Coolant Filter

icanreachit

Well-known member
Joined
Oct 2, 2011
Location
Arlington, VA
TDI
VW Golf TDI
Alright, first step out of the 101 forum. I've read that I should just flush the system thoroughly and be done with it. But, despite running the hose through it for hours, a few thousand miles later, the coolant always turns brown and I find specs of rust in it.

If you were to install a coolant filter (not asking if you'd do it), where would you locate it? I was thinking to install it where I've seen block heaters installed pictured as the green block (going to the oil cooler). This keeps me from having to cut any lines so that I can pull the filter and return the system to stock in 20k. However, everything I've found suggests to run it as a bypass loop instead of in a main line.

 

compu_85

Gadget Guy
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Sep 29, 2003
Location
La Conner, WA
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... None :S
Putting it there makes sense to me... if it got blocked up it would stop flow through the oil cooler, but wouldn't block coolant flowing through the head.

I'd want to monitor the filter closely, the oil cooler is important.

-J
 

Mongler98

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Mar 23, 2011
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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
no. go simple
So useing a garden hose is BAD nad probably the source of your rust.
You can flush it out with one but you need to flush it with distilled at the end. Tap water is #1 is your brown water.

Fill and draine 2 times with distilled, and put a 3 cups of viniger in it and run it for 10 minutes once up to temp. Drain and flush with distilled again but this time add about 2 to 3 table spoons of laundry detergant, HE if you have it and run that for 10 minutes after warmed up.
2 more flushes with distilled after hoseing it out to get soap out. You want to be flushing the heater core as well and every part individually. Dont run with the thermostat out as you wont get it hot, you want the heat to do the work for you.
DISTILLED DISTILLED DISTILLED
even if you drain everyting 100%, there is still like a quarter gallon left in the block and radiator. you want that to be as clean as possible.
NEVER add or top off with anything other than proper coolant and distilled water.

any filter is not going to stop this as its chemical reaction happening to your block vs catching some sediment from ages ago.

Iron out is a fantastic powder you mix with water, i used that once on an old 350sbc and it came out amazing at the end. but i found that it did not like the gaskets.
 

CtG

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Apr 28, 2019
Location
BCS, TX
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2002 Jetta 5-spd Sedan
Cascade dish washing detergent is an approved Caterpillar engine flushing agent, see no reason why it wouldn't work here to knock out loose gunk.
The regular gel detergent, their replacement for "Pure Rinse" is the one in question.
Per Cat, "add enough 269-1948 non-foaming detergent to equal approximately 2-3% cooling system capacity. Pre-dissolve the detergent in distilled water, add mixture directly to cooling system. Run the engine for at least 30 minutes. Drain the system and flush with distilled water."

Definitely do the distilled flush, the contaminants in tap water not only contribute to scaling, but can accelerate electrolysis and oxidization.


If you do determine to use a filter, make sure you use one WITHOUT the DCS pellets built in.
 

Mongler98

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Mar 23, 2011
Location
COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
You will never fit a filter under the hood that will flow the proper gpm (gallons per minute) that you need to not overheat and blow something like a hose or head gasket and still filter out what is actually turning brown.
I've been there done that sort of thing. Bad idea
 

Nero Morg

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Oct 19, 2017
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OR
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2014 A6 TDI, 2001 Jetta TDI, 2014 Passat TDI
Most coolant filters are bypass filters, and they're mostly to balance out silicate levels. You're better off running some stuff through your system to clean it out, like others have suggested.
 

icanreachit

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Oct 2, 2011
Location
Arlington, VA
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VW Golf TDI
Alright, sorry for being vague with the "hose" comment. The flushing history is as follows:
Purge by force with hose, distilled "flush", run up to temp and refill x 2
Then ran three days with the Prestone flush, again flushed with distilled till clear. Then up to temp, drain and refill x 2.

Two weeks later it's back every time. I've been through one heater core. I've done the flushing with the thermostat pulled to get the radiator.

I acknowledge that it's chemical, I don't leave anything in there but distilled and approved coolant (from IDparts or dealership). The root cause is when my brother borrowed it he put windshield washer fluid in. No idea how long it ran that way. No more than 3k.

I don't agree on the coolant filter not being effective as scaling likely occurred and will continue to come off until the system is again clean. A bypass route is preferred so that there is no potential overheat issue. Adding it in a known high pressure area with a T and connecting the other side to a known low pressure area with a T would prevent any system interference in the event it gets fully clogged. I am only using non chem added filters.
 

Nero Morg

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Oct 19, 2017
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OR
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2014 A6 TDI, 2001 Jetta TDI, 2014 Passat TDI
If you really want to add a filter, the best place I would imagine one would be on the anti aeration line that runs from the EGR cooler to the coolant resivour, since it has a constant flow of coolant. Just make sure you get a high flow filter.
 

Mongler98

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Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Let her soak with vinegar solution and rince and repeat. eventually you will get it out, might take a while you but will and the only way it with a chemical reaction to break it loss.
 

icanreachit

Well-known member
Joined
Oct 2, 2011
Location
Arlington, VA
TDI
VW Golf TDI
Alright Mongler, you sold me. I'll do what you subscribed, as follows:

Fill and drain 2 times with distilled
On 2nd refill, add 3 cups of vinegar, run 10 minutes once up to temp
Drain and flush with distilled again but this time add about 2 to 3 tbs of Cascade Dish Detergent, for 10 minutes after warmed up.
2 more flushes with distilled

Then I'll add the filter on the line headed into the heater core. If it clogs, no heat, but then again it's almost summer, so that's fine.
 

2003VW

Member
Joined
May 11, 2011
Location
Darlington, MD
TDI
2003 Jetta
coolant filter

Had an old truck which had rusty coolant I could never clean up by flushing. Added a bypass coolant filter in the supply line to the heater. After running for a month or so, coolant is now clear and no more rust.



Agree on using a 50/50 mix of the recommended anti-freeze and distilled or de ionized water.
 
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