Cooling System 101

Turbo Steve

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Location
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All Volkswagen's use only one kind of antifreeze or coolant, no matter what engine propels them - gas or diesel. VW calls this red-colored coolant "G-12" and mixes all cars shipped to the U.S. with a 40% solution of antifreeze and those going to Canada get a 60% for better protection.

VW's G-12 Coolant is a similar substance to Prestone's 5/15 Extended Life or Havoline's Dex Cool.

All VW engines use an impeller-type waterpump that is mounted into the cylinder block that usually is belt-driven. In the case of the A-4 TDI engine, the waterpump is driven by the Timing Belt, further adding more stress to this part that needs replacement at regular intervals, as it also drives the Injection Pump and Valvetrain.

VW radiators are all cross-flow in design, with plastic side tanks and obviously an aluminum core assembly. The cooling system capacity of the (ALH) TDI engine is 6.3 quarts or 6.0 liters.

Thermostats control two radiator cooling fans via a thermoswitch located in the side of the radiator's plastic tanks. As the water temperature rises, the switch closes to start the electric fans in one of the two following stages:
____________

Radiator Fan Thermo-Switch Operating Temperatures

* Stage I - Low Speed

Switch on...............197* - 206*F (92* - 97*C)
Switch off..............183* - 195*F (84* - 91*C)

* Stage II - High Speed

Switch on...............210* - 221*F (99* - 105*C)
Switch off..............195* - 208*F (91* - 98*C
____________

Naturally, running the A/C will also activate the cooling fans as well.

The (ALH) TDI diesel engine uses a 195*F thermostat that actually starts to open at approximately 185*F (85*C) and is fully open by approximately 221*F (105*C), with the central spring-loaded butterfly valve traveling about 0.28" or 7mm from closed to fully opened.

Note: Key data listed above and pictures below are courtesy of RB's 2000 Jetta / Golf Repair Manual - Section 19.

[ August 04, 2001: Message edited by: Turbo Steve ]
 

Turbo Steve

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Joined
Jan 11, 2000
Location
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TDI Cooling System Schematic



1 - Expansion tank
2 - Intake manifold
3 - EGR cooler
4 - Connector
5 - Heater core
6 - Coolant center line
7 - ATF cooler (Vehicles with automatic transmission)
8 - Coolant hose, upper
9 - Coolant hose, lower
10 - Radiator
11 - Oil cooler
12 - Coolant pump/coolant thermostat
13 - Cylinder head/cylinder block


Cooling System Components



1 - Connector
2 - Coolant hose, upper
3 - To heater core
4 - From heater core
5 - To connector in coolant hose, upper
6 - Engine Coolant Temperature (ECT) Sensor (G62) Blue in color
7 - Bracket
8 - O-ring
9 - Connector (Always replace)
10 - Bolt: 10 Nm (7 ft lb)
11 - Coolant line
12 - To radiator, upper part
13 - O-ring (Always replace)
14 - To expansion tank, lower part
15 - Bolt - 15 Nm (11 ft lb)
16 - From radiator, lower part
17 - Coolant thermostat
18 - Oil cooler
19 - Coolant or Water-pump
20 - Cooler For EGR
21 - To expansion tank, upper


Radiator Fan Diagrams



1 - Radiator
2 - O-ring (Always replace)
3 - Coolant hose, upper
4 - Connector
5 - Retaining clip
6 - A/C Cut-out Thermal Switch -F163-
7 - From connector on cylinder head
8 - From connector on cylinder head/connector
9 - From ATF cooler (Only for vehicles with automatic transmission)
10 - Electrical connector / Color: black
11 - Cap: Test pressure 1.4 to 1.6 bar
12 - Bolt: tighten to 10 Nm (7 ft lb)
13 - Coolant expansion tank
14 - From connector to radiator for EGR/connector
15 - To cylinder head
16 - Fan shroud
17 - Right coolant fan -V35-
18 - Fan bracket
19 - Retaining clip
20 - Coolant fan -V7-
21 - Bracket
22 - Coolant hose, lower
23 - Electrical connector / Black, 3-pin connector
24 - Coolant Fan Control (FC) Thermal Switch -F18-
* Stage 1. 0N: 92 to 97 C
* Stage 1. OFF: 84 to 91 C
* Stage 2. ON: 99 to 105 C
* Stage 2. OFF: 91 to 98 C
25 - Bracket


ALH Coolant Water-pump



1. Idler Pully Bolt
2. Idler Pully
3. Pump Housing Bolt
4. Coolant Water-pump
5. O-ring seal


Thermostat 195*F.



1. Mounting Bolt
2. Flange
3. O-ring
4. Thermostat


FYI - For draining G-12 coolant out of the cooling system, open the cooling system drain thumb screw (pictured below).

