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Author Topic: MK2 Heater core replacement! w/AC! & Heater core bypass!  (Read 17117 times)

July 14, 2009, 04:27:10 pm

jtanguay

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MK2 Heater core replacement! w/AC! & Heater core bypass!
« on: July 14, 2009, 04:27:10 pm »
Well I finally got around to posting how its done.  If anyone has suggestions feel free to add to this post, but please only relevant info to keep it clutter free.  Thanks

First off, both lower access 'panels' must be removed.  On the passenger side there is a strap holding everything together.  This has to be cut.  Next the glovebox has to be removed.  Now the center console must be removed.  The radio and other bits have to come out as well to make it easier to unhook certain ducts and replace the foam. Once you remove the duct for the two center vents, it should look something like this:


As you can tell from the picture, the foam has all rotted due to age and coolant spray.  I also discovered why I get air out of all vents regardless of selector position; the gear on the vacuum controller broke under stress from some sticky residue.  A little glue and its all better.

At this point you should disconnect the A/C lines.  I suggest using a short stubby wrench as it is very tight in this area.


Now, if you have turbo you need to remove the heat shield to access these two nuts on the firewall.  


Going back into the car, there is a bolt up under where the glovebox was.  In the picture below It's removed.


Now it takes time, patience, and a lot of wiggling to get the whole unit out.  After a big struggle, I was able to get it out.  Notice the clean floor mat  ;D  To separate the heater box, there are little metal clips.  The plastic clips can be wiggled free, or broken. Tape could be used on the joint to seal it up.


Time for some cleanup, etc.

Now for some new foam!


Here's the new heater core installed.  Make sure to put the adhesive foam that comes with it on as the fins will catch and get bent on installation without it, and it just makes a good seal!


And installation is reverse!   ;)

Another issue is that the heater core always has hot coolant running through it.  If you didn't want to take the time to replace the foam on the different flaps, you could always run a bypass system.  This would give nice cool air on an old beater during the summer, and even cooler a/c as well.  I'm definitely installing this mod!  The two main components that you need can be purchased from rockauto (that links you to a cart already filled with the two main components)

The vacuum solenoid:1990 CHEVROLET ASTRO 2.5L 2474cc 151cid L4 TBI (E)
Emission : EGR Vacuum Solenoid AIRTEX Part # 2F1120
(EGE Valve Vacuum Bleed Valve Solenoid)


And the bypass valve:Heat & Air Conditioning : Heater Control Valve
FOUR SEASONS Part # 74809  



The rest of the hookup is pretty easy.  All you need is a vacuum tee going from the solenoid to the bypass valve with vacuum from the engine, and a solenoid switch on the dash somewhere to activate flow when you want it.  Also, some 3/4" cooling hose might be needed, and some clamps as well.  Be sure to have the system hooked up so that hot coolant is only flowing when vacuum is applied to the bypass valve.  Now might freeze, but you won't have to pull over for another blown heater core
« Last Edit: July 16, 2009, 02:20:58 pm by jtanguay »




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Reply #1July 15, 2009, 06:25:58 pm

fdnyguy

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #1 on: July 15, 2009, 06:25:58 pm »
I coulda used this $700 ago...  ;D ;D ;D ;D


Stay safe, stay well. Jimmy.
Never forget what a "Religion of Peace" did on 9/11/01.

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Reply #2July 16, 2009, 02:14:40 pm

jtanguay

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #2 on: July 16, 2009, 02:14:40 pm »
 ;D  there might also be a way of just removing the heater box for some of you guru's out there...  maybe theres just enough room with the help of a mirror to get the rear metal clips?  but anyways, i hope this helps people out!


