REMOVE/REPLACE THE HEATER CORE IN A 1970 CUTLASS SUPREME CONVERTBILE

My dad was a convertible nut.  In 1951, at age 13, he bought his first car:  a ’48 Plymouth coupe.  Owned it for 6 months.  Hated it.  Didn’t buy another Chrysler product for 30-some years, and he hated that one too.  From then on, it was a run of Chevy convertibles up until he became a dad in 1968.  I got to hear about those convertibles growing up.  Combined with the Oldsmobiles we had when I was a kid, I guess that’s what steered me towards wanting a classic Cutlass convertible.

I bought the subject of this blog in April 1997.  I was looking forward to the occasional cruise with my dad and maybe even doing a repair or two with him where I was in charge and he wasn’t swearing and saying “you’re doing it all wrong”.  You know, a father and son bonding moment talking about the finer points of ignition points.  He died in July 1997, and he only got to take it for a spin with me once.  He liked the engine; “It’s got some scoot” was his comment.

One of the first repairs I diagnosed, on the day I drove the car home, was the heater core.  This was pretty easy to figure out, as the window would steam up a bit and you’d smell anti-freeze anytime you turned the heat on.  Fast forward to 2014.  The heater core STILL hasn’t been done because I’m lazy that way.  And because I’ve heard horror stories, starting with my dad, about how much of a bear a heater core job is.  With the dashboard off the car to replace the top switch, it’s time to roll up the sleeves and take on the dreaded heater core.

You know what?  Everything you’ve ever heard about heater cores is a bunch of horse feathers.  Other than being time-consuming, it was a pretty easy task.

The main reason I brought up my dad is because of the safety tips he gave me while working on a car.  It’s easy to get lackadaisical, but this is a 3800 pound hunk of iron that can kill you if you are careless.  As this job requires jacking up the car and yanking on hoses (heh), it’s a great time to bring up some of those safety tips.

TOOLS YOU’LL NEED

• A ¼” socket set, specifically the ¼”, 3/8”, and 5/16” sockets
• A 1/2″ or 3/8” socket set, specifically with a 7/16” and 9/16″ socket
• A 7/16” combo wrench
• A large catchpan
• Jack stands
• A good floor/garage jack
• Wheel chocks
• Don’t forget your towel
• Baggies, sharpie, flagging tape for sortin’ and writin’ stuff up

PARTS

• Heater hoses (optional, depending on condition of current hoses)
• Hose clamps for 5/8” and 3/4″ hoses (optional, depending on condition of current clamps)
• Heater Core (optional, you may want to rebuild the original if the car can sit idle for a week)
• Heater Case Gasket Kit (available from most restoration parts suppliers)
• Firewall Insulator (if you’ve got the heater case off, might as well replace it)
• Vacuum hose (different sizes, keep your pants on and we’ll get to it)

BEFORE YOU TRY THIS AT HOME:

Remove the Dashboard, Part I and Part II:  Many how-to guides skip this part or only have you remove a couple of things.  I can’t tell you what it would be like trying to tackle the heater core with only some of this stuff removed, but my guess is that it would not be easy.  You’d have little room to maneuver and precious little light to see.

1.  Drain Radiator.  If you’ve got the original Harrison radiator, there should be a petcock on the RH side near the bottom of the tank.  Put a large catch basin underneath; I find the big ones for doing an oil change work perfectly.  Open the pet cock and prepare for splashing, it should just be on there hand-tight.  There’s probably a better way of draining the radiator, but I don’t know what it is.

Ah, sweet lemonade. See what I mean about it being a mess to drain a radiator?

2.  Disconnect A/C Reducer Hose Hold-down Clamp.  This clamp holds down the line that takes warm refrigerant to the condenser.  I think I got the name right.  I’m not working on the A/C so I’m not looking it up.  It’s hiding a bit underneath the line that takes the cold pressurized refrigerant to the evaptorator.  There’s a screw attaching the hold-down to the plastic inner fender.  Should come off easy.

Here’s the two hold-down clamps you’ll need to remove the screws for.

3.  Disconnect Heater/Block Reducer Hose Hold-down Clamp.  This clamp helps route the aforementioned hose around the evaporator box.  Might as well remove the screw while you’re up here.

