Destructive evaporator removal... - PeachParts Mercedes-Benz Forum

1980sd · #1 07-13-2011, 09:27 AM

Been chasing AC stuff for a bit and and it seems the ONLY way to thoroughly troubleshoot/service/upgrade the system is to get the evaporator coil out for a thorough inspection and cleaning. Trouble is that it's hard and you risk screwing up a lot of stuff in the process.

Anyway...

Has anyone tried cutting it out through the glove box and/or behind the instruments? This would best be tried at a PNP with a battery operated dremel or something. Just start trimming the plastic around the area where the refrigerant lines enter the box and see if it could be done.

You would have to repair the hole created but it could be done once the evaporator was cleaned and replaced and it wouldn't have to be pretty because it's hidden.

I'd try it on a junker or 2 first to make sure you didn't screw up any of the flaps or anything.

Just a thought...

leathermang · #2 07-13-2011, 09:33 AM

Keep Dreaming...
you need some wands to spray the proper cleaners onto the fins.... and an inspection scope... $100 from Harbor Freight... wireless... very nice for the money... and you know how to clean the inside... adapt the old Txvalve to use as a tool...as the FSM says.... and the proper chemicals until what comes out is clean...
Proper spray wand design should be one of the instructions to come out of this project...

1980sd · #3 07-13-2011, 09:44 AM

Quote:

Originally Posted by leathermang

Keep Dreaming...

Have you taken the time to look at it or are you going on the assumption that "If it hasn't been done yet, it can't be done." Seems to be your fallback position...

Sears has a version of that scope too...

1980sd · #4 07-13-2011, 10:08 AM

The flat black part above the lines is some kind of soft rubber... Not sure if it gives access to the coil...

leathermang · #5 07-13-2011, 11:08 AM

There is a point at which ( and often comes about the time someone uses the word ' destructive testing' ) taking the next ' bigger hammer ' step sends the project into the stratosphere in terms of labor and money invested to get it back together...
You are a young guy... what ? 15-16 mentally... I have seen and destructed too many projects... and have them unfinished as proof of my theory..
LOL

1980sd · #6 07-13-2011, 11:26 AM

Quote:

Originally Posted by leathermang

There is a point at which ( and often comes about the time someone uses the word ' destructive testing' ) taking the next ' bigger hammer ' step sends the project into the stratosphere in terms of labor and money invested to get it back together...
You are a young guy... what ? 15-16 mentally... I have seen and destructed too many projects... and have them unfinished as proof of my theory..
LOL

True, true, all of it true...

Remember the old heater blowers on 70's GMs? You cut through the fender well on the passenger side to gain access? Put a sheet metal patch over the hole. Became SOP...

vstech · #7 07-13-2011, 12:32 PM

... chevy SOP... shouldn't really apply to a MB...

charmalu · #8 07-13-2011, 12:36 PM

Take a look at Dmorrison`s DIY on the evaporator R&R. starting at picture #107 you can see the ac/heater box removed from the car.

http://www.peachparts.com/Wikka/W123Evaporator

might give you an idea of what you are up against.

Charlie

ah-kay · #9 07-13-2011, 12:55 PM

Do not know about MBZ. I once replaced the evap on a Plymouth minivan and I took the easy path by cutting the plastic box that held the heat exchanger and evap, then I patched the plastic box afterwards. You may need to drain coolant as well. It is a lot of work that was why I did what I did. I did not drain the coolant in the van.

I think it is much ado about nothing based on the posts I have read so far on your A/C system. No A/C needs such extensive repair, you can never get it 'perfect', so to speak and it is a law of diminishing return.

Good luck.

Marvelicious · #10 07-13-2011, 01:46 PM

Quote:

Originally Posted by ah-kay

No A/C needs such extensive repair, you can never get it 'perfect', so to speak and it is a law of diminishing return.

I fully sympathize with him. Its not a matter of wanting to re-invent the wheel, its a matter of knocking the corners off of the one you have. I always feel that anytime an engineer puts together a system that needs maintenance they should be forced to do it themselves at least once. That way we wouldn't wind up with DIY's that take over a hundred pics to get to the part you're after. As far as Mercedes and GM not being comparable - they both made inaccessible parts, they should be beaten with the same stick! If it was as simple as just cutting a hole that can be patched, I'd be all for it, but it doesn't look like thats going to happen.

