View Full Version : Heater core removal and reinstall

02-08-2005, 02:57 PM
I have a 1990 535. It have metal lines that come into the heater core (no plastic). When I removed the core I took the lines off the core, but when I opened the box with the new core, it included the lines. Now I have tried to fish the lines throught the fire wall, but I am having troubles, and if I am having this much trouble getting them out, what am I going to have putting the new ones in that are aready attached to the core?

Second, Can I just use the old lines?

Hope someone can help.......


632 Regal
02-08-2005, 03:16 PM
do the lines disconnect right at the core?

02-08-2005, 03:37 PM
Yes they come through the fire wall and right to the heater core. I just didn't know if I could disconnect put in new o-rings and reconnect and not have problems. I really can't see how to get the new core in wihteh lines connected.

02-08-2005, 03:51 PM
Oh those things are a b!tch! If you think getting them out is tough... getting them back in is even tougher.

On the inside of the car at the rear of the foot compartment there is a clip holding the lines right before entering the firewall, remove that. If you dont care to much about the old lines, you can pull them through and they will get mangled, pulling from the engine compartment.

Trick is look very good at how they overlap each other, and when installing new ones theres a particular sequence which they need to be put back through the firewall. Sorry dont recall. But it's kinda obvious if you analyze the overlapping & twisting. But even then it's not easy, try messing around w/ certain ones being almost all the way to the core and others partially.

I think the whole removing & installing the lines took me close to 2hrs. butmy car has 3 aluminum lines, yours has?

02-08-2005, 04:48 PM
They are the 3 aluminum lines. I tried pulling them back into the cab, but it seemed like something was holding them up. I will look for those clips tonight when I get home.

How much more do I have to remove to get in to get the clips out or will I be able to see them? The other thing is do I disconnect them from the new heater core? And if I do, why could I just use the old lines?

George M
02-08-2005, 05:02 PM
If you look close inside the engine compartment right at the firewall there is a bolted clamp that secures the three pipes as they penetrate the firewall into the engine compartment leaving only nipples where the hoses attach. It is much easier to install the pipes to the core/plastic manifold if you remove this bolted flanged clamp bracket inside the engine compartment...a single bolt. You want as much freedom of the pipes as you can get to strike the right orientation to the plastic piping and the single aluminum pipe that fits directly to the core on the left hand side as you face the core. A further tip is the left most flange is best "rotated" out of position with a long screw driver leveraged off the other pipes leading down to the core. This single finger flange at the LH inlet to the core has a small bolt on one side and a finger that wraps around the core on the other side which isn't obvious without close inspection. You must rotate that flange free after removing the bolt and this typically takes more than hand strength because by design there is a slight interference fit to keep the flange from leaking. Use a long blade screw driver instead of tearing up your hand.
The other attached two pipes to the core/plastic manifolding is straight forward.
Do not overtorque the bolts upon reassembly and re-plug the HVAC control unit back into the harness and drive the car before you put it all back together after you install your new core and bleed the cooling system to make sure it doesn't leak.

02-08-2005, 05:21 PM
That one is going into my E34 file as "George M's heater core removal tips"! Haven't had the pleasure of doing that fix yet. And I thought the E30 heater core/valve was a fun removal/replacement.

George M
02-08-2005, 05:31 PM
Hi Jon,
There are a few tricks of the trade to that job. Also you want to be very careful not to lose the little nuts behind the core that secure the bolts on the front side. They are simply held into depressions behind the injection molded core header by gravity. I view the single bolt, finger flange on the left hand side aluminum pipe connection to the core as a bit of a design faux pas. Reading the engineer's minds, this is done due to packaging and quite frankly serviceability was too severely compromised...a D- design in other words. Jon if/when you remove this fingered flange, a trick is to bend the aluminum flange slightly back into itself for greater interference when you have it free from the core. That way when you rotate that flange back into position it won't leak which I believe is quite common when this job is performed judging by the design. As you mention about these cars....absolutely...the best stewards of repairing these cars are those that keep simple word files of tricks of the trade posted on this board.
Good Luck with your core when you do it and post if you get stumped along the way.
Use your digital camera every step to document everything so you don't get lost.

