Rust in cooling system

[rslifkin]

Lately, I've been having issues with rust in the Jeep's coolant. The Jeep came with old school green (and a pretty clean cooling system). I flushed it and changed it over to G-05 about 3 years ago, a few months after I got it. For the last year or two, I've been noticing a good bit of rust buildup in the system, mostly in the radiator neck and overflow bottle (not much rust comes out when draining the coolant).

I last flushed the system in April, so the current fill of coolant is only a few months old, yet the recovery bottle has a bunch of [censored] in it. The Jeep has no issues with air in the system, doesn't lose any coolant, etc. The coolant also smells fine and is still clear.

For reference, the motor is iron block and heads, aluminum intake manifold, the radiator is aluminum, there's steel t-fittings in the rad hoses for e-fan temp sensors (the rust could be coming from these), the heater core is aluminum (new core, the old one was copper/brass). I had the heads off the motor last summer at 136k miles and there was a light rust film in all the coolant passages, but no flaky rust or anything concerning.

The buildup in the system doesn't seem to be causing me any cooling problems, but it definitely bothers me. At this point, I'm just wondering what might be causing it and whether I should flush the system and change to a different coolant type. Any suggestions?

 

[Donald]

How about trying some RMI-25? I have added it to my Jeep and will add it to the other vehicles shortly. I have no cooling system issues just seeing if things could be even better.

People say good things about it on this forum.

 

[Boomer]

Are you using a 50% coolant/50% distilled water mix? Too little antifreeze can cause issues. Also, rust is iron oxide so for it to form, air has to be getting into the system. Does your radiator cap seal properly?

 

[rslifkin]

Originally Posted By: Boomer
Are you using a 50% coolant/50% distilled water mix? Too little antifreeze can cause issues. Also, rust is iron oxide so for it to form, air has to be getting into the system. Does your radiator cap seal properly?


Yeah, it's been a 50/50 mix (or a hair stronger) since I put the first fill of G-05 in. The rad cap seals fine, radiator always stays 100% full, no air bubbles blowing through the heater core, etc.

It's possible that it's not rust, but a byproduct of something else going on, but I can't think of what it would be (it's never had coolant types mixed to my knowledge).

 

[nitehawk55]

Could be a very minor head gasket leak on compression only ?

 

[doitmyself]

Did you use bad tap water vs. distilled?

 

[y_p_w]

Originally Posted By: Boomer
Are you using a 50% coolant/50% distilled water mix? Too little antifreeze can cause issues. Also, rust is iron oxide so for it to form, air has to be getting into the system. Does your radiator cap seal properly?

There's dissolved oxygen in water. Probably wouldn't rust as quickly as something in a wet, air exposed environment, but there can still be oxidation.

I saw an article on a couple of cars that were pulled out from a lake and probably contained bodies of people reported missing in the 1970s or earlier. The car bodies were completely rusted through.

 

[rslifkin]

It's always been 50/50 with distilled water.

I did have a head gasket leak at one point (pushing air into the system on compression only, wasn't losing coolant), but there was a noticeable air bubble in the heater core any time I ran it hard (and the coolant got very cloudy and smelled awful). I've had the heads off twice since then and have never had anything like that since. The leak came up around 117k miles (fixed at 119k when I replaced the heads and cammed it).

 

[rslifkin]

I just ordered up a bottle of RMI-25, so I'll give that a shot and see if it can clean the [censored] out of the system. My big curiosity is whether the system will stay clean or if the problem will return.

 

[Donald]

Originally Posted By: rslifkin
I just ordered up a bottle of RMI-25, so I'll give that a shot and see if it can clean the [censored] out of the system. My big curiosity is whether the system will stay clean or if the problem will return.


I am by no means an RIM-25 expert. But you leave it in, its not a flush. You scoop or ladle out the crud it floats to the surface.

 

[Kuato]

I'd think that PO did not maintain it well, and only put in new coolant when selling to make it look good. IMO that's whatever corrosion built up while PO had it, and you're doing the system some good. If it were mine, a radiator drain and refill every 18 months (plus overflow bottle cleaning) would be the plan.

 

[rrguy]

You mentioned byproduct, Its possible someone before you put some sort of coolant system sealant in there & its now working loose?
If the rust starts from being exposed to air for extended time, even before you had the jeep, it can be difficult to get rid of.

 

[rslifkin]

AFAIK, it's never had a sealant in the system. I have service records going back to when it was new, the coolant had been changed twice before I got it, IIRC (so it had gone kinda long between changes).

I've never gone more than about 9 months without draining it, as I always end up doing something that requires a drain.

I get the feeling it's not an issue from before I owned it, as I've had it for almost 4 years and put 57k miles on it and the problem has gotten worse over time, not better (issue wasn't there for the first year or so of ownership, showed up a couple months after I had the heads off the first time).

I've also replaced just about every part of the cooling system while I've owned it (all hoses, water pump, t-stat, heater core, radiator, cylinder heads).

 

[Kira]

Hello, Two things:
1) I don't know the scuttlebutt about your engine (whether it's prone to head gasket leakage etc.) but since you say the heads have been off, I'll assume they were put on correctly. Smell for exhaust in the coolant now. Look for evidence of coolant in your oil.

2) The RMI-25 product is said to surround crud such that it floats to the top of your reservoir and filler neck for easy removal. That is SO COOL if it works but I wouldn't go there before really cleaning the crud out first. You DO NOT want to create cubic feet of floating crud balls. They'd (the crud balls) would be everywhere in your system-not just waiting obediently at high points for you to scoop them out with your wife's soup ladle.

Empty the old dirty coolant from your system. With plain water at first run system cleaner, dishwashing machine detergent, TSP or other real cleaners through it until it's clean. Do final rinses with distilled water. It's time consuming. The number of times people recommend flushing a dirty system with plain water is astounding. Kira

ps What kinda cam and headers did you install? K

 

[cronk]

Who knows, could have been alot of old rust settled in the system that the G05 is cleaning out.
Give it a good chemical flush if it bothers you.

 

[rslifkin]

I have checked and found no signs of head gasket leakage, so I think it's good on that front.

I'm not too worried about cubic feet of crud coming loose, as the system can't be all that dirty (insides of the hoses are fairly clean, just a light brown film on a few, coolant is still clear, no significant solid [censored] came out when it was last drained and flushed a few months ago). Most of the gunk is just in/around the radiator neck and overflow bottle.

The RMI-25 came in, so I'm going to add it to the overflow bottle this morning and let it start cleaning that out, and it'll get slowly exchanged into the system from there.

 

[rslifkin]

After a day of driving around with the RMI-25 in the system, my previously clearish yellow G-05 has now become semi-opaque green. In addition, there's a bit of yellow-ish slime forming at the top of the overflow bottle, which looks much cleaner where the coolant has contacted it. I'm curious to see how much more builds up in there and how well everything else cleans up.

 

[chadmills]

let us know how it goes.

my system is also in desperate need of cleaning. rust is back after 3 days.