Mineral Deposits Build Up *UPDATE - It's Stop Leak*

[Powling]

So the other morning I noticed a large coolant leak coming from the expansion tank - wasn't too worried and figured I would replace the tank and be good to go. Well after some digging I quickly found that I had SUBSTANTIAL mineral deposit build up throughout the whole cooling system.

Not sure on what my next step should be here. I gave the entire system a good flush with water to get as much out as I could, which got all of the coolant and slime out, but I know there is still all of these hard deposits in there. That being said, the shiny flakes you see in the slime on my finger isn't metal, its white and doesn't have a grime / hard feel when I rub between my fingers.

What should I do next?

[roguetoaster]

Sure looks like stop leak, sure no one evee tried to fix a HG leak?

As to removing it, flush, refill, flush again, each time getting to op temp. Use any water for the first, move to distilled as you go on.

[Powling]

Sure looks like stop leak, sure no one evee tried to fix a HG leak?

As to removing it, flush, refill, flush again, each time getting to op temp. Use any water for the first, move to distilled as you go on.

From everything I’ve read it looks like it’s stop leak. Hard part is it’s all hard caked onto everything, not sludgey at all.

Im wondering if going a harsher route of a flush would work better? Or am I risking damaging the HG and any other components?

[roguetoaster]

I'd look at it this way, if the car is not overheating leave it alone, if you are having issues maybe be more aggressive.

Also haven't seen anything that would do a good job of cleaning that crap out without consequences.

[mrsleeve]

I agree that sure looks like head gasket in a bottle to me.... That said how long has it been since you serviced this cooling system, and what do you use for a water source when you do. Its a little late now but coolant over time develops a mild electrolysis property and that can eat away at parts, get your volt meter out and put a prob in the coolant and then ground off to the engine someplace, anything over 0.7v carrying capacity in your cooling system needs to be flushed out.

The reason I point this out is if you use tap water, if you let the system go too long, the electrolysis and temp cycling can cause weird reactions and sediment to occur from the dissolved minerals in your tap water and dissolved metal scavenged from engine components. I still think it looks like mostly like Bars Leak.

I would flush with h2o, at least twice, then I would rig up some combination of fittings to adapt to my garden hose and back flush (force water though the system opposite of normal flow direction) the system, doing the rad, engine (leave the t stat on the bench) and heater circuit separately, to get as much of that shit out of the system as I could. Once that is done, I would put it all back together and flush one more time with straight distilled h2o one last time, then put it all back together with new hoses and other while you were in there parts, using distilled h2o to cut my coolant of choice to 50/50. One has to as though is why is there a ton of Bars Leak in the system in the 1st place haven't you had this car for a long time????

[Powling]

I agree that sure looks like head gasket in a bottle to me.... That said how long has it been since you serviced this cooling system, and what do you use for a water source when you do. Its a little late now but coolant over time develops a mild electrolysis property and that can eat away at parts, get your volt meter out and put a prob in the coolant and then ground off to the engine someplace, anything over 0.7v carrying capacity in your cooling system needs to be flushed out.

The reason I point this out is if you use tap water, if you let the system go too long, the electrolysis and temp cycling can cause weird reactions and sediment to occur from the dissolved minerals in your tap water and dissolved metal scavenged from engine components. I still think it looks like mostly like Bars Leak.

I would flush with h2o, at least twice, then I would rig up some combination of fittings to adapt to my garden hose and back flush (force water though the system opposite of normal flow direction) the system, doing the rad, engine (leave the t stat on the bench) and heater circuit separately, to get as much of that shit out of the system as I could. Once that is done, I would put it all back together and flush one more time with straight distilled h2o one last time, then put it all back together with new hoses and other while you were in there parts, using distilled h2o to cut my coolant of choice to 50/50. One has to as though is why is there a ton of Bars Leak in the system in the 1st place haven't you had this car for a long time????

From chatting with a lot of people, I'm now 99% sure its stop leak solution from a previous owner...who likely used stop leak multiple times judging from the amount of hardened stop leak throughout the whole cooling system.

That being said, I've been researching best method to remove it and it looks like flushing the system multiple times with oxalic acid is the best route, so I'm going to try it on the thermostat and water pump housing first to see if it works then decide on next steps from there.

I've owned the car for roughly 4 years, in that time I never did a coolant flush or needed to top it up really. Thats my fault though, I should have done a flush and new coolant from the start.

[Gregs///M]

Looks like evidence of oil and coolant mixing too, head gasket failure, cracked cylinder head or block. Flush the system and I bet you will see chocolate milk again, there must be a reason so much Stop Leak was used.

[Powling]

Looks like evidence of oil and coolant mixing too, head gasket failure, cracked cylinder head or block. Flush the system and I bet you will see chocolate milk again, there must be a reason so much Stop Leak was used.

I actually don’t think this is the case - every oil change I’ve done there has been zero evidence of coolant in the oil, and the coolant I drained and flushed had zero oil / milky look to it.

The bottom of the expansion tank had a lot of silicone sealant around there o ring where someone must’ve seen a leak from there and rather than replace the o ring or tank they just used stop leak. I will say, the previous owner was an older lady with zero knowledge of cars so it’s likely she just poured stop leak in until ‘it stopped leaking’

[Powling]

This past weekend, after an exhausting amount of research, I decided to try the oxalic acid method on the thermostat and thermostat housing to see if this would break down the stop leak build up. 12 hours in a bucket with the oxalic acid and distilled water mix, and the old stop leak didn't even get soft.

Form what I read, you're suppose to try the acid flush for an hour only as any longer and it can eat away at the head gasket and other seals.

So now I am rerassembling everything, filling it up with BMW coolant and distilled water and leaving it at that. I didn't have any over heating issues before, so I am going to run it as is and see how it goes in the future. This will also give me time to source the parts needed for an M42 rebuild or to find a complete M42 with low km locally that I can swap in, in case this one decides to shit the bed soon.

[bmwman91]

Yeah, it is most likely fine to just put it back together. As long as you have a fresh thermostat in there, and the little bypass groove in the thermostat housing is clear, the stop-leak goop should not really pose a major problem. The small amount of decrease in thermal conductivity between the head/block and coolant should not be an issue unless you are taking it to the track in the middle of summer. The M42 cooling system is somewhat over-sized, especially if you live in a temperate place.