Evaporator Removal Necessary For Heat Exchanger R&R?

[Wide Open Cowbell]

Hello 500E masters,

Sorry if this is covered elsewhere. I've searched the forum and interwebs and service manuals for some pictures or reference to answer my question, but after getting my car back and running smoothly after an ETA replacement and while-I'm-in-there top-end intake / ignition / injector refresh, my merciless 500E continues the march towards my destruction. I've been greeted with the sweet smell of glycol when I mat the fun pedal, and determined the source to be under the dash. Not entirely sure if it's the core (heat exchanger) itself, or if I disturbed one of the supply lines when I replaced the three-way feed hose from the back of the engine block. Doesn't matter, really... the dash is coming out.

I know a wise man will replace the vacuum pods while in there (and I intend to), but tell me is it necessary to open the A/C lines in order to remove the heater core? Does the box have to come out? I realize that smart money would be on doing the evaporator at the same time, but from what I've read here it seems like the majority of of the huge time estimates apart from getting the dash out are related to the evaporator R&R, and my A/C system apparently just had a lot of work done by the PO and blows beautifully cold (and is not leaking). I really need to get this car back into operational status as quickly as possible.

Just asking the question so I can get parts ordered for next weekend. Thanks!

 

[gsxr]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

A heater core failure is wildly unlikely, so first rule out all other sources before your rip the dash apart. And if you don't have defective vacuum pods causing airflow issues, there's definitely no point pulling the dash, if the heater core is ok.

That said, the FSM indicates the heater core needs to be removed to access the center vent pod (not entirely true), and you definitely do not have to remove the evaporator as the evap sits behind it (towards the front of the car). And no, the AC system should not need to be opened, AFAIK. The evap labor is high because the entire heater box must be removed from the car, but for the heater core, the box can remain in place. FSM procedure:
http://w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Climate/83-622.pdf

Link to FSM index:
http://w124-zone.com/downloads/MB CD/W124/Main.html

A bigger issue will be obtaining the vacuum pods, several of which are NLA, however you can buy different pods (still available) and take them apart to swipe the items you need. There's a separate thread or ten about the HVAC vacuum pods / replacement / etc, search the forum for those.

 

[Wide Open Cowbell]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Thank you Dave! As always your information is invaluable. I've looked over your site in the dash section to familiarize myself with the vacuum pods and rebuild kits. But again as for now everything seems to be functioning well. I definitely will buy all the pods and diaphragm kits I can get knowing that it's going to be necessary at some point.

I can't imagine where else it's coming from, but I invested in an Snap-On pressure tester yesterday (how I've made it this far without one, I don't know), so when that gets here I'm going to be looking veeeery closely at that three way hose to see if it's maybe the source. But there are coolant droplets on the side of the box, so I'm preparing for the worst.

 

[gsxr]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

If there is a leak in the heater core, you should get coolant draining out the bottom, through the foam tubes that allow evaporator condensation to drain. These exit above the transmission and dribble over the top (forward area) of the trans housing.

Do you already have the dash off, btw? Where exactly are you seeing coolant?

 

[Wide Open Cowbell]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Yes that's exactly what's happening: coming out the drain tube through the bottom. I was confused because I sensed a heater core as soon as I smelled the glycol, but the carpet wasn't getting wet like every other car I've had it happen to. But after about 40 miles of driving I'd lost enough coolant for the low level indicator to come on. After filling it and going for another drive, I realized my boot was getting wet, and then I looked under the car and saw the drip. Pulled the dash knee pad and lower tray cover off and see the condensation on the side of the box, as well as above the pedals. My theory is there's a crack in either the core or a line that just opens up when the system is under a good amount of pressure.

My dog knew it right away... he's been obsessively sniffing my right pant leg since I got the car back on the road

 

[gsxr]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Aww nuts. That doesn't sound good. While you're in there, replace both foam drain tubes if they're original. Also a good time to do the ignition switch proactively...

 

[Wide Open Cowbell]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Thanks, I was planning on the tubes. They can be done without removing the box?

I wasn't planning on the ignition switch... will get one of those ordered as well!

 

[gsxr]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Thanks, I was planning on the tubes. They can be done without removing the box?

I wasn't planning on the ignition switch... will get one of those ordered as well!

The foam tubes are a PITA but yes, no need to pull the box. The ignition switch is purely optional, but the higher the miles on the car, the more I'd consider this as it's relatively inexpensive (~$60, IIRC?).

 

[Wide Open Cowbell]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

^^^ I have never seen a more accurate emoji.

 

[nocfn]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

HA! The ignition switch is much easier to get to with dash off, and remember that all electronics are controlled by that switch - nothing from china - buy MB! while the vac lines themselves are most likely fine, the elbows and such will no doubt not seal properly so grab new ones of those too.

 

[vatc5637]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

. . . The ignition switch is purely optional, but the higher the miles on the car, the more I'd consider this as it's relatively inexpensive (~$60, IIRC?).

FYI, just purchased one last week from Tom Hanson @MBCC for $72 & shipping. Also, Tom informed me that door and trunk tumblers are NLA.

 

[gsxr]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Also, Tom informed me that door and trunk tumblers are NLA.

OUCH.

 

[Wide Open Cowbell]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

Absolutely, went straight to the dealer and got shuffled around a bit to order my VIN-coded tumbler after work yesterday. Cost was $125 plus tax, so bit of a markup, but not enough to make me go find another source.

Also a big fan of replacing vacuum elbows, I'll be getting a bunch of those with the pods!

 

[gerryvz]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

I replaced my tumbler proactively several years ago, and kept the original one (it was still working fine).

I have a spare door lock tumbler/handle assembly with key, that I bought when I lived in Portland back in 2004. Just came across it today in my basement parts stash. Still new in the bag, never opened.

Came across a second set of new/never used/still in bag headlight wiper blades, too.

 

[gsxr]

Re: Evaportator Removal Necessary For Heat Exchanger R&R?

I have a spare door lock tumbler/handle assembly with key, that I bought when I lived in Portland back in 2004. Just came across it today in my basement parts stash. Still new in the bag, never opened.

Came across a second set of new/never used/still in bag headlight wiper blades, too.

 

[samiam44]

"The foam tubes are a PITA but yes, no need to pull the box"

In my area the factory style attachment clips for those tubes are available from the different hardware store assortments. Ace, true value and my local owned farm store.

 

[gerryvz]

It's a good idea to totally abandon the MB foam exterior/spring interior condensation drainage tubes, and replace them with rubber tubes of the appropriate ID/OD and cut them to proper length. They will never wear out after that.

 

[S70/2]

IIRC the correct hose ID is 7/8"