Heater Valve o-ring replacement

[George Davis]

I did this the other day, thought I'd post on it:

The heater valve lives under the approx. 3 inch black rubber plug on the bulkhead.

Parts needed: heater valve o-ring (more on that later).
Tools needed: flat screw driver; long needle-nose pliers; magnet can be very handy; pliers; small flat screwdriver; paper and marking pen.  Sketching and marking are important.

This is a quick, easy job if things aren't stuck, but be patient and DON'T DROP ANYTHING.
There is no need to drain any coolant.
Remove rubber plug.
Remove small screw and washer (magnet is useful); don't drop!
Note orientation of control lever on your sketch.
Pull off control lever and move aside.
Sketch the position of the little metal piece below the control arm (I call this the "travel limiter").
Put a mark on the travel limiter to show which way is up.
Pry or use long needle nose pliers to pull travel limiter upward and off the square section, then slide it out of the slot.  DON'T DROP IT.
Mark the top of the valve and show the orientation of the mark on your sketch.  This is to help get the valve back in the right way around.

The attached photo shows the heater valve with the control arm off.  If you look carefully, the travel limiter is visible, pointing to about 4 o'clock.

Grip the square section with pliers, not too tight, and see if the valve turns easily.  If it does, you can probably pull it straight out easily.  If it won't move or pull out easily, there are other methods that others have come up with, such as running in a screw and pulling or prying up on the screw.  Go easy with the pliers, it may be possible to damage or distort the square section.  Screw threads are 4 x 0.7 mm.

Remove old o-ring, clean valve body (but don't wipe off your marks!), install new o-ring and reinstall valve.  Installation is reverse of removal.  You might want to use some kind of grease on the o-ring, up to you (I didn't).

The o-ring:  I have ordered o-rings twice from one supplier, and gotten two different sizes.  Both sealed well, but the first was thinner than the second, and allowed easy movement of the heater control.  The second was thicker, harder to reinstall the valve, and it was very hard to move the heater control even with some grease on it.  I assume this hard movement would eventually cause the control to break, so I was not happy with it.  As far as I can tell, the second very tight o-ring was a US size, 1/2 inch ID, 1/8 inch thick, and 3/4 inch OD.  I believe the first o-ring was 1/2 inch ID, 3/32 inch thick, and 11/16 OD.


This time I used a 1/2 inch ID, 3/32 inch thick, 11/16 OD size, which I got at a hardware store.  When installed on the valve, this size 0-ring is only about 0.010 inch larger than the inside diameter of the valve, but it seems to be enough.   After installation I ran the engine up to temp and there was no leakage.  Note that this is not a recommendation to use the same size, your results may vary, etc. etc., it's just what I used.  If anyone gets an o-ring from an MB dealer, please post the dimensions (assuming it's metric).

Hope this is somewhat useful.


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George Davis
'69 280 SL Euro manual

[ted280sl]

George,
  Your description of the job is quite comprehensive. I replaced the "O" ring using this method once. I was back in there on another occassion and I removed the hood cowl. The hood cowl is easy to remove. Three screws on the front of the chrome. Two on the outside back of the cowl. Four screws on the back inside of the cowl which I need to be loosened. That allows for the cowl to be removed. There is the heater access flap. It is held on by four bolts. The flap can the be removed and the air cleaner. Now you have great access to the heater core valve and the linkage.
I hope this information is helpful.
Ted

[hands_aus]

The O-Ring I used was a BS (British Standard) No. 112 and was about 20 cents from a bearing shop.
I lubed it with a smear of high temp grease.

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[A Dalton]

A #112 and a 1/2 ID X 3/32 cross section "O" ring are both the same
and are correct replacement for the valve.

[George Davis]

Arthur, thanks, good to know I used the right o-ring.

Perhaps the main message here, aside from the procedure, is to watch out for the 1/2 inch ID by 1/8 inch thick o-rings, which some vendors might be supplying.  They make the valve very hard to move.