 

Drivbiwire

Zehntes Jahr der Veteran
Joined
Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
Steve do me a favor, I was out looking at my A4 Automatic and it appears that the above posted pictures are that of the Automatic TDI. After having done a few manual TDI's I have realized that the manual uses diferent routing style of the cooling system off of the head. The big diference is that on the auto TDI you do not have to remove the cooling system tube off of the head to remove the vacume pump, where as on the manual you do. I will try and find some pictures to compare but my impressions are that the automatic does NOT have supplemental glow plug heaters! I could not find them and that is when I realized that the cooling system on my 2000 TDI auto is different!

Anyway let me know what you find out.

This also explains why TDI automatics seem to be done faster when the dealer does the changes based on forum member feed back.

more to follow,
DB
 

Turbo Steve

Top Post Dawg
Joined
Jan 11, 2000
Location
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Pete:

Are you referring to the 3 Auxilliary Coolant Glow Plugs mounted at the end of the cylinder head on the driver's side?



My manual doesn't differentiate between transmissions. Perhaps more info can be found in a recent post on this because a few others have noticed this as well.

http://forums.tdiclub.com/NonCGI/Forum3/HTML/004267.html

If this is true, I wonder if this is because an automatic driven TDI engine naturally works harder than a more efficient manual transaxle or if there is something in the design that caused VW to eliminate the 3 Coolant Glow Plugs.

[This message has been edited by Turbo Steve (edited January 22, 2001).]
 

Ric Woodruff

BANNED, Ric went to Coventry.
Joined
Feb 19, 1999
What ever happened to the idea of a "Steve 101 Section"???

------------------
Ric Woodruff

"Worry gives small things a big shadow"


1998 Jetta TDI Custom Sport
 

Drivbiwire

Zehntes Jahr der Veteran
Joined
Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI


check out #9 in your diagram and compare it to the manual transmission TDI

1 - Connector
2 - Coolant hose, upper
3 - To heater core
4 - From heater core
5 - To connector in coolant hose, upper
6 - Engine Coolant Temperature (ECT) Sensor (G62) Blue in color
7 - Bracket
8 - O-ring
9 - Connector (Always replace)
10 - Bolt: 10 Nm (7 ft lb)
11 - Coolant line
12 - To radiator, upper part
13 - O-ring (Always replace)
14 - To expansion tank, lower part
15 - Bolt - 15 Nm (11 ft lb)
16 - From radiator, lower part
17 - Coolant thermostat
18 - Oil cooler
19 - Coolant or Water-pump
20 - Cooler For EGR
21 - To expansion tank, upper


Steve if you look at the flow of the system it appears that the coolant is routed through the EGR cooler and then into the heater core. If this is the case they are using the exhaust gasses to heat the coolant and a free source of heat without having to load up the electrical system.

I also realized that the Auto uses a 90 amp alternator and that the alternator may be the rumored load shedding type. When the engine is under heavy load or hard accel the alternator kicks off line to allow for more power to be developed. Another thing worth looking into!

DB

[This message has been edited by Drivbiwire (edited January 23, 2001).]
 

SoTxBill

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Joined
Dec 14, 2000
Location
its not the base, its the additives!!
TDI
13 passatdsg 10 jetdsg, 09 jetdsg, 2006 jetdsg, 2001Jet, 96passat, 86jet, 81 jet, 78pickup all vw diesel.
several comments..
1st the space shuttle is not as complex
2nd one of the hoses cost $70.. I know
3rd thanks for the great post
4th creating a 101 section might be a good place to "reference" back to..
5th.. what kind of anti freeze its it? is it a low silicate extended drain diesel antifreeze? 5 year 50,000 miles would be good inspite of what the book says.

[This message has been edited by TexasBill (edited January 23, 2001).]
 

gardentender

RIP, Gone But Not Forgotten
Joined
Feb 17, 2000
Location
Dullest Texxus
TDI
Jetta GL 5 spd, 2001, Galactic Blue
i agree on the "101" section, but not limited to just TurboSteve's dissertations.

TurboSteve, thanks for the great posts. Keep it up and I won't need a Bentley manual!!

Anything planned for the oil cooler, etc?

------------------
2001 Jetta GL TDI, 5 spd,
Galactic Blau/Tan,
manual ash trays,
loud radio/cassette deck, see-thru windshield
 

Drivbiwire

Zehntes Jahr der Veteran
Joined
Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
Yes the coolant is extended drain, the coolant is a VW specific number otherwise the same as other extended drain antifreezes.

DB
 

vwnut84

Veteran Member
Joined
Jan 16, 2000
Location
Saugerties NY
TDI
1982 Rabbit Diesel LS - 1991 Jetta Coupe 1Z tdi
Why on earth do you take a perfectly good design, and re-do it? The case here with the waterpump. Why put it on the timing belt, when it worked fine on the drive belts?

------------------
Chris - "There is a fine line between genius and insanity. I erased that line"
1985 diesel Jetta 328,000miles - My beater car, looking for another diesel come spring
1989 diesel Jetta 185,000miles - Mom's car

Real Volkswagens don't have power anything...
 

tadc

Top Post Dawg
Joined
Apr 13, 2001
Location
Stumptown
TDI
Golf GLS TDI, '01, Black
Excellent piece of work Steve.

