Cooling system sounds

Yankee7985 · October 15, 2004

A buddy of mine has a 99 Z71 4X4, and when he accelerates, you can hear a gurgling sound from behind the dashboard. The heater core is original and all the hoses are stock. Since buying new, he has taken it to the dealer, with nothing noted as being wrong. Thew have flused the heating/cooling system, and replaced the thermostat, to no avail.

citydriver · October 15, 2004

A buddy of mine has a 99 Z71 4X4, and when he accelerates, you can hear a gurgling sound from behind the dashboard. The heater core is original and all the hoses are stock. Since buying new, he has taken it to the dealer, with nothing noted as being wrong. Thew have flused the heating/cooling system, and replaced the thermostat, to no avail.

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Does the heat work OK? Or does it work only when he revs it up?

It may have an air pocket caught in the heater core, or the radiator cap may be weak and not maintaining the correct pressure....just a guess

Yankee7985 · October 15, 2004

The heat works fine. If it is an air pocket in the heater core, how can it be purged?

MountaineerTom · October 15, 2004

The heat works fine. If it is an air pocket in the heater core, how can it be purged?

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If you have a gurgling sound coming from what sounds like inside the dashboard, you probably have and air pocket in your cooling system. It’s an easy fix, here’s what you need to do.

1) Get a jug of DEXCOOL.

2) Park on level ground.

3) The engine needs to be cool, or just slightly warm is fine too.

4) Add fluid in the surge tank until the level is slightly above the split line on the tank (an inch or so).

5) Put cap back on loosely, don't allow it to build pressure.

6) Start engine and let it idle for a minute.

7) Cycle the engine from idle to 3000rpm in 30-second intervals until the engine coolant reaches operating temp and the thermostat opens.

8) Shut off engine and remove the cap.

9) Start engine and let it idle for a minute. Fill the tank to 1/2 inch above the "Cold Full" mark on the tank & put cap back on loosely.

10) Cycle the engine like before and wait for the thermostat to open again, then shut off the engine.

11) Put more fluid in if necessary, the fluid should be a half-inch or so above the Cold Full mark.

I've done this procedure before, and it worked for me.

citydriver · October 15, 2004

The heat works fine. If it is an air pocket in the heater core, how can it be purged?

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MountaineerTom covered it pretty well

99silveradoz71 · October 15, 2004

Just had that issue and tried the fix with negative results. Advisor at the dealer who replaced the water pump said they apparently reversed the hoses and that was the cause for me at least. Heck if I know...it doesn't gurgle anymore, so no complaints.

bomber · October 15, 2004

A buddy of mine has a 99 Z71 4X4, and when he accelerates, you can hear a gurgling sound from behind the dashboard. The heater core is original and all the hoses are stock. Since buying new, he has taken it to the dealer, with nothing noted as being wrong. Thew have flused the heating/cooling system, and replaced the thermostat, to no avail.

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I had posted my cooling system delema on the HD forum the other day. Here's how I made out.

I had a very similar issue. I did have an occasional gurgle here and there but I also had a coolant loss from my overflow bottle. In addition I could smell the AF once parked.

For me,

I repaired the leak on the bottle / hose connection.

Then I purchased a new NAPA radiator cap.now leaked out of cap on overflow.

So, I got a new overflow cap from a Chev Dealer.

I may still have a cooling issue, but I don't think so as there is no longer any leak from the recovery bottle, no smell once parked, or gurgle sound. Coolant level is good, recovery bottle seems more active also.