99 bravada awd 4.3 vortec...so has anyone ever heard a gurgling sound in your dashboard upon acceleration from stop lights? kind of like a water fountain or toilet LOL, is that what heater cores sound like when they go bad? and then there's the groaning in the rear suspension... time for that shackle and shocks upgrade?

 

Check rad fluid level

 

When checking rad fluid level, take a good look at the rad cap.

Rear suspension "groaning".....what causes this?

 

Yes this for the gurgling. Check the radiator cap too as mentioned also. You likely have air in the system.

 

In my 04, I've burped and purged all the air out of the thing half a dozen times after changing the radiator, heater core, and doing a complete coolant flush, and I still get the same exact noise. I've just learned to live it it... Radiator is full and I'm not loosing it, I have no engine temp problems and the heater works, for me it just is what it is...

 

That's odd

 

I just heard my dashboard gurgling. Makes me think there's air in the heater core.. I'v been having issues with losing water, fan roaring, goop, overflow tank never moves and now gurgling. So the new rad cap comes tomorrow, we'll see if that helps.

 

It does sound like a classic heater core noise. Are there any leaks on pass. side floorboard ? Bleed to remove air pockets. Remove hoses and clean out the htr core by reverse flushing it with low pressure, not high pressure water. Try to bypass the heater core to see if the noise goes away.......it's summer time. As you know the heater core replacement is a long, tedious job. That's why I am trying to come up with some small tests before you launch into that big project.

 

I changed radiator cap on mine to brand new OEM and it LESSENED it. Mine did the same "wading through water and swimming" sound since Day 1.

I seem to be the only one that does a gradual exchange of coolant (when cold) with a siphon hose. Coolant came out looking like mud first 10 times or so.

Point: After putting in fresh 50/50 mix and just keeping on letting it heat cycle (I used to "burp" it but decided there was no point...) it does not do this anymore.

And yeah, it probably either purged air or cleaned away a blockage of heated core.

I also drove it really, really hard since the heater core is very far away from the water pump.. becomes a pressure issue. Floor it, speed with it, drive it hard and all blockages dissipate eventually. But that is for another time.

My dash is basically quiet now. Might hear that noise slightly after a long journey coming from a light but it was worse when there was more water and less antifreeze in there. And I have not heard it in awhile.

 

The first thing that you need to do is bleed the system properly. Park the truck with the nose up, engine cold or at least not dangerously hot, radiator cap off, heater on full blast and start the truck, increase the rpm to say 1500. When the thermostat opens the fluid level will drop at the cap. Keep topping it off until the fluid is full, expands and comes out of the radiator cap opening. Put the cap on. Fill up the coolant reservoir to the line. Drive it on the highway. In the morning look at the reservior level and see if its dropping.

Does the heater work properly? If it doesn't heat properly then the recommended garden hose flushing is in order

As mentioned, any leakage on the carpet or steam on the windshield in defrost mode? That indicates a leaking heater core.

Any leaking elsewhere in the system when the truck is hot? Do you smell coolant? If this started and you did not open the system since the last time it ran properly then you probably have a leak. Is the coolant reservoir level dropping?

BTW, a leak can be a simple old school affair like the radiator or a hose but on these trucks it can also be the LIM gaskets which can be harder to stumble across. Check your oil if you have a leak and cant find it. That should get you started.

My truck has 205,000 miles and it has leaked at the radiator and the LIM gaskets.

George