Author Topic: Air conditioning drains  (Read 1163 times)

raueda1

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Air conditioning drains
« on: 26 May 2018, 08:38 AM »
Life was going so well!  Suspension is put back together after rebuilt hoses and valves.  Works great, no leaks, do drips.  Heater valve is fixed so the AC is blowing cold from the right places.  Impressively cold in fact. The operation of the whole goofy 4-lever system also becomes more apparent when it's working right.  ::)

After driving around an hour or so I felt a cold dripping on my foot from above the gas pedal (wearing flip flops).  This can only be water dripping off the AC coil.  Now I need to dry out the floor etc.  Fortunately the climate here is so dry that a kitchen sponge is dry as a bone in about 45 minutes so I'm not worried about mildew or rust. 
[As an aside:  this never happened before.  The system blew cool before and one vent was always hot.  Now it's really much colder.   It's now clear how when the heater valve was stuck open it was working at cross purposes to the AC.   That makes me wonder if that kept the system warm enough that condensation never formed in the past.]

Anyway, anybody got comments about clearing out the drain tubes?  Please, please don't tell me I have to remove the whole console to ream them out.  And the w116 doesn't have any air filters does it?  Never heard of any.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Air conditioning drains
« Reply #1 on: 26 May 2018, 09:38 AM »
Dave you might want to check if you still have "tar tape" around the expansion valve. Condensation forms around it and will drip if the unit is not insulated.
The AC drains on either side of the transmission but access is best done from below. It has these "fish mouth" ends on the drains which keeps critters out but can also lead to clogs.
If you need to redo the insulation use 3M Strip Calk. Great stuff.
Daniel
1977 450 SEL 6.9 - Astralsilber

Harv

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Re: Air conditioning drains
« Reply #2 on: 26 May 2018, 09:53 AM »
No cabin filters on the 116.
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raueda1

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Re: Air conditioning drains
« Reply #3 on: 26 May 2018, 10:10 AM »
Dave you might want to check if you still have "tar tape" around the expansion valve. Condensation forms around it and will drip if the unit is not insulated.
The AC drains on either side of the transmission but access is best done from below. It has these "fish mouth" ends on the drains which keeps critters out but can also lead to clogs.
If you need to redo the insulation use 3M Strip Calk. Great stuff.
Oh boy.  I'll try the drains first.  I kind of doubt it's the expansion valve or it would have dripped before yesterday.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Air conditioning drains
« Reply #4 on: 26 May 2018, 11:25 AM »
Dave you might want to check if you still have "tar tape" around the expansion valve. Condensation forms around it and will drip if the unit is not insulated.
The AC drains on either side of the transmission but access is best done from below. It has these "fish mouth" ends on the drains which keeps critters out but can also lead to clogs.
If you need to redo the insulation use 3M Strip Calk. Great stuff.
Oh boy.  I'll try the drains first.  I kind of doubt it's the expansion valve or it would have dripped before yesterday.

Yup the "tar tape tango" is NOT a fun job...
Daniel
1977 450 SEL 6.9 - Astralsilber

raueda1

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Re: Air conditioning drains
« Reply #5 on: 04 June 2018, 03:56 PM »
OK, I'm back to this problem and learned more since previous posts.  Unfortunately it doesn't look good.

It seems that what's dripping onto my gas pedal toes is coolant, not air conditioning condensate.  It happened again the other day with the AC off.  The dripping stuff feels like coolant.  It's kind of oily between the fingers yet rinses off clean with water.  Some of the pads under the dash and below the mats seem to have soaked it up; that's another problem. 

The only source of coolant  that I can think from the general area below the dash towards the transmission hump is a leaking heater core.  That's my worst nightmare.  Regardless, I'd like to verify it without disassembling the whole dashboard.  Putting a couple shut-off valves under the hood on both sides of the heater would isolate the heater core.  The theory behind 2 valves is to completely isolate the core from any cooling system pressure.  A single valve on the coolant feed would cut off flow through the heater but not remove coolant system pressure on it.  Assuming that the valves confirm a leaning core is it total heresy or just stupid to try that "radiator leak repair" stuff?  I guess I'd put it in, hope the leak gets plugged and then drain and refill the system.

Now back to the problem of the stuff soaking into the padding behind the large and impossible-to-remove plastic panel piece against the firewall behind the pedals.  See picture.  My thought was to repeatedly squirt water-free isopropanol (anhydrous, not the 30% water "rubbing alcohol") behind the plastic piece on top, as high as possible.  The theory is that isopropanol will absorb both water and the stuff in coolant.  As it drains down it can then be vacuumed out.  After numerous repeats the fluid behind the plastic would be displaced by isopropanol which would eventually evaporate (months?  years?) and be much less likely to rust than coolant/water.