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Reply #3August 01, 2009, 10:46:54 am

dieselherb1

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #3 on: August 01, 2009, 10:46:54 am »
I have pulled a A/C-Heater unit out of a 81 pickup. Wasn't too bad only 2 nuts holing it to the firewall-dash that I remember. Is the MK2 that much different? If so then sounds like main work installing into a MK1?
Herb

Reply #4August 11, 2009, 07:51:12 pm

truckoSaurus08

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #4 on: August 11, 2009, 07:51:12 pm »
I just tore the whole dash out. wish i would have known about this little trick sooner. That strap must be the giant zip tie thing on the evaporator box. Right?
I remember having trouble with those dang speed nuts.

Reply #5September 06, 2009, 09:59:14 pm

jtanguay

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #5 on: September 06, 2009, 09:59:14 pm »
I just tore the whole dash out. wish i would have known about this little trick sooner. That strap must be the giant zip tie thing on the evaporator box. Right?
I remember having trouble with those dang speed nuts.

yea the strap is pretty big :)

i forgot to give caveman props for giving me tips on how to git r done :) i probably would have cried if the whole dash had to come out, although its not as bad as it seems (its worse! lol)

that heater core bypass is my new best fwend.  ::) ;D no more heat bleed into my cool a/c and it just puts less stress on the heater core when the heater core really doesn't need to be used... for the win!!!


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Reply #6August 20, 2010, 11:29:40 pm

VW_Commuter

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #6 on: August 20, 2010, 11:29:40 pm »
FYI, I just received my vacuum solenoid described in this FAQ by jtanguay and it requires a special electrical plug.  I found one on Amazon but it probably can be found from many different sources.  Here is the link, http://www.amazon.com/gp/product/B001RPYVT8/ref=oss_product, for the one I purchased (it was the cheapest I could find and was a complete pigtail assembly).
« Last Edit: August 21, 2010, 08:48:02 pm by VW_Commuter »
Greg

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Reply #7August 21, 2010, 01:06:45 pm

honda_is_the_best

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #7 on: August 21, 2010, 01:06:45 pm »
is the MK2 dash harder to pull than an mk3? because i didnt find a mk3 dash all that hard to pull.

now, if you guys want a challenge, change the heater core on a mid 80s toyota pickup.. you end up with a bed full of dash pieces when you get to the actual heater core. it takes literally like 6 hours, iirc..
VW it aint just a car, its a way of life..... Boost, Soot, Repeat

Reply #8November 02, 2012, 10:38:07 am

JBG3

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #8 on: November 02, 2012, 10:38:07 am »
thanks for this thread!

I went the other route and pulled the whole dash out, but I had additional issues to resolve as well.

I was going to mention that instead of foam, what also works great if you have some, is stair treading on both sides-



Added benefit for me was that the treading had a safety stripe, so I now have a racing stripe inside my climate control.

Also, I had an additional problem in that my cable control had moved underneath, if you flip the control vent box upside down, there is a zip tie controlling the cable connection location for the door movement.  On mine it had moved, and the door would not fully redirect, ending with about a 1.5 inch gap either way.  I cut the zip tie, and moved where it grabbed the cable sheathing, so that at either end of the control level, the door actually redirected fully.

1986 1.6NA Jetta

Reply #9August 18, 2017, 12:25:25 pm

damac

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Re: MK2 Heater core replacement! w/AC! & Heater core bypass!
« Reply #9 on: August 18, 2017, 12:25:25 pm »
anybody have results for this setup long term?  found by accident searching google and never thought of such a thing.  i have a couple golfs i am fixing to get rid of so i think i will leave those stock.  ac is doing pretty good.

but for my own car if i can give the ac any help on those 100 degree days it seems like a no brainer.
1985 turbo diesel jetta

Reply #10December 21, 2018, 02:40:48 pm

Tamalleria

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MK2 Heater core replacement w/AC Heater core bypass
« Reply #10 on: December 21, 2018, 02:40:48 pm »
Hello Resurrector,

My heater core was leaking from several holes in the core. I brought mine to a local radiator shop and they re-cored my heater core for about 220.
The way the heater core is bolted into the housing very tight fit with brackets attached to the top and bottom tank will probably make it difficult to find a fitting core from another car.
Just my two cents.

Chris

 

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