Very little heat (again)

[Largeowner]

Like many Pagoda owners, I have a barely functioning heater.  I get air flow out the heating ducts, but the air never gets above luke-warm.

Last year, I flushed the cooling system with heater valve open.  This had no effect on the amount of heat.

This year I have been doing some research on possible problems:

1. Heater core valve in the wrong position.....I took the valve out per the instructions in the Technical Manual.  It was/is currently in the open position (with a fresh O ring and silicone plumbers grease).

2. Cooling system running too cool.....Nope, it warms up quickly and runs steady at 180 deg f (80 deg C).

3. Heater box controls (doors or flappers) stuck closed.....Nope they were visually inspected open, and I can feel air flow thru the ducting.

4. Air in the cooling system....Hummmmm, maybe so!  That would explain the luke-warm air if only a trickle of coolant is going thru the heater core.  The heater core also appears to be the high point of the system...I likely place for air to linger.

I have read the posts about how to "burp" the air out of the cooling system by raising the front end of the car and running with the radiator cap off.  This poses another problem...my radiator DOES NOT HAVE A FILLER CAP!  The only fluid access is through the expansion tank.  I don't know if this is an aftermarket add-on or "as designed" for my model year (67 230 SL).

My questions for the group:  How do I burp the system with no radiator cap?
                                        If a burp does not do the trick, where do I look next?

Thanks for your help,

Large

[graphic66]

I just unhook the left side heater hose and run it into a container with the engine cool and running with the heater on for a while and the radiator cap off and then hook it back up. This will also confirm that you are getting flow through the heater core. My 66' 230SL has the high output heat option and has great heat. I am not sure what the option consisted of. The valve has four possible ways to hook it to the actuating lever. I blow air through the heater core when hooking it up to confirm the correct position. No or little heat output is also a sign of low cooling water level.

[Largeowner]

Hello Graphic,

When you say the left side, do you mean the side WITH the heater core valve, or the side WITHOUT?

Thanks,

Large

[graphic66]

The side with the heater core valve.

[jameshoward]

I wonder (because I don't know) whether the incorrect thermostat would make a significant difference. There is, I think, a 79 and 87 degree thermostat, plus a few others (at least one) that also fit but which are wrong for the car.

[ja17]

Hello,

The correct thermostat, is actually double acting.   With cold engine coolant, the thermostat actually bypass's the radiator. All coolant is run through the heater cores. As the engine warms, the thermostat allows flow to the radiator as needed to maintain the 79* C temp. 

Make sure you have the correct thermostat first of all.  It has a disc built on below it to shut off a passage when the engine is hot.

The internals of these systems are prone to air leaks and flap problems after years of use.  Foam seals and plastic parts bind stick or break causing air leaks. As I recall there is more than one set of flaps in these boxes with foam seals.  A lot of cold air by passes the heater cores and ends up entering the cabin. I have a feeling that the flaps you are looking at are not the ones causing issues. Make sure the heater controls are moving the flaps full range.

Cannot remember all the details maybe someone has some nice photos of the internals.

[Benz Dr.]

If you live in a very hot summer climate the 79C thermostat is your best choice. It's too cold for winter or cool weather driving and you will never get enough heat to come out of the heater.
I put one in my own car and I plan to take it out because the engine won't come up to full operating temps unless it's 80 degrees outside.

[graphic66]

The hillbilly thermostat is a piece of cardboard in front of the radiator. This works quite well as a stopgap method to get heat without changing the thermostat and checking to see if that is your problem or just getting heat out of your car for a few times when it is cold rather than having to switch the thermostat all the time. Not for the purist, but living near Canada you learn to improvise to get warm. Just put a piece in front of the radiator and try it, adjust the coverage as needed, if you run to hot, cut some off, to cool ad some more. And of course, as stated above your system must be in good working order. 

[Ulf]

The radiator filler cap on my 230 is also placed on the expansion tank - isn't that normal?

Ulf

[ja17]

Hello Ulf,

Yes, the only filler is on the expansion tank on all W113s. Some sedans of the era were also like this.  The W110 chassis (230 carb. sedan)  used the same expansion tank. Merceds stuffed a 6cyl engine in the four cylinder chassis. (W110).  The radiator had to be placed up under the front body crossmember with no room for a radiator cap on the radiator, so the W113 expansion tank was used back on the firewall. 

[Largeowner]

The weather warmed a bit this weekend ,so I was able to do some further investigation.  I removed the ram air inlet, filter etc to gain access to the "air box" and the heater inlet doors (left and right).

I am beginning to think that a previous owner may have replaced the dash controls, and connected the cables backward.  When the pax side is selected "full hot" from the dash, the right side heater door is closed.....this seems backward to me!