4.  Loosen 2 Rear Lower RH Outer Fender Bolts.  These are what holds the dog leg of the front fender to the car body.  Find the “Cutlass” emblem and look down; they’re just in front of the rocker panel.  No need to remove them; just loosen them.  It’ll be obvious why in a few steps.

5.  Loosen/Remove RH Inner Fender Bolts.   Just in case these buggers stick, get them loose when the car is resting on the wheel instead of on a jack stand.  As my dad would say, don’t jostle a car that’s on a jack stand.  There’s a lot of these bolts; 13 if I remember the count correctly.  There’s 4 that are accessed from under the hood, at the front; 5 that run  the outer edge of the wheel well opening; 2 that secure the top of the inner fender to the outer fender (you can see where the tips poke through from the engine compartment) and 2 that are in the back and behind, securing the inner fender to the frame.   The last 2 cannot be reached until the wheel is off, so don’t worry about them.   The rest are pretty easy to get at.  Use a breaker bar if they put up a fight.

Four of the thirteen bolts holding down the inner fender. View from RH front corner, looking towards the firewall.

6.  Remove RH Front Wheel.  If you don’t know how to remove a wheel from a car, stop now.  Do not do ANYTHING else until you’ve taken a basic car maintenance class at the local park district or community college.  Then come back and continue reading.  Otherwise, here’s some of my dad’s safety tips:

• Put the emergency brake on and chock the other three wheels.  Did you know that wedges cut to make a hinge when falling a tree make great chocks?
• Only jack on the frame to lift the car; NEVER the suspension.
• Position the jack stand on solid, level ground.  Make sure the pin/ratchet is locked.
• Leave the floor/garage jack in place even after the car is resting on the jack stand, unless it’s gonna get in your way.
• When the wheel is off, put it underneath the frame right behind the jacking point.  The wheel is your failsafe should the jack stand fail.

7.  Remove The 2 Pesky RH Inner Fender Bolts From Step 5 That You Couldn’t Reach Because The Tire Was In The Way.

8.  Remove RH Inner Fender.  It’ll quickly be obvious why you needed to loosen the dog leg of the outer fender back in Step 4.  By moving that part of the fender outwards, you can work the inner fender around the lip of the outer fender.  Then the inner fender should pop right off.  As an added bonus, you can easily clean all the debris and dirt that builds up behind the dog leg.  Ever wonder why the lower front fenders of GM cars from this era rot?  Take a look back there after the inner fender comes off and you’ll have the answer.

9.  Remove Heater Case Nuts.  Look at all the room you have now.  All this work to get the fender off et al. is really just to get at one of the four nuts holding the heater case to the car.  All are easy to find.  The two hardest ones to get off are the upper right, which is sort of behind the A/C evaporator pipe, and lower left, which is kinda behind the transmission dipstick.  Don’t bother with a socket. These are self-threading nuts and they come off easily with a box wrench.

Locations of the 4 heater case nuts. In case you haven’t guessed, this is not a frame-off restoration.

10.  Put The Wheel Back On.  This is another dad safety tip.  His reasoning:  if you are goofing around inside the car, best to have the car as stable as possible.  It adds some extra time to the project, but the alternative is to risk having the car fall off the jack stand while you’re yanking on the heater case trying to get it out.  And it’ll be easier to get the heater hoses off if the car isn’t an extra 8 inches in the air.

11.  Disconnect Blower Motor & Compressor Hold-in Relay Wires.  These wires will be in the way while you’re removing the heater hoses.  Best to just move them so you don’t break them.

12.  Remove Heater Hoses.  Loosen the heater hose clamps and slide them down the hose to get them out of the way.  Note how the clamps are positioned; that’s the only angle of approach that makes sense if you need to get a screwdriver or socket on the clamp.

Every DYI I’ve read about heater cores says that getting the hoses off is the hardest part.  I cannot second this.  Here’s what I did:  I grabbed each hose, just below where the heater core throats are, wearing a pair of leather work gloves.  This is another dad safety tip, this one to prevent you from getting tetanus when you rip your knuckes open on sharp, slightly rusted sheet metal.  Works well on spark plug jobs too.   Twist the hoses clockwise and counter-clockwise until they ‘pop’ loose and spin with your motion.  Then they should come right off the heater core throats.

