Heater Hose Routing and Flow - PeachParts Mercedes-Benz Forum

Adriel · #1 11-06-2013, 12:14 AM

A long while back, went to a "D.Y.I." shop to see about addressing the bad monovalve. Well, they wouldn't let me see what they were doing and to top it off, stole my special hose vise grip! So I understand and recall from this Coolant hose in the way of Oil Filter Housing the hose attached to the block goes to the upper heater tube? Then how does the U shaped piece fit in?

Can anyone explain how the coolant travels? I recall somewhere seeing something, but alas, can't find it...

Thank you all in advance!

Zacharias · #2 11-06-2013, 01:30 AM

The heater hose coming out of the firewall into the head is returning coolant from the heater core back to the motor.

You refer to the "U shaped hose" if you mean you are looking at the Mercedes parts diagram, they show a U shaped hose but their parts diagrams are representative, not necessarily accurate. They in fact list six part numbers for that hose, dependent on model, and they are all different. (I happen to be shopping for one, so I know this.)

Many cars no longer have the factory hose and just have a generic length of hose installed there, or have the incorrect part number installed -- as is the case with my 300td -- and it's a royal pain to work around it.

You don't need a hose clamp to replace the element in the monovalve. You will get some minor spillage but that is normal.

rscurtis · #3 11-06-2013, 09:53 AM

The heater hose coming out of the firewall into the head is returning coolant from the heater core back to the motor.

I think you have that reversed- the hose on the head is the hot supply to the heater core. The mono valve is on the return side, as is the auxiliary water pump.

Adriel · #4 11-06-2013, 12:29 PM

Thank you all for the help!

Somewhere I have a picture or pictures of the right side, so think I can figure that out. The left side I have nothing.

I have attached pictures of the hoses I have. As you can see I am talking about the hose on the left that makes a U-turn.

Sad to see N.L.A., but next time I see a 300D, will see if the heater hoses are any good.

Oh, and the reason I pulled the metal pipes was to make it easier to pull the anti-sway bar and they are rusty. Tried the apple cyder vinegar trick, but only made them more rusty... Will go back to what I know: phosphoric acid. Just wanted something enviromentally friendly, but alas, there isn't anything.

eatont9999 · #5 11-06-2013, 12:35 PM

Quote:

Originally Posted by Adriel

Thank you all for the help!

Somewhere I have a picture or pictures of the right side, so think I can figure that out. The left side I have nothing.

I have attached pictures of the hoses I have. As you can see I am talking about the hose on the left that makes a U-turn.

Sad to see N.L.A., but next time I see a 300D, will see if the heater hoses are any good.

Oh, and the reason I pulled the metal pipes was to make it easier to pull the anti-sway bar and they are rusty. Tried the apple cyder vinegar trick, but only made them more rusty... Will go back to what I know: phosphoric acid. Just wanted something enviromentally friendly, but alas, there isn't anything.

Take your old hose to some parts stores and see if you can match it up with a section from another hose and just cut out what you need. You will have to buy the whole hose, though.

Adriel · #6 11-06-2013, 12:45 PM

Quote:

Originally Posted by eatont9999

Take your old hose to some parts stores and see if you can match it up with a section from another hose and just cut out what you need. You will have to buy the whole hose, though.

Why do you all not understand?! Maybe need to make it bigger?

What I need to know is, do I have all the hoses? If I do, then where does the one coming out of the block go versus the U-turn hose?

rscurtis · #7 11-06-2013, 01:26 PM

The hose coming from the head feeds the steel pipe with the "Y" connection that feeds both sides of the heater core. The return exits the firewall just to the right of the driver's side cowl drain tube, and crosses behind the valve cover to the mono valve. Let me know if you need a picture.

Adriel · #8 11-06-2013, 01:55 PM

Quote:

Originally Posted by rscurtis

The hose coming from the head feeds the steel pipe with the "Y" connection that feeds both sides of the heater core. The return exits the firewall just to the right of the driver's side cowl drain tube, and crosses behind the valve cover to the mono valve. Let me know if you need a picture.

Pretty please!

Thank you so very much!

rscurtis · #9 11-06-2013, 02:45 PM

Here are your pictures:

Adriel · #10 11-06-2013, 02:54 PM

Quote:

Originally Posted by rscurtis

Here are your pictures:

Thank you so very much!

So now I see I have all the hoses. Next step will be check the pile of hose clamps I have from a trip long ago to the yard and see if I have enough, as doubt the clamp stayed on when the core was bypassed.

macdoe · #11 11-06-2013, 11:11 PM

I paid 65 bucks for that hose from the head to the firewall that runs along the oil filter tower lid.... talk about a hose job....

Adriel · #12 11-06-2013, 11:34 PM

Quote:

Originally Posted by macdoe

I paid 65 bucks for that hose from the head to the firewall that runs along the oil filter tower lid.... talk about a hose job....

Well darn that is a lot!

If it were me, I just might use standard strait and use the wire coils to bend around.

daw_two · #13 11-07-2013, 06:27 AM

Hey --- I've got a 78 300D that I'm parting out. I'll take a look at the hoses tonight if you shoot me a PM.

Simpler=Better · #14 11-07-2013, 10:01 AM

You can always get a longer piece of generic hose and go around the outside of the oil filter

Adriel · #15 11-08-2013, 08:51 PM

So made some time this evening to get something done and this is one.

I am finding a lot of this scale in the tubes, with this peice one of the worse. Should I be concerned? Is it still useable?

Also, where does it go?

Second, what hose goes between the lower pipe and the left heater core pipe? Hard to tell in the kindly provided pictures...

Thank you all in advance!