[RickASolis]

ok im so tired of having a cold car. i have heat but its not good. if your not moving for a while it gets pretty good but i drive 600 miles every week on the freeway and the heat just gets horrible when driving on the highway. tired the usual suspects (monovalve, aux pump). it just gets cold when driving. im thinking a restricted heater core? my question is: there are 3 hoses going to the heater core. 2 that go to the top and one goes to the bottom of the core. why is this? every heater core i have seen had a inlet and and outlet? i wanna flush the core before i last resort replace it. car runs at 80c and has a normal warm up time (thermostat installed). i even tried putting cardboard in front of the radiator to help it not cool soo much but the car just ran hotter with the same lackluster heat.

can anyone identify which of the 3 is the inlet and outlet hoses? or better yet, looking at the front of the car, which hose is the coolant inlet going into the firewall and which is the return?

been a while since i posted, been busy workin alot. but in good news, i have been racking up killer miles (i would say 700 a week) on my car with not one problem or breakdown. gotta love a 126

 

[axeman59]

Heating

You want to restict the air flow through the radiator some how to keep your water temp up.

 

[ElRojo]

Sounds to me more like a vacuum pod issue--the ones that control the air flow from the outside. It could be that the flaps aren't closing appropriately, letting in too much cold air into the mix as you drive. I guess it could also be the flap seals themselves-- the foam is probably shot at this age. You said the heat is OK when standing (or driving slowly I suppose), so it would appear that the heater core is getting hot enough water. So rather than mucking about with the heater hoses, I'd look into the routing of air through the heater core. Is there a recycle switch in your car? Have you tried simply using the defroster setting (my car gets plenty warm with this, although it takes a while to get heat down to my feet). I realize that LA's balmy temps can't compete with an Indiana winter, but I'm just shooting out a coupla suggestions.

 

[graftdesign]

I have always thought the heat function on these cars was pretty mediocre... particularly for such a high-end luxury car. Both of my 126's had rather wimpy heating IMO. I don't know if that means they were both working improperly or that's just an inherent weakness in these cars.

I'm curious as to what the proper measure of heat function is on these cars? Are the heating systems supposed to have very strong heat equal to what a modern car would have? My point of reference for good heat is the last few new cars we have had - most recently a Toyota which blows really hard and gets uncomfortably warm very fast. Even my 99 LHS blows away the 126's in the heat department.

 

[RickASolis]

Well the last 3 of my 126 had great heating. Never had complaints so i dont think the cars have bad heat to start with. When I feel the heater hoses, the passenger side hose is hot and you can actually feel coolant moving thorugh the hoses. But the other hose is not really hot and when u squeeze the hose if fells like its empty. idk maybe ill just live with it untill the spring comes along. the car isnt like freezing i just wish it was a alot warmer in this cold weather. the car stays OK. im one of those people that just want it really hot though i guess, anyone who gets in the car with me (well the other cars) complains because its so hot inside the car

 

[rondor2]

heat and cold

My 126 heats pretty well but my 107 is terrible. My question on this subject is does the A/C compressor run When controls are on heat, or fefrost.

 

[grumpy420]

Grumpy's heat is pretty weak in the floor boards. I replaced the mono-valve, and I've experimented with the cardboard-over-the-grill; all with very little improvement. It will eventually warm up. Now the defrost on the other hand cranks hot, hot, hot. Oddly enough, I have never, never been able to get hot air into the rear seat from the vent between the two front seats. The A/C though is awesome...... Personally, I would just suffer through it. Maybe one of those small electric heaters from JC Whitney's that plugs into the cigarette lighter.

 

[ianrandom]

Hmm mine does similar. The heat is ok around town at zero degrees outside, but as soon as i hit the motorway it dwindles to not a lot and its freezing on a trip! Annoying since i mainly use the car for long journeys and not around town normally.
However mine was only getting to about 65 degrees on the engine temp gauge, so i guessed it was that. The thermostat was changed last year and its at more or less that temp now no matter the weather. So i pick it up tomorrow and it has a new stat, but they reckon it only got to similar temp on their test drive. They said they've also changed the engine temp sender unit just in case its reading incorrect.
I have started to wonder if the heat on these cars is just weak, but how can that be? It shoud be fantastic, surely?
Its a puzzle...

 

[ianrandom]

Grumpy's heat is pretty weak in the floor boards. I replaced the mono-valve, and I've experimented with the cardboard-over-the-grill; all with very little improvement. It will eventually warm up. Now the defrost on the other hand cranks hot, hot, hot. Oddly enough, I have never, never been able to get hot air into the rear seat from the vent between the two front seats. The A/C though is awesome...... Personally, I would just suffer through it. Maybe one of those small electric heaters from JC Whitney's that plugs into the cigarette lighter.

If you have the full auto system, i believe the manual says that between rear seats vent is fresh (non heated) air only, whereas oddly with the twin wheel system, hot or cold air can be directed through it.

 

[maximapitko]

I have 158F at idle and it drops down to 150F while driving on the highway at 0F outside temp. No complains here. I do a lot of flushes at work and I am still amazed at what a difference can a good flush do to the heat output. Start there....

 

[ianrandom]

Well, i have heat again, yay. The car runs at 85 degrees now with new stat, which had helped a bit especially around town, but hadnt stopped the dwindling effect when speeding up. It did get the heat coming a lot quicker though.
I changed the duovalve inserts for good used spare ones i luckily bought on the offchance i might need them some time ago.
I found that my old rubber diaphrams were completely detached from the inserts, so i have no idea how i still had control of the heating. They looked as if they had split a very long time ago.
It would do cold or warm as required, but the heat just dwindled on the high speed roads.
I thought that if the duo/monovalve diaphrams were split then the heater was just stuck on or off.
Obviously not, and after reading tonnes of posts on here, some people had said that with engine revs, dwindling heat could indicate duovalve fault. Such as this really useful piece of info; The Unofficial MB Diesel DIY Pages

So now its really toasty and only took ten minutes max! The heat comes on quick and gets really warm. Fantastic. Hope this is of help to anyone who looks it up.