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Yet another heater core, heater box replacement thread
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Yet another heater core, heater box replacement thread
The heater core in my 98 started leaking a few months ago. I bypassed it and put off the repair until knew I had some time. My son drives it and he was complaining about the cold (we are in Northern VA and it's been cold). I ordered the parts (heater core, AC evap core) and oem foam for the heater box to bulk head seals.
Started yesterday and got the dash free enough to move away from the bulkhead. Today I got the 5 bolts off holding the box to the bulkhead. Took about 4 hours total to get the heater box out. Took the old heater core. Was definitely leaking. Have to get some more foam tomorrow. Hopefully getting the heater core and evap core back in and get the heater box back in tomorrow. I read lots of threads and watched several youtube videos. Lot's of good info out there. I thought it would be a lot worse. Dash pulled back Success on the hunt for a heater box 24 yeard old heater core other side of the 24 year old heater core
Heh. I did mine in my '98 a couple of years ago, and the leaking heater core looked the same. What a mess. I see you were smart and pulled your seat out, which makes things much easier. Just be sure you use some good stick-on foam all around the heater core to get it to seal well. That helps a lot.
That 5th nut behind the engine on the firewall is a b!tch, isn't it?
I sleuthed around and eventually found a brass replacement heater core for mine. You should too if you look hard enough ..or use links below. It would be worthwhile. Here's why: Aluminum has a narrow "happy" pH range from 7.0-8.5. Outside of that range it begins to dissolve. And you know how think a h/c is. Other metals like Iron have their 'happy' pH range too. But Aluminum and Iron have different happy ranges. Brass has a range more closely resembling iron and it's a noble metal. Sure there are corrosion inhibitors in anti-freeze, but the pH range which satisfies both is rather narrow. A lot of premature aluminum heater core 'deaths' are due to poor pH, whereas vehicles with brass heater cores can often last decades, even if coolant ages and 'drifts'. It looks like yours corroded probably b/c of galvanic corrosion. Maybe replace your coolant (use distilled water too). Here are the happy pH ranges of come metals:
-Brass/SS ~9.0-10.5
-Aluminum 7.0 - 8.5
-Iron (steel) 9.0 - 10.5
You can search and read up on galvanic corrosion of engine cooling system components. 9.0-10.5 is the typical range, but then it's outside the range of aluminum. The scale is logorithmic ...where every point is a multiplication factor of 10. (from a neutral 7.0). 9.0 is as close to aluminum and you can satisfy both metals (almost). I used to work selling industrial boilers. You'd get an owner who had a few iron and copper boilers. Suddenly he'd buy an aluminum boiler (because it was 'cheap') and add that to the system which contained the Iron/Copper boilers. Well, after about 3 -4 years I'd get a call how it's aluminum heat exchanger crapped out.
If you plan to keep your XJ a while, consider hunting down a brass heater core. I found one for mine off ebay (they still sell them HERE). I bought an aluminum h/c initially for mine. The passages were smaller and a lot more. The copper h/c was more in line with my Cherokee's original and fit perfect. Note to others, early XJ h/c's are different than the later ones.
Heh. I did mine in my '98 a couple of years ago, and the leaking heater core looked the same. What a mess. I see you were smart and pulled your seat out, which makes things much easier. Just be sure you use some good stick-on foam all around the heater core to get it to seal well. That helps a lot.
That 5th nut behind the engine on the firewall is a b!tch, isn't it?
It took me awhile to figure out an easy way to get to it. I used a spare tire to stand on and found a ratcheting closed end wrench. that made pretty quick work of it. Probably took longer to get the safety catch and other holder off so I could actually get to the nut.
I sleuthed around and eventually found a brass replacement heater core for mine. You should too if you look hard enough ..or use links below. It would be worthwhile. Here's why: Aluminum has a narrow "happy" pH range from 7.0-8.5. Outside of that range it begins to dissolve. And you know how think a h/c is. Other metals like Iron have their 'happy' pH range too. But Aluminum and Iron have different happy ranges. Brass has a range more closely resembling iron and it's a noble metal. Sure there are corrosion inhibitors in anti-freeze, but the pH range which satisfies both is rather narrow. A lot of premature aluminum heater core 'deaths' are due to poor pH, whereas vehicles with brass heater cores can often last decades, even if coolant ages and 'drifts'. It looks like yours corroded probably b/c of galvanic corrosion. Maybe replace your coolant (use distilled water too). Here are the happy pH ranges of come metals:
-Brass/SS ~9.0-10.5
-Aluminum 7.0 - 8.5
-Iron (steel) 9.0 - 10.5
You can search and read up on galvanic corrosion of engine cooling system components. 9.0-10.5 is the typical range, but then it's outside the range of aluminum. The scale is logorithmic ...where every point is a multiplication factor of 10. (from a neutral 7.0). 9.0 is as close to aluminum and you can satisfy both metals (almost). I used to work selling industrial boilers. You'd get an owner who had a few iron and copper boilers. Suddenly he'd buy an aluminum boiler (because it was 'cheap') and add that to the system which contained the Iron/Copper boilers. Well, after about 3 -4 years I'd get a call how it's aluminum heat exchanger crapped out.
