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Thread: Looking for tips on how to approach getting to the heater core on my '72 Z

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    Default Looking for tips on how to approach getting to the heater core on my '72 Z

    My 1972 Z has the dealer installed AC. I know I can just start taking things apart, but if any of the forum members have some helpful tips on how to approach this I would be most thankful. I know I have a leak, but, at this time, don't know if it is the core or one of the hoses. As far as I know, this one owner car, before I bought it last year, has not had anyone try to get to the heater since the car was new.

    Thanks,
    Charlie

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    Charlie,
    I can't tell you exactly because its been a while since I disassembled one, but I believe the after market evaporator is in the way of getting to the heater core. Not an easy job and gets harder as I get older...
    Charles

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    I agree. At 67 it is not easy to get under the dash and do the work I used to do on my first Z car back in the late 1970s. I am going to try and see how far I can get into this project before I have to take it to my local mechanic. It would be great if I could get to the leak myself. I'll see.
    Charlie

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    I would pull the glove box first and get a good light in on the hoses. If it's just hoses then you can pull the heater fan and its motor and do that work instead of messing with the heater core. MY 76 still had the original hoses and they were almost porous. No actual big leaks, they just seeped coolant through the pores that had opened up.
    1976 280Z, with some minor modifications

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    Here's a thread that'll have some info. Starts at #12, http://www.classiczcars.com/forums/c...y-72-240z.html

    Likely the heater valve's leaking. Still available from Nissan. #32 has some tips on getting to it. Have fun!
    Last edited by siteunseen; 10-22-2014 at 02:45 AM.
    1972 240Z #918 New Sight Orange
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    Quote Originally Posted by Coastalman View Post
    At 67 it is not easy to get under the dash and do the work I used to do on my first Z car back in the late 1970s.
    I was originally going to suggest that it's easier to pull the whole dash first. If you've got small hands and are part contortionist it's not "really" necessary, but I've found the extra time I spent pulling the dash was more than made up for by the ease of working on the heater system after I had done so.

    No matter how you look at it, pulling the heater core out is a PITA. I feel for ya Charlie. Be careful of your back.

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    Hey Coastal Man, I have the same set up and will be pulling it all this winter. Please take pictures and let us know your process. Neither my aircon or heat works right now. I intend to delete the aircon and fix the heater.

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    I went thru the steps to pull the heater/blower assy in my '70 Z last year. Although I was able to remove them successfully w/o pulling the dash, I eventually decided to do that too... so I now have experience with both strategies and will offer these comments:

    1. I you decide not to pull the dash, you'll need to remove both the glovebox liner and the HVAC controls faceplate in order to gain the access you'll need to get the heater and blower out. Many steps along the way require a lot of contortion and will favor agility, small hands, good lighting, and a lot of patience. You'll need to detach the heater control cables from the heater/blower assy. The cable clamp on the water valve could be problematic if there's been long-term leakage. The water valve may be seized, leaking, or both.

    2. Removal of the glovebox liner is not an intuitive process, nor do there seem to be any good step-by-step instructions or photos available to guide you (incl. the FSM). It will not come out from the back (there's stuff in the way). It will only come out from the front. IIRC, I had to bow in the top edge first, and then bow in both sides. Eventually, if you bow in all 4 edges sufficiently, they corners will clear the opening in the dash by just enough to pull the liner out. If you're lucky, it won't tear or crumble in the process and might even be reusable.

    3. Once you've got everything freed up, the heater box assy can be pulled out from the passenger side (best to pull the blower assy first, as a separate unit -- caution: it may be stuck where it mates up against the cowl panel). Be sure you put down some newspaper on the pssgr-side floorboard, because you're going to spill coolant when you detach the heater hoses and when you pull out the heater box.

    4. When all is said and done, you may wish that you'd just pulled the dash first. It might just end up taking the same amount of time overall and it sure makes getting to the heater and blower a lot easier (for both removal and reinstallation). Also might make removal of the glovebox liner unnecessary (not sure about this -- maybe someone else can comment). Pulling the dash will also give you an opportunity to inspect and clean some key wiring harness connectors and replace all of the gauge lights (v. difficult to do with the dash in place, and nearly impossible for speedo and tach if your dash has a cap installed).

    Let us know what you decide to do.

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    Registered User Stanley's Avatar
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    Removing the evaporator was easy and made it easier to work in that area. My heater valve is all corroded and the hose connections leaked until I plugged the engine fittings. Need to replace the valve and hoses; not happy about that.