George Davis
'69 280 SL Euro manual

[hughet]

Thanks for the post, George. It got me fired up to fix my heater with winter coming. I had resigned myself to thinking that I would have to pull the heater core out to get the valve unstuck, but after reading your instructions I decided to try it again through the access port.
When I tried to remove the valve it wouldn't budge and I was afraid that too much force would break the neck of the heater core so I made a "puller" out of a 3 inch 4mm screw nut and washer and a 19mm deep socket. With the screw in the heater valve I was able to pull the valve up into the socket by turning the nut. It worked great.
I used a 2 stone brake cylinder hone for a light clean up on the valve body and put it back together. Now it turns like new.

Tom Hughes
St. Louis

[gugel]

I was told by one parts supplier that the heater valve is supposed to have two O-rings -- one with a round cross section at the top, and one with a square cross section at the bottom.  I notice the valve core does have a groove right at the bottom which looks like it could accept an O-ring.

Has anyone heard of this?  Is it true that the valve originally had two O-rings?

Chris Earnest

[hands_aus]

There was only one O-ring on my heater valve.  
So on here or yahoo I asked that question after removing my heater valve.
I was told back then that there was only one O-ring and that is all I have installed.
It works just fine.... for now.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[A Dalton]

One O ring ...
 The info on this type of stuff has been taken out of the BBB reprints , [ We call it the LBB -Little Big Book], but if one has the Original Factory ones , you can still find these jobs..
 They took out too many, far as I am concerned....
 * Note the removal tool..

 http://members.aol.com/ajdalton7/arthur1.jpg

[gugel]

Arthur, thanks for the excerpt from the original Factory BBB -- it really is a clear description.

As it turns out, when I was replacing the heater valve O-ring from above, I managed to push down too hard on the valve and lose it down into the core tank.  (Who knew expert German engineers wouldn't have put a lip on the bottom of the housing tube ?!?).  After I got done cussing, I pretty much decided there was no choice but to spend a few days removing the heater core and taking it apart to get the valve back.  But then I found your old posting under this topic:

http://sl113.org/forums/index.php?topic=2323,valve

describing how you did the same thing but then were able to retrieve the valve.  Your description not only showed it was possible, which I wouldn't have believed, but also included the essential idea of hooking the valve at the bottom and pulling it back up through the valve housing upside down, which I hadn't thought of.

So, using essentially the same method, I did manage to retrieve the valve!!!  

I hooked it with a wire hook made from a thin coat hangar, aligned it with the housing with the help of a pick along with the hook, and wedged it slightly into the bottom of the housing (don't ask how many tries it took).  Then I found the perfect tool to grab it from the inside and pull it up through the tube -- a VW distributor drive gear puller.  Many thanks, Arthur!

Chris Earnest

[A Dalton]

C,
 Very cool..
 I am glad I went ahead and posted the procedure.I figured someone else would have the same problem .. seeing , as you say, there is no lip on the bottom.
 The trick [ as I/we now know] is to put someting into the valve from the hose connector pipe so that the valve body can't drop..
 Antway... Welcome to the Fools Club !!!

"Experience keeps a dear school that fools will learn in no other "
B. Franklin.....

[ctaylor738]

This post was a great help to me in pulling out my heater control valve but I thought I would add my experience and solution.  My valve had two problems.  The ball and socket on the linkage were rusted together, requiring a little PB Blaster, and the valve was completely siezed and stuck in the housing.  

I little "square" on the valve should be left alone - I sheared one off on a 114 trying to turn it.  My solution was to put the screw back in and rig up a lever arrangment with vise grips on the screw and a large screwdriver.  See picture (re-enactment) for details,  Even with this, and after soaking with Blaster, it took a lot of force to get the valve out.

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Chuck Taylor
1970 280SL #14076
Falls Church VA

[waltklatt]

Chuck,
Luckily the valve body insert didnt get mauled by the pliers.
Next time and for everyone removing the valve to replace the ring.  Please use an old spark plug and thread the tiny end into the valve and then that will give you leverage to remove it easily.  The threading on the spark plug is exactly the same as the thread for the valve.
That will prevent any further damage to the valves.
My .02 cents worth.
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

[George Des]

Key is to not let the valve drop into the matrix. (Looks like no one went to the office today by the posts this morning by Alan, Walt, Chuck and me!!)

George Des

[ctaylor738]

Walt -

The insert was un-touched.  That's the point.  The screw goes back in the insert, and the pliers go on the SCREW, not the insert.