I've been following these threads with a good deal of interest because I'm motivated by what I think are the same factors: I don't mind doing a little extra work once, but I don't want to have to mess with it again - ever! To that end, goodbye r-4, hello modern condenser, etc... The tough part is plotting the curve of that diminishing returns arc.

leathermang · #11 07-13-2011, 02:13 PM

That is what I have been trying to say.... the evaporator is the bridge too far I fear because I am not sure that the proper parts are in line to compensate for the function of the TXvalve in the change over to orifice tube... right now , after reading my old Automotive AC book , the filters before and after the orifice...and the mechanism for low temperature control of the compressor... some kind of throttle suctioning valve and sensor to activate it...

ah-kay · #12 07-13-2011, 02:14 PM

Quote:

Originally Posted by Marvelicious

I fully sympathize with him. Its not a matter of wanting to re-invent the wheel, its a matter of knocking the corners off of the one you have. I always feel that anytime an engineer puts together a system that needs maintenance they should be forced to do it themselves at least once. That way we wouldn't wind up with DIY's that take over a hundred pics to get to the part you're after. As far as Mercedes and GM not being comparable - they both made inaccessible parts, they should be beaten with the same stick! If it was as simple as just cutting a hole that can be patched, I'd be all for it, but it doesn't look like thats going to happen.

I've been following these threads with a good deal of interest because I'm motivated by what I think are the same factors: I don't mind doing a little extra work once, but I don't want to have to mess with it again - ever! To that end, goodbye r-4, hello modern condenser, etc... The tough part is plotting the curve of that diminishing returns arc.

Work is slow this week so I am spending more time on the forum than I really should. I respectfully do not agree with you.

The car or A/C system was designed 25-30 years ago. There is a limit on how many corners you can round off, if at all. In my opinion, even if you replace everything anything, flush everything, the end result would not be as good as modern cars. It may be comparable. This is a given as the parts are still 'old' design.

I admire the OP's entrepreneur attitude and perseverance to get it done. I am just saying it is a law of diminishing return to get the last wrinkles out. I work in engineering, and it is my believe that no designers can get anything 100% perfect. Otherwise they will never get the product to market and costs a ton of money to perfect the last few %.

BTW: No one wants to do things over but the reliability of the car is the SUM of all components, not just the A/C. A/C can be perfect but the engine craps out that next day. Then what to do next?

Marvelicious · #13 07-13-2011, 03:46 PM

I probably have different expectations for an A/C system than most of you. 100 degree days are a rarity around my area, and this year I don't even think we've broken 90 yet (thats kind of unusual though). The fact that I fell I MUST have A/C is me being spoiled and used to modern vehicles. I use it when the temp gets into the mid 70's, so in the summer a car with no A/C is almost as worthless as one with a dead engine - I won't drive either one. That said, I think I can expect that this old system should perform up to my standards for a fair amount of time, if I repair it correctly.

Replacing the r-4 is a simple matter of me refusing to pay for garbage. Junk part that shouldn't have been on our cars in the first place. I'd switch to the Sanden with r12 or r134 - my opinion FWIW. Replacing the condenser is based on my reading indicating that this is really a good idea when you switch to 134 - which I plan to use since A: the car was already converted to it when I bought it, and B: my buddy will let me use his machine (which is set up for 134) to do the job. Plus, I've already got a parallel flow that I think I can just shoehorn in there. Of course, the receiver/dryer has to go as well, since the system is open.

So, by this point I've replaced half the system, hence the curiosity about going further. I think the OP is in the same boat. I understand the hesitance to replacing the TxV with an orifice and I think you guys are probably right about that. I also think you're right that the evaporator is probably too buried to make removal practical, and although I love the "make an access hole" idea in theory, I don't really think its likely: too much stuff in the way even for that.

Still, keep thinking outside the box 1980SD! This stuff is useful just as discussion if nothing else.

1980sd · #14 07-17-2011, 07:45 PM

The bottom of the heater core through the leg vent flap:

The evaporator is behind it/ above it... Hard to tell... This pic is actually better than I can see it.

The core of it looks good and clean but the mounting brackets are rusty

The box was actually flooding because the drain tubes were plugged. This caused me mucho headaches with flooded floorboards...

I need to get an inspection mirror in there and see if it's possible to get some kind of "wand" in there to clean them up. It's in a mostly watertight plenum that would catch any fluids sprayed in there and drain it through the floorpan.

leathermang · #15 07-17-2011, 07:56 PM

The center vents... and the air path if the blower is taken out...are prime possibilities for a wand for cleaning...
Hurry up so I can do mine....