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  1. #1
    FEP Power Member 85stanggt's Avatar
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    Default Heater Core Modifications?

    Just finished my intake gaskets. Installed a new heater hose with restrictor to protect the core. Now it's leaking, probably thanks to me getting the old hose off.

    I just ordered a replacement Motorcraft one, but the HC-5 cores now appear to not have any extra bracing for the lines like I've read some of the original Ford cores did. Also, they don't appear soldered all that special where the tubes meet the tank.

    2 questions:

    Should I have someone weld a brace onto the two tubes?
    Should I have someone weld the hell out of where the tubes are soldered/brazed to the tanks? That appears to be the weak spot on these things.

    Wait just thought of another question related to the install...can the dash be dropped enough without having to disconnect all the wiring connections on the sides and at the pork chop brace? Thanks
    Last edited by 85stanggt; 12-14-2017 at 01:37 AM.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

  2. #2

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    I'm not sure any of them are soldered real special. It's another of many automotive things that I believe a bit of overkill wouldn't hurt. Being super careful to not bend or twist the tubes too much is about all we can do. Having also learned this lesson the hard way in the past, if I am ever removing a heater hose, for whatever reason, I talk real nice to the core, lol, and carefully split the hose there lengthwise first with a razor blade... then a pretty easy twist and it comes off...
    Last edited by Walking-Tall; 12-15-2017 at 12:39 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
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    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #3
    FEP Power Member 85stanggt's Avatar
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    Haha yeah. I did think about splitting the hose because it was like fused to that core fitting real good. I think the core was seeping already though, because I would notice a film building on my windows occasionally. Plus you could kind of smell it. I was just in denial.

    I think I'm going to have someone weld a nice bead around the tubes where they meet the tank for extra strength and then add a "bridge" or brace of some sort to the angled tube to connect it to the tank for even more strength.

    Can the dash be dropped enough without having to unplug all of the electrical connectors? Or am I looking at doing all that again? Remove the center console? I saw V8only's thread from years ago, which is great, but the dash was already removed from the car.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

  4. #4

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    Personally I wouldn’t modify the new core. The heater core is not hard to replace, But it is time consuming. it will take a minumum of 5 hours. There are some helpful threads out there on how to remove the dash. I always pull the seats for additional room to work. Do it right pull the dash back and remove the case from the car. Some guys will tell you to butcher the case and use sealant to get cover back on. To me that’s a hack job and takes just as long as getting the case out. Here is a pick of my dash dropped just enough to get the box out.
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    Last edited by Lowetlx; 12-14-2017 at 01:58 PM.
    84 LX Vert. 5.0 5speed canyon red on white
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  5. #5
    FEP Super Member erratic50's Avatar
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    Lowetlx - that picture looks damn familiar.

    One thing I will mention is that if you happen to have a working AC system and no tools to reclaim the refrigerant then you are back to potentially needing to cut the box.

    whats crazy is that on my early production 1986GT I can lift the lid on the box and only had to barely nip one corner. Meanwhile with my son's 1986GT convertible you can't even lift the lid on the box.
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  6. #6
    FEP Power Member 85stanggt's Avatar
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    Quote Originally Posted by Lowetlx View Post
    Personally I wouldn’t modify the new core. The heater core is not hard to replace, But it is time consuming. it will take a minumum of 5 hours. There are some helpful threads out there on how to remove the dash. I always pull the seats for additional room to work. Do it right pull the dash back and remove the case from the car. Some guys will tell you to butcher the case and use sealant to get cover back on. To me that’s a hack job and takes just as long as getting the case out. Here is a pick of my dash dropped just enough to get the box out.
    Well that's the thing. For a job that takes a minimum of 5 hours, I do not want to have to do it again. I think just the shear number of these cores that have been replaced in all the 80s/90s era Fords indicates that the design and/or manufacture of them is highly defective. I don't think I've ever replaced a heater core in any of my or my family's other non-Ford cars. WTF.

    Now, I never like taking shortcuts working on my cars, but doesn't pulling the box require opening the A/C system? I don't want to, since it works great and is the original R12 still. From what I've read, I can get the cover open without butchering it if I just pull the box part way out. Is this not the case?

    How much did you have to disconnect to drop the dash that much? The electrical connectors are very hard to get apart.

    Quote Originally Posted by erratic50 View Post
    Lowetlx - that picture looks damn familiar.

