heater core flush instructions Dakota by Virused
 

Hello everyone!

I promised that I would do a tutorial for flushing the heater core, including pictures, so here it is. First off, I appologize for the terrible pictures; I will try to make up for it in explination. Please keep in mind that this was done on my truck, a 1999, 3.9 v6.

Step 1:

Locate the two coolant lines running into the heater core, which is on the interior side of the firewall. They will be located to the left side of the break booster.

Attachment 125956
Attachment 125957

Follow the lines around your engine bay and you will find that one line leads to your water pump, and the other line runs into your intake manifold. The coolant, which is the source of heat for your heater core, runs from the intake manifold, through the heater core, then into your water pump to start the whole process over again. Keep this in mind because you will want to flush in the OPPOSITE direction the first time.

*Note: It will be handy to have a friend to be able to help you, but not necessary.

Step 2:

Locate where the rubber coolant line meets up with the hard line of the water pump. This will be a much more convenient location to flush from. This will get slightly messy so lay something down under your truck, or do this job in a place that you don't give a sh*t about the floor. Loosen the clamp, and slide the hose off of the hard line.

Attachment 125958

Follow the heater core return hose around the back of the motor, to the left side of the motor. Before it returns into the intake manifold, it meets a coupler. This is located on the hose where it runs between the motor and the stock air box.

Attachment 125959

Loosen the front clamp and slide off the hose from the coupler.

Attachment 125960

Step 3:

You are ready to flush! Simply grab a garden hose and hook it up to the hose, running into the heater core, that you just removed from the coupler. I just held it together with my hands, but they sell adapters if you want to waste your money. ;) Have the earlier mentioned friend turn on the hose and let her rip! To avoid a bigger mess than you already have going, connect a hose to the end that is spewing water all over the place. This way you can aim it into a bucket, or into your neighbor's garage. Let the water run for a couple of minutes.

*Note: The bucket, besides shortening cleanup, will allow you to see any debris that was clogging your heater core.

Step 4:

Simply do the same thing, but in the opposite direction, through the hose that you unhooked on the other side of the motor.

From here, you can simply repeat steps 3 and 4 until you are running completely clear water. When done, reconnect all hoses. Make sure your coolant reservoir is full. Start the truck for 30 seconds, then shut it off. Open your radiator cap, slowly! I don't want to be responsible for coolant in your eyes. ;) Fill up to the top, and also make sure that your reservoir, once again is full.

You are done! Pat yourself on the back! I just hope you were having a couple of beers while doing this; for your own sake.


Dakota1stGen Dakota2ndGen

RE: heater core flush instructions
 

Thanx Virused! You are alot of help.

RE: heater core flush instructions
 

Anytime! ;)

RE: heater core flush instructions
 

Thanx this post finally got me off my @$$ and actually went and flushed my heater core it ran brown chunky water for about 5 5 gallon buckets full and finally started running clear water. Heater works Great now i'll probably flush it again in a few days just to be sure. It only ran the dirty water when i flushed it the direction with the garden hose on the end that connected to the pump and the bucket on the coupler end though the other direction just ran very slow but clean water but after i flushed it it ran full force clean water both directions

RE: heater core flush instructions
 

Thank-you!
Shows that I need to do it again!! The right way this time!!!

RE: heater core flush instructions
 

Anytime. If anyone needs to see how something is done, I never have a problem doing a picture tutorial. I have offered them up before when I was doing other projects, such as a lift kit and rack and pinion replacement, but no one wanted me to do them. Oh well. Thanks for saying thanks!

RE: heater core flush instructions
 

Great write up.
I'm going to place a link to this in the Gen 1 section (since everything is pretty much the same).

I believe your wrong. (I previously wondered about this, so I looked it up)
Attached is the coolant flow diagram for the 3.9L/5.2L/5.9L motors.


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RE: heater core flush instructions
 

Thanks for the follow-up! I wasn't sure about the routing myself either, but in the end, I imagined that it would be making a huge difference simply because you would be flushing in both directions. But thanks a lot for the post! Maybe next time I will look at the owner's manual just to make sure! ;)

RE: heater core flush instructions
 

I thought I would bump this back up for the people getting cold in the winter. ;)

RE: heater core flush instructions
 

we should get a sticky on this;)

RE: heater core flush instructions
 

I agree.
I stickied a link to this at the top of the Gen 1 board.

RE: heater core flush instructions
 

good work bud! thats one of those things i would have never even thought about doing. i can only imagine how bad the water is after six years. Well done, thanks!

RE: heater core flush instructions
 

I think the people have spoken. :D Why am I not a moderator? I guess I can have goals. ;)

RE: heater core flush instructions
 

Is it possible to get this stuck?

RE: heater core flush instructions
 

Thank you!

RE: heater core flush instructions
 

Very nicely done Chris.......I only have like 25,000 on mine when should I flush the radiator and change the coolent? I do not think it has ever been done from date of purchase from the dealer.

RE: heater core flush instructions
 

I would do a complete flush once a year. it's alot easier to do a flush then to change a heater core.;)

RE: heater core flush instructions
 

Thanks lil! Frequency of this project is something that can be argued, but I would think that every 10k miles would be a good idea. I didn't begin to have symptoms of a clogged heater core until 120k. However, if I had practiced the proper preventive maintenance, it would have never been an issue.

RE: heater core flush instructions
 

So i did what Virused said and everything was easy and right on. It took me about 15 min to do in a heated garage. Before i was just getting luke warm air, now it actually gets hot, and i get hot air sooner. Im just wondering how long this will last. If i loose hot air again im going to have to flush the entire system. But thanks a lot Virused!

