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Discussion Starter #81
orings are easy to get- you can look at a well-stocked hardware store or order online. There are online resources for material compatiblity with fuels. I think NBR is common and good. Mcmaster-carr will have them if you can tag onto an order cheaply.

Please list your resource that you find and the size/part number.

Glad you go the gasket installed....
I'm sure that Buna-N (NBR) will be appropriate. I'll take one of the existing o-rings to my local seal house and get it sized up and post the standard metric o-ring size number. For the record, I would not source o-rings from a local hardware. Quality levels of Buna-N seals varies all over the map as there are different material versions/durometers of Buna-N and getting them from a seal house is a much better bet. M-C should be an OK source. These are probably $.03 o-rings.
 

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Discussion Starter #82
I've got a problem with the car that isn't on my original list. Now that it's getting warmer again and I had a 4 hour drive today, I was reminded today.

What happens is that on more humid days, the A/C stops putting out cold air. I can turn the fan on maximum and very little air flows out of the vents and the car gets warmer and warmer inside. If I stop and turn off the car for 10-15 minutes and get back in, then it works fine again for another hour or so, then I repeat and it's working again. (I've had this occur on other cars as well on longer trips.) It's as if the evaporator coil is icing over blocking air flow and when I stop, it melts off and then will work fine until it ices over again. That's my best guess anyway. It gets very humid here in Ohio and today was humid.

Anyone have this issue? What's the cure? Clear a blocked drain hole? Vacuum dirt off the evaporator? Or is my diagnosis incorrect?

EDIT - I called the dealership and then did a search here and found a service bulletin about how humidity sensors were omitted from vehicles starting in 2006. I checked and sure enough, mine was omitted. So this could be the problem indeed! I bought a used sensor off of Fleabay for $10. Now just to get it recoded for the sensor as present. Hopefully that works!
 

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Why didn't you take it to the dealer for the humidity sensor since it was a service bulletin? It should have been a covered item and service.

John
 

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It's as if the evaporator coil is icing over blocking air flow and when I stop, it melts off and then will work fine until it ices over again. !
The evaporator coil is icing over. Your system is low on Freon. Get it properly charged and that will take care of your problems. My cdi did the same thing and I added a can of Freon. Members from this forum frowned on that because I did not fill it exactly to factory specifications, but at the time my cdi was 10 years old and I took full responsibility if I screwed up. It is working now and does not freeze up.
Mike T.
 

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Discussion Starter #85
Why didn't you take it to the dealer for the humidity sensor since it was a service bulletin? It should have been a covered item and service.

John
Sadly, this is not something that could have been considered warranty. I wish.
 

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Discussion Starter #86

The evaporator coil is icing over. Your system is low on Freon. Get it properly charged and that will take care of your problems. My cdi did the same thing and I added a can of Freon. Members from this forum frowned on that because I did not fill it exactly to factory specifications, but at the time my cdi was 10 years old and I took full responsibility if I screwed up. It is working now and does not freeze up.
Mike T.


I'm going to start with the humidity sensor and see how that goes. If this does not clear it up, then I'll move on to the freon. The dealer wants $300 for a drain and refill of the freon. I might take the gamble and do a little bit of freon at a time. My manual says it takes R134a. How much did you end up putting in yours?

I checked the capacity from the manual and is says 950 grams, which is 33.5 ounces. A typical can of freon is 12 ounces. Not that it means much; just thinking out loud.
 

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I'm going to start with the humidity sensor and see how that goes. If this does not clear it up, then I'll move on to the freon. The dealer wants $300 for a drain and refill of the freon. I might take the gamble and do a little bit of freon at a time. My manual says it takes R134a. How much did you end up putting in yours?

I checked the capacity from the manual and is says 950 grams, which is 33.5 ounces. A typical can of freon is 12 ounces. Not that it means much; just thinking out loud.
What I did and again others will chime in that I did it all wrong was to put a thermometer in the center vent, turn the temperature dials down as far as they go, and put the fan on speed three (middle(?)). The ideal thing is to have the temperature coming out of the vents to be about 40-degrees. Some cars it will be colder and freeze you, and others it will be hard to get under 45-degrees. Right now I am assuming that your vent temperatures are approximately 50-degrees, plus or minus 3-degrees. It is also good to keep the rpms up a little while filling. Lucky, I had a stash of freon that I purchased for $.75 per can of R134a. Those were the days! I think I installed a half can, and a month later another half can. About two years later I installed another half can when I noticed the evaporator coil freezing up. It has been good since then. I did notice once last year that it started freezing again, but I turned the ac off and ran the fan until it cleared up. I believe that happened in humid Florida.

I also read all the post about the humidity sensor. My thinking is that MB tweaked the system for the 2006 models so that the sensor was no longer required. They would not just delete something if they knew it would cause future troubles. Just my thoughts on this.

Mike T.
 

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Discussion Starter #88
...The ideal thing is to have the temperature coming out of the vents to be about 40-degrees. ...Right now I am assuming that your vent temperatures are approximately 50-degrees, plus or minus 3-degrees...

