Can I run Straight Distilled water in cooling system?

believer007

Active member
Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
Short story...

Got a Jolf, ALH...heater core jacked up by PO who ran random coolant in system. Just did TB, filled with G12, turned to mank. Drained and flushed with MB citric acid cleaner...stained driveway (came clean, eventually). Re-filled with new G12, again...still weak heat, and manky G12.

This is getting expensive.

The other day, I noticed that a lower engine speeds, I actually had better heat...I think that the mank in the heater core is starting to break up. Usually only have good heat at higher RPM.

QUESTION: can i run straight purified water in the cooling system while the temps are cooler (but not freezing), without damaging anything? Will the water pump care? Will the heat transfer ok without coolant, or will there be insufficient surface tension?

I drive 70 miles round trip to work everyday, most of it at 85mph/3000rpm...this seems to be breaking up the crap in my system - purified water is cheaper than G12, and attracts impurities...

Thoughts?
 

bbarbulo

Veteran Member
Joined
Jan 11, 2003
Location
Windsor, ON, Canada
For a couple of months, sure, why not. I wouldn't do it long long term for worry that corrosion may start. But for a little while, no issue. Water is a great coolant, no issue with surface tension.
 

turbobrick240

Top Post Dawg
Joined
Nov 18, 2014
Location
maine
TDI
2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
Yeah, I'd run and drain distilled water until it stops turning color. As long as you don't keep it in for weeks or let it freeze, it will be fine. Straight water is actually better at transferring heat than antifreeze mixture.
 

Ill Named

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Joined
Apr 17, 2011
Location
Central BC
TDI
2001 Golf, 2003 Golf
Once you get it cleaned, quit running g12. I switched both my cars to zerex g05 so I can have the same coolant across all my vehicles, including my Cummins. Way cheaper, more readily available and just as good.
 

Little-Stinker

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Aug 2, 2008
Location
Arizona
TDI
2003 Jetta Wagon GLS TDI...(Gold)
I've done it for a while in a pinch. No problems to report. Using Pentosin SF now. Cheaper in my area.
 

AnotherPerson

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Joined
Oct 24, 2015
Location
New Orleans
TDI
1999 Beetle
Gotta hope if the heater core is that clogged. That it doesn't blow a leak when it gets completely cleaned out that the goop is clogging.


Sent from my iPhone using Tapatalk
 

panteramatt

Veteran Member
Joined
Mar 27, 2015
Location
South Jersey
TDI
2003 golf
Im running straight water also. Are you guys saying running water will cause corrosion because I was planning on keeping it in there til winter.
 

believer007

Active member
Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
Thanks for the info, gang - I do appreciate it!

Pretty easy to drain and refill daily, thinkin' it will clear up after a few cycles.

Not too concerned about losing the heater core, I think that the mank in the system is a result of combining different coolant types, and using hard water to mix with. Sure, it could be plugging up a sieve, but I'd prefer to think positively!

If I were to run straight water (purified/distilled water) for very long, I'd put in some Redline Water Wetter to inhibit corrosion.
 

JoshWagen

Veteran Member
Joined
May 2, 2015
Location
Kansas City
TDI
Current: '15 GSW, '11 A3 Former: '13 JSW, 99.5 Jetta
If you want to speed the heater core unclogging process, you may want to consider manually unclogging the core. Disconnect both hoses at the core on the firewall and run some low pressure water through the core, alternating directions. I've seen videos of this being successful, although I might be hesitant to blast it with much pressure until you see water flowing through easily.
 

sisyphus

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Joined
Dec 8, 2008
Location
Appleton, Maine
TDI
99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
I did that using white vinegar to clean out the heater core. Rinsed w/ fresh water.
 

believer007

Active member
Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
If you want to speed the heater core unclogging process, you may want to consider manually unclogging the core. Disconnect both hoses at the core on the firewall and run some low pressure water through the core, alternating directions. I've seen videos of this being successful, although I might be hesitant to blast it with much pressure until you see water flowing through easily.