RE: heater core flush instructions
 

Anytime! You have to stay warm out there. ;)

RE: heater core flush instructions
 

These were some good instructions, thanks for posting them. I flushed mine today and got alot of 'gunk' out of the core.
The only issue for me is, after flushing the core, I still had the same problem of lukewarm heat. My temp stays steady at 160 degrees at idle. Driving its about 170 and a tiny bit more heat comes out.

I'm thinking its the thermostat. Could I be correct? How could i check that?

Thanks,

J

RE: heater core flush instructions
 

Sorry for the delay, I am out of town. Yes, the thermostat sounds like it could be stuck open. I would replace it and see if that takes care of your problem.

RE: heater core flush instructions
 

It is the t-stat for sure I had one fail on me and I had a freeway drive home at night. It wouldn't go above about 150 beause of the high airflow through the radiator.

RE: heater core flush instructions
 

I need to do this pronto. It takes a really long time for my truck to heat up. And even when the temp guage gets up there it still blows hot air. Now, if I'm on the highway, or it has been running for more then an hour at a decent speed I will sometimes get luke warm air, but it never is hot.... time to find a friend with a heated garage.

RE: heater core flush instructions
 

Hi, I just joined this forum. Thanks for the great info! I just back in the house from flushing my cooling system. I used the prestone kit and ran it until it was clear. I refilled everything, yet my heater is still barely lukewarm. The inlet hose to the core is HOT, the hose going to the water pump is still cool(?) What is going on??? Do I need to do it the opposite way, flush from the water pump hose, back. Thanks a million!!

RE: heater core flush instructions
 

yes, I would do a reverse flush on the heater core. that way all the debris comes out of the core, not plugged further in it. I jut did my 88 dak yesterday for te hell of it and I couldnt believe how much crap came out. I had good heat before but now its amazing

RE: heater core flush instructions
 

Ok, weird things are going on. Yesterday I did the Prestone complete system flush. Today I backflushed the heater core...twice. I took it for a spin and it really acted up. I started to get warm and I am thinkind what I did worked. Then it got ICE cold and began to overheat (it is15 degrees outside). I barely made it back in the driveway, then as I pulled in the driveway, the temp started to go way down and the heater started to blow lukewarm air again(????) HELP!!!! Is this a thermostat issue? I changed that once but bought it from Napa, the same place I bought some sh***y spark plugs. Does anyone have any ideas???

RE: heater core flush instructions
 

sounds like you have an air pocket in the engine. I would take the rad cap off and fill the rad up as full as you can get it. then start the truck up and rev it between 1200-1500rpm and keep filling the rad up as it's going down. and that should do it.

remember that you will have to wait for the truck to warm up before the coolant starts flowing.;)

RE: heater core flush instructions
 

Great!!! It must have been the air bubble!! I went from none to hot. Thanks for all the help, now I have a super clean cooling system with all the hot air I need. I am not out of the woods yet however. I have a condensor that is leaking. So come late spring, I will be working on that. Does anyone know if there is a thread for that somewhere?

RE: heater core flush instructions
 

It is done pretty much the same way you change out a heater core.

RE: heater core flush instructions
 

Flushed the core the other day. Over all it was rather clean. This led me to believe I had a bad themostat. 5 min later napa had the stat at my door I had the hose off and the gasket cleaned up. Put the new one in place cleaned everything back up, filled the radiator back up and fired her up. She blows hot air now.

The thing that gets me is my stat didn't feel bad. The spring still had alot of play with it. For the time being I just put another 195F back in until the spring time when I'll spend more time modding other things

RE: heater core flush instructions
 

You should also considerusing distilled water (low mineral content) to avoid corrosion of the radiator and fouling of the whole system. I was recently denied a warranty claim on a replacement radiator in another truck. The tank to core joint failed due to crevice corrosion caused by using ordinary tap water (we have a high mineral content well). The repair manual also states to use low mineral content water.

BTW, thanks for the procedure!

RE: heater core flush instructions
 

How similar is the layout of the hoses for the 4.7l engine?

RE: heater core flush instructions
 

I am not sure, but either way, just find your water pump, and follow both lines. One will run through your firewall and that will be the one that is going to your heater core. From there you can follow the line right next to (or above/below) it to the intake manifold. From there, follow the directions as stated.

RE: heater core flush instructions
 

thanks Virused. That's what I was thinking, but I wasnt sure just how different DC was thinking when they built the 4.7

RE: heater core flush instructions
 

I have been reading all the posts from virused and they were awesome...i never thought i could flush a heater core...but i did...junk came out and i still have kinda luke warm heat....i replaced the thermostat last night and JUST got done with the flush...i drove around for a bit and got it to temp and still luke warm heat....any ideas?

RE: heater core flush instructions
 

funny how dodge conveniently put that coupler there on the in line to the heater core. must be a common problem.

RE: heater core flush instructions
 

Is this problem still happening?

RE: heater core flush instructions
 

Lady D ... you might need to flush your entire coolant system. you may have cleaned your heater core, but its just getting clogged up again from the rest of the system when it starts to circulate again

RE: heater core flush instructions
 

Thanks for the tutorial. Was this done on a truck with AC? I was going to replace my heater core but it said that I had to drain the AC coolant I'd just had installed for whatever reason. If I could just flush the core without messing with the AC coolant, I'd be a very happy camper.