heater core?

leaving for work early I have had to use my defrosters more than previously. the air coming out is not hot but warm. Is this most likely a heater core issue? I have heard that GM cars of this vintage can develop heater core problems.

I have never had a vehicle with all this electronic "climate" control that tries to "think" how to best regulate temperature. I am used to more basic controls that will give ice cold air or hot air until I turn it down.
I have zero intention of driving this vehicle thru a Michigan winter, but when I want HOT air, I want HOT air.

With the electronic control if you crank the temperature up to it's max you'll get full heat out of it. What year is your car? 94-96 had a reverse flow cooling system which aided in plugging up the heater core, it's a fall tradition for a lot of us to flush it regardless of if it needs it or not.
Disconnect the hoses going to the core and flush it back and forth until you get good flow both ways and it comes out clear, you should have great heat after that.

95BRMW wrote:

With the electronic control if you crank the temperature up to it's max you'll get full heat out of it.  What year is your car?  94-96 had a reverse flow cooling system which aided in plugging up the heater core, it's a fall tradition for a lot of us to flush it regardless of if it needs it or not.
Disconnect the hoses going to the core and flush it back and forth until you get good flow both ways and it comes out clear, you should have great heat after that.

yes I have a 94 w/LT1.

thanks!!! I will flush it out soon. what is the MAX temp? I put it up to 90 and still got lukewarm air.

Set the temperature control to the hottest setting. This forces the system to stop blending cool air with the hot so you can compare.

All heater cores, and all cooling systems in general, can benefit from an occasional flush to get all the crud out. How long it takes to generate a new layer of crud depends in part on your choice of coolant. There is some evidence that certain long-life coolants may actually attack gasket material and many will crystalize if mixed with other coolants (eg: mixing GM Dexcool with anything else). Coolants contain additives to reduce corrosion, or reduce waterpump wear, but not all coolants contain the same types of additives and the additives may react with each other unpredictably.

Traditional blends used at the time of manufacture of these cars used silicates and phosphates as corrosion inhibitors. They work by building up a protective layer. However, phosphate especially can also react with hard water, forming excessive scale and the additives are pretty much depleted after two years or so in any event.

"Low silicate" coolants usually approach corrosion protection by reacting with the metal itself. They are generally more tolerant of hard water, but can react with certain minerals. Overall, the additives tend to last longer and these coolants are often marketed as "long life", with a change interval of about 5 years.

So to minimize problems with plugged heater cores and radiators:
Don't mix coolants.
Buy quality brand name coolant rather than discount stuff.
Avoid Dexcool.
Use only distilled water with concentrate or buy pre-diluted coolant that requires no water to be added.
Drain, flush and refill the system as per the recommendations for your coolant choice.

pretty much everything in the last 10 years is a "low silicate" coolant. and 5 years for a flush is a good rule of thumb for sure. since I do not know the history of the vehicle a full drain and flush is in order, with particular attention to the heater core.

well I finally got to flush it out. I have defrosters now. I will run some oxalic acid thru there for a day or two, flush it again and fill with coolant. I honestly don't think the car was flushed ever before. mud came out of the heater core and brown water everywhere else.

You could also check the temp of the coolant to make sure the thermostat is actually closing all the way. One that sticks will cause cool heat.

jayoldschool wrote:

You could also check the temp of the coolant to make sure the thermostat is actually closing all the way.  One that sticks will cause cool heat.

I will probably just replace it when I am done flushing and add coolant. it was plenty warm enough this morning and I will be parking the vehicle come November.