orange/brown gunk in cooling system

Pantelis Giamarellos pantg at
Tue Mar 13 01:37:01 EDT 2007

Ameer Hi,

Mixing the blue/green coolant with the orange one is an absolute NO NO.

Even when you completely replace one type with another and first clean
thoroughly with water it is supposed that you have to use a special
coolant system cleaner and neutraliser before filling up with the
different type of coolant in order to be able to do so.

We have the same problems with Land Rover vehicles and according to the
instructions provided by the technical director of LR here in Greece
those are the things that you have to keep in your mind.

1.  NEVER MIX blue/green with orange coolant.
2. ALWAYS USE the cleaning/neutralising liquid when you perform such a
change on your cooling system.
3. NEVER use tap water with blue/green coolant.
4. NEVER use de-scaled or distilled water with the orange coolant.  This
orange coolant is ORGANIC and tap water provides it with its nutritional
elements (in plain english tap water is its food)
5. NEVER keep the orange coolant for more than two years on a used car
or five years on a new car. It is even better to change it more
frequently than that.
6. If you use orange coolant and the cooling system overheats too much
it is better to change it.
7. The organic orange coolant leaves a very thin layer on the cooling
system's surface. This actually stops electrolytic corrosion which is a
known problem of mixing different types of metals and alloys, something
very common nowdays.
8. When the organic coolant dies the thin layer transforms into gunk
which blocks coolant passages inside the engine and radiator and this
results into the overheating problems and what you have seen as
orange/brown gunk.

All the above is valid for LR engines but I think it makes perfect sense
to also be applicable on other manufacturers engines.


Take care

-----Original Message-----
From: quattro-bounces at [mailto:quattro-bounces at]
On Behalf Of Ameer Antar
Sent: Tuesday, March 13, 2007 4:15 AM
To: Quattro List
Subject: orange/brown gunk in cooling system

Hi All, I've got a new mystery for you. This is from my '85 5kt with
less than 7k since restoring it...
So I had to replace the radiator fan switch this weekend because the
low-speed part flaked out. When I was in there I noticed some
orange/brown mud on the sensor and in the radiator hoses. The coolant
also looked the same. I was surprised because I replaced the coolant
with the blue stuff in October. Everything is new in the system, except
the reservoir. The engine was rebuilt and first run in June, and I
replaced/cleaned out all hoses, even the transmission cooler.
I doubt the fan switch dying is related, but it seems a little too young
to crap out like that. In a way, I'm glad it did to make me notice the
coolant. So what could be causing the coolant to turn brown after only a
few months? The only thing I can think of is in Sept. I bent a valve,
and after replacing the head using ARP studs, I took a little too long
to retorque the studs. I noticed that coolant was leaking out under the
head. So could exhaust getting into the coolant cause that? No real
issues with overheating or frothing reservoir. No water in oil, or white
smoke in the exhaust.
This weekend I flushed the entire system really well with a garden hose.
I also ran the engine with the hose connected to the engine coolant
inlet until the water came out clear. The coolant is looking nice now,
but I have to keep an eye on it. Is there any way to tell if exhaust is
getting into the coolant or should I be looking for something else?
Thanks in advance.

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