Thread: Coolant sludge - why??

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A while back I dumped the radiator to do some plumbing changes and the antifreeze was cloudy, but not excessively so and after straining through coffee maker filters am going to reuse as the test strip and volt meter say it's as good as new. Today, and before I put that antifreeze and water back in, decided to pull the engine pipe plugs, dump the rest of the coolant and add petcocks for the future. The crud that came out was almost sludge. Now, before someone say it had to be there from its earlier life, no, that engine was a brand new crate motor, with a brand new Walker radiator and all new hoses. Oh and I'm using distilled water along with the antifreeze.

WHY that crud???
(and that crud, it was deposited on my favorite tree stump in the woods to help kill skeeters later on)

By test strip I'm assuming your testing PH ?? Do you have underdrive pulleys? What (who's) anti-freeze?

Originally Posted by 34_40

By test strip I'm assuming your testing PH ?? Do you have underdrive pulleys? What (who's) anti-freeze?

pH strips, It's about 9+/- at present with recommended 8.5 to 11 (Prestone is said to be 9)

Pulleys are standard diameter - I'm not a fan of underdrive pulleys on a street driven car. Antifreeze, either Prestone or Peak (green, not the orange Dexcool for aluminum)

Probably from an assortment of leftovers from the manufacturing process of the heads and block, plus whatever dirt and dust got in the system prior to the engine being fired up....

Main reason is you are using a 50/50 mix,which means water and antifreeze. Just because you have antifreeze in a system does not mean you have total corrosion protection. Water will make rust and scale eventually and as the 2 mix will start to also get somewhat acidic. That combination will also get more muddy with time and cycling of the motor. Cycling is the motor getting up to heat and then cooling down after it's turned off.

Just like an air compressor. Heat and cooling down makes the water......soupy like.

Probably both right though I can say that it is not very acidic at a pH of 9+. And as far as cycling - that engine probably doesn't 100 starts in about 2000 miles. I do need to get some more test strips or a pH meter to keep track of the antifreeze deterioration in my vehicles

Usually the first thing that pops up in this type discussion is leaking head or intake gasket, but that may not be it.

Why not get on the horn to the Prestone customer service line and play 20 questions with them?

Originally Posted by Bob Parmenter

Usually the first thing that pops up in this type discussion is leaking head or intake gasket, but that may not be it.

Why not get on the horn to the Prestone customer service line and play 20 questions with them?

Bob - It would really upset me if my $$$$ Fel Pro Performance level gaskets were leaking. There are no indicators - slimy/greasy coolant or milky oil nor was there any loss of either.

I put a bunch of hot water through the engine yesterday - until the flow ran clear so what I think I'll do is keep an eye on it this spring - and with the added petcocks, it's easy to dump a small amount, and if it continues, harass Prestone and/or Peak as I really don't recall which I have installed as I have jugs of both.

Also, after doing a quick Google, this is not an unusual occurrence, and much worse with GM's Dex Cool.

Do you run an automatic trans with a cooler in the radiator??

Originally Posted by jerry clayton

Do you run an automatic trans with a cooler in the radiator??

Nope - the trans cooler is totally independent of the radiator.

I just sent an inquiry to Peak as Prestone's site said their 'certificate' was invalid.

Talking with either antifreeze company won't get you anywhere. The water is the main culprit.......water will make corrosion, simple and plain.

Actually, to make rust, you need AIR. Water alone will not make rust. An example would be deep sea wrecks that are wooden and are still there centuries later. Even wrecks in the great lakes are very well preserved because the water is very cold and deep with low oxygen contents.

I'm assuming that your radiator elevation rises (when hot) and falls (when cold). It's this headspace where the falling coolant can trap air into the coolant which gets left in the block. The air/water combo is what's attacking the bare metal. I'm wondering if the "catch-can" is to low and allowing an air pocket to develop. And now that you mention it, I'm wondering about my own car. I'm not worried as the cast iron will be along time before a catastrophic failure, but still.

Great topic Dave! Now my mind is curious!

Originally Posted by 34_40

Actually, to make rust, you need AIR. Water alone will not make rust. An example would be deep sea wrecks that are wooden and are still there centuries later. Even wrecks in the great lakes are very well preserved because the water is very cold and deep with low oxygen contents.

I'm assuming that your radiator elevation rises (when hot) and falls (when cold). It's this headspace where the falling coolant can trap air into the coolant which gets left in the block. The air/water combo is what's attacking the bare metal. I'm wondering if the "catch-can" is to low and allowing an air pocket to develop. And now that you mention it, I'm wondering about my own car. I'm not worried as the cast iron will be along time before a catastrophic failure, but still.

Great topic Dave! Now my mind is curious!

What you are describing, Mike, is free oxygen, that is molecules of entrained oxygen(air!) that is not part of the H2O combination. In the case of an automobile cooling system, it's a closed system, opened only when you check the coolant level or boil some of it into the overflow vessel(15psig). It can also happen if the water pump cavitates - but that usually wont happen unless the water level has gotten too low Boiling has happened only once to me - two years ago and that was because I didn't have the fan wired correctly and was fixed immediately after cool down. As far as my overflow/catch can - it's pretty high plus a good size compared to many. I did move it from one side to the other recently, but it's at about the same height.

Another plus with using antifreeze is that it does contain anti corrosives, water wetting agents, raises the boiling point a few degrees.

This is my coolant recovery system:

Originally Posted by IC2

What you are describing, Mike, is free oxygen, that is molecules of entrained oxygen(air!) that is not part of the H2O combination. In the case of an automobile cooling system, it's a closed system, opened only when you check the coolant level or boil some of it into the overflow vessel(15psig). It can also happen if the water pump cavitates - but that usually wont happen unless the water level has gotten too low Boiling has happened only once to me - two years ago and that was because I didn't have the fan wired correctly and was fixed immediately after cool down. As far as my overflow/catch can - it's pretty high plus a good size compared to many. I did move it from one side to the other recently, but it's at about the same height.

Another plus with using antifreeze is that it does contain anti corrosives, water wetting agents, raises the boiling point a few degrees.

This is my coolant recovery system:

Like I said Dave, to make rust, it takes air. Yes, free O2. Not part of the H20. All Tap water contains a level of entrained O2. And yes, the water pump can cause cavitation in the coolant and actually causes the O2 in the coolant to explode. With 25 years in water and wastewater treatment, I know those are the facts! The catch can thought was just that, a HMmmmmm I wonder moment out loud. Fluids seek their own level so I had a thought flash through the brain.

I know on my car the radiator fill is set into the side of the top tank. The very center of the top tank has always made me wonder how full the closed system is. It looks like your radiator is the same.

I'm not really concerned like I said earlier. The cast iron will probably outlive me and most of my family. But like you I'm wondering what's at the bottom of my block and will have to investigate.