system, how can I get out the rest. I thought about running the car to open the T-Stat and redrain the radiator and the hoses.
But then I thought if I do that, would the vacuum hold open the t-stat for refilling, or will I run into an issue getting the block filled after the t-stat closes while refilling with venturi suction?

I had no leaks before I did my repair (I had to pull the rear quick connect lines of the rear heater core in order to remove my rear evaporator for AC service..so there is a small chance that there is a leak there, but if it was, it would be a small leak...or a rear heater core from removing the hoses, but I was careful, but still had to do some wiggling and pulling to get them off.)

I need to diagnose to make sure it is not a rear quick connect seal or rear heater core before recharging my A/C since I would need to remove that in order to remove or replace the heater core.

 

[atikovi]

when I close the valves, I lose vacuum quickly down to about 10 HG. The hoses stay collapsed.

Could be anything from a hose clamp not fully tight to the drain valve not sealing tight. Were there any leaks before?

 

[Fitz98]

Could be anything from a hose clamp not fully tight to the drain valve not sealing tight. Were there any leaks before?

I had no leaks before I did my repair (I had to pull the rear quick connect lines of the rear heater core in order to remove my rear evaporator for AC service..so there is a small chance that there is a leak there, but if it was, it would be a small leak...or a rear heater core from removing the hoses, but I was careful, but still had to do some wiggling and pulling to get them off.)
I inspected the pipes when the core was out, no cracks or bends.

I need to diagnose to make sure it is not a rear quick connect seal or rear heater core before recharging my A/C since I would need to remove that in order to remove or replace the heater core.

 

[atikovi]

Get a coolant pressure test kit.

Amazon.com

 

[The Critic]

How well is the venturi adapter sealed? Is this one of those universal cone styles?

To be honest, that's a lot of coolant remaining in the system. Might need to drain more of it in order for the tool to work.

 

[mk378]

Need to test it under pressure. A simple way would be to fill it up and run it. Do not run the engine without the system at least as full as you can get it by pouring into the radiator.

 

[Fitz98]

How well is the venturi adapter sealed? Is this one of those universal cone styles?

To be honest, that's a lot of coolant remaining in the system. Might need to drain more of it in order for the tool to work.

This was an issue. My bottle has an overflow port (with just a piece of what looks like wire loom off that port) that comes off the bottom side of the filler cap area...right at the bottom, so the conventional seal adapters do not cover that well. My kit has a cone style, so I used that. I also plugged the overflow port with a cap. Same issue, but I am not ruling out that there is a leak at that connection somehow...that's a lot of connections and the expansion part of the main fitting is not fully inside the cap area when using the cone fitting.
Perhaps this poor setup might be allowing for a loss of vacuum as the vacuum pressure increases?

How can I get more coolant out of the system? There is 8 quarts unaccounted for.

I will try another fitting tomorrow and try to source a pressure tester locally to rule out visible leaks in my repair areas.

 

[atikovi]

View attachment 214791

I'd be using just that round seal along with a round adapter if necessary in the filler neck. Cones don't seal too well.

 

[D60]

Yeah, if a leak is the concern, just pressurize it as-is. I got the AP pneumatic filler (just a regulator with a gauge, basically). I should have done it sooner, it's so nice for a quick sanity check on an empty system after service.

I use it in conjunction with an Ares master kit that has the appropriate rad cap with the stupid mini disconnects (why can't we just use standard air discos on such tools?????)

Just connect to shop air and fills quickly. Plus if you have a leak, no additional pumping-- just crack the ball valve and it's instantly topped off again.

Ironically, the only leak I found on a '99 Ram was at the lower rad hose where the tension clamp was long gone and a worm drive had been substituted. Using soapy water to watch the bubbles, I was surprised at how much I had to crank on the worm drive to get it to seal. New rad and new lower hose.

 

[Fitz98]

I may be chasing a ghost...yeah, the venturi will not make or hold a vacuum (in this case...I have had success with it before on other occasions), but I just bit the bullet and filled the system with fresh coolant.
I did try beforehand to use a different venturi fitting and re-plug the overflow outlet, worse than before. When I started filling the system, the overflow plug had a small drip come from it out of the clear tube I clamped to a smooth shanked bolt.
Heated up the car 3 times and topped off twice as the heater cores and lines got filled and circulated.
No visible leaks while checking at the highest heated temperature, no wetness coming out of evaporator case drain tubes, no anti-freeze smell anywhere, sprayed all fittings and connections with soapy water, checked oil and transmission fluid for cross contamination, HOT air coming out of front and rear vents. so far everything is checking out O.K.
Level is holding steady now, but will need to exercise it some more to be sure and see how level holds up.