heat struggles at 0 degrees F, or while driving fast

[wonetwofour]

Hello,

Just curious and probably won't pursue this too much. I noticed last year I thought my heat wasn't working well at high speeds or low temperatures in the winter, or both.

Just got back from a Maine run where the temperature was 0-6 degrees Fahrenheit and the heat did struggle again.

Then I dumped it slowly nose first into a snowbank by accident ....and with all the snow jamming up the grill and air up front the heat was magnificent for a moment!!

But then I cleaned it off and the next day at 12 degrees and driving 70-80mph it was blowing cool again.

I don't know much about the heating and couldn't find a similar post. It was pretty darn cold on the drive home on the highway last night, so I'm just starting to realize I may have smelled coolant a few weeks ago too, but never investigated. I believe the heat works OK on a balmy 32 degree day.

Does anybody have heat that struggles only when speeding or extremely cold?

Thanks,
Chris

1992 400e 172,200

 

[gsxr]

That's not normal. Two things:

1) Your engine temp may be lower than normal, despite what the dash gauge says. How old is the thermostat? Engine temp should be 80°C or higher, even in sub-freezing temps. Ideally you would check the dash gauge against the live data from a digital scanner, which will show the temps from the 4-pole sender (which are generally more accurate)... on my cars the two are within 1 or 2 degrees. Or use an IR thermometer to check temps. If engine temp is below 80C the t-stat is likely bad (they should be replaced every 5-7 years on principle anyway).

2) The auxiliary coolant pump may not be working. Turn the key on all the way (engine doesn't have to be running) and set the temp wheel to max heat. The aux pump (in front of the CAN box) should be humming away. If not, tap it sharply and see if it comes to life. Either way, if not running, it's probably toast and needs to be replaced. I just replaced this on my one E420 and the other E420 needs it (pump is intermittent).

 

[mistermiata]

Chris,

I am having similar problems. My temp gauge rarely hits 80* on a below freezing day, and my heater struggles. I find using the recirculation button helps.

Dave...how hard is it to replace the thermostat?

Thanks!

Andy

 

[gsxr]

Good idea to use the recirc button - forgot about that, but it should help.

Replacing the thermostat is a nuisance but not terribly difficult. I would also replace the 90° hose which must be removed to replace the thermostat. It's even less fun with the fan clutch in place. The FSM procedure sure makes it look easy though:

http://www.w124-zone.com/downloads/MB%2 ... 0-1100.pdf

 

[wonetwofour]

Thanks for the responses and Dave thanks for the years of wisdom and instant diagnosis with your brain!
Indeed, my temp never exceeded 40 or so. That must be the culprit, and will check the fan too. Thanks!

Ahhh, I had one of those expense incurring weekends up at Saddleback Maine . My headlamp wipers/fluid hose got frozen stuck on and when I tried to disconnect the electric clip/connection from the whirring motor I inadvertently cracked the whole motor off the washer fluid reservoir. It was dark, snowing, and 0 degrees so I didn't think I could free up the frozen wiper assembly and chose to do what I did. So far a hurriedly chewed piece of gum in the hole it left did not stop the leak . I will try to find an adequate plug as opposed to find a new headlight washer motor (I believe a piece of plastic is irreparably damaged).

But I learned something which I should have known. After seeing many moose late at night on a deserted road in Maine (8, on 3 separate sightings that night), I finally wondered to myself and to anyone I met the next day "why do moose stand on the roads in the winter?" Of course!!! They are licking the salt off the roads!!!! Sometimes they will lay down on their front knees, making seeing them very difficult. They are the 2nd largest land animal in North America after the bison, weighing as much as 1600 pounds. And that folks is one reason there are hundreds of moose collisions every year. Be careful! And don't drive your Prius late at night in Maine!

Chris
1992 400e 172,300

 

[mistermiata]

Dave,

I am going to order the T-stat and O-ring. I looked on the EPC, there are 2 T-stat's and 2 O-rings based on engine #:

T-stat part # 116 200 0315....looks like for earlier models

# 119 200 00 15....looks like for later models

O-ring part # 015 997 04 45....earlier models

# 119 997 04 45....later models

Can you help clarify which one I need for my 94 E500?

Thanks!

Andy

 

[gsxr]

You'll need the early type, the "116" part number. The late style didn't get into production until the 1995 model year, AFAIK. The new t-stat will include a new O-ring, btw.

 

[mistermiata]

As always, thanks Dave!

 

[mistermiata]

Just a quick update.....

I replaced the thermostat and 90* hose today. Not a bad job took about an hour. As always with these cars, lack of working space in the engine bay was the biggest hassle.

Warmed the car up and took it for a drive, and lo and behold, my engine water temp got over 80*C for the first time this winter, and my heater blew warmer than it has all winter.....so I definitely had a stuck thermostat .

Next project is taking off the drivers door panel to fix the peeling door pocket!

 

[gsxr]

Cool! Uh, I mean, warm! Glad that solved the problem.

About the door pocket... what adhesive are you going to use? I had the worst time finding something that would actually stick...

 

[gerryvz]

Wouldn't the 3M "Super" grade Trim Adhesive work?

