For Those Who Replaced Heater Core: When Did Yours Fail?

[renns]

The problem is - how can you really tell if the heater core is bad? I have been losing a little bit of coolant in the past few months. Sometimes, the windshield is a little fogged up near the air vents. But why, if I haven't had the heater on the whole summer - I thought this bypasses the heater core completely?

I believe the 850's have no core bypass valve. Engine coolant makes the trip through the core year-round.

[Jippi 855 GLT]

96 850 failed at 260k, my moms 99 s70 was purchased with a bad hg which was caused by the hc that had 130k.

[Guest 850 newb]

Can a bad heater core really cause a blown headgasket?

I get a faint maple syrup smell every once in a while. Not losing much coolant...maybe have to top off 2-3 times a year.

I was going to wait to change the core until the coolant loss issue got worse.

Does this mean I am at risk of ruining the engine if I let the core go till really bites the bullet? Do the cores really go catestrophically or just start leaking worse and worse?

[Auburn T5]

first one didn't actually fail but rather the connectors did but I replaced it anyways...foolishly... because the new behr replacement itself has actually now failed less than a year later :angry:

[Fudge_Brownie]

A bad heater core can cause blow hg /warped head as a result of the bad heatercore venting the pressure and dumping coolant. As a result, the car is very likely to overheat, and if the car is continued to run while overheated, the failure occurs.

It seems like they tend to develop a small leak, and then finally "let go". However, no one can really put a number on exactly how long you've got. Even if the heatercore lets go and you notice and immediately stop the car... you're still stranded unless you by-pass it. Which motivates people to fix things ASAP.

[Piston Slapper]

Mine blew up quite violently at 150k ish. Wasn't even getting on it at the time, was stuck in traffic.

Wasn't that long after I had done the radiator.

[Jippi 855 GLT]

my cousins 98 s70 just started to fail, her car is damp from coolant i pulled the hvac drain hose and coolant started to leak out. her car had barely 110k

[erikv11]

...I have been losing a little bit of coolant in the past few months. Sometimes, the windshield is a little fogged up near the air vents. But why, if I haven't had the heater on the whole summer - I thought this bypasses the heater core completely?

...

I believe the 850's have no core bypass valve. Engine coolant makes the trip through the core year-round.

^^^ this

heater core runs coolant every time you start the car.

It appears very straight forward but if/when mine fails...I will likely replace with metal plate and bulkhead connectors. That $35 plastic stuff is for the birds and ~$15 for replacement clips/orings when you change the HC??? I can get some purdy BLUE AN fittings that will last indefinitely and still be ahead of the game...

like many I want to get rid of the coupler, just run hose through there or install something of decent quality/design.

what do you mean by "Blue AN fittings" ??

[cn90]

It looks like:

1. No consensus on the coupler. My car has 110K so I will leave the couple alone for now.

2. Will replace with Behr Heater Core + O-rings

3. The 2 Heater Hoses from the back of the engine to the firewall (where it is connected to the Coupler): leave them alone at 110K? Has anyone experience failure of these 2 hoses, if so at what mileage?

[Fudge_Brownie]

1. No consensus on the coupler. My car has 110K so I will leave the couple alone for now.

Nooooooooo, unless you don't mind labor, repalce that coupler. You will already be in there, you already be ordering parts (and paying for shipping) and you DO NOT want this sucker to crack and have a headache on your hands. The fittings will most likely be hard to remove from the coupler if they haven't been undone in a while and it will crack on removal.

I wouldn't say the mileage is as relevant as age is. It's plastic, it gets old and brittle no matter how far you drive each year.

It's a $38 part @ fcp

[Jaxx]

~110k, 99.

[Cal3thousand]

Nooooooooo, unless you don't mind labor, repalce that coupler. You will already be in there, you already be ordering parts (and paying for shipping) and you DO NOT want this sucker to crack and have a headache on your hands. The fittings will most likely be hard to remove from the coupler if they haven't been undone in a while and it will crack on removal.

I wouldn't say the mileage is as relevant as age is. It's plastic, it gets old and brittle no matter how far you drive each year.

It's a $38 part @ fcp

HUUUUGE +1 to this

Its the best 38 extra bucks you will spend. Really though, the difference in price from the coupler to the o-rings is less than that and the benefit is nearly immeasurable.

Are you a glutton for punishment? order the o-rings then.

[_HighVoltage_]

Hmmm...so if coolant runs through the heater core all the time, then it should be leaking all the time, right?

So why do I only get a funky smell when the heater is on, but regular air is fine?

[jdlc]

Hmmm...so if coolant runs through the heater core all the time, then it should be leaking all the time, right?

So why do I only get a funky smell when the heater is on, but regular air is fine?

For ACC, the flap that channels air from heating vent is shut closed at some setting (66 and lower in my observation) , so air will be coming from the AC vent, even if your AC is off. This would explain absence of coolant smell when temp setting is not high enough. Bottomline is, the 'heating' via htr core is always 'on', you just control a duct flap how much heated air you want to channel to the cabin.

[Fudge_Brownie]

Just replaced my heatercore and coupler this weekend.

The heatercore is cake to replace. At 145k/MY1998, mine did seem solid. No signs of previous leaks, and visual inspection seemed good.

But that damn coupler! Not only was it cracked and leaking, when I gave it a gentle tug to pull from the firewall, the two tubes running through it cracked in half. Tip for readers on installing this piece. It is held in by a metal plate on the engine-side of the firewall with two small torx screws. Undo these and you can pull the coupler.

I couldn't figure out how to undo the gas pedal which would have helped quite a bit. But I did take off the throttle cable from the pedal. Push the wire towards the drivers seat and pop the white retaining bushing out. It helps a little, keeps the tension off the pedal and gets the wire out of the way.

Pushing the new coupler in place was quite tricky because of the spacing. Once you get it lined up, you'll see the lip probably won't clear whatever plastic bin is behind the heatercore. I had to push pretty firmly on the coupler and wedge it in at an angle. Then I had someone else hold it in place while I 'finessed' it in from the engine side of the firewall. Eventually it popped in place and screwing down the metal plate pulled it in perfect.