Hear water dripping after shut down. Air in coolant?

[olliec420]

So I've noticed that after I shut off the engine I hear a sound of water moving. I really noticed it since its gotten cold and I felt like the heater wasnt as hot as it should be and started to look in to it. The radiator and surge tank appear full. The temp gauge is traveling more than I'd like when driving it. I'll watch it at a stop light and it moves a lot. Like up and down two cycles in 2 minutes. I put the scanner on it and the temp reading was going up and down but only 188 - 199, but in that short amount of time repeatadly. Which isnt that much of a difference but should it hold steady or fluctuate that much?

Today I got a pressure tester from oreilys and it was slowly falling (which I assume isnt good) but I couldnt see or hear a leak. Where are the hotspots to check for slow leaks? I tried to burp it and some air came out but not very much and the dripping sounds continued afterwards. I replaced the radiator cap today as well. It was plastic and the gasket looked flaky.

Also there is this weird stuff on the cap? What is this from?

 

[exp500]

Time for a coolant flush!
Check surge level, warm up truck,recheck surge tank. Shoot Radiator,hoses, Tstat and associated with temp gage.
Check for leaks while running, especially around radiator seams, recheck after shutdown while listening to it suck out surge tank.

 

[olliec420]

Time for a coolant flush!
Check surge level, warm up truck,recheck surge tank. Shoot Radiator,hoses, Tstat and associated with temp gage.
Check for leaks while running, especially around radiator seams, recheck after shutdown while listening to it suck out surge tank.

Surge tank level at cold was dead on. Surge level at hot was dead on. Heater hoses were hot. Once thermostat opened the other hoses were hot.
During pressure test I could not find any leaks but pressure did slowly go down. Everything appears to working correctly EXCEPT the sound of water dripping after shut down.

Maybe the cap was a problem with all that trash on the gasket, I put a new cap on yesterday. Metal not plastic. So I'll keep an eye on it while it figure out for a flush. Should flushes be done on a incline so as air doesnt get stuck in places?

 

[Marky Dissod]

Should flushes be done on a incline so as air doesn't get stuck in places?

Nose slightly down when releasing coolant, to help more coolant escape system. Not as important as
Nose somewhat up when adding coolant, to give air a better chance of escaping.
Bonus points for the patience to add coolant SLOWLY, the slower you add coolant, the less air you add.

There's a kit that people buy specifically for the purpose of introducing zero air, it takes its time naturally.

Years ago I had 9C1-LT1 Caprices; old ironblock LT1s are notorious for needing burping like babies,
but the GM burp fitting pees coolant all over the distributor on the FRONT of the engine.
I just accepted that for the 1st two weeks after adding coolant, I'd need to burp it with the coolant cap.

 

[buckwild27]

Flush that heater core extra good.

 

[Eman85]

Get a mirror and look at the 4 corners of the intake manifold, that is the most common place to leak. Other common leak areas are the radiator tanks and the water pump. At the age of these trucks we're to the point where anything could be leaking. Always the chances of a cracked head also.

 

[bill1013]

I had a similar issue which turned out to be a cracked radiator. It was just below on the top hose connection. The plastic cracked ever so slightly. It wasn’t until the crack was around an inch long that it became visible. After a few patch attempts I just broke down and got a new one.

 

[OBSandaNNBS]

You know what, I think I used to get this noise too, very briefly on shut off. I shrugged it off. It's a beater. (Mine is)
Lo and behold my heat went I intermittent on me. Took maybe a year. Now that's important.

Nothing in surge tank and the radiator drank a half gallon when hot. Nervous laugh at my own tolerance for neglect...LIKE A ROCK BABY!!