Thought about that, but those hoses and anything connected to them are a bit of a PITA to get to...

If the heater is this way, the main Rad probably is too - just because i don't have over heating issues now, doesn't mean that i won't in the summer!

thanks!
Tk
 

sisyphus

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Dec 8, 2008
Location
Appleton, Maine
TDI
99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
How long did you run it that way, and at what ratio?

thanks!

Tk

15 minutes probably. I got some clear vinyl tubing to put onto the fittings outside the firewall and set it up so I could pour it in one until it came out the other (both were pointing up). Then I flushed it out both directions with the garden hose.
Not much came out.
 

sisyphus

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Joined
Dec 8, 2008
Location
Appleton, Maine
TDI
99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
There's the possibility that your blend door isn't working anymore, either.
 

Smokin' Dually

Veteran Member
Joined
Dec 3, 2006
Location
N.E. Wisconsin
TDI
Jetta
Disconnect both hoses at the core on the firewall and run some low pressure water through the core, alternating directions. I've seen videos of this being successful, although I might be hesitant to blast it with much pressure until you see water flowing through easily.
I've done this on several cars over the years including our '01 Jetta. Include the EGR cooler in your flush and I think the hoses are easier to get to.

I also had to clear out non-G12 coolant and took a few hoses off and had at it with the garden hose. I drive the same distance to work as you and I think that after rinsing I filled it, drove to work, and drained it twice before adding the G12. It stayed pink.
 

totalloser

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Joined
Dec 24, 2010
Location
BFE CA
TDI
04 golf
Pure water will host electrolysis erosion of aluminum. I wouldn't do it regularly regardless of weather.
 

believer007

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Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
Pure water will host electrolysis erosion of aluminum. I wouldn't do it regularly regardless of weather.

I'm no physicist, but electrolysis is going to occur regardless of what type of fluid is in the car - just the same as it happens when you connect copper plumbing directly to galvanized plumbing. The purity of the water, nor lack thereof, has no bearing on the occurrence of electrolysis.

Check your facts, please, and show references for your statement. If I am incorrect, I'd like to know the specifics. I'm not interested in taking something as fact just because someone said it on the internet.
 
Last edited:

gatz

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Joined
Oct 29, 2005
Location
Windsor, CT
TDI
2005 Mk4 Golf TDI PD, 2006 MkV Golf GTI
We did this in an old Buick with a small crack in the rad. The water would boil & temp gauge would start to rise every 15 minutes or so, and it would need to be topped off. I would say try it anyway and see, your TDI's engine wont put out nearly as much heat but ambient temp in the summer could play a role. Water will boil around 100C and 50/50 G13 mix is good for ~130C according to the back of the bottle.
 

marinetech

Member
Joined
Apr 23, 2017
Location
finland
TDI
audi
Short story...

Got a Jolf, ALH...heater core jacked up by PO who ran random coolant in system. Just did TB, filled with G12, turned to mank. Drained and flushed with MB citric acid cleaner...stained driveway (came clean, eventually). Re-filled with new G12, again...still weak heat, and manky G12.

This is getting expensive.

The other day, I noticed that a lower engine speeds, I actually had better heat...I think that the mank in the heater core is starting to break up. Usually only have good heat at higher RPM.

QUESTION: can i run straight purified water in the cooling system while the temps are cooler (but not freezing), without damaging anything? Will the water pump care? Will the heat transfer ok without coolant, or will there be insufficient surface tension?

I drive 70 miles round trip to work everyday, most of it at 85mph/3000rpm...this seems to be breaking up the crap in my system - purified water is cheaper than G12, and attracts impurities...

Thoughts?
you could, but should not. coolant protects the hoses, block, and seals. over time water will corrode these components. i have seen large diesel marine engines with a ton of heat exchanger problems for this reason. and if you are driving very high milage electrolosis will speed up the corrosion, i think coolant is less suseptable to this
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
DO NOT do it.