CT

Chuck Taylor
1970 280SL #14076
Falls Church VA

[hands_aus]

3 years ago I broke off the spark plug thread in the valve while the valve was still in the valve housing.
I had to use a small 1/16" drill to put a hole in the remaining part in the valve.
A friend who was a manufacturing jeweller had some left hand twist drills that I used as very small ezy-outs.
The broken screw part wound out very easily.
I then bought a 50mm high tensile 5? mm bolt and prised it out like Chuck did.

As an aside...I don't know whether twist drill in the USA are Left hand or right Hand but in Australia they are Right hand. Left hand drills are almost impossible to buy.
I tried using normal ezy-outs but even the smallest was too big.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Longtooth]

The 'dropped' valve potential cannot be over emphasized enough.  I also had to retrieve mine (coat hanger wire and a lot of patience and retrying).... a 2 hr affair trying one's patience to the degree nobody should have to endure.  I think I wrote up the method I used on this forum at one time.  There's actually a pretty easy trick to getting it hooked and up out of the hole... I forgot the approach used but after i figured it out I spent 15 minutes getting it out.... that was after 2 hrs or more of trial & error spent unsuccessfully trying.

Also, I happened to have a long screw with the right thread and pitch so when putting things back in (finally) I used this screw.... into the tapped hole in the valve body. I recommend a trip to your local hardware store to find a good long screw (2" approx) with the correct thread pitch BEFORE any effort's applied to remove the valve.  You've no idea how easily it might slip and fall free down into the abyss until AFTER the fact..... worst case is when you've finally freed it up, breath a sigh of satisfaction with your mechanical aptitude and skill.... then finally go to pull it out and just the slightest push while trying to grap it with the needle-nose pliers.... and bye-bye valve!

I was also advised by an MB mechanic to hone the inside of the barrel just a tad before reinstalling.  I honed the bore for about 10 seconds (I just happened to have my Dad's little hone that I hadn't figured out what on earth I'd ever use it for, but kept in my "instruments" drawer just in case I ever found a need).

I used plumber's valve grease for lubrication.

The previously provided advice on physically marking (scribing)locations (orientations) of valve body and sketching the lever orientations will prevent an installation of things that doesn't work to open the valve when it's supposed to be open, or close it when it's supposed to closed... so I heartily second the advice given.

Let me add some sage additional advice... stuff rags around the entire opening under the rubber plug.... so that WHEN (not so much an IF) you drop something, it won't go down into the heater core that requires a major dissassembly inside the car.  This was the primary and most emphasized advice the mechanic gave me before I started.  ... 'cause one slip, and away it goes.... not to be retrieved by coat-hanger wires like the valve body can be retrieved inside the tank under the valve bore hole.

For such a simple little thing like freeing up a stuck valve body or replacing the o-ring, this little 'simple' and straight forward 20 minute job (end to end) is deceivingly full of not so simple issues that can stretch the job into hours... not to mention trying the patience of the best of men to the breaking point.

So the instructions can be modified slightly and simply to:

1. remove rubber plug

2. stuff rags around the valve opening area under the plug hole so that NOTHING can fall down into the heater core... 'cause sure as sh...it it will... Murphy always lurks most when the job's a "simple" one.

3. Go to hardware store and buy a 2" long screw with the correct thread size and pitch to eventually screw into the tapped hole in the valve body... when you get to that point later in the procedure... preferrably with a nice large head on it.

4. NOW and ONLY NOW you can proceed with the rest of the procedure already provided in George's opening post.

5. Instead of grasping the valve square top of the valve body with needle nose pliers, carefully screw the long 2" screw (see instruction #3 above) into the tapped hole in the top... holding onto the screw no matter what... I actually advice tying the screw to a strong string that hangs outside the opening hole (the one plugged by the 3" diameter rubber plug) far enough so that no matter what else happens, the screw will be retrieved... and if it's screwed into the valve body then the valve can always be retrieved as well.

6. When reinstalling the valve body with the new 0-ring, use the screw screwed into the valve body... with string attached to the screw as admonished above.... and push down on the screw to push the valve / O-ring into the bore.... and hang onto the screw!

7. Remove the 2" long helper screw, replace the lever over the square end of the valve body ... BUT DON'T try to "fit" the lever square hole over the square on the valve body... just get the square hole in the lever aligned vertically over the tapped hole in the valve body.... THEN IMMEDIATELY re-install the long helper screw back into the valve body hole. THEN, and ONLY THEN fit the lever's square hole over the square shoulders of the valve body... holding onto the helper screw.

