Has anyone done a citric acid cooling system flush?

[owner]

Has anyone done a citric acid cooling system flush on their T1N? I'm giving it serious thought.

Mines done over 400k km now, and its due new coolant. I don't have any real cooling issues, but I'd like to keep the cooling system in tip top condition, especially around the oil cooler.

Googling reveals that MB even sell a citric acid based coolant flush kit (not specifically for sprinter) and state the methodology and concentration. eg. http://dieselgiant.com/mercedes_citrus_flush.htm

So is it worth doing?

 

[Luc]

I can see the "theoretical" interest, but man, that's quite an involved procedure... Although I'Ve kept cars for longer than 10 years (and never really did coolant flushes), I've never had problems with the coolant system. I must be lazy/lucky? Interested in reading what more attentive people will say.

 

[lindenengineering]

Has anyone done a citric acid cooling system flush on their T1N? I'm giving it serious thought.

Mines done over 400k km now, and its due new coolant. I don't have any real cooling issues, but I'd like to keep the cooling system in tip top condition, especially around the oil cooler.

Googling reveals that MB even sell a citric acid based coolant flush kit (not specifically for sprinter) and state the methodology and concentration. eg. http://dieselgiant.com/mercedes_citrus_flush.htm

So is it worth doing?

Yes it is worth doing!
I offer the same and in some cases it can on gasoline (petrol) engines significantly reduce NOx output significantly on E failures. The purge out can shift collected sludge and deposits out of the block cooling jacket especially at the rear cylinder.

On the 5 banger diesel MB engine it will also clear that "hidden block transfer tube" which is pushed to the block top deck allowing coolant flow up from the block to head around #2 cylinder. The other area of partial seizure observed when an engine overheats.
Of course when an engine overheats and seizes due to neglect the block and head are "boiled out in a similar tanked solution to clear these deposits!
Its my shop policy on all engine rebuilds.
On the T1N sprinter its a bit hard on the alum radiator and the procedure might show up self sealed leaks or otherwise so be prepared to accept a radiator replacement prospect!
Good luck and if you do it let everyone know how much "marmite" solution comes out!
Dennis
Mechanic

 

[owner]

Luckily (or unluckily) I never got round to doing this, came close a couple of time, I have everything ready to go. But it turns out I already have some kind of headgasket leak or crack into the cooling system. So luckily I found that out before trying this method and blaming it for the damage. Unlucky in that I have a sick engine.

 

[owner]

Well now that the Chem-i-weld sealed whatever was causing my coolant problems (https://sprinter-source.com/forum/showthread.php?t=55824), I decided to do the citric acid flush. I like to live life on the edge what can I say....

1. I drained and ran through just tap water to flush out all the chem-i-weld now that it has done its job.

2. I ran through tap water with a scoop of frontloader washing machine detergent (low suds).

3. Straight tap water again.

4. Citric acid and tap water. 500g of citric acid powder dissolved in the water first. Run for 15 minutes at 2000rpm once operating temp is reached.

5. Straight tap water again.

6. 5l of MB coolant concentrate, and about 5l of de-ionised water.

In between each of these I drained at the radiator plug and also shoved the garden hose into one of the espar lines to pressure-flush lots of water through the system, allowing the flow out of the rad drain plug and out the radiator cap fitting and while running the engine at 2000rpm.

Some notes:
There wasn't as much crud as I was expecting, which I guess is a good thing? I got a half a handful of soft flakes of rust coloured gunk out (about 10mm-20mm long), and lots of small black hard flakey particles (maybe 2-5mm across), and the acid itself had changed colour from clear to deep yellow. It was really going to town on my system though. Once it gets up to temp it really starts to bubble away releasing some kind of gas at the radiator cap. Its almost like its boiling. Even after you shut down the engine, the bubbling continues as it eats away at stuff. Its kindof scary tbh.

So now I need to test/run for a week or so and check if the acid has eaten away the chem-i-weld repair (or has exposed other serious issues with my engine). If it has then I will drain and re-do the chem-i-weld process. I guess this shows how impressed I am in the chem-i-weld, it just worked so damn well that first time. But either way at least now I know my cooling system is sparkling clean inside. Even my radiator cap looks brand new just from having some of the solution splashed on it!

 

[220629]

"Mines done over 400k km now"

How many at the time of this flush?

... It was really going to town on my system though. Once it gets up to temp it really starts to bubble away releasing some kind of gas at the radiator cap. Its almost like its boiling. Even after you shut down the engine, the bubbling continues as it eats away at stuff. Its kindof scary tbh.

...

It does sound scary. Aluminum doesn't do well with acids. Lets hope some of the action was from mineral deposits. Is the tap water in your area hard?

Could you tell whether the black bits were plastic, rubber, or flocculants (clumped together soft bits from the chemical action)?

Keep us posted. Fingers crossed that your head sealant remains effective.

vic

 

[owner]

Shes done just on 430,000km now.

The black particles were hard. Some of them were magnetic. My guess is it was sediment that may have been trapped and was released by the acid.

Our tap water is very good and definitely not hard.

 

[owner]

Something I've noticed after a couple of days running...

Immediately after the flush the coolant temp is lower than it ever used to be. I use a permanent mounted OBD2 scanner for the past 5 years, so I am well used to seeing the normal coolant temp values to the nearest degree C in many, many conditions.

