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.

Simpler=Better · #8 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 · #9 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!

eatont9999 · #10 11-08-2013, 10:25 PM

Quote:

Originally Posted by Adriel

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!

I'm not sure where the hose goes but UGH, that is nasty! You might want to look into a citric acid flush. If that build up is in the hose, you can bet it is all throughout the cooling system.

Adriel · #11 11-08-2013, 10:45 PM

Quote:

Originally Posted by eatont9999

I'm not sure where the hose goes but UGH, that is nasty! You might want to look into a citric acid flush. If that build up is in the hose, you can bet it is all throughout the cooling system.

Eaton, thank you so very much for trying!

Did you see all the rust in the pipes? I thought the P.O. was right in using standard green, but apparently diesels need a special coolant to handle corrosion and hot spots caused by a compression engine. So will be switching to Zerex diesel formula, which isn't the same as what folks are using on here.

Before I make the switch, that is why I wanted to do Zerex Super Cleaner and Zerex Super Flush. figure to pull a hose or two and see if they made any difference. Should have per this: If you ever need to flush your coolant system... [Archive] - Massdriven Automotive Forums

Adriel · #12 11-08-2013, 11:13 PM

I found a good deal for the Zerex and as it turned out, form the came company I got the rubber from! Duh! Well at least I found out before going with another!

So should be on its way on Monday.

eatont9999 · #13 11-08-2013, 11:55 PM

Quote:

Originally Posted by Adriel

Eaton, thank you so very much for trying!

Did you see all the rust in the pipes? I thought the P.O. was right in using standard green, but apparently diesels need a special coolant to handle corrosion and hot spots caused by a compression engine. So will be switching to Zerex diesel formula, which isn't the same as what folks are using on here.

Before I make the switch, that is why I wanted to do Zerex Super Cleaner and Zerex Super Flush. figure to pull a hose or two and see if they made any difference. Should have per this: If you ever need to flush your coolant system... [Archive] - Massdriven Automotive Forums

In my grey 300SD, someone used straight water for apparently a long time. The corrosion was a concern. The coolant is still muddy brown even after several citric flushes. My case is an extreme example of neglect.

You can buy the citric flush from MB, or you can get it from ebay, etc for a lot less. It is simple citric acid in a dry form. It can be bought at health food stores as well. food grade or not, it does not matter. The acid chemically dissolves the rust deposits and other build up. Citric acid is environmentally friendly, so feel free to dump out the used fluid anywhere convenient.

De-oil the system first by running detergent like Shout through the coolant system. Run this for a day or so. Flush with clean water a few times, then mix and add the citric acid. Run that for a day, flush several times with fresh water. The last flush or two should be distilled water. Add 2 gallons of Zerex G05 and top off the rest with distilled water. Put the final coolant charge in only after you have replaced any hoses or other components.

Be warned that if you have any major corrosion problems, you could reveal a leak. If your heater core is questionable, you may not be able to use this method of clearing up your coolant system. If such is the case, you are soon to have problems anyway; as in corrosion holding your coolant system together. Most people do not have a problem, though.