If not, [for the record] what did you actually use GSXR?

Cheers,
Gerry

 

[gsxr]

Wouldn't the 3M "Super" grade Trim Adhesive work?

If not, [for the record] what did you actually use GSXR?

Good question. It was a small tube of something, and I think it was a 3M product. I'll have to go look and see exactly what it was. I tried a hot glue gun and that was a waste of time, think I tried some other stuff as well with poor results.

Here's a good DIY article on the Fruit forum, note that person used QuickTite SuperGlue Gel:
http://www.peachparts.com/Wikka/W124DoorPanel

 

[DerFuror]

About the door pocket... what adhesive are you going to use? I had the worst time finding something that would actually stick...

I had very good results using NAPA 4032 Super Trim Adhesive w/directional spray nozzle.

 

[mistermiata]

I was planning on using the QuickTite SuperGlue Gel mentioned in the peachparts DIY, although I may try the NAPA product that DerFuror mentioned.

 

[gsxr]

Update: For re-attaching door vinyl to the door panel, I used 3M Emlem & Trim Adhesive, #03601. This stuff worked pretty good. If the super glue fails, might be worth a try. Here's a link:

http://www.shop3m.com/70071349412.html

 

[sheward]

I have used contact cement for good results. Titebond is a good brand. A package of pinch clips from the paper clip section of Office Depot or the like works great for holding material to card. Follow directions carefully and only use new cement as it seems to have a short shelf life.

drew

 

[mistermiata]

2) The auxiliary coolant pump may not be working. Turn the key on all the way (engine doesn't have to be running) and set the temp wheel to max heat. The aux pump (in front of the CAN box) should be humming away. If not, tap it sharply and see if it comes to life. Either way, if not running, it's probably toast and needs to be replaced. I just replaced this on my one E420 and the other E420 needs it (pump is intermittent).

Unfortunately I need to revisit this thread....

Just returned from a 700 mile ski trip (Vermont and back) and the E500 performed flawlessly and was a joy to drive, however.....my heat at idle was non-existent unless I cranked the temp wheel to full heat. I am assuming it is the aux. cooling pump as mentioned by Dave above. I checked it as per above, and heard no humming from what I believe is the aux. cooling pump

What has me a little confused is the fuction of the mono-valve and its relation to the aux. coolant pump.

Also not sure of the location in the engine bay of them both.

I took some pics, maybe you guys can tell me whats what!

1st pic is directly behind the CAN box(that is the box with the label "Battery in Trunk" in yellow, correct?).

2nd pic is behind the CAN box right up against the firewall.

3rd pic is in front of the CAN box.

Last picture shows why I needed HEAT!

 

[gsxr]

1st pic is the monovalve, this controls the amount of coolant flowing to the heater core.

2nd pic is the air blower assembly which cools the CAN modules.

3rd pic is the auxiliary coolant pump.

 

[mistermiata]

Thanks Dave!

Do you have a part #? I am having trouble finding it on the EPC.

I found it on Autohaus, they say it is OEM Bosch and is $56.

Cant find it on Parts.com by searching by name, need the part #.

Which do you prefer for this part, Autohaus or Parts.com?

Thanks Again!

 

[gerryvz]

Get it at Autohaus.

NEVER use the "name" search at parts.com. ALWAYS use the MB part number search ONLY.

Cheers,
Gerry

 

[gsxr]

The aux coolant pump is Mercedes part # 001-835-13-64, the Bosch number is 0-392-020-026. I got the aftermarket Bosch as it's waaaaay cheaper than OE.

 

[mistermiata]

Just checked Parts.com, O.E. is $186!

Dave, any tricks to the R&R? Do I need to drain any coolant?

Thanks!

 

[gerryvz]

Indeed this is one of those situations when you can get the same or very similar part to OE via Autohaus and save some big bucks. Same thing with things like distributor caps and rotors. That is a big savings though - very cool.

However, you do have to be careful with other parts, because sometimes the stuff that Autohaus carries is not as good quality as OE. That's when this forum comes in handy for people, because people can tell you where to buy smartest and which brands to buy or not buy.

Cheers,
Gerry

 

[gsxr]

Dave, any tricks to the R&R? Do I need to drain any coolant?

Yes, drain the antfireeze; and if it's either the evil green stuff, or more than 3-4 years old, do a full flush/refill procedure with the correct MB / G-05 antfireeze.

Replacing the pump is a nuisance as you can't easily access the hose clamps. You'll need to unbolt a few brackets that may be in the way, and you'll probably need to slide the rubber holder off the pump motor as well. Then you'll need some 1/4" drive extensions and a U-joint with 6mm/7mm socket to loosen the clamps. Some coolant may spill out even with the radiator drained; paper towels can soak up the spillage.

 

[wonetwofour]

Hello,

I can close my problem in this thread in hopes of building the search-able terms and solutions on this message board. My thermostat was found faulty and replaced and my heat works great again! Thanks for the tips here!

If the heat in a w124 m119 vehicle does not blow hot, check that the thermostat is operating correctly. A new thermostat fixed my problem of cool air blowing from the heat in cold operating temperatures.

Thanks,

Chris
1992 400e 176,200