Just wondering if anyone has figured out the heater issue, where the driver side blows cold and passengers blows hot? I’ve been reading threads for hours and it’s a super common issue, however I haven’t seen anyone actually comment on what it ended up being? Possibly still hasn’t been figured out?

Ive read that people flush and replace the core, change motors, etc - but nothing seemed to work as far as what I’ve read.

I’ve been having coolant system issues - and it all started with the drivers side heat going cold, and now it’s spiraled into a whole other mess.

still currently bleeding the system to see if I’m all fixed but, now everything is blowing cold.

 

Really? I have read dozens of threads that explain the issue. Its quite simple, the core has input and output on the passenger side. So debris tends to build up and settle on the driver side. Over time, especially when the wrong coolant is used or never changed, it clogs up and heat output drops on that end. People have cut them open to show the build up. If its not bad, flushing can work. If its a little bad, citrus flush can help. If its bad, then sometimes a sonic pushing type flush can work (require core removal).

 

My two cents:

I'm flushing my core as we speak. I bought a recirculating pump to cycle CLR through the system. I had it on closed loop for both sides maybe a total of 12 hours. Used the whole gallon bottle, maybe a 60% / 40% concentration. I can't tell help much it helped, but there was minimal sediment in the bucket.

I also bought a heater core flushing tool at the same time. This is what seems to get the debris out. I have it in my garage, so I capture the sediment everytime I get to about 5 gallons. I've flushed it probably 25 - 5 gallon buckets now, and I still get sediment out of the core. The normal flow must go in the left heater core pipe when facing the front and exit the right. I am flushing through the right side, and continuously am getting the sediment. I've examined the sediment several times, and it looks to me like it is plastic. The color of the plastic looks to be a the murky green (like the bleed crossover), black, and occasionally white. It looks to be plastic everytime.

I've read somethings about OAT and them eating plastic. I'm NOT saying that is what happening here, but my intuition makes me think that it is what is happening. I just bought the car, and have some of its service history, but nothing on how often and when the coolant was flushed. All I know out of the 15+ or so cars I've owned (mostly imports) that run the green coolant, older, and my youthful neglectful history as it related to flushing coolant only, I've never had a heater core blocked. Coincidence, maybe, but I may just flush out all this old OAT and change it to a glycol based coolant.

Update:

Done. The core is flush, there is little to no debris coming out of either side. The MVP here is the heater core flush tool. It seems like the heater core is the "filter" for the coolant system. I think if you're going to use CLR, use it AFTER you have flushed out all the sediment for it to be effective. I think there was a plastic sediment wall that prevented it from going down further. It wasn't calcium lime or rust. I flushed out a piece of rubber gasket after flushing out a bunch of sediment. If I were to guess on the amount, it would have been roughly a 2 hand cupped full of sediment. I still think it is plastic. Near the end, it was like I hit the debris "motherlode" or hit bottom. Then what I would have expected to come out looked like sand and dirt (not the plastic). I only had a few more buckets after that to get the flush completely clean. I'll update you all when I put the car back together (doing valve body, washer reservoir, and and sunroof drains) then I'll update you all on the heat.

 

Mate of mine just replaced his heater core after experiencing the hot/cold problem, he found that by cutting out a 2x4" piece of trim from the console you can remove the core without dismantling the entire dash.
He then just made some pieces up so that the cut piece now just screws back in place, this would also be a very effective of flushing the core with it out of the vehicle.

 

Update:

It took me this long among other work I was doing (sun roof drains, full carpet detail, driver seat reupholster, windshield reservoir bottle replacement, coolant overflow replacement, permatex intake components, and more ...) but I can successfully say that flushing the heater core solved the problem. I now have heat on the driver's side, and it is HOT!

One side note, disregard what I was saying about the plastic. I hooked up my water line to my hot water heater, and some debris was continually coming of of the hot water tank. Once I realized this, I went back to the closed loop flush on both sides to ensure that there was not any debris left. Because of this, I probably power flushed the heater core with over 500 gallons of water since I thought there was so much debris. Maybe this is also why it was successful, but it likely shouldn't have taken that much. I also don't know if the CLR, power flushing, or both were primarily responsible for solving the issue.

So for all of you looking at replacing your heater core, for about the same price (in tools you'll have for the next time), I believe you can also bring yours back to life. Mine was ICE cold when demanding heat. Not even warm by a little bit. And now it is back.

I was also able to bleed by radiator in one shot. I've heard of others having this issue, but all I did was put it on ramps, let it idle to op temp, then raced it, and then bleed it from the coolant reservoir. I did pop open the bleeder tee once, but I was primarily able to do it by the coolant bleeder plug. Drove it around and no issues. You'll see bubbles near the top, also make sure you have enough fluid in there. I'm running radiator flush through it now, so I'll test my method again in a few days.

T

 

I was having the same issue and I ended up buying some CLR Pro Radiator flush, diluted it in three gallons of distilled water in a five gallon bucket with an aquarium circulation pump connected to the input/output pipes with clear vinyl hose, and ran it through the heater core for about 2.5 hours (maximum recommended time for the product), swapping the hoses a couple times to reverse the flow (this definitely helped clear some buildup deposits). Then I flushed the core with pure distilled water for a little while before refilling the core with coolant and reconnecting the coolant hoses. Then you must properly bleed the coolant system.

After doing this, my heater is working great and often gets too hot! Give it a try! Pump was only $18 on Amazon, and 5/8" vinyl hose fits the pipes snuggly.