1991 5.8

Well the heat is working intermittently in the old beast. I'm rather convinced it's due to a nearly plugged heater core, as it will eventually start working but only after some higher RPM driving has been done.

I've never actually flushed a heater core before, but I've heard that a nozzle and a garden hose works. I've also heard of some guys using air pressure.

Recommendations? Thanks.

 

I've used a garden hose before with some success. The key is to not use too much pressure, otherwise things can blow apart and leak. Disconnect both heater core hoses, and use the garden hose to flush water through in both directions.

 

Why not just replace it? A new one is like $30. And Its not that bad to replace.

 

A garden hose isn't going to create enough pressure to harm anything. Probably just some debris in their like you assume so hose away.

SCRebel why spend more money and create more waste if you dont need to

Scott

 

Aftermarket cores suck. I'm on my 5th one.

 

X2! I paid $19.99 for mine new!. It's been working for 5 years. Flushing will not get everything out. You will also put whatever is clogging the heater core (if that's the problem) in the rest of your cooling system. Anything that will break loose will end up in your radiator, thermostat or blocking or clogging something else including shortening lifespan of water pump. We are lucky in that it is soooo easy on our trucks! If the heat is working intermittent; then your heater core is probably not plugged. It sounds like you may have an air pocket or check the vacuum hoses that control the vent doors. In particular the blend door. (I'm about to do this with mine!)
When I was less experienced on another vehicle, I tore up a dash board thinking it was the fan, or heater core. Turned out to be a five minute fix under the hood. It was a vacuum hose that ran under the battery tray. A battery had leaked a couple of years prior, damaging the vacuum hose. After giving up on the problem; 3 (yes I said 3) stealerships could NOT solve the problem! I spent a ridiculous amount of monies, time and drama! Finally took it to an auto HVAC specialist who fixed the problem, and had my ex-wifes chevy venture minivan ready within 90 minutes! The system on that minivan is same as on our trucks! (funny thing also the Corvette used the same parts as the minivan as well!) Did I mention: I HATE MINIVANS!

 

did you try running a devoted ground wire to it yet?
info you should know:
http://www.awrracing.com/media/electrolysis.pdf

if you've simply had enough,take your heater core to a radiator shop and they can build you a copper brass factory replacement,but it'll likely run upwards of a hundred bucks.

 

Replacing the heater core, if its clogged, takes the trash out of the engine and its cooling system. Its very possibly to flush out the core and get it working, but then that trash might clog the radiator, or cooling passages in the engine.

I got my core from NAPA. Been running it for 6 years.

 

Ummm how? lol it is a completely separate part from the engine and rad.
If you flush it out there will be no trash in it anymore. Unless you reverse the hoses the coolant flow stays the same and the junk stays where it is.

Remove both hoses and run water through it both ways NOTHING is getting back to the rad or engine, it ends up on the ground. Completely safe, not gonna harm anything. Worst case scenario you waste 10 mins flushing it and you are back where you started.

Scott

 

Thanks for all the useful tips and discussion, guys. It's also coincidentally due for an oil change so I will probably do them at the same time.

I suspect that the heater core is plugged or at least partially blocked because up until a few weeks ago, EVERY time I would initially start and drive the truck, I could hear coolant filling the heater core. I've owned this truck for a little more than 2 years and it has always done this. Then a few weeks ago it quit, and the heat started acting up at the same time, so I'm at least going to start with a heater core flush. If that doesn't do it, then I'll move on.

Thanks again. You guys are great.