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Broken heater core, coolant inside of car


hjb981

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:( Today, on my way to get some dinner out because I was working late, there was an explosion-like sound, then a dripping sound (for a second) and then some coolant (maybe a cup or less) came out on the floor on the passenger side. I guess that either the heater core has broken, or a hose has broken or come loose. What do you think - which are the possibilities?

How can I diagnose this and check exactly what has broken? Do I start in the engine compartment or passenger compartment? How easy or hard is it to fix this kind of thing?

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You have to remove the passenger side sound insulator and heater core cover to see what is going on. Meanwhile, you can probably bypass the heater core by redirecting heater hoses under the hood. I have done that in emergency on my 4.9 liter. Probably you can do that on the Northstar as well.

The saddest thing in life is wasted talent

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Thanks adallak. I have found some info on the net and also on the other forum, with some fairly detailed procedures for taking out the gloves compartment and stuff behind it to get to the heater core. The thing I am wondering about are the hoses you mentioned that connect to the heater core under the hood - how do I find and remove them? I may be able to find them on my own tomorrow when it is light, but are they hard to get off, and are any special tools required? Are they clamped on with clamps that you can loosen with a screwdriver, just like the bigger hoses that connect to the radiator?

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When my heater cores have bursted, they did the same thing except they dumped much more than a cup into the passenger floor. I would figure on changing out the heater core. Once they get about 10 years old, it's just a matter of time before they fail.

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Thanks adallak. I have found some info on the net and also on the other forum, with some fairly detailed procedures for taking out the gloves compartment and stuff behind it to get to the heater core. The thing I am wondering about are the hoses you mentioned that connect to the heater core under the hood - how do I find and remove them? I may be able to find them on my own tomorrow when it is light, but are they hard to get off, and are any special tools required? Are they clamped on with clamps that you can loosen with a screwdriver, just like the bigger hoses that connect to the radiator?

You cannot miss heater hoses. They are 3/4" and go through the firewall. Disconnecting them can be a challenge. At least there was not much room in my 4.9 engine bay. You'll see all the architecture of the heater hoses if you follow those two inlet and outlet hoses connected to the heater core.

The saddest thing in life is wasted talent

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Thanks adallak. I have found some info on the net and also on the other forum, with some fairly detailed procedures for taking out the gloves compartment and stuff behind it to get to the heater core. The thing I am wondering about are the hoses you mentioned that connect to the heater core under the hood - how do I find and remove them? I may be able to find them on my own tomorrow when it is light, but are they hard to get off, and are any special tools required? Are they clamped on with clamps that you can loosen with a screwdriver, just like the bigger hoses that connect to the radiator?

You cannot miss heater hoses. They are 3/4" and go through the firewall. Disconnecting them can be a challenge. At least there was not much room in my 4.9 engine bay. You'll see all the architecture of the heater hoses if you follow those two inlet and outlet hoses connected to the heater core.

OK, after a look in daylight I see what you mean :). I think I should be able to get them off and back on.

One more question: Is there an easy way of draining the coolant from the engine block when it is cold? Would it come out with a closed thermostat? Since very little coolant actually came out of my cooling vents, I guess that there is plenty left (the reservoir was very close to the normal level when I checked it). I don't want to warm up the engine when the heater core is leaking...

A little bit of luck in all this: it happened at the beginning of spring, meaning that I still had my rubber floor mats that I use during the winter in the car. Everything came on the rubber, so I don't have a completely messed-up interior. Question: Will I need to clean the air ducts from coolant, or will they dry by themselves when I run the heater?

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Thanks adallak. I have found some info on the net and also on the other forum, with some fairly detailed procedures for taking out the gloves compartment and stuff behind it to get to the heater core. The thing I am wondering about are the hoses you mentioned that connect to the heater core under the hood - how do I find and remove them? I may be able to find them on my own tomorrow when it is light, but are they hard to get off, and are any special tools required? Are they clamped on with clamps that you can loosen with a screwdriver, just like the bigger hoses that connect to the radiator?

