heater hose - '87 300E
 

So I ordered the molded heater hose from 'Phil' that goes between the back end of the engine into the heater core (driver's side). Removed the air filter and oil filter to get the best access. Lighly sanded/cleaned the barb to remove any deposits, pushed the hose all the way onto the barb/nipple (I thought), tightened the hose clamps securely, installed new oil and air filter filters then fired up the engine. It leaks now worse than ever!

Is it possible that the barb/nipple is loose and leaking in the head or is there some magic trick to installing a simple heater hose on a Mercedes!!!

Look closely at the end the hose connects to on the engine, two 6mm allen bolts hold the lifting eye bracket on- there is a o-ring on the other end of that bracket inside the head thats probably the source of your leak.

Thanks John. I will take a closer look tomorrow but don't like the sound of that 'inside the head'! Does the head have to be removed to replace that 'o'ring?

Finally got a close look at that back engine lifting bracket...it seems the heater hose barb/nipple is spot welded to the bracket. Because it is so close to the firewall, I can't get the bracket off with regular Allen wrenches so I need to get some hex bits. My guess is that John is right and I need to replace that 'o' ring...the bracket has water/antifreeze stains on it so it looks like the leak is coming from there. Does anyone know the size of the 'o'ring and is it something i can pick from Lowes/Home Depot, or do i have to drive across town to the Mercedes dealership?

So the MB parts department at Tysinger's in Newport News couldn't locate that 'o'ring on their computer...I knew i was in trouble when they didn't know what a lifting eye was. The parts man was insistant that the rubber heater hose I got from 'Phil' and just installed was a metal line...

Anyway, he sold me a $2 'o'ring but i think it was just to get rid of me! I also got a 6mm hex bit so i am hoping to get the lifting bracket off today. Anybody know how or where that 'o'ring is supposed to be installed...it is leaking so badly that i'm guessing the old one has totally disintegrated?

Not sure if anyone has had this problem before but anyway, maybe someone will get something out of this.

When i got that lifting bracket off, sure enough there was the remains of what was probably an o-ring. It was hard and brittle and snapped when i was removing it so it's likely the original.

Ran the car with the heat on max for 10 minutes and no leaks yet (no heat either but it will probably take a while to get all the air out of the system). So that was hopefully the problem...fixed for $2.10!!!

Many thanks to John who pointed me in the right direction but beware, seems like MB doesn't show this o-ring in their parts department's computers.

I just read your post...
 

I had the same problem on my car. One of the pros in this site sent me in the right direction. It has been a few years since I replace the O-ring but, it was one of the cheapest repairs I have done on the benzo...