Well today I removed the leaking heater core from form my new S90. (The 97 S90 is just a re-badged 960). It was nightmare to remove. It involves removal of the entire ECC unit which contains fan, all servos, evaporator, heater core, sensors, air distribution housing etc etc. This unit is about 3ft wide, 30lbs and resides under the right hand side of the dash. To remove involves major disassembly of the dash, removal of many plugs and vacume lines and draining of the R134. It took 7 hrs. I now have it out and have disassembled it to accesss the heater core, sticky coolant everywhere, what a mess!

New heater core goes in next week and then will reinstall the ECC unit.

If anybody plans to attempt this job I will be happy to offer advice and encouragement.

Will post results with pictures next week.
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David Hunter

You must have been a gluten for punishment the day after Valentines to do the job. I get 9 hours from start to finish and still have customers complain until they see the complete dash on top of their car and nothing left in front.

Hola David,

I need to replace the heater core on 960 and I read your post.

I am looking for some help with this procedure since you already did it can I borrwow some of your notes!!!


Thanks,

humbertoflores63@hotmail.com

I did that job 10 yrs ago. I do not have any notes but can tell you what I remember. at the time i had a paid 1 yr subscription to All Data on line manual for the car, used that as a guide.

Basically the entire AC/heater module with all the ducting and servos is removed from under the dash. It is held in place by 3 or 4 bolts that extend through the firewall with 10mm nuts on the engine side. Of couse you will disconnect the heater lines and AC lines at the firewall. I think I removed the glove box and a lot of the dash trim. Seem to remember that there was a corrugated metal safety bar that had to come out from under there and duct connections. Also I believe there was part of the center consol that had to be removed in order to have clearance to wrangle and angle the whole unit out. Keep notes and/or pictures as you disconnect things. Once the module is out replacing the actual heater core was easy. Check the vacume servo motors while you are in there.

I did have some difficulty re-wrangling the unit back into place and lining up the firewall bolts to their holes in the firewall. You will also have to vacume and recharge the AC freon.

Consider carefully if you really want to attempt this job. If the heater core is leaking into the passenger compartment you always have the option of bypassing it at the firewall and going without heat.

When I bought my 97 the driver's mat was soaked with coolant. Fortunately, the problem was solved by tightening up the heater hoses. Coolant was jetting into the passenger compartment with no evidence of a leak in the engine compartment.

A couple of months ago I had a heater hose burst on a Friday night on the way home from work. The garage was full of projects and I barely had room to get around and replace the very expensive molded hoses. I have had a little coolant dripping out of the duct above the gas pedal ever since. Failing health of a family member made it impossible to devote any time to this.

First task is to remove the hoses and make sure the connection is not the issue. Telltale deposits at the firewall, indicate that this could be my problem..... again. Wish me luck.

Dave,

If you can document this R&R as best you can (photos help a lot as well), we can get it put on the FAQ's so that when it's our turn at this, we won't be re-inventing the wheel.

Thanks
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1998 S90 062,700 1995 964 142,100

I will do that in the best way I can, it is a very detailed job. I followed the procedure in AllData's on line manual. There were some differences in what they describe and what I had to do. This got me on the wrong track and made the job somewhat more difficult. It may be that there description was for and earlier 960 model year, not sure.
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David Hunter

Hello All, Just got to exposing the heater core on my ancient '88 740 GLE. "What a nightmare" barely describes it!! The best that can be said is that the central housing/plenum breaks away from the A/C part. Am using the Chiltons manual, which covers 140 to '88 740-780. The instructions are very brief - like "Remove central distribution unit" no mention of how many screws to look for. Well, 25 years is the life expectancy, I suppose. The symptom is the strange fogging of the windshield, and all four carpets icky sticky wet, and loss of coolant, of course. Have lost count of how many trim panels, etc. have been removed. Hope that some designers can come up with cleaner concepts for the future. Shorting out the core hose ends was a cinch - just take a 2" length of 1/2" copper house piping, and solder a brass compression ring at each end - maybe find a suitable plastic equivalent? Omar Jette, Montreal

Any idea why this five-year-old unit would have failed? When you get it out, cut it open and let us know what you find.

Steve, I have the core on the bench but have not cleaned it up yet to inspect it. A very quick examination shows it may have leaked close to where the lower pipe comes in where there is a small copper reservoir or tank. When I have some time I will clean it up and I plan to pressurize it with a bit of soapy water inside and try to see where the leak is, then dissect it. I ordered a "Four Seasons" brand core from RPR. Hope it's a good quality unit, I definitely do not want to do this job again. '

By the way if the evaporator needs changing it would be a breeze, disconect on the outside of firewall, remove about six screws inside and it slides right out.
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David Hunter

David, keep us posted on your diagnosis. What kind of coolant were you using, btw?
And if you have a writeup, let me know for the FAQ.
Steve
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See the 700/900 "FAQ" at the menu bar top screen left side.

Four Seasons is fine. I wonder if your system has some electrolytic problems. See the FAQ for information about poor grounds and corrosion caused by electrical voltage differences. Test using a DVOM in the coolant.