If you plan to keep your XJ a while, consider hunting down a brass heater core. I found one for mine off ebay (they still sell them HERE). I bought an aluminum h/c initially for mine. The passages were smaller and a lot more. The copper h/c was more in line with my Cherokee's original and fit perfect. Note to others, early XJ h/c's are different than the later ones.
If I had done more research, I would have gotten the copper core for sure. The person I bought the jeep from had blown the engine. His two boys replaced the water pump and used well water to refill the cooling system. I replaced the engine and flushed the system, but I'm sure the well water didn't help anything. I need to get this project done so will go with the aluminum core I bought. I used an aluminum one in my YJ too.
Thats ok, but then consider setting your tk's pH to be in the 9.0, 9.2 range. Adjust with sodium hydroxide (lye), or a couple drops of Lemon juice or citric acid ...both of which you may have around the house. That'll keep the iron happy, and closer to the AL h/c. Use new anti-freeze and distilled water.
https://www.ebay.com/itm/314204579075
If you buy the tester above (they work great btw) ..keep the buffer solution in a tupperware or jars/etc, for future recalibration.
Got the new heater core and evap core in. I put foam around both for cushioning. I was super happy that the two halves went back together so easily that I didn't get a pic. doh!. The styrofoam liner under the evap core was not in great shape, but I was able to use waterproof tape to piece it back together. Not ideal, but didn't have much choice there. I did a quick test fit and the box went back into the holes with no problem.
I bought a couple of nylon drill wheels from harborfreight to take care of the remnants of the foam between the box and the bulk head. Ran out of light and heat from the sun so will finish it up tomorrow. Wasn't nearly as bad as I thought it would be but not a fun job either. Less than stellar condition styrofoam. Box back together awaiting final new foam ont he front
Son of bit*h, sheet. Was going great until I tried to put the steering column back in place. the plastic block just won't line up with the studs. Maybe the whole column slid out a bit from having weight on it. Lunch break and then back to it. HE Heater box going back in here boss Plastic block on the column won't align to studs more perspective.eater box is back in, dash is back in. Now it's the steering column and random dash bits. Then re connect the heater hoses and do the AC.
Problem solved with a 2x4 and a mallet. I pushed my head against the steering wheel, positioned the 2x4 and pushed up on the wheel while giving the plastic block a few whacks. Slipped on. Hopefully get everything back together tonight so I can be done iwth this project. Would have been 2 days int he summer with more sun light. It's tough working in the cabin without sunlight.
Yay. Have heat again. Now just have to do the AC, vacuum out the car and put the seats back in. Than onto the 3 other vehicle/motorcycle projects I have.
Finished everything up. Have a couple of things to go back and look at. I accidentally cracked one of the vacuum lines going to the purge valve. I accidentally cracked the vacuum line going ot the ball/reservoir on the front bumper. Heat shrink tubing and some electrical tape fixed it for now, but I need a better solution. Last thing is the tilt steering wheel. It moves up and down but doesn't lock in place. You can set the position low, but then the wheel can still move up. Looks like a very simple mechanism. Ans last, the positive battery terminal was way past it's fresh date so off to get new battery terminals. Did a quick temperature check. getting 140+ on heat and seeing around 20 on AC. I'll call this job a victory. Also have a Ph tester coming from amazon so I can check the coolant Ph in this car and my wrangler since they both have aluminum heater cores.
At least I know how to do this job now. My wife has a 99 that we have owned since new. I can't imagine that heater core is too far behind. then again, I have done almost all of the maintenance on that Jeep and it has always had distilled water and has gotten regular coolant changes.
Closing the loop on this since I got my Ph tester and finally got around to measuring the Ph in the XJ and my YJ. The coolant in my YJ is a couple of years old and measured 7.54. The coolant in the XJ is pretty fresh and measured right at 7.0. It is very cold out (mid 30s) and the YJ coolant was not hot but warmer from a drive earlier int he day. The only reason I mention the temp is the calibration instructions say it should be calibrated at 77 degrees fahrenheit. Ph does vary with temperature so I'll have to take readings and record the temp of the coolant.
did you put a brass or aluminum heater core in your jeep. I understand from several different people that the aluminum one does not last. The brass one is hard to find as I believe it is not made anymore.
11-20-2022, 04:41 PM
Yet another heater core, heater box replacement thread
