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Garage => Mechanicals => Topic started by: Punker on 29 June 2020, 05:01 AM

Title: 6.9 creeping coolant loss
Post by: Punker on 29 June 2020, 05:01 AM
Hi guys,

as reported I changed the radiator hoses and the thermostat on my 6.9. Unfortunately I am now losing cooling water. About 1.5 liters per 100 kilometers. Pretty stupid. I haven't found a leak although I suspected the control of the automatic air conditioning (it's always a bit wet there).

Does anybody have a tip how I can proceed to find the leak?

Thanks for your tips on this annoying topic
Bjorn

Title: Re: 6.9 creeping coolant loss
Post by: raueda1 on 29 June 2020, 09:47 AM
If your leak just started when you changed hoses I doubt it's a coincidence.  Clamps need to be surprisingly tight or they absolutely will seep.  Loosen, wiggle the hose around to reseat and retighten.

Other than that?  Leaking heater core or heater hoses?  I had a kind of always-wet floor situation and that's what it turned out to be.  OTOH, 1.5L/100km is a lot, mine was much smaller.  Still, worth exploring.
Title: Re: 6.9 creeping coolant loss
Post by: daantjie on 29 June 2020, 11:22 AM
Maybe also replace the radiator cap, they are super cheap.
Title: Re: 6.9 creeping coolant loss
Post by: Punker on 29 June 2020, 02:36 PM
many thanks for your tips . I have already replaced the radiator cap. I will check the hoses. Is it actually possible to remove the control unit for the automatic air conditioning and kill the connected hoses?

Plan a longer tour to Berlin in 2 weeks. Then I can't lose that much water.

Greetings
Björn
Title: Re: 6.9 creeping coolant loss
Post by: raueda1 on 29 June 2020, 06:54 PM
Quote from: Punker on 29 June 2020, 02:36 PM
many thanks for your tips . I have already replaced the radiator cap. I will check the hoses. Is it actually possible to remove the control unit for the automatic air conditioning and kill the connected hoses?

Plan a longer tour to Berlin in 2 weeks. Then I can't lose that much water.  Greetings
Björn
Can you clarify?  AC doesn't interact with the cooling system at all.
Title: Re: 6.9 creeping coolant loss
Post by: Jed on 29 June 2020, 09:52 PM
I think he is referring to the heater servo for the ACC...yes that can definitely leak.....
Title: Re: 6.9 creeping coolant loss
Post by: revilla on 30 June 2020, 06:44 AM
Yes, 1.5 litters/100 Km is a lot!
But coolant liquids are made to leave a white trace once dry. So it should be easy to identify the leaking spot.
If you suspect the acc servo, yes, you can isolate it (by-pass) for your trip. There was a recent post about it. I'll try to find it.
Better to find the leaking point(s) and fix rather than the frustrating path of changing parts left and right in a trail and error approach. That can be expensive and you might find yourself chasing shooting stars. Not good.
Cheers
Title: Re: 6.9 creeping coolant loss
Post by: revilla on 30 June 2020, 06:50 AM
Found it.

https://forum.w116.org/mechanicals/ac-nightmare/msg146314/#msg146314

If you need details on how to perform the bypass let us know.

Title: Re: 6.9 creeping coolant loss
Post by: Punker on 30 June 2020, 01:40 PM
Many thanks for the recommendations. In the next few days I will have time to tackle the problem with your recommendations. I'll keep you informed.
Many greetings
Bjorn
Title: Re: 6.9 creeping coolant loss
Post by: PosedgeClk on 30 June 2020, 09:05 PM
I am surprised that no one has suggested the fluorescent dye. There are fairly inexpensive kits whereby you purchase a dye and a UV illuminator and trace down the leak shortly after running the dye through the system.
Title: Re: 6.9 creeping coolant loss
Post by: Randys01 on 01 July 2020, 03:01 AM
how about a little look into the motor?
Title: Re: 6.9 creeping coolant loss
Post by: Trapo on 09 July 2020, 05:00 AM
Quote from: Randys01 on 01 July 2020, 03:01 AM
how about a little look into the motor?

Randy's suggestion is sound.  I found coolant dripping into the oil pan through a hole behind the water pump. If your oil measuring stick comes out "mayonnaise" color as Randy called, you found your leak.