Black silty deposit in coolant overflow

[Mark_VM07]

Hello all,

Fistly, I applogise if my issue below has already been discussed. I couldn't find anything here or from google seaeches.

I own a second-hand x-government lease vehicle - CM diesel bus, mid-roof. It has been regularly serviced every 10,000km. Before a trip from the gold coast to brisbane today, I checked the fluids and noticed that the coolant overflow bottle now has a darker appearance above the fluid line. Upon closer inspection, including an internal swipe with the finger, there is a dark silty deposit clinging to the coolant bottle, it is not greasy or oily. The red coolant aslo appears to not be as red as it normally is, but I can't be certain of this. I also noticed that there also appears to be a every so slight deposite of this material sitting in the bottom of the coolant bottle. The majority of this deposit is clinging to the internal surface of the bottle above the water line.

The coolant level doesnt appear to have changed. There is no white residue on the dip-stick.

I have not noticed any problems driving the car, it runs like a trian as usual. I've owned the car for about 4 years and I've never had any problems or repairs. The odometer has 116,000km on it. I bought the car with 70,000km on the odometer, and after purchasing the vehicle and obtaining service records from the fleat manager I discovered that it had its engine replaced. The engine runs fine and doesn't use a drop of oil.

Has anyone come accross this before? What can it be and what may need to be fixed/replaced.

I've attached a photo. Sorry, I don't have cable inspection camera for a better view. As you may be able to see, there is only a slight coating of the black silty material. I have another photo looking down into the coolant, which shows an ever so slight deposit on the bottom of the bottle. I couldn't work out how to attach more than one photo, so prehaps I may be able to attach it in an added post to this discussion.

Many thanks,
Mark.

[Mark_VM07]

I had a discussion with a future brother-inlaw, who rebuilds high performace engines. He said the black silt is either a carbon deposite (indicating a blown head gasket) or rubber (indicating a hose has started to break down. I'n all my years of car ownership, and I've had a few old cars, 40+ vinatge vehicles, I have never come accross the deteriation of rubber as suggested, but I guess its possible, maybe they down make rubber hoses like they used to.

He also mentioned that there are hydro-carbon (HC) chemical/chemistry tests that you can get to test for HC in your coolant. After searching the internet, I came accross this Australian company that sells a HC chemical tester http://liquidintelligence.com.au/produc ... -test-kits

When I find the time I will try the HC test, as I have another car that has a suspect blown head gasket that i can also use the tester on.

As promised, I've added some additional photos. When i get around to it I will take another photo showing the exteria of the overflow bottle, which shows discolouration due to this black silt.

The car has no other signs indicating that it has a blown head gasket, so I hope its only a rubber hose that has staryed to break down. The car is now 9yrs old, so I guess it is possible that a hose somewhere has started to deteriate.

[DodgeRover]

Just looks like sludge, when was the coolant last changed?

[gotgcoalman]

Could be residue left in the pipework from the previous engine ?

Do you know why it was replaced.

[Mark_VM07]

I was told that the governement employees let the car run out of oil and they cooked the previous engine. Who knows?, maybe it had a water leak and they cooked it by running it with no coolant and they didn't look at the temp guage when they were driving it. Being a bus, and buying the vehicle in a shabby interia state (e.g marker paint on one of the back seats, broken sections of the back floor where they had obviously dropped something heavy, and grease on some of the seats), and only having 70,000km on it as a 2007 vehicle, my guess is that the vehicle was used to transport work crews to local construction/maintenance sites.

Being concerned that I had just bought a vehicle with 70,000km on it (3.5yrs ago), with no idea of how many km the replacement engine actually has on it, I made some enquiries, but I didn't get very far.

The RMS (the NSW road and vehicle authority) wouldn't provide any free info on the replacement engine. RMS said I could pay for info on the doner vehicle, but I wasn't confident that their info would be all that useful. Maybe I would have got the last odometer reading of the doner car when it was last inspected for a road worthy.

The guys who serviced the vehicle when the governement leased it said the lease company always over service their vehicles and they replace parts with better or like for like parts. This gave me some comfort in the quality of the vehicle, and given that it hardly uses a drop of oil and pulls like a train, I confident that the engine is good.

This black silt has only appeared at 116,000km. I'll take a look at the previous owner service records to see if I can work out how many km, and the date, as to when the car engine was replaced. It seems a bit odd to me that residue from the cooked motor would show up now all this time later, but I guess it could be possible.

[Mark_VM07]

Coolant was changed only about 3-4 months ago when it was professionally serviced.

[Mark_VM07]

Just noticed my earlier mistake...should read VM Transit bus and mot CM. I've got a CM valiant station wagon stashed away in the barn ready for a retirement project.

[Altransit]

You VM is what we know as a Mk6 (I think), so we're looking at a 2.4 Litre Duratorq diesel engine (RWD?)

These aren't known for head gasket problems, at any mileage; any sort of water/oil contamination is usually from a faulty oil cooler which are easily bypassed (as a test)
These engines are also capable of very high mileages without major problems, if looked after

That contamination could well be the ancient residue of a previously cooked engine

[DodgeRover]

Have you used the heater recently rather than the aircon? Could it have come out of the heater matrix?

[Mark_VM07]

Yes, its the 2.4 turbo diesel with the duratorq motor, 2007 model here.....as per example shown in the photo below.

I may have had the heater on very briefly (3-5min) on a recent cooler night.

I think I'll flush it out, clean the reservoir bottle, and see if the silt comes back. I'll run the car with and without the heater on to see if the source is from the heater.

[Mark_VM07]

Yes, 2.4 turbo diesel duratorq....2007 bus as per example shown below.

I think I may have had the heater on for 2-3min recently.

I'll flush it out, clean up the overflow bottle, and see if the silt comes back with or without the heater on.

[knobby1]

She's a Mk7....anything late 2006 up to ~2013 are Mk7's. 2.4 Liter will be RWD as well...the FWD's are 2.2Liter. Whereabouts in NSW are you..??


Is the deposit in the coolant reservoir oily in consistency...or is it more carbon like?? As mentioned it could just be crud left over from previous engine.... it's also possible the oil cooler is leaking a tad but this usually fills the cooling system with oil pretty quickly.

Lord Knobrot

[ARNEeurope]

did you figure out what is was? i have pretty much the same situation (van went perfect 15.000km...no issues), difference in my reservoir tank: it looks like hardened oil... doesn't feel oily..like you have described. i attach picture. could not find any info...if it was a headgasket issue...i would have difficulties moving the car right? like you have described, no signs of any error when driving...

[knobby1]

did you figure out what is was? i have pretty much the same situation (van went perfect 15.000km...no issues), difference in my reservoir tank: it looks like hardened oil... doesn't feel oily..like you have described. i attach picture. could not find any info...if it was a headgasket issue...i would have difficulties moving the car right? like you have described, no signs of any error when driving...

He hasn't been on here for 18 months and the last post was nearly 6 years ago.

Oily deposits usually indicate a blown oil cooler.

Lord Knobrot