Help! Heater Box overheating?

[wldcat10]

Hows it going everyone? I need help with something. I've noticed that after I park my truck I hear a bubbling sound like boiling water coming from the passenger side behind the dash. I'm thinking it's my heater box, but I dont know what I need to do to fix it? Any help would be appreciated, thanks!

[John Fabris]

that would mean you have a leak in your cooling system. Check your heater hoses (in the engine compartment), and if you don't see a leak (look for white build up, calcium) then its possible that your heater core is bad and needs to be replaced.

[71 super]

You have a leak as john said, core or hose. Not to bad to fix, but will have to drop your inner fender if a non air truck.

[ChevLoRay]

Find a cooling system pressure tester and pressurize your cooling system. If you can't borrow one, then a service station or garage should have one and can pressurize it for you. When I was at Sears Auto Center, we also had one so Sears, or a Firestone or Goodyear store are other possibilities.

[BluTrukker]

I had a 91 chevy that had the same sound. Not constant, but occasionally. When I changed the engine, apparently I got an air bubble in the heater core. I tried everything to get it out, but nothing worked. I drove it like that for 3 years until I sold it.

[swamp rat]

I agree it sounds like you will have to open the heater box up and find out if your core is leaking, doing a pressure test is a good place to start, if there is a leak it won't hold pressure, then you would have to pinpoint the leak

Also make sure you have the water hose from your intake manafold (outlet) port routed to your lower heater (inlet) port? the core is suppost to fill from the bottom to the top to purge the air out of the heater core the top shopuld go ether to your radiator if you have the connection, or back to the port on the waterpump..

[Andy4639]

Look in the passenger side floor board and see if there is any sign's of leakage in the floor under the carpet or floor matting.
Ok, then if not look out in the engine bay under the passenger side and see if you see any signs of it. If you can't find anything wet. Take the bottom and top heater hoses off and put your water hose on the bottom one and turn it on and see if it's blocked up. If not then it's a hose leak somewhere.

[raycow]

Definitely check for leaks first. Now after you don't find any......
When you shut down an engine, water in contact with hot spots can start to boil locally, since there is no longer any circulation to carry away the heat. This is not harmful in itself. However, the vapor bubbles created by the boiling are lighter than water and want to migrate to high points in the cooling system, which just happen to include the heater core.

Ray