Weird cooling system cool down vortec 5.0

[McSweeney]

I have a 1997 c1500 5.0 vortec and after running the truck and shutting it down i get bubbles in the reservoir from the overflow hose from the rad. It only happens when the truck shuts down, and i dont actually lose any fluid. Its almost like a quarter of a quart just pushes back out of he radiator into the reservoir when cooling off but very aggressively. I have no overheating issues, and like i said i dont lose any fluid. Just some leaves the radiator back into the reservoir upon cooldown. Its really weird and ive been told multiple times to ignore it since the cooling system is doing its job but i think it seems off.

 

[Nad_Yvalhosert]

Your radiator cap is junk. Its not holding the pressure and venting to the resrvoir.
Replace the radiator cap.

 

[McSweeney]

Your radiator cap is junk. Its not holding the pressure and venting to the resrvoir.
Replace the radiator cap.

Ive replaced it twice, the current one is gm genuine

 

[Schurkey]

How hot does the engine run? (REAL temperature, not necessarily what the dash gauge reads.)

When was the last time the cooling system was flushed, including having the block drains pulled so the debris in the bottom of the water jacket is removed?

What is the freeze (and therefore the boiling) protection of the coolant?



Engine coolant temp always climbs after shutdown. "Deep heat" in the engine warms the coolant which is no longer circulating. If the cooling system pressure is near the cap pressure to start with, shutdown increases pressure further--beyond cap pressure. Then coolant vents out the pressure cap. When the temp decreases, it's pulled back into the radiator.

 

[McSweeney]

How hot does the engine run? (REAL temperature, not necessarily what the dash gauge reads.)

When was the last time the cooling system was flushed, including having the block drains pulled so the debris in the bottom of the water jacket is removed?

What is the freeze (and therefore the boiling) protection of the coolant?



Engine coolant temp always climbs after shutdown. "Deep heat" in the engine warms the coolant which is no longer circulating. If the cooling system pressure is near the cap pressure to start with, shutdown increases pressure further--beyond cap pressure. Then coolant vents out the pressure cap. When the temp decreases, it's pulled back into the radiator.

It runs at about 185-190 and holds very well. I dont honestly know if the water jackets been flushed but i highly doubt it. Ive replaced the water pump, thermostat and hoses so it has mostly new fluid. Id have to check the protection of the coolant

 

[east302]

It runs at about 185-190 and holds very well. I dont honestly know if the water jackets been flushed but i highly doubt it. Ive replaced the water pump, thermostat and hoses so it has mostly new fluid.

Is that 185-190 from a scanner reading the coolant temp (ECT) sensor? Dash gauge is pretty much for decoration only or to alert to an oh-sh*t event.

To confirm, did you bleed the system after that and were the symptoms there before those replacements?

It doesn’t do it while running, right? Oil looks good…not like a milkshake? No steam from the exhaust when warmed up?

 

[mr_josh]

Let’s establish… how many bubbles? A couple? A lot?

 

[McSweeney]

Is that 185-190 from a scanner reading the coolant temp (ECT) sensor? Dash gauge is pretty much for decoration only or to alert to an oh-sh*t event.

To confirm, did you bleed the system after that and were the symptoms there before those replacements?

It doesn’t do it while running, right? Oil looks good…not like a milkshake? No steam from the exhaust when warmed up?

Oil is always clean, no water whatsoever. No smoke out of tailpipe. The 185 is from reading the coolant temp sensor. Quite a lot of bubbles. Like maybe 10 bubbles then stops for a second, then starts again in a cycle for a minute or so. It only does it when the engine shuts off. It really seems like it wants to relieve pressure but does it to dramatically, or maybe one of the intake gaskets are shoving air into the system? Ive never seen this before but ive only been working on cars for about 6 years

 

[McSweeney]

Let’s establish… how many bubbles? A couple? A lot?

A decent amount, kind of a cycle of a few bubbles then a pause, does it for a minute or 2 while it cools off

 

[east302]

Did you bleed the air out after the work? Engine cold, start it with the cap off and let the air burp from the radiator (when the thermostat opens) until it stops.

It wouldn’t hurt to do it again.

Has it ever been overheated?