You cannot miss heater hoses. They are 3/4" and go through the firewall. Disconnecting them can be a challenge. At least there was not much room in my 4.9 engine bay. You'll see all the architecture of the heater hoses if you follow those two inlet and outlet hoses connected to the heater core.

OK, after a look in daylight I see what you mean :). I think I should be able to get them off and back on.

One more question: Is there an easy way of draining the coolant from the engine block when it is cold? Would it come out with a closed thermostat? Since very little coolant actually came out of my cooling vents, I guess that there is plenty left (the reservoir was very close to the normal level when I checked it). I don't want to warm up the engine when the heater core is leaking...

A little bit of luck in all this: it happened at the beginning of spring, meaning that I still had my rubber floor mats that I use during the winter in the car. Everything came on the rubber, so I don't have a completely messed-up interior. Question: Will I need to clean the air ducts from coolant, or will they dry by themselves when I run the heater?

Why do you want to drain the engine block? If you are careful, you will not spill a lot of coolant when you take the heater hoses off the heater. Just be ready to plug them up or redirect to bypass the heater core.

I do not think there is a lot of (if any) coolant in air ducts. I would not do anything, it will dry out eventually.

The saddest thing in life is wasted talent

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Why do you want to drain the engine block? If you are careful, you will not spill a lot of coolant when you take the heater hoses off the heater. Just be ready to plug them up or redirect to bypass the heater core.

I do not think there is a lot of (if any) coolant in air ducts. I would not do anything, it will dry out eventually.

Sounds like a good idea, thanks :).

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  • 3 weeks later...

I have now successfully replaced the heater core. :) Thank you for tips and ideas.

I included a description of how I did it below, with a link to some pictures of the procedure on Picasa. It is quite long and detailed, and intended as step-by-step instructions for someone who has not done this before.

/Jonas

Procedure for replacing the heater core on a ’97 DeVille.

Pictures: http://picasaweb.google.se/112056579231243335600/97DeVilleHeaterCoreReplacement?authkey=Gv1sRgCN3bjeDPsrS8rgE&feat=directlink

0) Put the front passenger seat as far back and down as possible to get some working room. This has to be done before disconnecting the battery. (I thought of this last when writing this, hence the number 0).

1) Disconnect the negative battery terminal (fig 1), and make sure that it will not accidently swing back against the battery. This is important because you will work close to the passenger side airbag, and also disconnect connectors to the A/C Programmer.

2) Open and empty the glove box. At the rear of the glove box compartment, there is a small access door (fig 2a). Open it by pulling on the left side. Behind it, there is supposed to be a connector for the airbag that you should unclip. My car lacked it (fig 2b), so I did not have to unclip anything, and I later found that it had been put away to the right side by someone.

3) Unscrew the six torx screws, and remove the glove box by pulling it out. There are four screws behind the glove box door, and two go through the floor. Be careful with the electrical connectors attached to the left side of the glove box (fig 3). I disconnected them and completely removed the glove box to eliminate the risk of damaging the cables or connectors from supporting the weight of the glove box, but some people have managed without disconnecting it. I used a screw driver to carefully push the lock tabs of the connectors, and then pulled them out.

4) Remove the black plastic panel under the dash panel, above the front passenger’s feet (fig 4). It is held by three plastic retainers – the kind that looks like Christmas trees, and the “branches” work as barbs. You just pull them out and later push them in. They can be a bit hard to pull out, but using some tool and wiggling a little can make it easier. The panel has some foam on the other side, which will likely be soaked by coolant. Just rinsing it with water should get it out. Do that at this time, so that it has some time to dry before you reassemble it. It has three holes in the front of it, and they go over three yellowish spikes in the car. Make sure to get them mounted properly – a shop once missed that after trying to install an electricity outlet for a passenger compartment electric heater in my car, and it looks normal, only that the carpet will suddenly be hard to fit properly. I discovered it four years later, when I was changing the heater core…