If you insist on using distilled water go get some Fleetguard inhibitor intended for diesel engines and mix that in the appropriate ratio. This will provide corrosion protection (which you NEED) but remember that straight water provides ZERO freeze protection and your thermostat is designed for the elevated boiling point of a 50/50 coolant/water mix. If you get localized boiling in the cylinder head (most-likely place for it to happen) you run the risk of cylinder head cracks, and yes, it does happen.
 

believer007

Active member
Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
DO NOT do it.

If you insist on using distilled water go get some Fleetguard inhibitor intended for diesel engines and mix that in the appropriate ratio. This will provide corrosion protection (which you NEED) but remember that straight water provides ZERO freeze protection and your thermostat is designed for the elevated boiling point of a 50/50 coolant/water mix. If you get localized boiling in the cylinder head (most-likely place for it to happen) you run the risk of cylinder head cracks, and yes, it does happen.
Thank you for the info - not looking to run this long term, only to get the crap in suspension, and then flush it out immediately after driving.

I've done the drive and flush 3x's now, and believe I have grabbed all that I am going to at this point. Time to reverse flush the core. Local VAG tech at dealership recommended using 50/50 CLR on recirc, which is what they do.

Will do that until the flow rate increases, then long flush with water, and refill with the appropriate mix. That should get me to where I need to be...and then on to the AC issue! (100psi both sides, static...120 HS, 75psi low side dynamic...X-Florida car, black...suspect AC Compressor is done.)
 
Last edited:

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
If the system has pressure and the compressor is not making nasty noises when engaged but is not producing pressure there are very good odds that the RCV is bad and the compressor ITSELF is fine. Fixing it properly requires (1) a new drier, (2) a set of gaskets and the RCV itself and (3) some of the correct compressor oil and CARE to make sure you don't get anything in the open lines when it's apart.

The drier MUST be replaced when the system is opened (there are also two O-rings on it and a couple of the compressor fittings that must be replaced too but those are minor); it's not expensive.

You won't know if the compressor is lunched until you take it apart; swab the inside of the lines when you take them off and if you have little metal flakes in either, it's done. If so cinch it back up, lock out the compressor (remove the fuse so it CANNOT be turned on) and figure out how much you like the idea of $750+ worth of parts and a day and a half to rip the dash out of the car to change the condenser, evaporator, compressor itself, dryer and maybe the lines and expansion valve. On a car this old it's probably wiser to change them rather than flush them but you MUST at least flush them or the new compressor will be destroyed almost immediately if any of the particles that got spewed out when the compressor failed find their way back to it, and if they're not cleaned out of there they eventually will.

If both sides are CLEAN and show only oil and a bit of discoloration (NO metal-tinged anything) then pull the compressor out of the car and put a RCV + gasket kit in it, a new dryer with about an ounce of oil for it (plus whatever you lost when you unhooked the compressor), and then have hard vacuum pulled on it for a couple of hours and (assuming nothing leaks) a by-weight freon charge put in it. If you have the gauges and equipment fixing a bad RCV is a few hour job and ~$75 worth of parts. If the compressor is grenaded internally it's big bucks no matter how you slice it. Unfortunately most auto A/C places (all?) will NOT investigate the RCV possibility (which would be a couple of hours of labor and $100 worth of parts) and fix it that way; they'll sell you a $1,500 AC rebuild job soup-to-nuts instead, and there's no legal way to discharge the system without taking it to an A/C place to have it evacuated; it's (quite) illegal to intentionally vent the refrigerant.

BTW while I've seen people say this can be done with the compressor in-car I wouldn't try it. It's NOT hard to remove and if you get any dirt or other foreign material in it you will cause the compressor to grenade down the road and wind up with the big bill anyway. Take it out and do it on a bench where you can be extremely careful about cleanliness and avoiding contamination. You'll also spill materially less oil this way and thus have to guess less.

My '03 is doing the same thing and it's going to get torn apart here sometime soon - it's my kid's car now and it's producing SOME cooling; she's leery of having it torn down and having NO A/C if the compressor is lunched and she's faced with either no A/C ever (in Florida) or forking up $750+ and a couple days or more of downtime -- so the timing on the job is on her at this point.
 