Despite all the horror stories and tales of terror, this took me all of 3 minutes to do.  So there.

You’re done on the outside of the car.  Time to head back to the interior. Other online guides that I’ve read aren’t very clear about what needs to be removed so the heater case comes out.  Despite the blurry photos, I will be very clear in telling you what needs to come off.  Especially since the guys that wrote the service manual took the day off when it came to this part.  Seriously.  Here’s the entire procedure as outlined in the Oldsmobile Chassis Service Manual, page 1C-8:  “The heater core can be removed after removing the heater case assembly.”  Gee, thanks guys.

13.  Remove the Defroster Adapter.  Say that ten times fast.  There’s one screw that holds it on, smack dab in the front.  Remove the cardboard ducts and the adapter comes off.  Easy as pie.

Location of the defroster adapter screw.

14.  Disconnect Temperature Control Cable.  There’s one screw holding the cable assembly to the controller.  After that, lift the tip of the cable off the controller tab.  Done.

Removing the temperature control cable.

15.  Disconnect 2 Vacuum Lines.  The picture is blurry but the lines you need to remove are easy to find.  The first one is hooked up to the defroster control valve on the far LH side of the heater case.  The second attaches to the mode control valve on the back side of the case, facing the fire wall.  Knowing that this might be a problem, GM engineered a small nylon splicer in this hose.  (But they didn’t leave access to get at the convertible top switch. Huh.)  Remove the hose at this splice.  Don’t forget to use flagging tape to label the hoses.

16.  Remove 2 Screws Holding Heater Case to Firewall.  There’s one screw right of center top, and another right of center bottom.

Location of upper heater case attaching screw.

Location of lower heater case attaching screw.

17.  Remove Heater Case.  Congratulations, you are now ready to remove the heater case.  Assuming you were careful and did not bend or deform the heater core throats, the case should come off with a wee bit of wiggling.  Put a couple old towels down in case you get any drippage.  Better to ruin an old towel than the carpet.  Though if you neglect the heater core for 17 years like I did, the carpet may be ruined already.  I got lucky, sort of.  Only the firewall gasket was ruined.  That’s OK.  It’s 44 years old and needs to be replaced anyhow.  This is what is commonly referred to in the antique car hobby as a MAW:  Might As Well do it with other stuff out of the way.  After all, when’s the next time you’re going to have the heater case off the car?  2084?  That’s when the Robotron invasion happens, we’ll be too busy panicking to worry about fixing an old car.

18.  Remove Temperatue Controller.  Now we get to the meat ‘n taters of the project.  This controller operates a door that regulates the mix of warm air from the heater core and cool air from outside/A/C evaporator.  Pop the spring off the controller.  Next, remove the three screws; you may have to move the control around a bit to access them all.  With the screws out, wiggle the control and it should come right off.

Location of screws for temperature door control.

Here’s a tip to help you align the control when you reassemble the heater case:  use a sharpie to outline the control on the case.  When it’s time to reassemble, just line it up with the template you drew.  If you are worried about defacing your heater case, wipe the sharpie off with some acetone when done.

18.  Remove Heater Core Cover.  Flipping the heater case over so you are looking at it from the back, you’ll see 8 screws on the side with the heater core.  The 4 around the edges hold the heater core cover to the heater case.  The other 4 hold straps that attach the heater core to the cover.  You can take them all off right now, if you so choose.  Doesn’t much matter.

Heater core cover and heater core strap screws. Magenta arrows indicate cover; red arrows indicate straps.

And there she is.  Your wonderful, leaking heater core.

Yeah, I’d say your heater core is bad.

If you look closely, you’ll see a metal flange holding the two throats of the heater core together.  The flange was put on Harrison heater cores to hold the throats in proper alignment for installation.  Aftermarket cores won’t have it.  Aftermarket cores are also made out of thinner materials.  An original core will also have the Harrison logo stampted on the “bottom”.  Now it is decision time:  should you have the old heater core rebuilt?  If you have a radiator shop nearby, explore the option.  It’ll cost a bit more than an aftermarket core, but it is likely to last just as long if not longer.  Might be worth looking into, so that years from now, the next person to take it off will find the original heater core and think it lasted a bajillion years.  It’ll be awesome.  You’ll blow their fucking minds.  Unless they’re running in panic from the Robotron invasion.