8. Now make the final adjustments to angles and orientations, and THEN, when everything's properly aligned, carefully unscrew th helper screw and install the little retention screw that holds the lever to the valve body.... don't push! down!... just let the little screw's threads get engaged with the tapped hole threads and give it a couple of turns to insure it's well engaged... now the valve can't drop thru (since the lever's holding it from going down).  Then finish screwing in the retainer screw and torque down.

See how easy that is?.... no sweat, no potential for having to spend hours fishing valve body's from the tank... or disassembling the heater core inside the car and reassembling it.... just a few well placed rags and a little 2" long properly threaded and pitched screw.

BTW, the magnet wand can be used to fish the dropped washer and little screw from the folds of the rags you placed around the opening.... beats trying to do this by removing the rag and letting the washer, or little screw, or whatever fall into the abyss while removing the rag(s) to retrieve from the inner folds.

On the other hand, we learn best by making our own mistakes... so give it a shot without my modified instructions.  Once bit.... etc.

Longtooth
67 250SL US #113-043-10-002163
'02 SL500 Sport

[merrill]

so, here is a follow on question.

i am trying to replace the rubber grommets or covers for where the heater tubes go thru the firewall.

on my car the tubes are not centered in the holes, rather they are low so it is impossible to get the new grommets installed.
is there any way to raise the heater core up so the tubes are centered in the holes in the fire wall?  

better yet, can this be done with out tearing most of the car apart?

thanks
matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[al_lieffring]

quote:Originally posted by merrill

so, here is a follow on question.

i am trying to replace the rubber grommets or covers for where the heater tubes go thru the firewall.

on my car the tubes are not centered in the holes, rather they are low so it is impossible to get the new grommets installed.
is there any way to raise the heater core up so the tubes are centered in the holes in the fire wall?  

better yet, can this be done with out tearing most of the car apart?

thanks
matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

Matt

When I set out to free up the stuck heater valve in my 66 I found the heater core was drooping down. It turned out that the brackets that bolt the heater core to the cowl had come loose and needed to be soldered back onto the core.
When I pulled it out I found the metal plate had come off the bottom of the core also.

al

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[TheEngineer]

Did my heater valve yesterday. It wasn't turning off. That worked against the airconditioning. Found the control lever bent, but also found the round rubber cover should really be replaced. Does anyone have a part number for it, or a source please?

[Douglas]

Gernold at SLTechW113.com stocks the correct rubber plug.

Douglas Kim
New York
USA

[66andBlue]

quote:Originally posted by theengineer

.. but also found the round rubber cover should really be replaced. Does anyone have a part number for it, or a source please?

Hello Engineer,
cannot find an M-B part number but SLS sells it for 4 Euro.
See: Group nr. 83 Heater System, part nr. 22. http://www.sls-hh-catalogue.de/bin/dbframes.phtml?mid=IN02


Alfred
1966 blue 230SL automatic

[Naj ✝︎]

quote:Originally posted by theengineer

 also found the round rubber cover should really be replaced. Does anyone have a part number for it, or a source please?

A 113 987 2444 is still a good number but in the past has been superceded and I got what looked like a poster tube end-cap. It was not even the right size - bit too small [!]

So, Good Luck...

naj

68 280SL

[KUMARB]

I am reinstalling my heater coil and just read this thread on o-ring replacement. The thread gave me some valuable information. There were a couple of questions in the thread which appear to be still unanswered. That's why I am posting this reply hoping it might help others.

(1) I bought my o-ring from a local Mercedes Benz dealer, Brumo's Motors. Its part number is 000 835 58 98 and cost me a couple of dollars. Dimensions of the ring are approximately 2.91mm ring dia.x17.79mm OD11.97mm ID.

(2) The rubber cap (2" dia rubber cover for heater valve access hole on the top of the firewall) was not available at the dealership. Therefore, I bought it from Miller's for $7.00. It does not appear to be of the same quality as the original one.

Thanks,

[KUMARB]

I am reinstalling my heater coil and just read this thread on o-ring replacement. The thread gave me some very valuable information. There were a couple of questions in the thread which appear to be still unanswered. That's why I am posting this reply hoping it might help others.

