Heater Core Replacement in 91 Caprice

Hey guys,
I searched the forum and have been reading some old threads about heater core replacement. I read that it's easier to take the passenger seat out and that there is one screw that is hard to get to.

I was wondering if anywhere along the lines someone has done a step by step write up with pictures of this procedure. I have done heater cores in other vehicles where the whole dash and heater box have to come out. I am just trying to figure out what the easiest way is to get at it.

Any help is greatly appreciated!

Thanks,
Collin

It's honestly nowhere near as hard as some guys make it out to be.

Disconnect heater hoses. Pull the passenger seat. Unbolt the lower dash plastic piece, then there's a black plastic cover. Undo it, making sure to get the one screw down by the firewall itself and the floor (7mm screw if I remember right). Undo the big clip, pull the old core out, put the foam pieces on new core, slide it in, replace plastic piece, replace under dash cover, replace seat, replace hoses.

Why do you need to pull the passenger seat?

yakko wrote:

Why do you need to pull the passenger seat?

That is the first thing to do, it makes the job so much easier. Your back will thank you. If you don't do it, your feet will be hanging out the door and the top half of you will be wedged between the seat and dash.

Tom

Stingroo wrote:

It's honestly nowhere near as hard as some guys make it out to be.

Disconnect heater hoses. Pull the passenger seat. Unbolt the lower dash plastic piece, then there's a black plastic cover. Undo it, making sure to get the one screw down by the firewall itself and the floor (7mm screw if I remember right). Undo the big clip, pull the old core out, put the foam pieces on new core, slide it in, replace plastic piece, replace under dash cover, replace seat, replace hoses.

Great, thanks for the insight Stingroo. That sounds much easier than other heater core jobs that I've done. So it's mainly just the one screw against the firewall that is a pain to get to?

yakko wrote:

Why do you need to pull the passenger seat?

It lets you lay flat to do the job. Otherwise you have to be some kind of contortionist/Chinese gymnast to fit in there. It's only 4 bolts to pull the seat, and one electrical connector if you have a power seat.

You'll thank me later.

There is one screw holding the core to the box internally. It is a 7mm as well. Remember to take the drain elbow off before trying to remove the tray.

Depending on what year you have, the hoses can be a pain to remove. The quick disconnects on the earlier cars are difficult to get to. When you squeeze the nylon tangs, you have to remember that the white nylon part stays with the heater core. You have to transfer them to the new heater core, or get new ones. I believe the LT1 cars have standard screw clamps holding the hoses to the core. Give the hoses a little twist to make sure they are loose. There is an O-ring inside of the quick disconnect. Make sure it is intact.

There are two screws that are difficult. The one over the trans hump can only be removed with an open end or box end wrench. The difficult one is beside the pan drain. you have to pull the carpet and the insulator back, which requires removal of the kick panel by the door, and that requires removal of the sill plate. Once you have that out of the way, you can access the screw. I use a deep socket, short screwdriver to 1/4 drive adapter, and a battery terminal ratchet that fits the screwdriver adapter. You can use a flexible drive, but I found the above mentioned combination to be the best combination. I have replaced the trays at least 8 times. All of the screws are 7mm on the cars I have worked on. When inserting the blind screw, I use the deep socket/adapter to turn it in with my fingers, and put the ratchet on to tighten. Do not tighten the screws excessively, because they screw into plastic.

I also take the original seal out and put a nice bead of silicone in the channel. The original seal is usually damaged when you remove the tray, and I believe they are not available anywhere.

6 bolts on the seat, 10 or 13 mm don't recall exactly
  The screws for the black cover are 6mm on TBI cars and 5.5mm on LT1 cars go figure?

The screw by the firewall you probably won't get it back in but don't stress about it.
Also be careful with the clip holding the core I broke it pretty easily and used tie wraps to hold the new one up.

Have fun

The first time removing the heater core takes a little time. I think it took me close to 4 hours. But the second time I had to do it, was like 1 3/4 hours to do it. Really not a bad job.

I think the hardest thing was removing the heater hose from the core, where the pipe sticks out of the fire wall. There a little hard to reach, then you have to deal with those spring type clamps that GM uses and the hose is almost glued to the heater core pipes. I think it took me an hour or more to take them apart.

The second time I did it, I just cut the pipes at the firewall with a hacksaw blade, 5 minutes.....done.

Good luck


Tom

interesting factoid. TBI 9C1 cars have those snap fittings like the fuel line and they are biatch to get off. I have a set of the green hoses for a TBI but haven't needed them yet....

I cut the core off at the firewall to then a pair of needle nose to twist out the old tits stuck in the hose.

The quick release clamps are not hard if you understand how they work. Most people try to remove the white part with the hose. If you press the sides in so that the white parts are beyond the black piece, it slides right off with minimal effort. The white plastic part stays with the heater core. I had a set removed by cutting them, but since then I have been able to remove them without destroying the core. If the core is leaking, I guess it does not matter. You can use the white nylon pieces over again.

The ones I am referring to are those metal spring clamps not the plastic. They are a pain.

I have never seen the spring clamps on any B-body.

Maybe I'm not calling them the right name, but they are all over my two wagons and they are metal.

I know exactly what your are referring to, and I have never seen them on the heater core hoses.

Thank you for all of the help fellas, I am going to be tackling this within the next couple weeks. I was lucky enough to score a NOS Delco core, it was the last one this supplier had so I'm hoping it's geriatric age doesn't make it leak. I have had bad luck with aftermarket cores on other vehicles so figured I'd try to stay OEM. I will keep you all posted, and thanks again.

-Collin

Good move using the Delco. My first RMW the original core lasted 220K. I replaced it with a genuine, made in Mexico NAPA one; which lasted 12K.

Tom C.

Yeah I lucked out and scored a Delco one on eBay when I did mine. It was like $35.


Gotta love the Internet.

You can solder the leak, and use the old one over again. I did that and it only cost me about $1.