5) Pull the heater hoses from under the hood. Before starting this, protect the left front fender with a towel or similar. The heater hoses are located on the engine side of the firewall, at the right side of the car (fig 5a, 5b). Pulling the hoses can be a bit hard, because space is limited. You will also have to be careful not to damage the electrical connectors, vacuum lines and A/C connections when you pull. I managed to rotate the hose with my left hand, and simultaneously pull it with my right hand. I put down my right hand from a different place, a little further down the hose to do this. I had the kind of clamps that are tightened/loosened with a screw, but I think that the normal ones have clamps that can be opened with a pair of pliers. The area right behind the heater hoses (on the firewall) is made of black plastic, which is likely to be very brittle from heat etc. Therefore, if you try to pry off the heater hoses, you will most likely break that plastic. I would guess that one of the plastic pipes/nipples that the hoses are attached to could break off (if the heater core developed a crack there, for example). If that happened, it would probably be really hard to get the piece out of the hose. I do not know if there is any big risk of that happening, though.

6) Remove the A/C Programmer. It is a metal box attached to a black bracket with many colorful vacuum lines and electrical connectors attached to it (fig 6a). It is attached with a single screw on the right side – be careful not to drop it when you unscrew it, as it may go down between the carpet and floor pan. On the other side (cannot be seen) there is a small spike on the bracket that fits into a hole – good to know when reassembling it later. The spike is visible in figure 6b. You will need to disconnect the electrical wires (pink-blue connectors), but leave the vacuum lines (the colorful ones) where they are (fig 6b connected, 6c removed). The electrical connectors have tabs that need to be pinched in order to pull them out, and you may have to pinch, wiggle and pull for a while to get them loose. Move the A/C Programmer out of harms way, so that any coolant dripping from the heater box or core will not spill on it.

7) Unclip the upper and lower control rods on the heater box (fig 6a, 7a, 7b). The heater box is the big black box that can bee seen through the glove box hole. On control rod is on top of, and the other underneath the heater box. Before unclipping the control rods, photograph them carefully, so that you can later reattach them with the exact same setting. If you can see exactly how many turns of thread that is visible on the other side of the white plastic clip (as in fig 7a, 7b), then you can reclip it in the same way later. To unclip the rods, use a screwdriver and carefully twist it to pop of the metal screw from the plastic (fig 7c). Take care not to damage the plastic.

8) Open the heater box by removing the two screws. One is visible through the glove box opening, the other is about 6 inches or 15 cm below it. With those screw removed, the heater box swings open like a door (fig 8).

9) Remove the heater core. There are two screws that fasten the bracket (fig 9). Remove the bracket, and then pull out the heater core.

10) Clean off any coolant that you can see in any of the places that you have opened.

11) Install the new heater core. First, remove the old foam air seals and install the new ones that comes with the core, at least if it is an AC Delco (fig 11). It is hard to see in there, so take a good look exactly where the seals go before removing the old ones. With the new seals in place, put in the new heater core and secure it with the new bracket that also came with it. Both the air seals and the little soft pad on the mounting bracket had deformed on my old parts, and that is probably the reason to use new ones when reinstalling.

12) Put things back together again – reverse of taking them apart

13) Clean the carpet on the passenger side. This includes the one which is attached to the car (floor liner). I thought that I was lucky, because I thought that the rubber floor mat that I had put in instead of the cloth one for winter had caught all the coolant (it looked like it, fig 4), but it turned out that much of it had gone straight below the floor liner / carpet. Once I got the heater blowing warm air at it, it smelled quite bad. Beware that the floor liner can be wet underneath even if it looks dry. I used towels and soaked it, dried it, soaked it, dried it and so on (fig 13). After that it will still need to be dried some more by evaporation. I have not tried removing the floor liner, but it would probably be the best way of cleaning it.

Some repair manuals suggest partially draining the engine block for this repair. I did not do that, and it turned out that the leak had already drained it enough – almost nothing spilled when I disconnected the hoses.

If you spill any coolant on the ground, make sure to clean it – it tastes sweet and is poisonous, so cats and dogs etc lick it up and die if they find it.

When I did this repair I used a description from this source:

http://www.cadillacforums.com/forums/cadillac-tech-tips/84229-re-heater-core-replacemant.html read 2010-04-20.

Edited by hjb981
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Nice write-up and great pictures. Look at that crack in the plastic side tank... I would replace the OEM heater core with an aftermarket all-metal one.

The saddest thing in life is wasted talent

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