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  #1  
Old 01-07-2004, 07:47 PM
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air circulation question

I'm working on my 87 260E to troubleshoot the cause of headaches that it's giving me while the temp control is on the heat mode.
The headache makes me open up the window while i'm driving. however the headache goes away when the temp control is shifted to cold temp and the heater turns off.
Economy mode or A/C mode, I've tested both.
here's the question: basically it's the heater that seems to cause the situation.
If it were the coolant, I don't smell any coolant.
what are some of the simple tests to find out if it's a leaking heater core ? the coolant level is full.
more over I'd like to know what additional vents from the outside into the cabin are used that are different from the fresh air mode.
thanks.

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Old 01-08-2004, 02:17 AM
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If you aren't losing coolant then the heater core isn't leaking.

You can test the pressure of the cooling system with the engine off. The monovalve should be full open with the engine off. If it's holding pressure, the heater core's not leaking... unless it only leaks when it's hot.

There is only one outside air intake in the area of the windshield wipers. Maybe you are sucking in fumes and when you switch to AC/cooling the system switches to recirculate which shuts out outside air.

If your car has a manual recirculate button, engage it when you're not getting headaches then switch to heat mode. You should get 5 minutes in heat mode before the recirc mode self-cancels.

You might try a carbon monoxide detector from Home Depot. It should be sensitive enough to work in your car. I understand that you're supposed to mount a CO detector low, unlike a smoke detector that you mount high. Maybe CO stays in the footwells when it's cold and rises to the level of your nose when it's warm.

FWIW, I get headaches in any environment that's too warm for my taste. That includes cars, buildings and towns.

Sixto
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  #3  
Old 01-08-2004, 02:31 AM
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Thanks for the reply Sixto.
I did infact buy the CO detector from Home Depot last week. It give out readings from 0 to 999 of CO detection.
The detector never gave a reading above 15 which as per the manual is normal.
As for the re-circulation mode, I tried that as well.
Now, since my vacuum actuators are acting up, my center vent never blows cold air when the temp is set to cold. The only air coming in the car at hot or cold temp is from the side vents and the floor vents.
So far my research shows that headaches can be caused by two reasons. Either the fumes of coolant or CO.
My only confusion is, in either case why does the cold temp not show the same symptoms as hot air ... ?
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Old 01-09-2004, 01:33 AM
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The next thing I can think of is to unplug the auxiliary coolant pump and monovalve and pinch the coolant lines to the heater core. Dress warmly and go for a ride. See if you get a headache in heat mode. If not, then it's a heater core leak.

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  #5  
Old 01-11-2004, 03:14 PM
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Given the other tests have failed, I'm leaning towards the fact that it could be the heater core. Question is, how will the dealer confirm this ? I don't want to pay them hours of labor just to diagnose this. and Given it's -15 degrees here in NJ these days with the wind chill factor, I don't want to induldge in doing this myself at the moment either
At worst case if it is the heater core, I've read posts where the labor charges are 18 hours to replace this and the heater core itself being 900 or so... is that correct ?
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  #6  
Old 01-11-2004, 03:36 PM
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I had the same issues with my 300E but it was the A/C condenser. Replaced it myself and saved a bundle. But these are a problem. Check the sight glass and make sure you have refrigerant. Good luck
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  #7  
Old 01-11-2004, 04:00 PM
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Benz300

If you have a leaking heater core, there should be evidence: Loss of coolant, telltale smell, wet caret/interior, coolant in tank slowly going down.

One way to test the system is to use a pressure test. Often on older cars the weakest link will emerge. So it might be that there are other hoses and/or the heater core.

If, it is a heater core, if! then the hours for repair are generally correct. I have hear a few hours less. Someone who is experienced can do it faster.

The heater core shouldn't be that much. My guess without looking it up here at FastLane is about $200 +/-. But, when you have it all apart, you must replace any of the vacuum actuators. You don't want to have to do it all again a little while later.