I also read all the post about the humidity sensor. My thinking is that MB tweaked the system for the 2006 models so that the sensor was no longer required. They would not just delete something if they knew it would cause future troubles. Just my thoughts on this.

Mike T.
Thanks for the info on how you handled the cooling temps. 40F sounds awfully cold, but maybe that is right. I just tested it with a lab grade thermometer and it was at 45F, but it is just 70F and raining here today. I would have expected it to be really cold on such a cool day. So indeed, it may be low.

I've worked with car OEM's for years in my industry. More likely - Bean counters started looking at where to save money as the 211 body style was "mature" and was going to be phased out by 09. The omission was more likely a calculated "business risk" model, knowing that they would get past warranty and minority of areas of the world had the kind of humidity/temp situations where it would be a problem. And there is also the fact that this only happens when you have been driving for some time; typically 2+ hours. So both the humidity condition and the long drive have to occur simultaneously, which is certainly a small minority of the people that drive W211's.
 

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I agree that it's a good idea to add the humidity sensor. Done to both of mine (one by PO, one by me). On the one car, AC would cut out on long trips when it rained...got REALLY muggy! Haven't had an issue since I replaced the sensor. Cheap on Ebay...easy to code.
 

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Discussion Starter #90
I agree that it's a good idea to add the humidity sensor. Done to both of mine (one by PO, one by me). On the one car, AC would cut out on long trips when it rained...got REALLY muggy! Haven't had an issue since I replaced the sensor. Cheap on Ebay...easy to code. FYI it's not just a matter of setting the sensor to present. There is another setting or two if I recall correctly....something to do with what is governed by the sensor reading.
I don't have a STAR tool, so I have to trust the dealership will get it right. I really should buy one of those tools. Pricey though.
 

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Thanks. What are prices being paid? I found used on ebay for less than $20, but $170 new.

John
I got mine for under $20 a couple of years ago...no need to buy new IMO.
 

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Discussion Starter #95
Thanks. What are prices being paid? I found used on ebay for less than $20, but $170 new.

John
I bought mine used for $11 including shipping on Fleabay, but $20ish seemed about average for a used one. The MB dealers want $175 new. So yes, $170 seems about right.
 

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Discussion Starter #96
Just finished replacing my thermostat, flushing the coolant system, replacing the coolant reservoir, removing the fan shroud cleaning up the front of the engine and replacing the belt. For the record, they didn't make the block drain screw easy to get to, did they?!?! Took me a while just to find it as the WIS doesn't show it for the 648 motor.

And yes, the vacuum filling system is DEFINITELY the way to go to refill the coolant. That is a pretty neat deal. Makes life easy. I was within 1" of the maximum fill cold mark when I took off the cap after filling. I'll never fill a coolant system any other way again! The $89 cheap-o Chinese version of the vacuum pump is just fine and came with every imaginable cap. It's hanging chain is crap, but I just let it hang by the QD fitting with the hose draped over my hood. I had to change out the QD fitting when I got it to fit the QD's I use, but that is simple. The directions sucked, but it doesn't take a rocket scientist to figure it out.

https://www.ebay.com/itm/28-PCS-Radiator-Pressure-Tester-Vacuum-Type-Cooling-System-Refill-Kit-W-Case-New/264160737779?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 

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Discussion Starter #97
I've noted that the rear main seal may need replacing within the next 50K, perhaps sooner. There is definitely oil under the engine in front of the tranny. It looks to be a slow leak, so probably doesn't need replaced tomorrow. Anyone here ever tackled that fun job? I'ts been years since I've done a rear seal, but the last time I did one myself (30+ years ago), I remember the time it took. Dropping the tranny, special tools, etc.

Found it in the WIS STAR maintenance under "Removing/installing the end cover". Of course, there are going to be a lot of other procedures to do before you get to this one in the manual, like dropping the tranny and removing the oil pan.
 

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I've got that same engine oil residue on the bell housing of my transmission, but the Rear main seal is totally fine on my car. I had the transmission out last month and had a chance to inspect the rear main seal, and after 450k miles the back of the block is still dry.
 

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Discussion Starter #99
I've got that same engine oil residue on the bell housing of my transmission, but the Rear main seal is totally fine on my car. I had the transmission out last month and had a chance to inspect the rear main seal, and after 450k miles the back of the block is still dry.
That is GOOD news. No great news.

Scott
 

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Discussion Starter #100
Injector Drain Fitting O-Rings for OM648

orings are easy to get- you can look at a well-stocked hardware store or order online. There are online resources for material compatiblity with fuels. I think NBR is common and good. Mcmaster-carr will have them if you can tag onto an order cheaply.

Please list your resource that you find and the size/part number.

Glad you go the gasket installed....
I've sized the o-rings for the injector drain fittings and found that they are 3.5 x 1 mm. They also appear to be standard Buna-N (NBR). This is actually not an easy size to find locally and I ordered some from Fleabay. $2 for the orings... $3 for the shipping! LOL

https://www.ebay.com/itm/Metric-Buna-O-rings-3-5-x-1mm-Price-for-50-pcs/202307451453?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Mine were actually still quite pliable, so I put the originals back into service until new ones arrive. The new drain line is now in place.
 

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