    One thing I will mention is that if you happen to have a working AC system and no tools to reclaim the refrigerant then you are back to potentially needing to cut the box.

    whats crazy is that on my early production 1986GT I can lift the lid on the box and only had to barely nip one corner. Meanwhile with my son's 1986GT convertible you can't even lift the lid on the box.
    So I may be able to get the cover of the box off enough to get the core out without having to evac the A/C. I hope it is not a convertible thing with the lack of space up there.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

  7. #7

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    You can find a shop that can evacuate and recharge the ac, or butcher the case. That’s up to you. The dash has to be pulled at least that far either way you choose. The following are the main connectors you will need to disconnect; all the steering column harnesses. The cluster harnesses, the connectors in the right kick panel to body to dash harness. The connectors to the console. Once the dash is dropped, the ones on the blower motor. The antenna, the vacuum harness.
    84 LX Vert. 5.0 5speed canyon red on white
    99 cobra, electric green on medium parchment, vortech s-trim

  8. #8

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    Let me add some additional tips. Prior to removing the heater core flush the cooling system to get as much of the old coolant out, then once you've replaced the core and drained as much as the remaining water out of the cooling system refill with the newest version of Ford coolant. I did this when I replaced mine a few years ago because the newer coolant is much improved with anti-corrosive additives than the older version.

    One other tip, syphon out the system with a tube as far down into the radiator as possible, you'll get more out that way, use a 5/16th" or 3/8th" flexible tube you can get at the hardware store.

  9. #9
    FEP Power Member plumkrazy's Avatar
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    Default

    Does the Speedometer have to come off? Have to do one or 2 soon
    1 of 3 1985 Silver Grand Prix Capr's
    My first New car and still own 1986 Capri

  10. #10

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    Some people may be able to reach up from below the dash and disconnect the speedo cable. If you can’t reach it the cluster has to be removed to disconnect it.
    84 LX Vert. 5.0 5speed canyon red on white
    99 cobra, electric green on medium parchment, vortech s-trim

  11. #11
    FEP Power Member ccurtin's Avatar
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    Quote Originally Posted by plumkrazy View Post
    Does the Speedometer have to come off? Have to do one or 2 soon
    Trick to make it easier to get the back: trace the cable in the engine compartment, unbolt it from the frame, then you get easily 6-8 inches of space to either get your hand in there.
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    1984 Capri Turbo RS - Alive after 7 years! Build Thread
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  12. #12
    FEP Super Member erratic50's Avatar
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    Default

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Size:  82.4 KBThe main reason for heater core failure is not poor quality cores.

    Ive ran my car nearly 1/2 million miles. I've replaced the core 4 or 5 times -- I cannot remember for sure -- and I've used every quality of core you can think of. They have all lasted about the same for me before I really started looking more deeply at this.

    ill add that I am a firm believer in spirited driving. I do not believe in shying away from a gas pedal for fear of "hurting" the car. In recent years I've added a Typhoon EFI intake on top of the original unrebuilt 5.0L HO in my 86GT that has a few boltons. I routinely power shift it at 6100 .... because it's fun. Once the intake swap my shifts went from 5300 up 800 and now I see the rev limiter at 6250 sometimes. My car has reached a point of not just blowing heater cores but also PS lines.

    I say this all because blown heater cores and PS lines doesn't have to happen.

    Frequently the cores are cracking in some manner near where the lines attach

    Heater cores blowing is often a combination of several factors- here are my observations

    - often poor maintenance! Flushing and filling cooling systems is what keeps up anticorrosive agents so the antifreeze doesn't become corrosive. Not my car mind you --the head gaskets are still intact too..... even though my motor was subjected to some NOS along the way. (Lucky, I know)

    - usually high RPMs especially before the thermostat opens (wait til after the motor is warm)...... GUILTY! Let her scream the second the needle on the temp gauge moves.... but define unusual right?! Come on Ford! it's a Mustang so design for it guys!
    -----> Oh wait they did, but only in the PI cars and the Cobra! Takeaway -- The flow restrictor on the inlet hose is a critical add and it's cheap! Keep the pressure held back near the pump not the core or you may pop lines.

    - insufficient leak through hole on the thermostat. It's great to have a car that warms up fast but pressure management was out the window. two 1/8" holes in the thermostat body for bypass is what I suggest.

