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  #1  
Old 03-19-2005, 06:52 PM
LarryBible
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300E Evaporator Time!

Well, the time has apparently come. I did a podectomy last year and the refrigeration system was holding very tight at that time. I was afraid to disturb the evaporator, but I would not be surprised if my moving it around slightly when loosening the unit to move it enough to replace the heater core disturbed it enough to finish it off.

The good news is that after doing the podectomy, I am not near as fearful of this job as I was before that ordeal.

There are several incidental issues that I find interesting. I had dye in the system and I find no traces except a VERY light trace on the spring that originally reinforced the condensation drain tube underneath the car. It looks as if there might be dye at the connecting piece between the diaphragm at the top of the expansion valve and the expansion valve itself.

Another incidental issue that bothers me is that even though the system was low on refrigerant the clutch is still engaging which tells me that the low pressure switch is not working. I have a new one in my parts collection so that will get replaced in the bargain. The static pressure was about 40PSI.

My thinking is that maybe I should go ahead and replace the expansion valve just to be safe.

All this work to be done, and this is now a car that I don't really use anymore. I drive it occasionally only because I love driving it. Now that I work at home, I replaced my old farm pickup and I have a small car that is fun to drive for general running around. I can't justify keeping this car, but at the same time I can't stand to part with it. I guess it will now serve to keep rust from forming on my wrenches.

So, it will get an evaporator, expansion valve, filter drier and a low pressure switch. I will also replace the rubber elbows on the pods since they have been suspect.

Everyone needs a project or two.

Have a great day,

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  #2  
Old 03-19-2005, 07:31 PM
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Larry:

I'd replace just the expansion valve and seals first to see if that is the leak -- dye will run down the pipes and it may get into the evaporator case and hence out the bottom. Saves all that work....

I still have a leak on mine, didn't fix it last year, will need to keep looking. The 0-rings between the hose manifold and pump blew, and I replaced the pump case seals too (may have been a mistake....).

Will have to look at the hose set (ouch!!!) and the condensor next....

Peter
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  #3  
Old 03-20-2005, 07:03 AM
Pete Geither's Avatar
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Did the evaporator on the 400E a couple of months ago. There was no doubt when I pulled it out as the bottom half of the evaporator was covered with oily moisture.
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Old 03-25-2005, 07:17 PM
LarryBible
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psfred,

Thanks very much for your suggestion. I went back out and looked at the expansion valve again with the UV light and it looked very much like a pretty good leak between the top diaphragm and block.

After I was looking at it with a droplight, however, that's when I saw indications of oily residue. I got an expansion valve and when I got the old one off, there was no doubt that it had been leaking profusely.

I replaced the expansion valve and the r/d last night and pulled a light vacuum, about 22 inches or something and closed the manifold valves. I came back to it this morning and it had lost no vac at all. I evacuated for a few hours while doing a few other things and then charged it.

It now works very well, but of course it was 71 degrees out. I'll have to wait a few months for the real test.

Had you not made your suggestion, I might not have examined the TXV so carefully and missed it. There is still a possibility that the evap is leaking, but if it is, I don't think it is a bad leak. Time will tell.

Thanks again for your valuable input.

Have a great day,
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Old 03-25-2005, 08:11 PM
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Larry:

Any time! You've done the same for me.

The expansion valve indeed has as history of failing in that exact location.

I have a firm philosophy of diagnosing before fixing, and always fix the cheap stuff first!

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #6  
Old 03-25-2005, 10:10 PM
dtf dtf is offline
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Larry what is a 'podectomy'?
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  #7  
Old 03-26-2005, 08:39 AM
LarryBible
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dtf,

Sorry for speaking in code. There are about a half dozen vacuum pods in the 124 climate control system that operate various doors and flaps. They will deteriorate with age, not mileage. You have to pull the dash to replace them, so it is strongly advised to replace all of them if you are replacing one because it is about the same amount of work. Since it is a significant job, someone here on mshop coined the phrase "podectomy."

psfred,

I too believe in thorough diagnosis, although I sometimes get antsie and dive in. In the case of the 124 evaporator, it has such a failure history that it is all too easy to make a quick scan and then just jump on the common failure. Since I was not going to tackle the evaporator job for awhile, I might have examined a little closer given the size of the job.

There are some folks here that feel that 124 evap failure is 100% inevitable, I personally think that not 100% of them will fail. I also find it hard to believe that I will be lucky enough not to be one of the people that dodge the bullet.

Have a great day,
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  #8  
Old 03-26-2005, 09:27 AM
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Quote:
Originally Posted by LarryBible
dtf,


psfred,

I too believe in thorough diagnosis, although I sometimes get antsie and dive in. In the case of the 124 evaporator, it has such a failure history that it is all too easy to make a quick scan and then just jump on the common failure. Since I was not going to tackle the evaporator job for awhile, I might have examined a little closer given the size of the job.

There are some folks here that feel that 124 evap failure is 100% inevitable, I personally think that not 100% of them will fail. I also find it hard to believe that I will be lucky enough not to be one of the people that dodge the bullet.

Have a great day,
Larry,
It's possible that 124s don't have a high failure rate. As Peter indicated the dye runs down the tubing and appears to be coming out of the evap case. Maybe most of the 124 evaps have been changed because of this mis diagnosis. Years ago many heater cores were changed in the 116 chassis, because of coolant on the floor on driver's side. The fact is the hose clamps on the inlet hose would relax and a stream of coolant would pee through the grommet in the fire wall. All that was needed was to remove wiper grills and tighten clamps.

Peter
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  #9  
Old 03-26-2005, 09:42 AM
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If a podectomy or evaporator replacement is required due to age or leaks, doing both is the prudent thing to due considering the amount of work required to do either. A smarter move is to also replace the heater core will the dash is off. Again it is a little extra money but a drop in the bucket if you have to go back in to replace it at a latter date.

Tim
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  #10  
Old 03-26-2005, 04:33 PM
LarryBible
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Tim,

I do agree that replacing the pods if the dash is apart is a good idea, but replacing the evaporator or heater core just because the dash is apart would not be justified unless there are indications of them leaking. The pods always deteriorate with age, but this is not necessarily so with the other two items.

The evaporators are not guaranteed to fail and niether is the heater core. In fact, I believe that disturbing a tight a/c system to replace the evaporator might cause more problems than it cures. If it ain't broke, don't fix it.

When I did my podectomy last year, I did in fact replace the heater core because it had previously leaked and I had stopped the leak with bars leaks for what I considered a temporary fix a year or two earlier. Since I was going under the dash I would certainly replace it while there. Had there been no other indications of heater core failure, I would not have done it.

Also, once I saw that pulling the dash was not as horrible as some folks claimed that it was, I decided that since the a/c system was showing no signs of a leak, I would not disturb the evap., thus did not disturb the a/c system.

Have a great day,

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