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Brown equals rust. Rust equals time and frequency of servicing.

Well it could also be mud. It depends if it's a brown or orange..and even then dirt changes colour depending on where you are and where it is/has been. Just flush the coolant, dump it out and start again. Fill it up with good coolant. I'm guessing it'll just reduce the cooling slightly due to rust not exactly being a great transfer layer for moving heat energy.

possibly a dumb question but..

should you flush the rad a few times with water prior to adding
new coolant to getting any other rust/dirt etc out?

Any problems with this idea?

Gents sure you can flush your radiator but if the core is in poor condition it needs to come out and be attended to. Sort of like you teeth- you brush them daily but from time to time you go to the dentist to remove the plaque with the right equipment.

is the coolant oily?

well check your engine oil cap and the dip stick if there is white oily foam/residue...... if that's the case, then you need a new head gasket

do rotary engines have headgaskets? probably called something else.

Radiator water usually turns brown after you've boiled. I guess the steam scours the insides a bit more than just hot water. It's God's little way of telling you you weren't watching the temp gauge enough.

You should figure out why you might have boiled. Too spirited? Not enough radiator area? Not enough coolant volume? Airflow restircted? Timing retarded? Weak mixture? Wrong motor?

SuperMazdaKart wrote:do rotary engines have headgaskets? probably called something else.

Water Seals, with all the same symptoms of a blown head gasket.


Hey Mike, How did i miss your post you might have sorted it already but here's a reply anyway
Sludge can build up in the passages through the housings, one engine i dismantled had so much sludge that many of the passages were completely blocked,
The thing is, the side housings made of iron were only slightly rusty and not blocked, but the alloy rotor housings were blocked with a funny browny sludge, like clay but many times softer.

Till that point i thought as they told us at school, alloy doesn't rust, but i think here it may act as a sacraficial Anode with steel. meaning it will rust and prevent the iron from rusting, hence the sludgy type rust,

The good news is this was off an engine sitting for years with just water(no anti-corrosion coolant), and after removing the soft sludge it appeared fine, no flaking of the alloy.

So i would recommend a flush which should easily remove any build up, i doubt its bad, especialy if you had coolant in it, Give it a try and check the water.

as for an overheat, they can take a bit, i had mild overheats many times due to blocked radiators, but never broke a water seal.(they have a steel protector if built properly.) but have seen them broken, so just give it the simple test.

I guess it depends on wether you left it with plain water or not, but even if you did, the passages through the engine are much larger than the radiator and, might free up in the engine but can still block the radiator, which is what i would remove and clean out first.

Cheers
Matt.

I'll be doing a coolant flush in the near future (primarily because I want green coolant, not red ). I've spoken to a local workshop mech. It's for the BP engine, not sure how it will apply to a rotary...

Buying: new coolant, a heap of distilled water (any left overs can be drunk ), radiator/coolant cleaning stuff.
Doing:
Start with a cold engine (so you won't burn yourself). Pretty much follow the instructions on the cleaning fluid. Dump the old coolant (into a bottle so you can properly dispose of it later), fill the car up with distilled water and the cleaning fluid.
Start the engine, leave it idling for 5 mins, then take it for a quick 5 min drive around the block. This should allow the thermostat open and close a few times.
Dump the fluid (again, into a container), then start the rinse/lather/repeat cycle(s) - fill up with coolant, run for a few mins, dump it. Do it again until the water runs clear.
Fill up with coolant, run the car for a bit more (to get the air out), top up again.
Should be done!


As for the brown, I have the same problem. It looks and feels like clay (albeit massively watered down). I've been told that's a symptom of mixing red and green coolant.

lil_mike wrote:The motor was sitting with anti-corrosion coolant in it for the whole time so it wasnt just water thankfully. This was the first time the car was dríven hard in a while so it would make sense if it was clearing out all the crap inside.

Sounds fine then and should sort easily, I doubt there is much build up left in the engine, mostly moved in the Radiator(the highest point). Follow redwards steps, and should be all sweet.

Get a liquid cleaner as its easier to use. The granules variety are good but can clunk up if you pour it straight in without premixing properly with water, but both are fine if used to instructions.

Cheers
Matt

Hey man my coolant is also really brown, like mud brown...

Its always been green before.

I do drive the car more agressivley these days.

The rad is OEM the plastic top has lost its colour and is now a shade of green (was black I think)

I flush and change the fluid in summer every year... 30% AF and 70% H2O (distilled reverse osmosis) and a bottle of water wetter.

Is it an indication that the rad is on the way out or is it an indication that Im just thrashing the car these days??

I think it's an indication that the coolant is dead.

deminerlised water with half a bottle of Water Wetter does better

33percent ethylence glycol with 67 water coolant does better then the 50/50 coolant from what i've read.

Yeah Im kinda sure that the more AF you add the more you retard the effectivenss of water as a coolant.

AF only lowers the freezing point, acts as an inhibitor to corosion and has a lube effect on pumps. Im not worried about freezing.