Of course, you’ll reverse all the steps to put things back together.  DO NOT OVERTIGHTEN THE HEATER HOSE CLAMPS!  Refer to the post on radiator replacement for refilling the engine coolant.

Here’s a list of some of the MAW mini-projects you can do with the heater case out:

• Replace the vacuum lines, esp. the one on the back of the heater case.
• Replace the firewall/under-dash insulation.
• Replace the heater hose clamps.
• Replace the heater hoses.  These things seem to last forever.  If your hoses look deformed, or proved to be impossible to remove, you should replace them.
• Replace the heater case gaskets.
• Wash and recondition the various parts of the heater case.  Acetone or a parts cleaner for metal.  Soap and water for plastic.

REPLACING A RADIATOR IN A 1970 OLDSMOBILE CUTLASS SUPREME WITH A/C

This is my first post regarding a repair.  I’m going to go into repairs so that if you are not a car buff, or you will never get close to doing this kind of repair, you might still enjoy reading it.

I’ve been working on cars for 30 years and I’ve heard a lot of derrogatory terms used for repair jobs that use shortcuts, all based on ethnic stereotypes.  I’m not going to use any of those terms.  I’m going to use the term Mr. Bungle.  Every repair will talk about Mr. Bungle.  How would Mr. Bungle do a radiator repair?  He’d go to his local car parts store and get a bottle of a “stop leak” product and pour it in.  That stuff don’t work.  It may buy you some time, but that’s about it.  It also gums up the tubes in your radiator, reducing its efficiency.  And it may also screw up your engine.  Don’t be a Mr. Bungle.  Just fix the damn radiator.

This repair was done the end of December 2013 by my mechanic, so this post is based on at least 4 other radiator jobs I have done on GM cars in the past.  First, here’s a list of parts and tools to have at the ready:

• 3/8″,7/16”, 1/2”, and 9/16” open-end wrenches.  One of each should do.
• 3/8″,7/16”, 1/2”, and 9/16” sockets.  A 3/8” drive should work for this job.  You won’t need a lot of torque unless the car is in really rough shape.
• Lift ramps.  You can also use jack stands, but save yourself the jacking and crawling around to place the stands.
• Penetrating Oil
• Flathead screwdriver
• Container for anti-freeze.  Parts stores have these flat containers with a large open mouth for doing oil changes.  Get at least one for draining fluids from a car.  If you plan on re-using the anti-freeze, get a separate pan for anti-freeze only.  You don’t want to cross-contaminate fluids.
• Container for transmission fluid
• Slipjaw/water pump pliers; may be needed for step 2
• Radiator mounts:  These are two pieces of rubber that fit on the lower radiator cowl.  These keep the radiator from vibrating and bouncing around while you are driving.  Any restorations part source worth their weight has these.
• A good radiator shop:  These are becoming harder to find as modern radiators become disposable.  Take the time to find one.  Trust me, you’ll need it.
• Distilled water:  this is to mix with the antifreeze.  Don’t use tap water, especially if you have hard water.  The minerals build up in your radiator, blocking tubes, decreasing efficiency, and shortening its lifespan.  Distilled water costs a buck a gallon at your local grocery store.  That’s a lot cheaper than another radiator repair 5 years down the line.
• Time:  be prepared to not drive the car for a few days.  Don’t wait to do this a day before the car show.

Only Mr. Bungle does anything with the coolant system when the car is warm.  Unless you want second degree burns on your upper body, do this when the car is cold.  Now, on to the radiator change!

0)  Disconnect battery.  This is an optional step.  You aren’t doing anything electrical, but I ALWAYS disconnect the battery when poking around under the hood.  It’s a safety thing.

1)  Put car up on ramps or jack stands.  You’ll need to get underneath to avoid a lot of swearing and scraped knuckles.  If you use ramps, swap this with Step 0 or else you’re going to have a hell of a time driving the car up on the ramps. Don’t forget to engage the emergency brake or put wheel chucks behind the rear wheels once the car is up on the ramps.

