Blew up a heater core

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I was driving the 1984 Cavalier home from my friend's house and I was accelerating from a stop. I probably shifted at 4K (not really sure, no tach) and I smelled coolant.

Then the windshield started steaming up and I tried the defroster and it just made it worse.

It's 6 miles from where the heater core blew up to my house and the car made it without overheating.

I checked under the hood, everything looked OK, then shined a flashlight under the car and saw coolant dripping from behind the engine. (It's been raining all day, but that amount of drippage was not from water splashed up under the car...)

I found one on Ebay for $25 shipped. That's about the only source, the heater core for 1984 Cavalier with AC is obsolete but the one for the car without AC is still available. Go figure that one out.

Also found a heater core bypass hose on Ebay so I can at least get this thing drivable again before replacing the heater core. Which doesn't appear to involve removing the dashboard on this car, thankfully.

I've never blown up a heater core before. I feel so accomplished.

At least it happened close to home. Get all the parts on this car that are going to break, to break close to home.

EDIT: The coolant was last changed on this car, prior to my doing it a few months ago, likely sometime before 1998 and definitely before 2010 when it was parked and sat for 10 years.
 

brianl703

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Doesn't look too bad of a job?

1664692240992.png
 
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38 years old is a good life for a heater core and you got a very good price for a replacement. Saying my heater core "blew up" is somewhat exagerated. "It sprung a leak".

If original, I would replace all old hoses while you are at it.
 
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A friend once told me to have a new heater core pressure tested at a rad shop prior to installing. I took one to a rad shop and they were more than happy to do it in their dunk tank for very little. Also check You Tube to see if anyone posted the process. Remember that if there is a lip on the tube, press the hose completely over top and past it. The clamp goes upstream of the lip and not overtop the lip. Rookie mistake. Good luck!
 
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I think GM makes a flow restrictor/ pressure reduction valve for heater hoses so it doesn’t get the full force of the cooling system rushing through it. Perhaps your cavalier could use something like this if high RPM possibly caused the failure.
 
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I think you got your moneys worth.

Hopefully you don't have to evac the AC to get the heater core out. If you only drive in the summer you could just bypass it?
 
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I did this in my '99 S10. Was going up the mountain in 3rd gear (2.2 4 banger, giving it all it had!) with the heat on when all of a sudden the windshield fogged up and I could smell the coolant. Had to pretty much Ace Ventura it to get off the mountain home. Sure enough the bottom of the core gave out. Took a good while to get the coolant to dry up in the bottom of the box...
 
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If this let loose at 4k today, would it have failed next year if you never took it past 3k? seems to me that it was on its way out no matter what, once it starts corroding it’s a matter of time.

[Makes me wonder about all the 5k shifting I do in my beater now… :( ]
 

brianl703

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If this let loose at 4k today, would it have failed next year if you never took it past 3k? seems to me that it was on its way out no matter what, once it starts corroding it’s a matter of time.

[Makes me wonder about all the 5k shifting I do in my beater now… :( ]

On this car 3K is about 60MPH in top gear. So it could very well have blown out just from highway driving. Probably failed due to the coolant not being changed for 20 years, even though it was parked for 10 of them. The radiator was leaking too, and I replaced it. The hoses were replaced too, both heater and radiator hoses. And in another post I mentioned the flushing tee I found in the heater hoses that was leaking.

I just checked the coolant level in the radiator and it's only down a couple of inches. Based on what I saw pouring out behind the engine I would have thought it would have lost more coolant.
 

brianl703

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I’m more shocked that an 84 Cavalier is still on the road.

It has about 93K on it. Most of those miles were accumulated in the first 8 years of it's life. After about 1991 it wasn't driven much and from what I can tell with emissions test records, it was driven about 3000 miles from 1998 to 2008, when the last emissions test was required (25 years old not required anymore). And it was parked in 2010 due, I believe, to a fuel pump failure. I found the clutch interlock wires removed from the clutch switch and jammed together. It was my dad's, and I had to get it out of his garage after he passed away so my friend and I put a new fuel pump in it and it started right up.

I think my dad had it towed to the house and left in the driveway, then used the starter to move it into the garage, which is why he bypassed the clutch interlock switch.

Before he passed away he told me it just needed a battery.

I do know he used Mobil 1 in the engine since it was new. He worked for Mobil as an A&P mechanic.
 

OVERKILL

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I had this happen on my '87 Mustang GT. Was driving a bit "spiritedly" and downshifted to 2nd, hit like 5K and the core went "BLAPOOOOF" and there was a LOT of coolant. Ran it on a bypass for a few months until I got a replacement core and did the Cirque de Soleil contortion trick to swap it out without pulling the whole dash.
 

brianl703

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I had this happen on my '87 Mustang GT. Was driving a bit "spiritedly" and downshifted to 2nd, hit like 5K and the core went "BLAPOOOOF" and there was a LOT of coolant. Ran it on a bypass for a few months until I got a replacement core and did the Cirque de Soleil contortion trick to swap it out without pulling the whole dash.

Was the replacement core aluminum or copper/brass like the original?
 

OVERKILL

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You don't hear about heater core failure as much on newer vehicles.

Though that maybe due to better coolant.
Yes, I'd say a lot of that has to do with better coolant. I've seen "old green" not get changed frequently enough and it ate the intake manifold out of a SBF, lol.
 
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