Yesterday i spent a good 6 hours taking my dash apart and following little vaccuum lines around to no avail. I finally decided that there is a valve in the vehicle somewhere that lets the hot water from the radiator into the heater core, and it wont work, and i cant find it, nor do i know what it looks like... If anyone can help me get some heat, id really appreciate it... Also, there is a solenoid or something on the intake manifold right by the seat for the thermostat. What is this? any type of info on how to remedy will really help me out.

 

More likely than not, your heater core is plugged... The heater core is continuously circulating coolant when the engine is up to operating temperature. If it is plugged, you will not get any heat out of it.

Now, after reading your other post, I have come to find out that you have a '96... Please provide that information either in your posts (time consuming), or place it in your signature (preferred method). This information should include anything that can help us diagnose your problem.

Now, knowing that you have a '96, you have the SCFI vortec v6. If the solenoid you speak of is about the size of a soda can, then it's your EGR valve.

 

So if the radiator line going into the dash from the mainfold isn't hot, then the heater core is plugged? because it seems that the two lines; one going from the mainfold to the firewall,(to core?) and another next to it comes from the firewall to the water pump (core return?) , neither has anysort of heat, so im assuming they are both just filled with stagnant radiator fluid and nothing is flowing.

 

oh, and yes, i was talking about the EGR valve. thanks.

 

Yup, that is a very good assumption. You can attempt to flush the core (both forwards and backwards) to remove any debris/corrosion that is in there by just removing both of the lines running to the firewall and alternating which line you flush into... If it is plugged solid, you are going to have to replace it. A stiff vinegar solution (40% vinegar, 60% water) left in the core overnight may loosen the deposits, but if the corrosion has set in pretty good, it may open up leaks into the interior of the vehicle.

 

Thanks for your help, swartlkk, ill have to try that tonight and see how bad the clog is.

 

Kyle,

If both of the lines going into the heater core are cold then wouldn't it be prudent to check the thermostat also...if it is stuck (open/shut) then that would affect the temps of the heater hoses at least one side...

 

Yes, you are correct. In this case, I would check the upper radiator hose for heat. If you have a sensitive hand, you can also feel the coolant flowing through the hose.

*Assuming a completely clogged core (ie. no flow)* It depends on how much run time the vehicle has had as far as how hot the heater hoses get. If you drove the vehicle around town for an hour, and both were still cool, then I would point to the t-stat. If you just warmed it up to operating temp (3-5 minutes of running it) and checked, they both could still be ice cold. This is because the coolant in the hose is stagnant (no flow). The only way it can heat up is through conduction from the moving coolant in the engine block and from heat conducting through the hose (which should be about equal on both hoses). I guess it is possible for the flow through the coolant passages to produce a very small induced flow in the hose, but it's effects wouldn't reach all the way to the firewall for some time. And it is possible that both hoses would heat up at the same time, but they would still not get anywhere near as hot as say the upper radiator hose.

Most of the time, you catch a clogged heater core *before* it is completely clogged. Now you have a deminished heat output situation. This situation is what can cause the supply hose to be hot (engine coolant temp hot) and the return hose to be cool (sometimes ambient temp cool). This results from the lack of flow through the core. Hot coolant is flowing in, keeping the supply hose hot, but due to the surface area of the core and the deminished flow through the core, the incoming air is removing any and all heat from the coolant. This causes the cool return line.

So there are two situations that arise from heater core problems. Sorry for the long winded explaination. I had more, but thought better of it... It got too wordy as it is.