The same is true on the driver side, full hot dash selection closes the door (but the linkage to the heat exchanger control valve is full open).  However, the linkage positioning looks correct per the photo in the tech section for control valve setting.

Am I missing something?  What position of the heater doors puts air thru the heater core?

Thanks,

Large

[jeffc280sl]

no message

[awolff280sl]

As Jeff describes, when the flaps are up air is supposed to flow across the heater core to be warmed. But bear in mind that in order to get air flowing across the core either the blower must be on or the cowl flap must be open and the car moving. By design warming will be more efficient if the cowl vent is kept closed and just the blower is used to recirculate the cabin air.

[Largeowner]

Thanks guys,

That confirms what I thought.  It seems the previous owner has connected up the cables backward.

Thanks again

Large

[Largeowner]

Upon further review.....

In speaking with Bob Possel, it has been determined that the heater core valve is open as depicted in the attached photo from the Tech Manual.

Direct linkages being what they are, the only way this relationship is possible is if the driver side door is CLOSED.  Bob confirms that the OPEN position bypasses the heater core and is for cooling the footwell area.

This is probably more than you ever wanted to know about the heater!

Thanks for all the replies!

Large

[awolff280sl]

It's always good to clarify things on the forum for future reference by members. The confusion may be a result of using "open" and "closed" when referring to flap position. I think that more accurately (and if I remember correctly) one could say that when the flaps are "vertical" that air is directed directly down into the air distribution box, and that when the flaps are "horizontal" the air flows forward and then down to the heater core.

[bpossel]

I am no expert...  but to me it seems that when you move the lever to "red" to turn on the heat, what it does is open the heater valve to enable the flow of radiator fluid through the heater core...  also it closes the top flap which encases the heater core in an air chamber...  When you turn on the fan, it then blows the heat out from the air chamber and into the cabin of the car...

When you turn off the heat, it closes the valve bypassing the heater core.  It also opens the top flap to allow air to keep the core/air chamber cool.

I am sure that others may have a better explanation of the system?

Bob

[jeffc280sl]

no message

[Jonny B]

I am with Jeff on this one. The wide end signifies more (of what is the appropriate lever) However, I think that if the left side heat lever is set to the low end of the cone,in to the center of the four levers, the right side heat lever does not do much of anything, since the driver side control is the master. Yes?

[66andBlue]

...  since the driver side control is the master. Yes?

Correct. From the owner's manual:
The heating of the fresh air can be steplessly controlled and separately for left and right car end by means of heater levers {red} (3 and 4). If the left hand heater lever (3) is completely set to "cold",no warm air will come out on right-hand end, even if the right-hand heater lever (4) is opened.
Make sure that during heating the air volume control lever {blue} (1) is not set to "closed" because the amount of incoming air is determined by this lever.
For additional ventilation during summer driving summer air vent holes are located one each at right and left of the dashboard.
The air circuit can be channeled by swiveling or folding louvers on the openings. Simultaneously,
fresh air is circulated into the leg room. The control lever below each louver serves to regulate the air flow during summer driving.
Lever pushed in: air outlet closed.
Lever pushed out: air outlet opened.
For winter driving the air outlet should be closed.
The summer ventilation functions only with the air volume control lever (1) in position "open".
If the side panes are cranked up at a speed of more than 75 mph (120 km/h), we also recommend
closing the air volume control lever.

[bpossel]

Thanks Guys for clarifying this!

Question....  looking at the picture of the heater valve below, is the valve installed incorrectly?
Bob

[awolff280sl]

Jeff, I'm going by memory and I'm not up to taking the cowl off to double check, so maybe bear with me. What I remember is that there are 2 different air flow pathways for air that enters the hood cowl. One pathway is straight down to the air distribution box, but the other pathway (which  is blocked when the flaps are up or vertical) is actually forward and then down to the heater core.

[jeffc280sl]

no message

[bpossel]

Here is a pic I found..
This picture shows the flap down and you can just see the edge of the heater core exposed.
When the flap is up, it would close off the air flow to the core.

With flap down and core exposed, is this the "heat on" condition? or heat off condition?

The answer to this should help ensure that the valve is positioned correctly in the core...

Comments with this picture?

bob

[Largeowner]

Bob's photo is also representative of the situation in my car.  A dash selection fully toward the red triangle results in the door in a closed (horizontal) position, and I can see/touch the top of the heater core.  With the door in this position, my heater core valve is OPEN.

I have heard opinions both ways and I just want to know if this set-up is correct? 

Maybe someone can post a cut-away picture from the BBB.  The exploded diagrams in the tech manual are not detailed enough.

Large