How soon should the coolant system...

blykins · #1 (**permalink**) 03-15-2005, 10:38 AM

...pull coolant back out of the expansion tank after shutting the engine off? Does it usually happen a few minutes later when everything starts to cool down?

Since I have put the thermostat in the engine and installed my expansion tank, I have noticed that IMMEDIATELY after shutting the engine off, there is a gurgle for like 2-3 seconds and then it stops. It sounds exactly like a sink drain, right in the area of the expansion tank. It sounds like it's sucking the coolant back in right that second.

The engine runs at 190 all day long....never overheats. Doesn't even spit any coolant out of the expansion tank to the ground.

Do I just have a little trapped air that needs to be bled out of the system?

Tony Radford had this same problem awhile back and he posted on it. I emailed him and he said his problem was trapped air, and they drilled a little hole in the thermostat to fix the problem.

Any ideas?

trularin · #2 (**permalink**) 03-15-2005, 11:25 AM

Gurgling is the response of the heat in the engine being transfered to the fluid. It expands and is forced to the expansion tank. Then as the engine cools, the fluid contracts and pulls residual fluid from the tank to fill the void created by the shrinking volume of coolant.

As long as no air is introduced and a small amount is kept in the tank, it is considered a sealed system and should reliably cool the engine for years.

Got the same setup. Works great!

trularin · #3 (**permalink**) 03-15-2005, 11:26 AM

Sorry, didn't see the second part.

Yes, drill a 1/16 to 1/8 hole in the T'Stat to allow all the air to escape to the radiator.

blykins · #4 (**permalink**) 03-15-2005, 11:51 AM

Tru.....do you think this is normal operation though? I've never heard gurgling immediately following shutdown.....You think it's the just the transfer of fluid/maybe air through the expansion tank that I'm hearing?

Keep in mind there is no gurgle during engine operation....just after the engine shuts down. Then it sounds like a sink drain.

Hotfingrs · #5 (**permalink**) 03-15-2005, 11:54 AM

Generally the hole is drilled in the thermostat, in the event it fails to open, you will still have a little water being pushed through the engine and won't destroy it. It takes a little longer for the engine to heat up, but worth the peace of mind.