Does this make sense?  Any other possible sources of coolant under there?  And does anybody have specific cut-off valve recommendations?  Thanks for helping, as always.

ps - yes, apparently I do still have the tar tape on the expansion valve.  I wish that were the problem. Bad as it may be, fixing that seems less horrible than pulling out the heater core.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

raueda1

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Re: Air conditioning drains
« Reply #6 on: 04 June 2018, 03:58 PM »
Forgot to attach picture of the plastic firewall cover.

-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

rumb

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Re: Air conditioning drains
« Reply #7 on: 04 June 2018, 04:11 PM »
yes that pad is near impossible to remove.  I made a strategically placed knife cut or two towards the right side  in order to free the bulk of it.
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Squiggle Dog

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Re: Air conditioning drains
« Reply #8 on: 04 June 2018, 05:05 PM »
Fortunately, the dashboard may not need to come out to remove the climate control case. I think that once you have the center console and lower dash panels out, and the top vent removed from the heater case, the heater and air conditioning hoses disconnected, that you can slide the case out from under the dash. I haven't tried it this way before. Make sure that you put a rag or something against the sharp metal around the ignition switch area, because it can scratch up the case when the case is nearly all the way out.

I also think that you can remove the heater core with the climate control case in place. If you can get the clips off to remove the lower flap section of the case, and get the front cover off of the case, you should be able to disconnect the heater hoses and pull the heater core straight out. Here's hoping.

The heater core is the only source of coolant in the cabin. The hoses connect in the cowl, so even if those were leaking, they'd have to make their way past the firewall grommets, and you'd likely see more coolant leaking out of the cowl drains than in the cabin.

If you need a heater core, I have a spare that's untested. I advise against leak fix. At least the radiator shop guy hates it and says he'll refuse to work on a heater core if it's ever had that stuff in it. Shrug.
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daantjie

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Re: Air conditioning drains
« Reply #9 on: 04 June 2018, 05:12 PM »
Dave regardless of the approach best to take note of all items to be replaced and to bomb them out in one go. I like the "while I'm in here might as well fix everything" approach as I detest redoing a job. And I hope you are a contortionist of sorts as dash work is not fun. Much less for me in trying to squeeze my frame and fat fingers into all the nooks and crannies :o
Daniel
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Squiggle Dog

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Re: Air conditioning drains
« Reply #10 on: 04 June 2018, 05:14 PM »
Oh, and when you see the condition of the foam on the flaps, you'll want to replace that, too. And then it will go on from there... I couldn't believe the high expense of high-temperature adhesive-backed resilient silicone foam. I spent over $200 just on foam to redo my flaps, or "blend doors" as they are called.
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ptashek

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Re: Air conditioning drains
« Reply #11 on: 05 June 2018, 04:35 AM »
And you do want to sort the flaps "while in there"... I made the mistake of not doing it during the restoration, nobody really thought of it to be honest. And as Murphy's law would have it, the foam failed miserably within the year after. Now I have a random clanking sound coming from under the dash whenever the car hits a bump.
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raueda1

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Re: Air conditioning drains
« Reply #12 on: 05 June 2018, 08:38 AM »
OMG.  Thank you gents (I'm assuming that we're gents here -?), great info.  You've convinced me to return to this particular problem later.  This is a fair weather car, after all.  The heck with the valves to the heater core, I'm just going to cap the hoses in the engine compartment for the time being.  I'll still try the solvent displacement technique to clean up the coolant behind the firewall panel. 
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Air conditioning drains
« Reply #13 on: 05 June 2018, 09:28 AM »
Indeed this is a "worm hole" of a job which can quickly turn into a nightmare.  Winter driving might be "interesting" without a properly functioning heater in Utah ;D  But if you plan to park it for the winter then yes I would let sleeping dogs lie for now...
Daniel
1977 450 SEL 6.9 - Astralsilber

Jed

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Re: Air conditioning drains
« Reply #14 on: 22 June 2020, 06:14 PM »
Hi dave,
restarting  an old thread...wondering if you ever got back to this problem?

Went for a drive today in 85 degree weather.  Ac blowing cold...also wearing flip flops :)

After about 45 minutes and on two separate occasions..felt liquid on my accelerator foot/toes when I turned right.  It sure felt like water and was cool and odorless.  I assumed it was condensate from the AC not draining, but now I am not so sure after reading your post.  Ill have to take a closer look at the underbody AC drains and check the floor mats and foam pad for saturation.  If it was from the heater core wouldn't it be hot? and I would think the cabin would have that distinctive ethylene glycol smell?

Ill let you know...
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