Question about Cars & Trucks
Check your coolant level make sure it's full. Make sure your thermostat works. Are the hose going to the heater core connected or bypassed. If bypassed you probably need to install new core. If connected try a coolant flush as there could be a clog
Posted on Nov 11, 2014
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Posted on Jan 02, 2017
SOURCE: 1999 1500 silverado heater
Sounds like the blend door in the ducting has failed, this door is what controls the temp of the outlet air by blending heat and outside air or AC cooled air.
Posted on Nov 07, 2008
I had the same problem on my 1999 Pontiac GA 3.4 litre. Replaced a bunch of stuff. It just kept pushing the coolant out the overflow once the temp got to 200 + like to drove me nuts. Ended up being that reservoir. If you measure the O.D. of the cap(brand new cap) and the I.D. of the reservoir filler neck there is no way it will seal(even tried to fit a different type cap,no luck). The system has to be able to build pressure or the coolant will boil out at 212. Causing the coolant to be pushed out the reservoir. Why? you say or How? did the filler neck increase in size. I dont know but GM has write ups about this problem. They say sand it with a piece of sandpaper to smooth it. Maybe someone sanded it way to much?? Around $40 bucks and I was on my way. Hope this helps someone.
Posted on Apr 11, 2009
Since your blower is working and it is a heat issue,thats where we'll
start,First thing is have you checked the coolant level in the radiator when
engine is cold,make sure it is filled to top,next verify you have coolant in
reserve ,Start your van and get it up to normal operation temperature,If your
heat gauge on the dash works correctly it should be 190 degrees,Now lift the
hood and locate the two heater hoses going into the heater assembly at the fire
wall,Both hoses should be hot to hold on to,if both are hot and no heat inside
your problem will be the blend air door in heater assembly.
if neither hose is that hot you need to replace the thermostat in the engine to get it up to 195 degrees.
if one hose is hot and one is luke warm then the heater core is blocked and to blame. hope this helps you.
Posted on Jan 05, 2010
Two things can be the problem,first,try adding ,a little freon,if it is low,it will only cool one side,then if this does not help,there is a door actuator motor that controls this,it could be not working,the dash has to come out to replace this actuator motor,if this was at all helpful,please rate,thank you.
Posted on Jul 13, 2010
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