    - lack of core bypass system like is present on most similar age GM vehicles as well as many imports...... there are likely ways to retrofit this. It makes the AC work better too. Or just bypass the heater core manually in the summer.

    - frequently, use of (incorrect) higher pressure rating radiator caps -- trying to use PSI to reduce boil-overs. Guilty! Then I went to a 3 core stock style radiator and kept the high pressure cap. I've since went to a modern FrostBite 169 and a stock pressure cap.

    - in EFI cars very short rubber heater core lines that flex poorly combined with metal lines mounted solid on motors that rest in aging and often parished motor mounts......... twist away with force there goes the core!

    - aging transmission crossmember mount and bushings. Again -- twist away or perhaps even more like pull. Btw - allows changing drivetrain angles, this also kills front U-joints reliably!


    My answer:
    Recently new motor mounts and trans mount
    FB169 radiator
    LMR heater core restrictor
    stock pressure cap
    mc parts heater core
    stock temp thermostat
    UPR under drive kit (slows water pump and PS pump)
    Summit Racing 93 Cobra water pump pulley clone -- speeds water pump up to near 1:1 vs crank which is still 10% underdriven vs stock waterpump

    I popped the heater core and PS pump lines on one of first outing after adding the Typhoon intake. Pretty much the first time I missed a gear and hit the limiter it made a big display. I thought I had finally killed the old mill..... guess not. Lol.


    IMO the most critical is mounts followed by flow restrictor followed by thermostat bypass holes followed by pressure cap.

    I don't think I've seen the last of broken heater cores. My engineering background tells me unchecked movement causes fatigue. There are ways to stabilize the heater core lines where they come through firewall and mount them to the firewall. A clamp system is needed. It's a valid approach and I suspect it's needed if we are going to see cars with 350K+ on one heater core. Some may say it is overkill, I suspect it's mandatory to make any heater core pass the test of time.
    Last edited by erratic50; 12-15-2017 at 09:58 PM.

  13. #13

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    First heater core I did took me about 12 hours, just to get the old one out. Of course I waited till the middle of winter, I remember running an extension cord out to the car and using a hair dryer to heat up my boots. Got cold and wet quick having to run in and out of my garage through the snow.

    Us cougarbirds guys are spoiled, no speed cable and most of my cars haven't had a console, another huge time saver. Last one I did took me a little over an hour from start to having a running and driveable car with a good heater to test for leaks. but I've got tons of practice on them, taking my time and fully installing the interior (I like to take my time, I add foam or rubber adhesive strips anywhere there's a rattle) probably two hours, maybe 2 1/2.

    I will say this though, every heater core I didn't put a restrictor in didn't last more then a year or about 40k miles. Every one I put back in when I replaced the hoses, I haven't had any problems out of, old or new.

    X2 on splitting the hoses, a cheap "radiator hose pick" also makes a world of difference if you don't wanna break stuff. On bigger, stronger and easier to get stuff, I loosen and move the hose clamp then get a pair of pliers on the hose. Break the hose loose by twisting it, then it usually slides right off.

    I'd be afraid to risk an old/unknown heater core to that though.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  14. #14
    FEP Power Member 85stanggt's Avatar
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    That was exactly the problem. That heater hose was just about welded to the neck. I had to twist until my arm hurt to try to break it free. The restrictor is in there now.

    I am going to bring the new core to a local welder and have him weld a nice thick bead at the junction of the tubes and the tank and also have him weld a bridge of some sort to stabilize the hoses. I'll blow the old core out first with compressed air to expel as much coolant as possible. I already bought rubber stoppers to jam in the ends of the old core so I don't dribble any leftovers out.

    My plan is to pull the whole dash again for complete access and visibility. I feel like it's only a few more connectors to just pull the whole damn thing out of the way.

    Then the question becomes: pull the box down and try to access through the top cover OR evacuate the system, put in a new drier, and recharge it.

    I remember looking at the box and thinking that I could access 3 of the 4 screws. The back right one is the hardest, but with it dropped 3 inches or so like v8only showed in his write up , I feel like I should be able to get to it and get the cover off. Then I don't have to worry about the A/C system.

