No pressure in coolant system

JASON GALBRAITH

MEMBER
2008 GMC YUKON
5.3L
V8
4WD
AUTOMATIC
129,000 MILES

I had a heater core hose pop off because of a broken fitting. I replaced the fitting and then tried to pull vacuum on the system with one of those venturi things to test my fitting and fill the system. The vacuum gauge did not move so I rented a pressure tester from Advanced. It w ill not build pressure at all and I see no leak. What do I do next?

3 Replies

HARRY P

MECHANIC
2,292 POSTS

If it is not building pressure anywhere, it means that you have a sizable leak somewhere in the system. I would fill it with coolant and then start it and run it until I see a stream, and then try to follow it. It kind of sounds like something else must have popped or cracked when that hose came off and it is leaking somewhere that you simply cannot see with a pressure tester.

Or it could be that the pressure tester that you are using is not sealing up properly when you hook it up or something is wrong with it.

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Friday, June 9th, 2017 AT 7:14 PM

JASON GALBRAITH

MEMBER
2 POSTS

Heyman,

Thanks for the response. It turns out the fitting for the pressure tester was missing a gasket so it held pressure and I know not to trust rented tools.

So I ran the truck for 20-30 mins and it formed a puddle underneath and a steady drip. It was coming from the hose in the pic I attached which is off the bottom of what I believe to be the evaporator. Is this just a condensate drain? Could it be more than normal because the coolant system has more water than coolant right now? Once I confirm there is no leak I'm gonna drain it and refill with 50/50. (If I can get the airlift to pull vacuum)

Thanks again,

J.

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Saturday, June 10th, 2017 AT 4:50 PM

HARRY P

MECHANIC
2,292 POSTS

From what I can see that does appear to be just a condensation drain. In the future I'd say don't run the A.C. When checking for a cooling system leak. You could see extra drainage there if its unusually humid where you are. In my opinion, make sure its full and check it for leaks again. If you don't see anything leaking, drive it a few days, cautiously at that, and then check it again. Let us know.

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Saturday, June 10th, 2017 AT 9:09 PM