Around town it would always sit at 86 degrees (187F), rock solid. It would have occasional excursions up to 87C (189F) , and sometimes down to 85C (185F) on colder days.

On the freeway it could get as high as 88C (190F) if climbing a decent hill at speed and then you can hear the viscous fan kick in and it holds at 88C.

This is all in what I would call normal year round conditions which for Melbourne is usually between 10-30C (50-86F). But we do have occasional very hot days in summer, 46C (115F) is my PB of the past 10 years...

In the van the most I have ever seen was 102C (215F) which was on a very long run up steep hills on a 40C+ day (104F+) with AC going full blast. I really backed off at that point. Prior to that the most I saw was 96C (205F) stuck in a traffic jam on another 40C+ day with AC on full blast. I have an alarm come on on my OBD2 device to alert me if temps go above 95C (203F), so I know it has only been those 2 times.



After the flush I am now seeing 84C (183F) most of the time and 85C the rest of the time. I've never ever seen her drop to 84C before, ever. 85c has always been the lowest, and that is usually in ambient temps <20C. It was 25C here yesterday and the day before, where I was seeing the 84C more often than not.

It still jumps to 87 when loaded (but does so more rapidly) but then it very quickly drops back to 84/85 afterwards. Also if I idle and run the heater blower, the temp drops quite quickly down to 80. It never did any of this before.

I haven't tried her on the motorway yet. And no sign of pressure in the system yet so keep those fingers crossed for me.

I wonder if my thermostat has been damaged by the acid? or maybe its all just working more efficiently now? The warmup time seems about the same as before.

 

[lindenengineering]

Thanks for posting these observations!

I tend these days to use a BG flush product ( a convenience thing) if doing a normal cooling system service. When its engine rebuild time and the block is "tanked", the prep focus is to remove all the sludge and deposits that dwell behind the back cylinder and the jacket wall on high mileage units...
There is also a coolant transfer tube inside the block (removable) between #1 & 2 cylinders which get well choked up. It gets pulled put when a head is off for gasket job to judge how much "junk" is sat in the lower depths of the block.
This what seems like a minor appendage must be providing a vital additional flow of coolant from the lower jacket up into the head. Certainly on engines that have suffered extreme heat failure there is a tendency for the block to distort at #2 cylinder area crank cap. Often that means a line bore to recover it in some cases. (A bit of thermal & mechanical stress at work?)
In many cases a clean block and cooling system does perform similar to how you have described!
Two thumbs up mate!
Dennis

 

[owner]

Its been well over 2 weeks now since the citric acid flush, and I am pleased to report that my Chem-i-weld repair is still working 100%.

The citric acid flush has definitely changed my cooling system for the better. But I'm still not sure if it has done something to my thermostat or not. It still takes about the same time to warmup from cold, maybe very very slightly longer now. The main change is seeing 85C almost all of the time on the freeway. It used to be pretty much rock solid 86C at my normal cruising speed of 105kph GPS. So now it will only hit 86C if I am going up a slight hill. A longer/steeper hill will see 87C now, whereas before it would reach 88C (which is when the viscous fan kicks in).

The biggest difference now are the excursions below 85C. If I'm idling for more than 30s, it drops to 84C. This simply never ever happened before. And if i'm on overrun for more than about 10s at pretty much any speed, it will drop from 85C down to about 82C depending on how long the hill is. Then there is also the heater I mentioned earlier, if I run the dash heater blower with the engine at idle it will drop to 80C (and lower) pretty fast. Around town the temp is all over the 83-87C range depending on the load the engine has been under for the past 30s or so - Low 80's temps if predominantly on overrun, 84C if idling, 84/85C if cruising at constant speed on flat ground, and 86/87C if working hard.

I think the acid may have free'd up some junk buildup around my thermostat maybe? But either way doing the flush was like flipping a switch - from being solid 86C before the flush, to being the above.

Anyway its coming in to summer here now so I will just leave it for now and maybe revisit the thermostat after summer.

 

[wayne poulsen]

Hi Dennis

Is it the BG Universal Cooling System Cleaner that you refer?

https://www.bgprod.com.au/products/bg-universal-cooling-system-cleaner

Ta
Wayne Poulsen
Fremantle West Australia

 

[Tardis]

Yes it is worth doing!
I offer the same and in some cases it can on gasoline (petrol) engines significantly reduce NOx output significantly on E failures. The purge out can shift collected sludge and deposits out of the block cooling jacket especially at the rear cylinder.

On the 5 banger diesel MB engine it will also clear that "hidden block transfer tube" which is pushed to the block top deck allowing coolant flow up from the block to head around #2 cylinder. The other area of partial seizure observed when an engine overheats.
Of course when an engine overheats and seizes due to neglect the block and head are "boiled out in a similar tanked solution to clear these deposits!
Its my shop policy on all engine rebuilds.
On the T1N sprinter its a bit hard on the alum radiator and the procedure might show up self sealed leaks or otherwise so be prepared to accept a radiator replacement prospect!
Good luck and if you do it let everyone know how much "marmite" solution comes out!
Dennis
Mechanic

I have the head off on my engine. Is there a way to just acid clean the engine block to save damage to the radiator?

 

[Maine-coast]

So when you drain the coolant..you have buckets and drain the radiator..how do you get the coolant out of the block? I never seem to it all out..but I also don’t want to purge coolant on the ground

 

[Cheyenne]