Rust Colored Coolant

95Voy/3.0L
Last April, I emptied the cooling system and noticed rust colored fluid. I reversed flushed the system with a kit...good to go. In October, I added an inline coolant heater and again noticed rust colored fluid while draining the system. I flushed the system a second time. Yesterday, I spot check the system by draining a few ounces of fluid, and 'tis rust colored. I've been using a 50/50 mix of Prestone & water. How could I tell if the rust is originating in the radiator, block, or both?

There shouldn't be anything in the radiator to rust. There's no steel or iron. It's coming from the block. Just change it again. It's really hard to COMPLETELY flush the system, mind you...

Also, most anti freeze comes premixed now, don't cut this down.

Another thing.... You're always supposed to use 50/50 mix of water and antifreeze. Never supposed to use straight antifreeze. The anti corrosion additives of the antifreeze are supposed to keep it from rusting. So I would say probably you never quite got the thing fully flushed. Remember when you flush you're supposed to have the heat on full.

HI,

Be very vareful with this issue, because it sounds like your transmission fluid is leaking in the coolant. The transoil is cooled in the radiator and is coloured dark red and goes to brownish when getting older in the trans.

I just lost my car, because of this reason; transoil in the coolant and water in the transoil. Tranny is toast because of the water and all the rubber seals and pipes in the enginecoolant system are shot because of the elastomers in the tranny oil.

The coolant looked like chocolat sauce

Gerard

Thanks for the response. I reviewed my maintenance log and I wrote that one of the engine block drain plugs was rusted on the tip. I've read online that a disintegrating water pump impeller could cause rust in the coolant, but as with the radiator, I thought the impeller was formed from aluminium alloys.

I'm going to have an oil analysis done by Blackstone labs to see if any coolant exists in the oil, indicating a leaky head gasket.

While that's always good to do, I think you may want to think about having the oil analysis done on your transmission fluid to see if there is any coolant in it.

However, the fact that your tranny hasn't gone out in the midst of this does tend to suggest that the problem isn't with transmission fluid getting into the coolant.

Additional info: 3-sp tranny, 114K miles, last changed @ 101K. I purchased the vehicle from my wife's grandfather @ 67K miles. Fluid was never changed, but it was nice and red when I did the first drain @ 75K.

Latest hydrometer reading of the coolant indicates 50/50 coolant/water mix. When I did the flush last April, I did not use a flushing agent...just 15 minutes of running water (reverse flush kit) with the heater on high. Maybe I'm wrong, but I believe that attempting to remove all that rust at once with a flushing agent would result in a clogged radiator or heater core. Any thoughts and/or experiences with using a coolant flush agent like Prestone Super flush?

Are you sure this is rust and not DEXCOOL Anti-Freeze, both Chrysler and GM used and still use DEXCOOL and it is Orange in color.

Are you sure this is rust and not DEXCOOL Anti-Freeze, both Chrysler and GM used and still use DEXCOOL and it is Orange in color.

That's something I hadn't thought of. However, I back-flushed the system for 15 minutes last April and opened an engine block drain plug and radiator plug to complete the drain. I didn't view any orange during the flush procedure. I've only seen and used "the green stuff" in the van.

I'm leaning toward a rusty block since (a) I viewed a rusty drain bolt tip, and (b) the records from the previous owner indicate just one antifreeze drain and no flush prior to 74K miles. I'm now questioning the use of a flushing agent to help remove the rust from the block. It seems to me that this may do more harm than good.

Are you sure this is rust and not DEXCOOL Anti-Freeze, both Chrysler and GM used and still use DEXCOOL and it is Orange in color.
Chrysler never used dexcool.They use red coolant but it is called H.O.A.T. coolant

Are you sure this is rust and not DEXCOOL Anti-Freeze, both Chrysler and GM used and still use DEXCOOL and it is Orange in color.
GM's dexcool and what chrysler uses are not the same . GM uses dexcool which I think is more pink and chrysler uses what is called HOAT which is orange in color , while they are both extended drain coolants they are not the same and cannot be mixed together .

I have yet to do my '99 van, however I have done lots of other cars and I always use a cleaner. Never had a problem with ongoing rust or plugging of the radiator. Believe me I've cleaned some neglected systems and never had them plugged. YMMV
My method is to first drain the old coolant and then reverse flush with plain tap water. Next I use the heavy duty cleaner (usually Preston Super Flush) that is run in the system for a period of time, again with tap water. This is followed by another reverse flush and drain with tap water. I fill it with distilled water and run/drive it for an hour. This water is drained and then I fill with 50/50 distilled water and coolant. Probably over complicated but I know people who do multiple washes/rinses with distilled water. I think it's a piece of mind thing.
I never have coolant issues or leaking/plugged radiators...so what ever works!

...I always use a cleaner. Never had a problem with ongoing rust or plugging of the radiator. Believe me I've cleaned some neglected systems and never had them plugged...

Thanks for the input, webbee. With this recurring rust issue, I think I'm forced to re-evaluate my beliefs and flush the system with Super Radiator Cleaner. Your method seems thorough/compulsive enough for a neglected system...I must try it!