Boiling coolant - bad water pump?
Thread Starter
Racer
Joined: Oct 2002
Posts: 452
Likes: 158
From: Newark, DE
Boiling coolant - bad water pump?
When I shut my motor off I can hear coolant boiling. Not really when I drive around town, but if I run it hard, it will boil for a couple of minutes when I shut it off. Could this be a bad water pump, or is it something else? My temp gauge never goes over 200. Is it just from all the heat in the motor when you stop running the pump that does it or do I have a bigger problem?
Race Director
Joined: Aug 2000
Posts: 10,854
Likes: 3
From: HONOLULU HAWAII
[QUOTE=GTLocke13]When I shut my motor off I can hear coolant boiling. Not really when I drive around town, but if I run it hard, it will boil for a couple of minutes when I shut it off. Could this be a bad water pump, or is it something else? My temp gauge never goes over 200. Is it just from all the heat in the motor when you stop running the pump that does it or do I have a bigger problem?[/QUOTE
Appears you have air in the system....Do you have a closed recovery system? If not...you are sucking air instead of water back in.
Appears you have air in the system....Do you have a closed recovery system? If not...you are sucking air instead of water back in.
work on this first 
Senior Member since 1492
Joined: Aug 2000
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
FWIW, I've had that happen to 4 vehicles over the years. Boiling coolant right thru the over flow tank! 
Each time it turned out to be a clogged corroded radiator.
Each time it turned out to be a clogged corroded radiator.
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,501
From: Little Rock AR
Water pumps do 1 of three things. Pump water, leak out the weeping hole under the bearing because the seal is shot, or completely fall apart. They are pretty simple things realy.
Check the cap and overflow system.
-Mark.
Check the cap and overflow system.
-Mark.
Team Owner
Joined: Feb 2003
Posts: 30,183
Likes: 313
From: Lake Norman NC
I had the same thing happen to me this summer...turns out my distributor came loose, and i was running very low on timing,..caused the motor to get hot enough on a hot day to boil out of the tank after shut off.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Very likely you have either a bad radiator cap or one of too low a pressure rating.
All engines go through heat soak once fully up to temp and then shut off. The coolant temperature will always rise and if the cap doesn't hold the pressure rise from the increase in coolant temperature you will have boiling and gurgling.
From a wrenching perspective, a cap is far cheaper than anything else that you can do to reconcile the problem except for ensuring the coolant level is correct for your car. Everything else both costs more and takes more time if you're not sure what's causing it.
All engines go through heat soak once fully up to temp and then shut off. The coolant temperature will always rise and if the cap doesn't hold the pressure rise from the increase in coolant temperature you will have boiling and gurgling.
From a wrenching perspective, a cap is far cheaper than anything else that you can do to reconcile the problem except for ensuring the coolant level is correct for your car. Everything else both costs more and takes more time if you're not sure what's causing it.