02-08-2005, 06:06 PM

I hope taht you are still there, mine has three (3) aluminum pipes that run from the engine compartment, through the fire wall and two go into the top left side of the heater core and one goes ont he front of the heater core, just off center (I think). There is no plastic piping at all, just hte plastic on the heater core. Have you seen this set up before? I am not by my car so I am not sure if it is held in the same as you discribe. I am hoping that I remeber how everything goes back together, as i pulled it a part two weeks ago and have not been able to get back to it (not to mention that they had sent me the wrong heater core, the one with all three hoses attaching to the front).

The one thing that I was really wanting to know is, is it really needed to put these new aluminum lines in or can they be reused and will it seal up to the core if I use them?

Hope you can help or maybe someone that has had the same problem.


02-08-2005, 07:15 PM
I replaced the heater core in my 91 535 about a year ago. I looked at the Al tubes and figured they would be more trouble than they're worth to fish out then back in again, especially considering that the tubes themselves were unlikely to fail.

Definitely replace the core and use the new o-rings of course. I think the o-rings are the parts that are most likely to leak anyway. Clean off the old tube mating surfaces, and if they are not bunged up from pulling the old core, I would just reuse them. My core did not leak after the fix, so at least one data point says this method is okay. :)

In retrospect... I might even have tried just replacing the o-rings and not even the core, but getting to it is such a PITA (haven't tried the sneaky, don't-have-to-remove-the-center-panel method that others here have written up) that I figured I might as well replace the core while I was there.


- Robin

George M
02-08-2005, 07:36 PM
Stephen, post a picture of your set up and the board should be able to help. Bottom line is the aluminum piping as Robin mentioned is not a wear item.
The O-rings however that seat the pipes to the core MUST be replaced and they cost pennies. You may have a car that does not have a plastic piping manifold. BTW do you have climate control thumb wheels in your HVAC control panel for respective foot wells? My guess is no and you have manual heating controls...only a guess and perhaps why you don't have a plastic piping manifold that connects to the cores two right hand side inlets. I have not seen that design but doesn't matter....the job is not that difficult...don't be daunted. You can also use the ETK as a pictorial reference. If you don't have a digital camera and you get stuck, simply borrow one so you can illustrate to the board what your problem is.
Good Luck,

Aaron Bakos
02-08-2005, 09:16 PM
More documentation is always better, and I say that because I'll be changing mine out soon and I'm rather curious about how to go about it.

Best of luck!

02-09-2005, 11:51 AM

The whole tear down took me about 2 hours. I started at the back of the car and worked forward. Probably the hardest thing was not knowing how it was all held together, and then I got the the heater box and it looked nothing like what anyone else had discribed (no way could this be done in a "short Cut Method"). Last night when I got home I got back into it. I have a 1990 535i with an automatic trans. that was built 01/90 and it has the knob like climate control that you turn like a dial. I think this is why I have the three aluminum line, with 2 going into the top left hand side and one going into the front (I think anything after this date will have a three hose connection across the front of the unit with plastic lines that connect to aluminum lines). Anyway, the first heater core that was sent to me was the later of the two I am talking of and only comes as a heater core. when the correct one arrived it included the aluminum limes that were already conected tot he new heater core. What I was thinking I was going to have to do was to fish these lines into the aready confined space and then through the firewall. :( After reading Robin's post I decided to just disconnect the new lines that were sent, put new o-rings on the old lines, put it all together and purg the system. guess what...........NO LEAKS!!!!!!!!!! :D This took about 2 hours as I wanted to make sure everything was correct (I suck at plumbing in the house, and was hoping it was not going to be that way on the car). I figure now I have about an hour to put the dash back together. 5 Hours!!!!!!!!! (better then the 10 that I was told it would take by the repair shop at $1,200 to complete). I am into it right at $200 with parts and supplies. Works for me and that included cleaning the carpets and all the parts that needed it.

It is not a hard job at all. I think that it is more intimidating then anything. I used a Chilton manual for the tear down and a whole lot of looking around at the parts for the actual removal of everything. That is why I thing I can have it back together in about an hour.

Good luck to anyone doing this repair.

Thanks everyone for helping me on this. Next it is on to the driveline, that one seems real strait forword.