Water sloshing in dashboard

**JonnyQuest** · 11-01-2009

I just bought my wife an 04 Grand Prix GT (103k miles). There's a sloshing sound coming from the dashboard area, the prior owner said something about the a plug in the heater core, and water in trapped in some tube.
Not sure what he meant (neither did he really), he just told me someone gave him a quote of $250 to fix.
I also searched back through the history on this site, and only came up with one similar problem with the same year GP, and a remedy was never found (or posted).

Can anyone shed some light on the issue?

Thank you!

**cerick08GP** · 11-01-2009

Well, heater cores or what ever your problem is doesn’t seem like a common one. But what is strangely common is that people like to never add coolant, don’t ask me why.

If your radiator is plum full, then I would say you simply need a new heater core.

**JonnyQuest** · 11-01-2009

I googled the problem and seems somewhat common, certainly not as common as the water/floorboards issue (which I had on my 98 GP).

Don't want to sound like a complete idiot, but how do I "burp" the radiator or purge it??

**cerick08GP** · 11-01-2009

A car’s coolant system usually purges itself. I would first ensure your radiator is completely full, and also check your over flow tank that should be at the “normal” mark. If you can’t see the mark, IIRC, there should be about 4 inches of coolant in it.

Next drive your car until it gets to a normal operating temperature (~195F), with the car still running crack open the purge valve right next to your thermostat valve. It is a small brass valve, open the inner part of it with a 6mm wrench. Purge until you get a solid stream of coolant, use a rag to catch it. Then get back in your car, drive around (highway speeds are best) then turn your heater on full heat. All the way to the red, any fan speed is fine. After about 2 minutes, put it back on cold. Wait a minute then go back to full heat. Now purge the thermostat again, and check the over flow for proper level. You should be golden, if not you have a blockage or something else going on.

**TheOtherNick** · 11-01-2009

Could be water trapped around the evaperator.

**Liquifire** · 11-02-2009

First off to purge the radiator(not sure on the gen III's, but this is on the gen II's for sure.) you just purge air by using the bleeder screw on the thermostat waterneck housing. Secondly, I thought that our cars came with a "catch tray"(not sure of technical name)of sorts in the dash area that have a drain tube in them. if this tube is plugged the tray could have gotten water in it and now it sloshes around. These were originally intended to catch any leaks from the heater core so that they dont explode or leak coolant onto your cars floor. Thay is my guess as to what you may be hearing as well. This tray should be located under your heater core. Hope this helps...

**ZR1Vette09** · 11-03-2009

I would be it's just an air bubble caught in your heater core. I actually have a little bit of the same issue in my 06, but when I had my 2000 blazer it was TERRIBLE. Could never get it fixed and it came down to either put up with the noise or pay $1000 to get a new one.

**rddude67** · 12-31-2010

JonnyQuest - I am experiencing the same issue on my '06 GP. Did you ever resolve this on your car?

**JonnyQuest** · 01-01-2011

I ended up flushing the radiator. Then sold the car.

The sloshing did go away, but then the heater wouldn't really work. Got tired if the issue.

**rddude67** · 01-03-2011

thanks for getting back. For anyone else suffering this issue:

Low coolant levels seem to cause air bubbles to develope in the system, and make it sound like water sloshing/squirting sound under the dash (heater core). As it turns out, my car (80K miles) was leaking a good amount from the water pump. I replaced it, refilled the system, and still had the issue. Did some more driving, made sure the coolant was full, and drove it more. Eventually, it went away (2 days or so). Maybe there is a better way to bleed the system, but eventually it worked itself out.

**yellow600r** · 01-03-2011

since im a gm tech and got tired of this problem i bought a tool that fits on your coolant over flow tank.. You hook air to it and it sucks all the are out of the system and it will colapse the hoses and if theres a leak youll know it and hear it even if the radiator is cracked or the intake gaskets are bad... Then theres a hose that goes into the coolant bottle so when you take the are off it sucks up coolant and no air pockets.. Use this on doing radiator changes or head jobs or just to get the air out of the system so easy and takes no time at all..

**Liquifire** · 01-04-2011

you have a pic of this tool or know where to get one from?

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