    Edit: the core came early (thanks Amazon!). So Saturday instead of Tuesday. But it is apparently pretty hard to find someone who can or will weld brass. So it looks like I'm left with just going with it as is. If it's not in by Monday, I'll make some more calls.
    Last edited by 85stanggt; 12-16-2017 at 11:18 PM.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

  15. #15
    FEP Power Member 85stanggt's Avatar
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    Well that was a bear. I removed the whole dash and did my best to pull the box out some. I removed 3 of the 4 lid screws (skipped the passenger rear -- I don't know how ANYONE would get that one) and was able to get the lid up no problem to slip the core out.

    I think it's hard on the evaporator to pull that bracket out the way V8only showed in his thread, so I would recommend just loosening it and then loosening the two nuts for the heater box studs on the firewall to give enough wiggle room to get the box to tip down. I hope I did not damage something and create a leak trying to get that thing off...

    There is enough slop to get the box down with the evaporator connected without undue pressure from what I could tell. Buy some rubber stoppers at Lowes to stick in the end of the old core to avoid dribbles. Use a socket or a second set of hands to hold the lid open and slip the old core out.

    My box had no sealer in it. Not sure why it would be critical. But it made clean up way easier. I used a wet paper towel to get the residue off around the plastic. The blend door foam was soaked in coolant, so I used a funnel with a tube and rinsed it thoroughly with water. It all drained out the evaporator drain, which was also all full of coolant. That made the rinsing way easier than if it was leaking inside.

    I think the core had been leaking for awhile, as evidenced by all the crystalline build up. But it really sprung a leak when I replaced the inlet heater hose. The old core was leaking right where the inlet tube is soldered to the tank. Same as every other core.

    I "modified" the new core myself by placing JB weld all around the necks of the tubes where they are soldered to the tank. That should seal it nicely if the solder corrodes away as it seems to always do. Since the new Motorcraft part does not have the curved tube welded to the tank, I made a JB weld bridge to glue it to the tank. Any little stabilization will help. I hope the JB weld will do well...the radiator cap is only 16 psi and the restrictor is in the line. I feel like people have used JB weld for way crazier things.

    Anyway, I took a bunch of pictures, which may take me awhile to get up. I figured it may help others when doing this job.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

  16. #16
    FEP Power Member 85stanggt's Avatar
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    Here are the pictures. I'll include my notes for future "expedited" dash removal.

    New Motorcraft HC-5 core with soldered joints:


    One looks like it even has a bubble in it! I reflowed the solder


    JB Weld added around junctions:


    Remove air cleaner, disconnect battery, drain about 1/2 to 1 gallon of coolant, remove heater hoses, and loosen clamp on receiver-drier:
    (before removing outlet hose, get another length of hose and plug it onto the inlet. Blow in the hose to expel remaining coolant from the core)


    Plug ends of heater core with rubber stoppers:


    Remove seats, console (3 electrical connectors to unplug first), gauge trim, steering wheel trim, understeering wheel dash trim, L&R kick panels, dash pad, glove box (for easier access to connectors):


    Working from passenger side to driver's side:
    Unplug 3 connectors in passenger kick panel - 1 green, 2 gray
    Convertible top power cable (blue plug into gray plug - may be easier to get once dash is pulled away)
    Under dash light
    Blower motor & blower resistor
    Vacuum tubing plug
    Blend door cable
    Radio antenna


    Now at the middle under the radio:
    Unplug black 8 pin connector
    Unplug neutral safety switch plug (may need red box out of the way)
    There is another connector around there that is hooked onto the metal, just pull it off, it will come out with the dash
    There is also a black box screwed to the metal frame. It is hard to unplug, so I just unscrewed it (may be easier to do with dash pulled away)

    Now under steering column:
    Unbolt red box and let hang, no need to unplug
    Unscrew the two screws below the fuse panel
    Unplug 7 connectors in steering column
    Unplug speedo cable (may have to wait until column is dropped for more room)
    Unplug brake light switch plug
    Unscrew intermittent wiper module (black box, and slide large gray plug next to it off the mount in the metal frame) and let hang (will come with dash)
    Drop hood release lever


    Driver's side:
    Unplug all 12 connectors in driver's kick panel (most are unique, there was one 4 pin gray plug that had two female matches, 1 was not used, so mark which is which)
    Unplug driver's door switch

    Prep for dash removal (need helper):
    Drop steering column
    Unplug speedo cable if not done yet
    Remove all 5 upper dash screws
    Remove 4 lower dash bolts (one driver, one to left of radio, one below glove box, and one passenger side)