I just did the 190e's heater core several months ago. Never did one before. Not hard, just a lot of pieces and parts. I took my time, took pictures, made sketches and notes, bagged and labled groups of parts AND replaced all the vacuum actuators.

It spanned two weekends. I went into the house and came out to find a neighbor couple peering into the car "We wanted to see the car that had the dash board explode"!

Haasman
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  #8  
Old 01-11-2004, 04:53 PM
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Haasman,
I envy your dedication !
I suppose I could take that route as well IF that's the last resort but for that I guess I'll have to get the compression test done first.
but yes at the end I'll definitely have to do that myself because I simply refuse to pay the dealer 18 hours of labor at a rate of 95/hour. i say NO to that. even the though just makes me angry.
The vacuum actuator are bad for sure. the dealer already tested them with the pressure test procedure. So ofcourse if i decide to take the dash apart I will be changing them.
The only thing that I"m trying to figure out at the moment is why the heater alone is causing the headache. I can live with the actuators being bad and air only coming out of the lower vents. but I can't drive a car in -20 degrees in NJ with the heater causing headaches and the dealer suggesting they don't know what to do !
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Old 01-11-2004, 08:38 PM
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Smile

Benz300, well thank you!

Question: If you leave the same settings on your heater controls but just roll the temp wheel deep into the blue area, do you get headaches?

Is your cowling cover with leaves and/or debris? That is the area by the wiper?

Is your air intake system to the car stock? What color/type coolant are you using?

Reach down beside your console and in the area where the heater outlet is, check for moist carpeting.

You didn't answer my coolant loss question .....

I want to know the answer to this .....

Oh, and BTW, you could do the heater core yourself. It isn't that hard. There's plenty of help right here.

Haasman
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  #10  
Old 01-11-2004, 09:13 PM
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Haasman,
I've been monitoring the coolant level for the past two weeks now, no loss whatsoever.
I checked the carpets for any dampness, none.
No debris, leaves etc because I make sure i clean that every day
THe air intake of the car is stock, however the coolant is not original mercedes, it's the green coolant but has been that way for the past five years. I kept it green even after I replaced the radiator.
as for answering the heater control setting : with all the other settings the same, when the temp control dial is moved from the cold (low temp) to hot (high temp) settings, the headaches appear, and as soon as the temp is put back on the cold settings i immediately feel the sooting fresh air coming back in the cabin and can literally start breathing again. It's not just the headache, it's also the loss of fresh air that i sense. granted the heated air comes in but somehow I can't breath with that heated air. and that never happened before...
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  #11  
Old 01-11-2004, 10:12 PM
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Hmmmm ..... have you tested your recirculation vacuum controller/system?

As I understand it, the air goes through the heater core whether or not hot water is supplied to it (thus the function of the temp control).

I am wondering whether somehow your system also goes to closing off the fresh air portion of the system.

Try this (yes I know right now it is crazy with the low temps) turn on the AC, try to get it running and outputting cold air. Make the recirculation work. Does the light come on?

Do you get the headache feeling right away?

Haasman
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  #12  
Old 01-12-2004, 12:15 AM
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Haasman,
ok i tried what you asked. and here's what I found.
with the a/c on and circulation mode on as well, yes the light for circulation does come on and i do hear the flips working to go into recirculation mode. with the a/c on all the time when the temp control is on cold mode it's all good, with the same exact setting, circulation on, a/c on, when i turn the wheel to the hot setting the headache comes back.
and yes, that's what i've been wondering all along as well, i'm not sure whether there's a seperate (fresh air) vent that works while the temp control knob is on the heat mode. because that's what it feels like as if the fresh air just vanishes when the heat is turned on, and when the temp is set back to cold i can literally smell the cold fresh air breeze come in again.
so does this make any sense so far ?
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  #13  
Old 01-12-2004, 12:19 AM
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Brian,
the freon on the car is full. it just came back from the dealer after having spent 1200 on new compressor, clutch and fill up of R12. so the part of the freon is good with no leaks.
but a good suggestion nevertheless had this not been taken care of already.

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