The vinegar goes into the heater core through the small hoses in the firewall. Disconnect the hoses at the heater valve carefully and flush with water. Blow it out (Lung power via mouth on hose) then pour in white vinegar. Let sit for about 20 minutes and flush with water. Blow out again and repeat until out of vinegar. The longer you let it sit, the better. I gave up and ran a small bottle of CLR cleaner through it for about 1 minute too. I need to move the temp selector half way now or it gets too hot in the XJ now.

 

thanks discman, I cleaned mine out today, but used this prestone stuff. believe it or not, a fly came out when I was doing this! now tell me how exactly that gets in there?
Anyways I'm looking forward to the heat. I didn't expect it to be such a messy job, I had coolant everywhere. would have been much easier if system was drained.

 

Hey there. We just got through with the same problem. My hubby and I took out the heater core [2 weeks and several arguments later ] and took the core to a radiator shop to have it flushed out. A mechanic professor suggested the flush after the fact that we had tore out the whole dash.
We had previously hooked up our garden hose to the hoses at least 4 times and got some gunk out but a lot of clear water. We thought that was it, and that the core had to be broken.
No, we were wrong! The radiator shop sprayed just a pressurized water hose in the core and holy cow!! Not kidding, 3-4 minutes of crud pouring out of the core.
My advice is get it flushed out at the shop. 10 minutes and no cost is worth more than hours and hours of labor and messy arguments!

 

But, if you already had it out you should just buy a new one and reinstall.

 

Yeah.. I tried the prestone stuff when I flushed my system over 2 weeks. I needed something a bit stronger than Prestone flush. Vinegar and CLR to the rescue.

Yeah, you need to drain the coolant down a bit before doing this procedure.

 

drain the whole cooling system, open up the block plug, get most of the antifreez into a bucket or some kind of low pan. stick the water hose into your rad and let it run until u see clear water,maybe pull the heater hose off and put the water hose to it too for more pressure, then seal it up, put in prestone flush stuff either the 15 minute stuff or the 3 day stuff and like u guys say, vinager too? then fill up with water, cap it and drive around for an hour or 3 days. with your heat on and off. then drain it again and run water thru it until u see clear water. its best to do the whole system because there is junk in the rad that will go back into the heater core again. maybe flush it with distilled water? then put the 50/50 anti freeze in. thats what im gonna do with mine, i hope i dont spring any leaks from it afterwards.

 

ok maybe ill use clr, hell they say to use it on your coffee pots anyways. so how bad could it be. how much did u use diskman? did u use vinegar at the same time? and how much of that did u use? i can get the udiluted vinegar from work, but it might be too strong. and it freezes at 66 degrees too.

 

Had the same problem of not enough heat on my 97 xj, so I tried the core flush and it has helped (as of this AM anyway). I took both heater hoses off at the front and placed a 3/4" plastic nipple in the hose that went to the bottom of the core. To that, I rigged up with other fittings my water hose. The hose going to the top appears to be 1/2" and I rigged an extension to that just to get it out of the engine compartment (not necessary, but cleaner). I flushed out more gunk than expected off of just household water pressure. I then took the hoses loose and put in about 1 pint of vinegar so that it would flow into the top of the core, hanging the hoses up so that it wouldn't drain. Waited about 20 minutes, hooked the hoses back up and flushed again to get the vinegar out. Easy job, no vinegar smell, and fingers crossed that this works a for a while.