    Pull dash back (with helper):
    Roll up a towel to put under the radio to set the dash on for support
    Unplug 4 connectors on pork chop brace while helper holds dash from falling on you
    Unplug brown connector next to pork chop group
    Unplug under dash light and fog relay
    (If not done already) unscrew that little black box next to the radio
    (If not done already) unplug convertible top power wire on passenger side
    Remove dash


    Lower heater box by removing the two upper bolts, the lower bolt left of the evap drain, and the two nuts against the firewall:


    Remove the front two screws from the cover and using a tool like the VIM HBR5 mini ratchet, use the 5/16" side to remove the driver's rear screw. I did not need to deal with the passenger side screw, and I probably couldn't have reached it anyway. Lift the cover and suspend with a suitable object (deep socket in my case).


    You will see the mess once you remove the core:


    Here's the POS:






    Clean the box really good. I rinsed the coolant-soaked blend door foam with fresh water and let it drain out the evaporator drain as my coolant was doing:


    Slip the new core in (may need a second helper to guide it through the firewall. And then reinstall everything the reverse. Yikes! What a job...you don't want to do this twice. I would recommend finding someone who could weld your core for sure. The solder is unacceptable and will corrode and start leaking again in time.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

  17. #17
    FEP Super Member erratic50's Avatar
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    Good job! AC lines in our 86GT were wedged so tightly we couldn't drop the box at all. Unfortunate. The only up side if there is one is we haven't encountered any negative impacts from cutting the box and piecing in new abs with sealer.

    Ideally if we ever pull it down for a full restore we will address it then.

  18. #18

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    Nice write-up, I have done a few of these, just have to put in the time. I would probably stick with the Motorcraft core although the new ones are usually aluminum which could be better or maybe worse. At any rate, good luck with it!

    Mike
    1982 GT 351W, retro hyd roller, ported Pro Comp heads, Tremec, M2300K brake kit, Recaros...needs paint!
    1984 LX 5.0 Vert *SOLD*
    1993 Cobra #3971 mostly stock *SOLD*
    1966 FFR Cobra replica 383W, Vic Jr heads, Vortech YS, TFS Box intake, 652rwhp, crazy fast!
    1987 GT in MM&FF May of 97 "Not Fade Away" white and purple. Sold 1999

  19. #19
    FEP Power Member 85stanggt's Avatar
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    Quote Originally Posted by erratic50 View Post
    Good job! AC lines in our 86GT were wedged so tightly we couldn't drop the box at all. Unfortunate. The only up side if there is one is we haven't encountered any negative impacts from cutting the box and piecing in new abs with sealer.

    Ideally if we ever pull it down for a full restore we will address it then.
    Oh that's a bummer. I did have enough play to get the box down just enough to slip it out. Any less and I would have been stuck. They should have designed the box with a door on the front, not on top. Doh!

    Quote Originally Posted by FoxFords&FFR's View Post
    Nice write-up, I have done a few of these, just have to put in the time. I would probably stick with the Motorcraft core although the new ones are usually aluminum which could be better or maybe worse. At any rate, good luck with it!

    Mike
    Thanks! It is a Motorcraft core, which from what I read is brass? I'm sure that is better than aluminum which would corrode like crazy. I did see that the 4 seasons heater core has the bent tube welded to the tank like the original Ford ones. But it's aluminum, which I wasn't going to do. It's a bummer that Ford (or whoever) still haven't decided to WELD the brass tubes to the brass tank instead of soldering/brazing the tubes to it. It is the solder that corrodes and eventually leaks, especially if there is any mechanical movement of the tube, since the leverage on the fitting at the tank is huge.

    I think it will last longer now that I have a restrictor in the line. I also think the JB weld may be a smart addition, since I use that stuff on the side of the fuel bowls of the carb where those caps tend to leak and it seals things up great. It's not usually a major leak when the solder lets go, so let's see in 10 years what happens.

    Also a note: leave extra length on the heater hoses in case of any engine movement.

    Hopefully the pictures help some people in the future and explains exactly what is needed to be disconnected to remove the whole dash. The first time I did this, I unplugged or removed many things that didn't need to be touched. It all comes out as a unit, which makes things much quicker and easier.
    1985 Mustang GT Convertible
    Stock and original @ 213k, except for dynomax ultraflos.

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