Cooling System Sediment: Stop-leak or something else?

[rtadams89]

I got my M35A2 recently with 9,000 miles on it. I put a coolant filter on (in a bypass setup) at about 9,500 miles. Just now at 10,000 miles I pulled the filter and cut it open to see how much had been caught. I was surprised to see the whole filter clogged with what I can only describe as mud. My initial reaction was quite the freak out, as the sheer volume and consistency looked like someone dumper a bunch of dirt into the cooling system. After thinking about it, I'm wondering if it isn't stop-leak though? I know the previous owner replaced the radiator shortly before I bought the truck. My thought is that the old one was leaking, someone dumped in (a lot) of stop leak and never flushed the system when the radiator was replaced. Does what you see in the picture look like stop-leak, or do you think it is something else/indicative of a real problem? If it is stop-leak, I'm assuming most of it has been caught by this filter; should I flush the whole system or just replace the filter and expect it to clog up more quickly before all of the stop-leak gets caught?

 

[gimpyrobb]

I wouldn't sweat it much every one thats put a coolant filter on and cut it open has had the same crud. It should diminish as time goes on.


Just keep an eye on it.

 

[rtadams89]

I was expecting to find some sediment/junk, just not that much...and not mud.

 

[gimpyrobb]

You have to consider the micron rating of the filter. I would expect sediment at like 100micron or more.

 

[Csm Davis]

These trucks are known to have a block full of mud like that. I personally think that they all should be cleaned out before putting them on the road, most have spent decades sitting and rusting from the inside out.

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[rustystud]

These trucks are known to have a block full of mud like that. I personally think that they all should be cleaned out before putting them on the road, most have spent decades sitting and rusting from the inside out.

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Another thing is the casting material. When these blocks where cast at the factory they used special sand and clay mixtures to form the coolant passages and other holes like oil passages. Then after casting they shake the blocks to remove the casting sand mixture. That is why there are holes on the side of every engine block made out of cast-iron. It is to remove the sand mixture. They are then plugged with "Welch" plugs though everyone calls them "freeze" plugs. They will not save a block from freezing either. They just push-out when the blocks freeze. A problem a lot of older blocks made in the 1950's and 1960's and even some in the 1970's had was this sand did not all come out. Due to the make-up of the sand mixture it would sometimes "bond" to the cast-iron (the factories changed the composition of the sand mixtures to prevent this in later engines). Unless the engine had a heating problem the factory never worried about this retention problem. Now fast forward. The engine has been in service for years now and the sand mixture has slowly come loose. This "free" sand is floating around the engine and usually doesn't cause a problem since it is very fine, and a lot of it comes out when the coolant is changed. Sometimes though the engine overheats and causes the sand to come loose in large quantities. This can cause the radiator to plug up. I have seen two trucks that did just that. One dumped so much sand that the lower part of the radiator was blocked up three inches high ! So to prevent a blockage I always "purge" my coolant system every 4 years by "back flushing" the coolant system. There was a company years ago that would remove the "Welch" plugs and then use high pressure water with little nozzles on long probes to reach inside the block and remove all the rust and scale and sand. This was done on high-performance engines. This actually helped a lot especially if you had a "hot" running cylinder and could not find the problem.