2)  Drain radiator.  Make sure you loosen the radiator cap before draining. You may or may not have a petcock to drain the radiator.  You should.  I have an original Harrison radiator, and it has a petcock.  The nipple on the petcock can accommodate a hose to make draining easier.  On my car it is the same size as the overflow hose.  Since the overflow hose needs to come off anyways, just pop it off and fit it over the petcock.  Something tells me that’s what GM intended with the original design.  You know, back in the days they designed things with ease of repair in mind.  If you don’t have a petcock, skip to Step 3 and drain in Step 4. Ha, made you read the whole thing before I told you that.

3)  Soak transmission cooler lines with penetrating oil.  Look just below the radiator cap nozzle.  There’s two steel lines that attach to the radiator.  This is your transmission cooler.  I don’t know how efficient it is, but if it was good enough for the guy who designed it, it’s good enough for me.  Spray some penetrating oil on them and let it soak in. You don’t want to break these.  They’re a pain in the ass to replace and not so easy to find these days.

If you don’t see steel lines heading into the tank, then you don’t have a transmission cooler.  Which means you don’t have a Cutlass Supreme.  But that’s OK, this repair will still work.  Just skip this step.

4)  Disconnect radiator hoses.  Hope and pray that the hoses aren’t stuck to the nipples.  Whatever you do, don’t use wrenches, pliers, screwdrivers, whatever to remove the hoses.  Bend the hose nipples and you’ll never get a good seal on the hoses again.  Be patient and work them off by hand.  If they’re stuck on that tight, cut the hoses and replace them.  You’ve probably neglected their replacement anyways.  Besides, a blown radiator hose is no picnic.  I find it easy to just remove the upper hose entirely.  The lower hose can stay hooked up to the water pump, but remember that some coolant from the engine will drain out.  Have a catch pan ready.

5)  Remove fan.  There are four nuts/bolts that mount the fan to the fan pulley.  I think they are 7/16″.  Maybe 3/8″. Just make sure you have a full set of tools at the ready, at least the “big 4″ wrenches mentioned above.  If you have to run back into the house to get another tool, don’t come crying to me.  Anyways, just take the fan off.  I don’t recall having to remove the belts to do this.  Some will say you don’t really have to take the fan off.  But I like having extra room to move around.

6)  Remove fan shroud (if you have one).  The fan shroud directs air flow from the fan over the radiator making it cool better.  Contrary to what some have told me in the past, it’s not a safety feature.  Look at the thing.  It’s not gonna stop you from losing your hand if you’re fool enough to get close to the fan.  There’s four body bolts holding the shroud on; 2 up top and 2 down low.  With that pesky fan out of the way the shroud lifts up and off.  Oh, and because you removed the upper radiator hose like a good girl or boy, you don’t have to mess with the upper radiator hose support bracket.  Just leave it on the shroud.

You have to stop and think:  if the shroud improves radiator efficiency, why didn’t GM make it standard equipment?

7)  Remove upper radiator cowl.  This is the part with the tune-up label on it.  You use it to rest your elbows on while you pretend you know your way around a carburetor.  There should be four body bolts holding it in place.  I think they are 9/16″.  I don’t know.  Refer to what I wrote in Step 5.

8)  Disconnect transmission cooler lines.  Remember how you started soaking those a couple of steps ago?  They’re ready to come off now.  I don’t remember the wrench size.  It’s probably 1/2”.  If I have to tell you again to keep a complement of tools at the ready, then stop what you are doing and ask your neighbor to finish the job.  He or she might be better at following directions.

9)  Remove radiator.  Lift the radiator up and out.  It’s that simple.

From here on out what you do depends on where the leak is.  Over 99% of the time the leak is in one of the tubes on the core.  This is a good place to have a leak.  A winner is you.  Go to Step 11.  The other 1% of the time the leak is in one of the tanks.  This is a not-so-good place to have a leak.  Go to step 10.

10)  Get a replacement Harrison radiator.  Buy it from a salvage yard or get a radiator you know to be a Harrison.  DO NOT BUY AN OFF-BRAND AFTERMARKET RADIATOR!   In my years or working on GM cars I have NEVER found an off-brand radiator that is an exact fit.  In my opinion they aren’t worth the hassle.   Harrison is the brand name for the GM-manufactured radiators.  If it’s not a Harrison it’s a waste of money.

