I found this in my cooling system




And i'm wonder where did it come from, it is not a sludge but hard fine crystals, i didn't find sludge anywhere else in the system and those crystals are present on the thermostat cover and very little of fine sediment in the expansion tank
I suppose system need flushing but anyway i want to understand what i'm dealing with

Thx

 

Stop leak?

 

Probably MIXED COOLANT.

When the system is filled with DEXCOOL and someone adds regular GREEN it usually turns into a brown sludge.

 

Somewhere at the beginning of car ownership i did top up pink coolant with yellow one, later on i understood my mistake and flushed it all, also draining both banks and then topped up with yellow stuff, but maybe damage was already done
Yes i dropped in bottle of liqui molly stop leak year ago, but this coral reef looks a bit too excessive for good reviews it has.
On the third thought, maybe some coolants are just based on the tap water and prone to precipitate minerals which shouldn't be there

 

Besides sludge, the picture kinda looks like oatmeal with little chunks in it making me think of either little dessicant beads or some sort of congealed fibrous material, so may be a combination of mixed coolant types AND stop-leak product. Its possible that something like CLR or other radiator flush would dissolve it. I've used CLR with an external circulating pump to free up a clogged heater matrix. Good luck.

 

What is consensus on flushing an older system, will it damage seals or it is just an urban myth?

 

Standard flushing agents work fine on our cars cooling systems. Done it a few times to clear heater matrix and on Supercharged cars it's a matter of course on service points.

 

Ok, thx guys for your input, i will act accordingly

 

Hi The system may have a leak which has been blocked by a product like bars Leak Chem i weld or K stop. Often used to stop head gasket leaks or even cracked heads if the gap is small but also for leaks in radiators.
It should be added slowly or it can cluster with disastrous results on the fine tubes in radiators. Best to remove a quantity of coolant and dilute the additive considerably, adding as coolant circulates.

 

No, not really, it was loosing few oz of coolant a year so nothing significant but i thought i will drop the bottle there to have it stopped
just few days ago thermostat gasket gave up so i suspect it was the cause of my tiny leak