Heater Valve o-ring replacement

[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.