LukeA08

Hello all. I have been playing around with my jeeps heating issue for almost a month now, and I am running out of suggestions myself. I am in Alberta, Canada, so temperatures get around -45C. I am by no means a mechanic, but can normally follow instructions fairly well. I have a 99 Jeep Cherokee, I6 4.0. It will only blow warm air when the heat is on. I have flushed the heater core twice. This was done with just a regular garden hose with very hot water on a jet setting. I noticed dirty water and debris came out during this process. After about 5 minutes I noticed the water was running clear through it. Still no heat. I just changed the thermostat with an aftermarket part from Canadian Tire. Still no heat. I am not sure if I made a mistake with the above processes, but I believe I didn't. Just looking for some info, and advice on what to try again, or try next before taking it in to someone for a pocketful of money. Thanks all in advance for any help!

ExTrEmExJ99

I too have a 99 and I have had the same problem. I tryed everything from a head gasket to a new radiator. The other day I flushed the heater core ( its like the 5th time) and I tryed CLR. I took both lines off from the motor and used a air hose to blow all the coolant out of the heater core into a catch can. Then I held both lines up and poured in some CLR and the added water to fill both the lines up. I let it sit for about ten minutes then I drained and flushed with clean water and used the air hose to blow out the water. I repeted this untill I used the whole bottle of CLR and then I hooked up one hose and filled up the other hose with coolant untill it was full then connected the hose. I noticed that the CLR was cleaning some pretty nasty stuff out of it. I would recommend that you dont leave the CLR in there any longer than 10 minutes it might eat the heater core. But that is what I got to work for me I have nice and warm heat now.

tjwalker

I think it is very possible that your heater core is still partially clogged.

Here is a video of the CLR technique. Worth a try.

RTorrez1

I would NOT recommend using CLR at all. I will damage the heater core. Just keep flushing it with water in BOTH directions. I can take several times to break everything loose. Just because when you flushed it, it doesn't mean it's clean. Just keep flushing.

ExTrEmExJ99

^ I disagree worked perfect for me if used in moderation thinned with water

foxmxrcer

I've done this method many times on many vehicles at work, saves the Customer A LOT of money. Get yourself a drill operated water pump, normally found in the plumbing section at the hardware store. Disconnect both heater hoses and hook the pump to one of them. Grab a bucket and fill with hot water and radiator flush. Put a hose from the heater core in the bucket(this will be your return line)and put a hose on the other end of the pump and into the bucket. Run for a few minutes that way, then switch hoses to flow the flush the opposite direction. Go back and forth a couple times until you feel it's cleared up. Now, slowly poor the bucket out, and see what dirt remains at the bottom. you may be shocked. But, clean the bucket out, and run just hot water threw both sides a few times to clean the flush out, re attach hoses and give it a try. Other thing could be blend door issue.

djb383

It plainly states on the CLR web site "do not use in a automotive radiator". Isn't a heater core a small radiator?????

foxmxrcer

For all political and liability purposes, don't use it. Do people use it? Yes. Successfully? Yes. Unsuccessfully? Yes. But you can do just as much damage with radiator flush as you can with clr, both are acid based, which is worse? I would assume clr since the manufacturer states not to use it.

LukeA08

Hey all. I just wanted to thank everyone for their input and help. I was able to work on the jeep last night. I flushed it about 3 times each way before pouring 50/50 CLR and water into the hoses and core to sit for about 15 minutes. I flushed once again and poured the rest of the CLR in mixed with water to sit for another 15 minutes. I then did a final 3 flushes each way before starting the jeep up. I let it get up to temperature and the heat coming out of it was unreal! The CLR flush really does do wonders! Thanks again everyone.

ExTrEmExJ99

I told u so there are a lot of haters on here but sometimes something works so good and if you are careful it works for you too.

tjwalker

I have always taken this position on using CLR for a clogged heater core.

Use every other flush technique first. You want to use the least aggressive technique necessary to obtain results. However, If less aggressive techniques don't work and you are sure the issue is with the heater core, try the CLR technique.

Think about it. If it is a last ditch effort, what do you have to lose as next step is replacing the heater core anyways?

I have used it successfully and I will continue to recommend it.

cpdr26

I just flushed out my heater core yesterday. Thermometer reading from top vents by radio were 91 degrees, and my footwell area was blowing about 80 degrees. I disconnected the lines and ran hot water through first, then Prestone super flush (let it sit too), then hot water twice, then I tried the TJWalker reccomended CLR method (not full concentration, diluted) and then another round of hot water. After that, I had a small drill pump and recirculated hot water till it was nice and clear.

Hooked everything up, went for a drive to get it up to temperature aaaaaaand......its colder than it was. I'm about 80 degrees from top vents

Do I need to try a stronger solution of CLR or go straight CLR since my last one was maybe about 20% or so?

Radi

Something else to check if you are having heat problems is that hot water cutoff valve (if you have one- not all do) in the heater hoses. If the hoses that run along the valve cover are both hot while those going to the core are only lukewarm...the valve isn't working right.

Mine disintegrated, I installed a NAPA replacement. Fine and dandy until it got cold out.
I bypassed it and cut the thing open- there is a plastic diverter in there that sends water through the core in one position and routes it back to the engine in the other position. No seals inside, the thing probably sent half the hot water right around the edges of that diverter and back to the engine instead of the core even when fully open. The difference in heat without it was amazing.
The factory units may have been good, but the aftermarkets are worth checking if you have heat trouble.

PocketsEmpty

The valve you speak of only applies to Cherokees up to model year 1991. OP states that his is a '99 in which case he does not have to worry about this valve as the water pump is directly connected to both heater core hoses, and coolant always flows through the heater core. There is a vacuum-actuated door that controls the flow of air through the core.

I used a high-pressure garden hose to backflush and forward flush my heater core after having virtually NO heat, and this raw sewage came out...



And that's even diluted with clear water after it cleared up. My heat works really well now...interested in the CLR or even hot water techniques to see if I can get more out of it. My PO used stop-leak in my Jeep cooling system due to a leaky freeze plug and radiator so I've been fixing it the right way ever since.

brianrich07

I have a 96 and mine has a valve.