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    Quote Originally Posted by Namerow View Post

    4. When all is said and done, you may wish that you'd just pulled the dash first. It might just end up taking the same amount of time overall and it sure makes getting to the heater and blower a lot easier (for both removal and reinstallation). Also might make removal of the glovebox liner unnecessary (not sure about this -- maybe someone else can comment). Pulling the dash will also give you an opportunity to inspect and clean some key wiring harness connectors and replace all of the gauge lights (v. difficult to do with the dash in place, and nearly impossible for speedo and tach if your dash has a cap installed).
    I would recommend Option #4. If you have one person to help - pulling the dash is really a far easier and better way to go. Trust me - this is not something you want to do upside-down cramped up under the dash. Even if you take the passenger seat out, so you can get under there - It is no fun when you are 25 and shear frustration when you are 65+. Pull the dash, do a complete "refresh" job on everything under there - Do it all once and be done. Hire a young helper.. maybe you can find a local Z Car enthusiast near you.

    FWIW,
    Carl B. pushing 70...

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    I would investigate a little further before attempting to pull it. When I bought my car from the PO, it still had factory looking braided hoses on the heater core and heater valve. The hoses were cut off at the firewall and the heater was bypassed. Although the hoses looked okay from the outside, I obviously still cut em out and replaced them. When I pulled it all apart I found that the heater valve was corroded and nasty. I assumed that's where the leak originated that had them cutting the heater hoses. I'm not one to throw out possibly good parts without testing them, so I cleaned it up with some steel wool until it looked presentable again, ordered some hoses from MSA, and finally put it all back together last night, expecting the 40 year old core to leak, or the valve to spray, but after running 30 minutes at temp not a sign of the slightest leak.

    I guess what I'm trying to get at, is be sure that's your issue before ripping it apart. You can buy UV dyes, rent radiator pressure testers (P/N 9300 at Autozone iirc) that will help you verify your leak before gutting the car to get to the core.

    I'm 23 and I was NOT looking forward to pulling my heater core out... Thankfully I didn't have to...yet. Datsun trucks are far easier then the cars.

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    Metalmonkey47 makes a good point. I found that the heater valve ('water cock' in Datsun-ese) in my Z was frozen solid at the main pivot point of its linkage. This apparently frustrated the previous owner to the point where he/she forced the 'TEMP' control lever so hard that it bent the control cable. I simply soaked the heater valve in water-based parts cleaner for a week, then cleaned and lubricated the linkage and put a drop of Armorall on the valve's push-pull shaft where it pokes out of the casing through a small, neoprene, disc-style gasket. Now it works and seals just fine.

    That said, most of the foam gaskets in my car's heater box and blower housing had disintegrated from age. The control lever assy also needed repairs, along with cleaning and lubricating. Although the system might have worked after the heater valve and control cable were fixed (the heater core was fine), I'm not sure that it would have worked particularly well.

    In the end, it all depends on what final result will satisfy you. It may very well be worth pulling the heater valve first and either servicing it or putting in a new one. If you go this route, though, be prepared for a hour or two of awkward work. IIRC, you will need a 1/4"-drive socket set and a stubby Phillips screwdriver (and maybe an offset Phillips screwdriver too). One or two of the Phillips screws may be reluctant to loosen, so its worth spraying all the fasteners with penetrating oil a week or so before you get started.

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    Once the evaporator is removed, it's possible (with contortion, a small extension mirror and/or a small camera) to see the core, valve and hose fittings well enough to see where the leaks are, by the corrosion and coolant stains. As mentioned above, maybe the core is OK.

    If and when I get around to doing mine, I'll probably put a restrictor in the heater line, to reduce the chance of future problems. Got that from a Mustang site. Sounded like most Mustangs from certain years blew out the heater cores from too much water pressure at high rpm.

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    Quote Originally Posted by Coastalman View Post
    My 1972 Z has the dealer installed AC. I know I can just start taking things apart, but if any of the forum members have some helpful tips on how to approach this I would be most thankful. I know I have a leak, but, at this time, don't know if it is the core or one of the hoses. As far as I know, this one owner car, before I bought it last year, has not had anyone try to get to the heater since the car was new.

