RMI-25 leaving brown film inside radiator

[tom h]

actually, this post is in reference to my 94, 5.7L Chevy Blazer, but since I was intending to refill the 87GN's cooling system with just water & RMI-25, I thought posting here might be OK.

Anyway, 6 months ago (June) truck's radiator had a leaking side tank replaced, and I also had radiator rodded out. I refilled with plain water (16 qts) and 8oz RMI25.

This weekend I start flushing cooling system so as to add fresh water, RMI25, and anti-freeze (for upcoming ski trips).

Radiator neck, cap, and heater hoses have a brownish film coating them. Brown film rubs off. It rust-colored, but the film really isn't rust.

This concerns me ... when I ran regular water & antifreeze, never recall having any noticeable amount of brown film buildup.

There have been a lot of positive comments about RMI-25, but I don't like what I see in the truck's radiator.

Based on what I see, I'd be reluctant to run only water & RMI25 in the GN ... but I know a lot of you do. Maybe some antifreeze + water + RMI-25 is safer ??

Any ideas what gives?

 

[325DR]

tom h,

I have the EXACT same problem. Distilled water + RMI-25 only. I took off the radiator cap and noticed this brown film building up in the neck. It is also floating in the over flow a little bit. Hopefully someone has some info on this.

 

[tom h]

Another observation ...

the old coolant after it was drained into a pan, had lots of small brown particles in suspension.

Presumably this a good thing, and indicates RMI-25 is doing its job: keeping crud like this in suspension so that it doesn't plate or coat onto the cooling system internals.

But still the brown film built up, anyway.

 

[Two Lane]

Always use distilled water, no matter with what.

 

[jmidolo]

All the brown crud is stuff that was stuck inside your cooling system...it means the RMI is working. Years of running AF and corrosion is being cleaned up....I had this when I first switched to RMI. After the first flush, it was gone.

Joe

 

[gnXfan]

Originally posted by jmidolo
All the brown crud is stuff that was stuck inside your cooling system...it means the RMI is working. Years of running AF and corrosion is being cleaned up....I had this when I first switched to RMI. After the first flush, it was gone.

Joe

ditto

and ditto the distilled water post too

 

[Nick Micale]

What Joe and the others said about the brown crud is correct. It is cleaning deposits from inside the motor, radiator and heater core and holding it in suspension. Antifreeze will not do this as the additive package it contains no cleaning agent.

For years we have recommended with first use of RMI to flush after a few hundred miles. When the "brown crud" is very little, a 6 month flush program is recommended.

More detailed info and FAQ's may be seen on my web site.

 

[tom h]

Guess I'll continue with regimen, then!

On the truck, I will have to run Antifreeze + RMI25, as I will be driving in freezing weather.

On the G/N, I'll use just RMI+distilled, and remember to flush it frequently in the first few months.