Author Topic: Draining and cleaning the cooling system 6.9  (Read 441 times)

Jan S

  • Classic
  • **
  • Posts: 102
  • W116 Enthusiast
  • Location: Norway
Re: Draining and cleaning the cooling system 6.9
« Reply #15 on: 10 October 2021, 01:48 PM »
Thanks for comments/advice, nathan and UTn_boy!

I'm currently undecided wether to open the bolts or not. We'll see .....

I'm in the process of finding/buying a few aging hoses. The coming week I will buy the Comma Xstream G48 coolant (spec according to MB 325.0).  And I need to find some citric acid, should be easy .....

I will do the job when all hoses have arrived.
1975-mod W116 450 SE with 6.9 engine

Jan S

  • Classic
  • **
  • Posts: 102
  • W116 Enthusiast
  • Location: Norway
Re: Draining and cleaning the cooling system 6.9
« Reply #16 on: 10 October 2021, 03:56 PM »
Good luck with the hoses. You will find that you have to cut them from generic hoses.
That water gurgling sound you hear is air in the system.
Ive just done a complete overhaul of my cooling system:
you will  find it is a weeping hose somewhere. Its quite a job replacing hoses ...in addition to making them,,..new clamps/thermostat out and checked/AAV  etc.

There is something very screwy with the hoses for these tubs,. My spare parts manual hardly goes near them..and when it does it has no part no but a no of xxx?
When I contacted Tom H at MBCC he said they only had one of them and no picture?!!...so I took it sight unseen and I reckon it is the one that goes from the back of the head to the heater valve.

Will the new coolant mix up well with the clean water trapped in the block and the heater? I hope everything will circulate and mix well as soon as I start the engine?

Is there an easy way to get rid of the gurgling under the dash? As you mentioned, Randys01, probably trapped air somewhere .....
1975-mod W116 450 SE with 6.9 engine

ptashek

  • W116 Addict
  • ****
  • Posts: 2,193
  • W116 owner
  • Location: Ireland
    • History of ZV9485
Re: Draining and cleaning the cooling system 6.9
« Reply #17 on: 10 October 2021, 11:40 PM »
Quote from: Jan S
Will the new coolant mix up well with the clean water trapped in the block and the heater? I hope everything will circulate and mix well as soon as I start the engine?

Yes, the water pump will mix it all in no time.

Quote
Is there an easy way to get rid of the gurgling under the dash? As you mentioned, Randys01, probably trapped air somewhere .....

Set heating to max, and let the engine warm-up so that the thermostat opens fully. The system should bleed itself. Keep an eye on coolant levels for a few days, and top-up as needed.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

Jan S

  • Classic
  • **
  • Posts: 102
  • W116 Enthusiast
  • Location: Norway
Re: Draining and cleaning the cooling system 6.9
« Reply #18 on: 11 October 2021, 11:52 AM »
Thanks, ptashek!

Another question for you all:

the cooling water hose from the bottom of the reservoir tank to the bottom of the radiator (A 116 500 0175) is no longer available. I need to find a standard hose and improvise.

However, the specs seems odd (measured and/or estimated without removing the hose):
inner diameter at radiator = 18 mm / outer diameter at radiator = 26-27 mm
inner diameter at reservoir = 26 mm (estimated given the wall thickness)/ outer diameter at reservoir = 34 mm

The inner diameter at the reservoir seems to be 8 mm larger than at the radiator? See pic.

Have the previous owner force fitted the 18 mm hose onto the tank which is 26 mm?

Or what could be at play here?
1975-mod W116 450 SE with 6.9 engine

rumb

  • W116 Addict
  • ****
  • Posts: 1,738
  • MB Enthusiast
  • Location: Fort Collins, Colorado
Re: Draining and cleaning the cooling system 6.9
« Reply #19 on: 11 October 2021, 04:42 PM »
The original 116 pn tank has a smaller pipe on it. The newer 126 pn tank has a larger pipe.

If you get a new tank then use the smaller diameter hose from radiator to tank.  Then put a short piece of larger hose at the end of the hose and clamp one end to the tanks and slide the other end over the smaller hose and clamp it all together with 2 clamps. You may need a @3/4 short piece of copper pipe to put in there to clamp against.

The W126 hose is large at the end like in your picture.  I dont know if it's completely compatible.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Jan S

  • Classic
  • **
  • Posts: 102
  • W116 Enthusiast
  • Location: Norway
Re: Draining and cleaning the cooling system 6.9
« Reply #20 on: 12 October 2021, 02:05 AM »
So I have a W126 tank  :'(

Thanks for the solution, rumb!
1975-mod W116 450 SE with 6.9 engine