Last edited:

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
For a couple of months, sure, why not. I wouldn't do it long for the long term for worry that corrosion may start. But for a little while, no issue. Water is a great coolant, no issue with surface tension.
From what I remember of what I learned in school, and from running & working on race cars water is a pretty good lubricant & heat transfer medium on its own, but not great on its own....

But water alone has a very high surface tension value which limits its ability to cool that well as temps rise....

The best way I think of to explain this is to have someone understand this is to have them picture what mixing antifreeze coolant into water does to help water's ability to cool is to think of a water bug walking on top of the water without getting wet...

Then see what happens to that waterbug happily walking on top of the water if you add a drop of soap into the water....You will see that the lowered surface tension from the drop of soap sends the poor bug into the water to take a swim....

this is what an antifreeze/water mix does, it lowers the surface tension to the point where the water can more easily make contact with the metal transferring the heat more thoroughly cooling the engine better & faster when faced with extreme heat events or pulses produced by driving over extreme terrain.

So the antifreeze coolant mix serves two main jobs,
first is it reduces the base water in the mix's surface tension so it can more easily absorb & transfer engine heat...

second is its ability to raise the boiling point & lower the freezing point.....

what we used to do in the race cars I ran & worked on was add something called wetter water which lowered the coolant/water mix's surface tension increasing its ability to more quickly absorb the heat then remove it....

If you have a clogged heater core there are flashes which can be used for a ~week or so of driving around going through the heat cycles as long as nighttime temps for that period are above freezing in the place you keep the car in.

Once you get done with long term flushing of the coolant system, drain the caustic rinse into a catch basin.

Then will need to use a hose hooked up to the system to flush the stuff out of the system once the cleaning is done it should be diluted enough not to cause a problem if it gets on the ground.

If you are worried fill the system once with clean water then catch it coming out....then do what is described above...

Over the years on many vehicles which have had their coolant systems neglected, I have had positive results from doing this, getting a completely operational cooling system again...
 

turbobrick240

Top Post Dawg
Joined
Nov 18, 2014
Location
maine
TDI
2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
Many track cars use just water and a surfactant(water wetter). As long as the system is pressurized, the water won't boil until well over 100*C.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Again if you're going to run straight water then use the Fleetguard diesel inhibitors. Incidentally the reason track cars run straight water is that Ethylene Glycol transports less heat (by quite a bit) than water does; running straight water improves the heat transport capacity of the cooling system materially (~10% or so.)

For the same reason I have run straight water + inhibitors in some marine diesels in non-freezing environments. Many older engines (Detroit Diesels to be specific) had marginally-sized heat exchangers as they used original units for that purpose but were marinized by some other company and their output was massively increased over Detroit's original specs (sometimes by 50% or more!) Since the heat exchanger tanks were NOT upsized this led to a real problem with cooling system capacity, especially in tropical climates where the seawater is often 80F or even warmer. Running straight distilled water + inhibitors in the engine frequently is the difference between an engine that runs at a nice stable temperature under load and one that slowly creeps up until it overheats.
 

believer007

Active member
Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
If the system has pressure and the compressor is not making nasty noises when engaged but is not producing pressure there are very good odds that the RCV is bad and the compressor ITSELF is fine. Fixing it properly requires (1) a new drier, (2) a set of gaskets and the RCV itself and (3) some of the correct compressor oil and CARE to make sure you don't get anything in the open lines when it's apart.

The drier MUST be replaced when the system is opened (there are also two O-rings on it and a couple of the compressor fittings that must be replaced too but those are minor); it's not expensive.

You won't know if the compressor is lunched until you take it apart; swab the inside of the lines when you take them off and if you have little metal flakes in either, it's done. If so cinch it back up, lock out the compressor (remove the fuse so it CANNOT be turned on) and figure out how much you like the idea of $750+ worth of parts and a day and a half to rip the dash out of the car to change the condenser, evaporator, compressor itself, dryer and maybe the lines and expansion valve. On a car this old it's probably wiser to change them rather than flush them but you MUST at least flush them or the new compressor will be destroyed almost immediately if any of the particles that got spewed out when the compressor failed find their way back to it, and if they're not cleaned out of there they eventually will.

