Soft Sludge/Scale in Coolant Tank

retmil46 · **Posted:** Sun Jan 25, 2009 3:46 pm

Decided to swap out the coolant in the CRD this weekend. '87 MB diesel uses the same type coolant, and MB recommends changing it out every 2 years - also getting ready for the grand tour next week of FL and TX for job interviews.

Last time the coolant was changed out was 3 years ago, dealer flushed out the system after showing him 2 jars of sand I cleaned out of the radiator and coolant tank.

I'd noticed what looked to be a small amount of dark material accumulating again in one spot of the coolant tank, so I pulled it off to flush it out.

Besides that, the entire inside of the tank was coated in a layer of pinkish sludge/scale that gradually flushed out after several times filling the tank with water and sloshing it vigorously. There was also a ring of this same scale/sludge in the overflow section where some coolant had vented past the radiator cap.

My best guess is that when the dealer performed the flush, they used city tap water instead of deionized or distilled water to mix in with the new coolant - this accounting for the formation of the scale/sludge.

I replaced the coolant with a 50/50 mix of Zerex G05 and distilled water.

BlackLibertyCRD · **Posted:** Sun Jan 25, 2009 3:59 pm

I have 63k of hard driving on mine and coolant is still clean. I would guess that the engine block wasn't clean from the beginning with the sand still in it. I thought we had 100k coolant installed in our CRD?

warp2diesel · **Posted:** Sun Jan 25, 2009 5:02 pm

Casting sand is often a dark red color, antifreeze could have changed the color.

Manufactures do every thing including vibrate the heads/engine blocks and shot peen to get all the sand out, but, they don't always get everything. Shift changes, break times, or an urgent nature call can result in casting sand left in a corner some place. Since our VMs are wet sleeved, I suspect the sand was trapped in the head and got washed down into the rest of the cooling system.

retmil46 · **Posted:** Sun Jan 25, 2009 7:45 pm

BlackLibertyCRD wrote:

I have 63k of hard driving on mine and coolant is still clean. I would guess that the engine block wasn't clean from the beginning with the sand still in it. I thought we had 100k coolant installed in our CRD?

Mine looked clean as well, both thru the tank and when looking down into it. It wasn't until I pulled it off and started flushing the small amount of dark material out with water that I noticed the scale/sludge - small "chunkies" floating in the water, and holding the tank up to the light you could see darker tinted patches where the sludge was still adhering to the tank.

Wouldn't doubt that in a gasser it would be 100K, or even 100K as far as freeze protection - but as far as a diesel, with the other chemistry going on and corrosion protection in particular with the wet sleeve liners, your guess is as good as mine.

I decided to err on the side of caution - MB has used the same type of coolant since the early 80's, and the engine in the '87 is a similar design as far as an aluminum head and cast iron block - and on that '87 diesel they recommend changing it every 2 years.

You could fill books with all the discussion regarding the best coolant chemistry for diesel engines, SCA additives, coolant filters, etc - take a look at the Penray website and you'll understand what a contentious issue it can be.

warp2diesel · **Posted:** Sun Jan 25, 2009 9:24 pm

I used to give away my waste coolant to a recycler when I ran a repair shop. He would test the pH and correct the stuff and sell it to Truck Fleets. He would also do on site recycling for his truck fleet customers. Since most of the large ORT are wet sleeved, checking with the truck fleets on what is acceptable pH would be a smart thing to do.

Any ORT mechanics out there know what pH is good to run :?:

onthehunt · **Posted:** Sun Jan 25, 2009 10:36 pm

Anything close to 10.

warp2diesel · **Posted:** Mon Jan 26, 2009 9:08 am

I did a check and found the following article to put it straight on pH: http://www.eutechinst.com/techtips/tech-tips10.htm

For other compounds like silicates to protect the Aluminum in the radiator: http://www.imcool.com/articles/antifree ... sgobad.php

It is also recommended to flush and fill every two years to prevent leaks in the aluminum radiators. Other additives help suppress or eliminate the pitting of wet sleeves that was a problem years ago (1980s). I plan to pick a coolant that complies with the specs that the ORT engine manufactures call for.

naturist · **Posted:** Tue Feb 03, 2009 5:31 pm

pH of 10? Whoa, really??? I am not an engine guru, just a lowly chemist, and a surprised one at that, as a pH that high in an aqueous system will generally etch aluminum fairly rapidly. I'm surprised, but bow to the folks in the field. If 9.5 to 10 works best for the system, so be it, I just am astonished.

warp2diesel · **Posted:** Tue Feb 03, 2009 7:29 pm

Very Tiny amounts of exhaust manage to leak past the head gasket and into the cooling system. In the days of high sulfur fuel, the exhaust would be slightly acidic and slowly sour the cooling system. As a proactive measure making the coolant alkali, you are buying time. When the coolant drops below the 9.5 pH changing out the coolant prevents the coolant from eating away the engine. Additives in the coolant do jobs like lubricate the Glass Ferrite water pump seal and other functions to preserve the hoses, static type seals, and radiators. You could invest in a centrifuge and stay on the good side Of Home Land Security and let them Know you are not a Terrorist, add the needed additives to old coolant and recycle it. For me replacement is cheaper.

Hypothetically, when the fuel is pure and contains nothing that can turn into an acid, we may be able to never change coolant. But since Air contains Nitrogen, I am not holding my breath

Soft Sludge/Scale in Coolant Tank

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