How do you identify a Harrison Radiator?  If memory serves, there’s a Harrison  logo stamped on the top of each tank.  Look for it on the side.  Just below that will be the part number.  Each tank will have a metal tag on it with several codes.  They match up to the build sheet, and told the assembly line worker what type of radiator the car was supposed to get:  3-row or 4-row, transmission cooler or not.  If you have a Cutlass Supreme you probably have a 3-row radiator.  If you have a Cutlass Supreme and you have a 2-row radiator a previous owner replaced the radiator with whatever he/she could find, or they had a shitty mechanic.  You should be worried.  I’ll go into a bit more detail on the radiators later.

If you work for a company that makes off-brand radiators, don’t write me and tell me I am full of shit.  Just make your radiators to spec.  For something that often costs in excess of $400, it should fit like an avocado pit fits into an avocado and it should last as long as the original, which in this case made it 40 years.  When I had my 1970 Cutlass in the shop for a radiator replacement, my plan was to put the replacement radiator in, save the original radiator, and have it re-cored later.  Money was tight and it was cheaper to go with the replacement.  The mechanic went through 3 off-brand radiators that were supposed to fit in a 1970 Cutlass with A/C.  None of them fit and he eventually just had the old Harrison radiator re-cored so he could finish the damn car.  Which takes us to Step 11…

11)  Re-core your radiator.  This is where a good radiator shop comes in.  They’ll remove the old radiator core from the tanks and weld a new core in.  This is usually more expensive than a replacement radiator, but it’s good in two ways:  you keep the original radiator that came with the car, and you’re virtually guaranteed an exact fit when you reinstall the radiator.  And if it’s a good shop the welds will be strong and the radiator should last another 40 years.

This typically takes a few days.  This is a good time to do the little things that often get neglected.  Polish the wheel bezels on your Super Stocks.  Lubricate the car’s hinges.  Stuff like that.  Oh, and don’t forget to…

12)  Replace radiator mounts.  These are two pieces of rubber that fit on the lower radiator cowl.  They keep the radiator from vibrating and bouncing around while you drive.  Being at the front of the car they get exposed to all the shit that is on the road.  These things get a lot of abuse.  Since you have the radiator out of the car, replace them.  Most of the classic car parts warehouses carry these.  Last time I did a radiator they cost something like 10 bucks.

While you’re down there, clean the lower radiator cowl.  I’ve found dirt, sticks, leaves, grease, roadkill parts, etc.  All sorts of nastiness gets in there.  Chances are it will be 20 years before the radiator gets removed again, so clean it up down there.  It’ll help prevent rust and corrosion.

13)  Install radiator.  You’ve got your refurbished, good-as-new radiator back.  Follow steps in reverse and put everything back together.

I can’t stress this enough:  DO NOT OVERTIGHTEN THE TRANSMISSION COOLING LINES!  You crush those tubes and they’re going to leak, leaving you to wonder why your car doesn’t upshift when you’re going up a hill or why it won’t go into reverse.  Just snug them up.  Same goes for the radiator hoses.  They only need to be snug.  They don’t need to be tight.  If the hose is bulging even slightly around the clamp, it’s too tight.

14)  Re-fill coolant.  This isn’t just putting anti-freeze in the radiator and calling it a day.  You want as little air in the system as possible.  Assuming you followed my advice and you have a Harrison radiator, there are fill line indicators inside the tank.  Pour coolant in up to the line.  Put the cap on, but don’t tighten it.  Start the car, making sure the heater is open.  Run it for a couple of minutes. Stop the car and check your coolant level.  You’ve probably bled some air out of the system and the coolant level is a bit lower than it was when you started.  Top off and repeat the procedure.  You should only need to do this twice to get the right amount of coolant into the system.  If you go a bit overboard, the excess should empty out via the overflow hose the next time you are cruising down the highway.

You’re now done and ready to drive.  If you did everything right you can drive the car 500 miles and not have to worry about stopping every 30 minutes to make sure there aren’t any leaks.