If both sides are CLEAN and show only oil and a bit of discoloration (NO metal-tinged anything) then pull the compressor out of the car and put a RCV + gasket kit in it, a new dryer with about an ounce of oil for it (plus whatever you lost when you unhooked the compressor), and then have hard vacuum pulled on it for a couple of hours and (assuming nothing leaks) a by-weight freon charge put in it. If you have the gauges and equipment fixing a bad RCV is a few hour job and ~$75 worth of parts. If the compressor is grenaded internally it's big bucks no matter how you slice it. Unfortunately most auto A/C places (all?) will NOT investigate the RCV possibility (which would be a couple of hours of labor and $100 worth of parts) and fix it that way; they'll sell you a $1,500 AC rebuild job soup-to-nuts instead, and there's no legal way to discharge the system without taking it to an A/C place to have it evacuated; it's (quite) illegal to intentionally vent the refrigerant.

BTW while I've seen people say this can be done with the compressor in-car I wouldn't try it. It's NOT hard to remove and if you get any dirt or other foreign material in it you will cause the compressor to grenade down the road and wind up with the big bill anyway. Take it out and do it on a bench where you can be extremely careful about cleanliness and avoiding contamination. You'll also spill materially less oil this way and thus have to guess less.

My '03 is doing the same thing and it's going to get torn apart here sometime soon - it's my kid's car now and it's producing SOME cooling; she's leery of having it torn down and having NO A/C if the compressor is lunched and she's faced with either no A/C ever (in Florida) or forking up $750+ and a couple days or more of downtime -- so the timing on the job is on her at this point.
Thanks again for the info!
 

believer007

Active member
Joined
Sep 18, 2016
Location
Boise, Idunow
TDI
2004 Jetta Wagon TDI
From what I remember of what I learned in school, and from running & working on race cars water is a pretty good lubricant & heat transfer medium on its own, but not great on its own....

But water alone has a very high surface tension value which limits its ability to cool that well as temps rise....

The best way I think of to explain this is to have someone understand this is to have them picture what mixing antifreeze coolant into water does to help water's ability to cool is to think of a water bug walking on top of the water without getting wet...

Then see what happens to that waterbug happily walking on top of the water if you add a drop of soap into the water....You will see that the lowered surface tension from the drop of soap sends the poor bug into the water to take a swim....

this is what an antifreeze/water mix does, it lowers the surface tension to the point where the water can more easily make contact with the metal transferring the heat more thoroughly cooling the engine better & faster when faced with extreme heat events or pulses produced by driving over extreme terrain.

So the antifreeze coolant mix serves two main jobs,
first is it reduces the base water in the mix's surface tension so it can more easily absorb & transfer engine heat...

second is its ability to raise the boiling point & lower the freezing point.....

what we used to do in the race cars I ran & worked on was add something called wetter water which lowered the coolant/water mix's surface tension increasing its ability to more quickly absorb the heat then remove it....

If you have a clogged heater core there are flashes which can be used for a ~week or so of driving around going through the heat cycles as long as nighttime temps for that period are above freezing in the place you keep the car in.

Once you get done with long term flushing of the coolant system, drain the caustic rinse into a catch basin.

Then will need to use a hose hooked up to the system to flush the stuff out of the system once the cleaning is done it should be diluted enough not to cause a problem if it gets on the ground.

If you are worried fill the system once with clean water then catch it coming out....then do what is described above...

Over the years on many vehicles which have had their coolant systems neglected, I have had positive results from doing this, getting a completely operational cooling system again...
Thanks, and I agree..I've used RedLine Water Wetter in various cars that i have...great stuff.

Not too interested in running anything through the entire system for very long, as I just replaced the Tbelt and all...don't really want to damage the new water pump/seals. Everything else flows - it's time to isolate and conquer!
 
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