Diesel Cooling System Flush

Last update May 28, 1998

Subject:   Re: antifreeze
Date:       Tue, 17 Feb 1998 15:47:00 -0700
From:      "Matthew Stabnow" <homespun@btigate.com>
To:          cummins

> I want to replace the antifreeze.  I see the drain on the radiator.
> Should you drain also at the block, or is that unnecessary?

According to the factory service manual it is recommended that the cooling system be drained and flushed every 24 months or 24k miles which ever occurs first.

(copied from factory service manual)

(1) Drain the cooling system. (Radiator drain plug)
(2) Disconnect the radiator lower hose from the water inlet connection.
(3) Remove the heater core inlet hose from tube.
(4) Attach water supply hose to heater tube.
(5) Back-flush the engine until clean water exits the water pump inlet.

(1) Close radiator drain plug
(2) Reconnect radiator and heater hoses
(3) Fill the cooling system with a 50/50 mixture of water and antifreeze.

The 5.9L  Diesel Engine is equipped with a one-way check valve (jiggle pin). The check valve is used as a servicing feature and will vent air when the system is being filled.  Water pressure (or flow) will hold the valve closed.  Due to the use of this valve, the engine must NOT be operating when refilling the cooling system.

Use a 50/50 mixture of water (distilled or demineralized recommended but not required) and low silicate Ethylene-Glycol antifreeze.  Do NOT use Propylene-Glycol antifreeze.

NAPA also has low silicate Ethylene-Glycol antifreeze.

Matt Stabnow

Subject:    Re: AF
Date:        Thu, 14 May 1998 18:15:20 -0400
From:       gemcuttr@juno.com (Stephen B Clayton)
To:           cummins

> is it detrimental to add contaminated (read not distilled) water to  the cooling system? 
> i know that some areas have a significant amount of minerals present in tap water.
> this can only add to the mineral build up in your radiator and block passages.

It is far better to add regular tap water to the engine than distilled or "softened" water. Remember, water is an extremely active substance, chemically speaking - it will always tend to leach out minerals or metals from its surroundings.

If you were to add chemically pure water to your engine, the minerals and metals the water would try to leach out would be from the engine itself! Of course, the purer the water, such as distilled water or "soft" water, the more metal it will grab for itself. I wore a hole through the cylinder head bolt of a VW Vanagon by using "pure" water once - $2000 is a heck of an expensive lesson!

If your water contaminant is iron, I wouldn't worry too much about that. If the contaminant is high mineral content, I wouldn't worry too much about that either. But before you add water to the engine, you can test the water, if you like. Simply take a clean glass, fill it, cover it and let it sit for about 6 hours. If there's a lot of crud on the bottom, simply filter the water through a some kind of media, like paper or cloth. Or better yet, just fill one or two 5 gallon plastic buckets, cover them and let *them* sit for 6 hours, and scoop off the clean H2O from the top and use it in the engine. This is *especially* good to do if your water system uses lots of chlorine in the water. Left unmodified, chlorine is *death* to metal, especially iron - it forms a weak hydrochloric acid! Letting water stand, especially in sunlight or heat, allows the chlorine to outgas or disassociate, and the water will be better for your favorite ride!

Sometimes cast iron blocks on various engines will flow lots of rust, despite repeated flushing and cleaning - the cast iron has been "activated". When this happens, I use dilute phosphoric acid and tap water - usually 50/50. Avoid the body prep phosphoric acid that contains a latex rider - what you want is plain old phosphoric acid. A product called "Ospho" works well. I add the diluted acid to the engine and run for 5 minutes, then drain and fill with coolant. The phosphoric acid converts the iron oxide (rust) into black iron phosphate, which is fairly stable. If there is a little acid left in the engine, I don't worry about it - when it finds rust it will convert.

Important: Please remember this is a last ditch effort to passivate the engine block's cast iron, used only as a last resort before pulling, disassembling and hot-tanking the block.

Steve Clayton - Tampa Bay Area, Florida, USA
<gemcuttr@juno.com>         ICQ 11636704
 Megilah Bereshith 12:2-3