96 Suburban gurggling water under dash

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I am getting gurggling water sounds under my dash in the heater core area, Ive pulled the bottom of the box off and its bone dry . . heater core is fine and I have good heat. Let me back up one day . . . yesterday when I heard this I thought for sure heater core, on my way home from work it got a little hot (temp gage shot up to about 220-240 in about 2 sec up from about 180 then came right back down, thsi whole process happened in under 5 seconds, the truck did not overheat) I pulled over and had to add a gallon or more to the rad. Drove home about another 20-25 miles with the temp and heat working fine. Got home pressure tested the system and the pump was bad, put on a new water pump, thernostat, rad cap and had the entire system flushed. Today it runs good with no temp problems, heat is fine, no leaks but I still have the water gurggling sound??

What Gives??

Chris

posted by  69396Chevy

most likely still have an air pocket in the system remove the rad cap start the truck and run till thermostat open you will see it swirl in the rad and upper hose will get hot keep topping up the system till its full make sure to top up over flow bottle to the full hot or when it cools it will draw air back in

posted by  osborste

But Ive had the system power flushed with a machine that pushes water through the entire system, I would think this woudl have gotten rid of any air in the system.

posted by  69396Chevy

try it i've dont it the air will stay in higher places like water in a cave you have air pockets

posted by  osborste

you have air in the system.remove the rad cap.let it run at idle for a few minutes at idle,the air will dissipate put the cap on when the water level is still at the top of the filler neck.if the problem is still there,you may have damaged your head gasket ,that tempertaure cycling can be that too.

posted by  the lobster

This isnt the problem, Ive let it run for awhile and the rad didnt go down. I also just took it on an overnight trip driving about 1.5 hrs each way down the freeway which should have eventually pushed the air out. Still making the same sounds, what can anyone else suggest?? SOmeone told me the an AC component (either accumulator or another item can make noise like this but not sure where it is)

posted by  69396Chevy

could be the headgasket on its way out, had a Gm in last week that had been making gurgling noises for about 3 months...tested the gases in the cooling system and sure enough they were combustion gases...

posted by  hammerthief

now theres something i didn't think of if the head gasket is going the compression from the cylinders would pump air in to the cooling system you might check the overflow bottle when you here the gurggling sound might see bubble's like boiling water. sooner or later someone comes along with somemore experiance

posted by  osborste

it looks like a can with a couple of ac lines going to it probably located by the firewall.if you remove the ac clutch relay,the compressor will not come on.if the gurgling goes away you know its in the ac system.i still think that one of the head gaskets is leaking.have you done a compression test?if you gat a big difference in readings from cold to hot,there could be a problem.also,what does the coolant look like ?you could have a hairline crack in any cooling system component,a hose,the pump etc.if there is a way that you can hook up a t in the line and run a pressure gauge,a pressure difference could show up.as you drive it .do you lose coolant?have a analyser on the exhaust and check for excess vapor.

posted by  the lobster

Well the temperature variatio went away completely after I replaced the water pump and thermostat. I had check the coolant system with a pressure tester at it was obvious what the problem was with water pouring out the pump. It holds a steady 180 now, I have a compression gage so I guess my next step is check cylinder compression and see what they read.

posted by  69396Chevy

thats what i would do if you are sure that the cooling system is rock solid.
if the compression cold is 130 say,and drops to say 120 when hot,suspect a gasket......

posted by  the lobster

Well Im nto so sure now . . another leak may have popped up somewhere. Noticed a spot on the ground this morning after it had been fine for a few days.

posted by  69396Chevy

I have researched this same problem, and found a reference to a washer in the heater core - apparantly it is on the inlet side of the core closest to the engine. There is a flow reduction washer inside the inlet tube. This washer wears over time, becomes loose and starts flapping in the water flow, causing the gurgling noise. Remove and discard the washer, and the problem goes away. The washer is about 1/2 inch inside the inlet, so you need a small hook device to remove it. It looks like a washer for a garden hose. Once you hook it, it comes out fairly easily.

posted by  davejyd

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