(1) I bought the o-ring from a local Mercedes Benz dealer, Brumo's Motors. Its part number is 000 835 58 98 and cost me a couple of dollars. Dimensions of the ring are approximately 2.91mm ring dia.x17.79mm ODx11.97mm ID.

(2) The rubber cap (2" dia rubber cover for heater valve access hole on the top of the firewall) was not available at the dealership. Therefore, I bought it from Miller's for $7.00. It does not appear to be of the same quality as the original one.

Thanks,

[KUMARB]

I want to append my reply. I measured the dimensions of the rubber o-ring with a digital caliper. Rubber is hard to measure, it gets easily squeezed and dimensions changed. I think the nominal dimensions of the o-ring should be 3mm ring dia x 18mm ODx 12mm ID.

If you are buying a non-OE o-ring, just make it to match above dimensions.

Thanks.

[scoot]

quote:Originally posted by KUMARB

 

If you are buying a non-OE o-ring, just make it to match above dimensions.

Considering what a pain in the ass it is to do this, just buy the one from MB and spend the extra $2....

[wwheeler]

I think the point is to be sure to buy a metric o-ring. The o-ring cross section should be 3MM which is .118. 3/32" is (.094) and 1/8" is(.125). The o-rings you buy at a hardware store will be US standard and will not be metric. The 3/32" could leak and the 1/8" size is too tight.

NOTE: All o-rings are slightly thicker in the cross section than the nominal size to allow for sealing.

[rmmchl]

you had better tie dental floss to that 4mm bolt when you are trying to pull the valve out---------------I dropped mine in and had to take the heater core out and all of the dash to get it out-If this very tragic thing happens-you might as well have the core cleaned , checked , and soldered at a good radiator shop

[KUMARB]

I just replaced the rubber o-ring. I had the heater core out, cleaned and pressure-tested.

I cleaned the valve cock, fitted o-ring and lubricated it. Then, I inserted it into the valve body. I pushed it in a little hard, it went all the way inside the valve body. If I had pushed the cock in any harder, it surely would have fallen into the core body making its retrieval almost impossible. Fortunately, I had a long 4mm bolt screwed on the cock. What surprised me is there is nothing to stop the cock from falling into the core body until you attach the metal cover plate (metal piece with a stop ear tab and a square hole in the center) to the cock.

Attaching a 4mm bolt is a great idea. Also, do not push the cock too hard, just enough so that the top of the cock in just below the slot cut in the valve body so the metal cover plate can be installed.

Thanks,
 

[Benz Dr.]

Pretty simple way to avoid moving the heater tap down into the core. I use a spark plug which threads into the tap and gives a nice handle to pull up or push down.
Always move the tap down just a little if it's stuck and then pull it back up until it starts to move. Since both pieces are brass they will sieze up but not usually so tight that you can't free them up. The tap should be polished to a smooth finish and high temp grease applied before you insert it into the core. Work the tap back and forth, up and down until it moves freely ( using the spark plug ) before you set the idex and the limiter.. If it doesn't move with little more than finger pressure it's too tight and things will break over time.
There's a small piece of linkage in there that looks like throttle parts that you should lube well along with all the cables. I never even think about doing this job unless I pull the air scoop and flapper at the base of the windshield. ALL of the pieces have to move freely or you're just fooling yourself.
After you get it moving you should move all of the levers at least once a month to keep them working freely.

[hands_aus]

I tried the spark plug trick.
The threaded section broke off in the valve body while it was in the heater unit.
I had to drill the centre of the broken thread out... that was a trick.
Then when I tried using an easy out even the smallest tool was too big.
My friend who is a retired manufacturing jeweller had a series of left hand twist drills.
I inserted a small one into a tap piece and manually tried again.
The drill bit into the broken threaded spark plug and came out very easily.

After that I bought a high tensile steel bolt which did the job very nicely.

[Benz Dr.]

Did you use a Bosch spark plug? Not sure how you could break off the end of the plug in there but I've not really considered this to be a possibility.
I make sure it's moving before I use the spark plug trick. It's it's siezed up tightly then you would need to get it moving first. The spark plug is more for placement and less for using as a pry bar.