    Thanks,
    Charlie
    I removed the heater core last year. But in the end it wasn't the core that was leaking but the hoses and the valve that's on the passenger side. Like some other members said here, try to do a pressure test to the heater core first before removing it. I removed the core in a bout 1, 1/2 hours, you need patience and broken hands hehe. The front control panel needs to go out and remove the connecting cables, also remove the glovebox. After you removed a few hoses. The heater core is holded in place with a few screws. After that you can pull it out to the right, passenger side, with some wiggling. Don't know about the AC stuff though. I feel pulling the dash is far more of a hassle.
    HLS30 32581, 5/71 Matching numbers

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    Here is an update on my leak. The background is that last winter, the first I had owned the car, I tried the heater and had the windows fog up and a strong smell of antifreeze. I shut the valve via the slide on the dash and everything cleared up. I knew there was a leak. Since I was working on other issues I did not work on the heater at that time. Now, with cooler weather coming, I wanted to be able to use my car in the winter. After getting the advice from the forum, I pulled out the glove box, pulled the vent hose off and was able to see the valve and hoses. I ran the car to get it warm and then engaged the heater valve with the slide control. After watching the hoses and valve for awhile, I could not see a leak. I drove the car for 20 miles with the heat working just fine. No smell and no leak. Heat was working fine. Since the car had been barely driven for 10 years before I bought it, could the valve have dried out and then when I first used it "re wetted" some kind of seal that then expanded and begin to function as it should have? I have left it all exposed so I can watch it, but for now it is working fine. Thoughts?
    Charlie

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    If you're going to drive it then i'de get tool that crimps the heater hose leading into the heater core.
    so if it pops while you're driving you can pinch it off. Then i'de get a gallon or 2 of water inside antifreeze
    bottles and store them behind the seats. Mine popped under the dash one nite and it was a hellish nite
    getting home. Now i carry 2 gallons in the car at all times.
    Last edited by hr369; 10-27-2014 at 02:59 PM.

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    Good advice!

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    Quote Originally Posted by Coastalman View Post
    Here is an update on my leak. The background is that last winter, the first I had owned the car, I tried the heater and had the windows fog up and a strong smell of antifreeze. I shut the valve via the slide on the dash and everything cleared up. I knew there was a leak. Since I was working on other issues I did not work on the heater at that time. Now, with cooler weather coming, I wanted to be able to use my car in the winter. After getting the advice from the forum, I pulled out the glove box, pulled the vent hose off and was able to see the valve and hoses. I ran the car to get it warm and then engaged the heater valve with the slide control. After watching the hoses and valve for awhile, I could not see a leak. I drove the car for 20 miles with the heat working just fine. No smell and no leak. Heat was working fine. Since the car had been barely driven for 10 years before I bought it, could the valve have dried out and then when I first used it "re wetted" some kind of seal that then expanded and begin to function as it should have? I have left it all exposed so I can watch it, but for now it is working fine. Thoughts?
    Charlie
    That tells you right there that there's a 90% chance the core is the issue. If the valve or hoses were leaking, it wouldn't get onto the core, meaning you wouldn't be fogging windows as you drive and blowing moist air through the vents.

    it's possible the core corroded around the leak from seeping, and it's just a ticking time bomb. I had the exact same issue in my 620. I took it apart and found it leaking everywhere. Ended up un soldering the tanks and it was a mess. I couldn't get it soldered back together because it had a 2 piece tank, so I took it to a radiator shop and paid them $60 to soak the core/tank in solvent, and re-solder it. The results were good.

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    I've read where a guy put some type of valve in between the in and out at the engine bay fire wall right before it enters the cabin. He said it bypasses the heater core in the summer months to help cool the cabin. I can't find the thread right now but I will. It sounded like an idea I'd like to try.
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    Quote Originally Posted by siteunseen View Post
    I've read where a guy put some type of valve in between the in and out at the engine bay fire wall right before it enters the cabin. He said it bypasses the heater core in the summer months to help cool the cabin. I can't find the thread right now but I will. It sounded like an idea I'd like to try.
    We actually had a pretty productive discussion on one of the Facebook pages last night (I think it was Datsun Parts and Needs) about overheating issues around the last two cylinders cause by bypassing the heater and feeding hot coolant back to the rear of the head. Apparently someone has measured the rear of the cylinder head at about 220 degrees under a 50hp (or so) load at somewhere around 3000rpm and 170 at the front with the heater bypassed straight to the rear of the head. I'd love to find those links again to reference.

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    This issue of bypassing the heater has come up many times. The correct way is to BLOCK/PLUG the heater hose connections at the head and lower rad hose fitting at the front. Do NOT just join these inlets/outlets effectively short circuiting the rad and putting hot water at the back of the head. I know it is super tempting to just connect the front and back heater hose fittings with a nice piece of hose as you don't have to find two big bolts or equivalent to use as plugs, but DO IT. It will save your engine or at the very least prolong its life.

    That said, if you have to do it as an emergency on the road when you heater core or valve suddenly blows, do the jumper hose/short circuit thing, and get home safe, its not an instantaneous damage thing, but remember to fix it right SOON.
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