A couple points of discussion: my car claims to have 3-speed radiator fans. Is the 3rd speed perhaps "AC on"?

Re: load-shedding alternator- This seems like an unlikely scenario to me. When the alt "disconnected", the system voltage would drop from 14ish volts down to 12ish. This would almost certainly cause a noticeable change in headlight brightness, dashboard illumination, etc.
 

NYTDI

Veteran Member
Joined
Mar 23, 2001
Location
Mid - Hudson
TDI
1999.5 Golf TDI AUTOMATIC trans. GLS w/PLX package silver/black cloth
According to Texaco their Dexcool equiv. is not approved by VW. One of their research/test labs is located in my area so I called locally to get any more info. I was told that they feel that the VW coolant is signifigantly the same as Dexcool but they know that it is not ident. to it and VW has not approved Dexcool for use in their engines. No harm should result from the use of Dexcool.

If you have hard water use distilled water to dilute the coolant when you refill the system.

Dexcool is a farce, it may extend the life of your pump somewhat but do not leave it in your system for more than 2 years. The horror stories will be many in the next few years.

I stand corrected on VW approval of Texaco "Dexcool". Perhaps a recent development, My inquiry to them was almost a year ago.
http://thegenesisnetwork.equilon.com/genesis/prodinfopdf/out/HAVOLINE%20DEX-COOL%20EXTENDED%20LIFE%20ANTI-FREEZECOOLANT.pdf

[ June 18, 2001: Message edited by: NYTDI ]
 

SoTxBill

Top Post Dawg
Joined
Dec 14, 2000
Location
its not the base, its the additives!!
TDI
13 passatdsg 10 jetdsg, 09 jetdsg, 2006 jetdsg, 2001Jet, 96passat, 86jet, 81 jet, 78pickup all vw diesel.
nytdi,, what are you hearing?? i was under the impression that the extended drain that all the manufactors are switching to is suppose to have additives that last longer than two years...

as cheap as antifreeze is, i would rather change sooner if there's a problem.. thanks bill
 

Turbo Steve

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Joined
Jan 11, 2000
Location
.
I wouldn't worry about using DexCool in your VW. I am in mine, and when I flushed the OEM coolant, I even added an extra Prestone coolant fortifier to provide additional lubricants for the waterpump.
 

NYTDI

Veteran Member
Joined
Mar 23, 2001
Location
Mid - Hudson
TDI
1999.5 Golf TDI AUTOMATIC trans. GLS w/PLX package silver/black cloth
What I am being told by both ind. and GM mechanics is that while the extended drain coolants have been refomulated so that they impact pump life less than the old coolant the Dexcool has a tendency to "fall apart" if there is any boilover or excess stress on it, like when a cap goes bad. Apparently solids start precipitating out and start to clog heater core and radiator. Ask a GM mechanic how many clogged heater cores they have had to deal with due to this junk. I don't know if VW coolant is any better, at the price the stealer wants it should be perfect.

When I inquired, Prestone told me they reccomend AGAINST putting their rust inhibitor & pump lube additive in the extended life coolant. It contains some of the things (silicates I believe) that were formulated out of the "Dexcool" so if you add it the coolant becomes regular not extended.

The common thread I heard (from mechanics)was to treat "Dexcool" like the old stuff and flush every year or two and after any "stress" on it. I never did annual flushes w/ the green stuff, I do every other year and in the "off" year I add a bottle of the inhibitor/lube. I'll do every other year w/ the extended life and keep my eyes open for a compadible additive for the off year.
 

Turbo Steve

Top Post Dawg
Joined
Jan 11, 2000
Location
.
Thought bringing this thread to life in the middle of the heat might help cool things off for a few of you!
 

cumminsfromthecold

Veteran Member
Joined
Oct 27, 2006
Location
HumCo
TDI
'84 Toyota 1Z 4WD x-cab
TDI Cooling System Schematic



1 - Expansion tank
2 - Intake manifold
3 - EGR cooler
4 - Connector
5 - Heater core
6 - Coolant center line
7 - ATF cooler (Vehicles with automatic transmission)
8 - Coolant hose, upper
9 - Coolant hose, lower
10 - Radiator
11 - Oil cooler
12 - Coolant pump/coolant thermostat
13 - Cylinder head/cylinder block


Cooling System Components



1 - Connector
2 - Coolant hose, upper
3 - To heater core
4 - From heater core
5 - To connector in coolant hose, upper
6 - Engine Coolant Temperature (ECT) Sensor (G62) Blue in color
7 - Bracket
8 - O-ring
9 - Connector (Always replace)
10 - Bolt: 10 Nm (7 ft lb)
11 - Coolant line
12 - To radiator, upper part
13 - O-ring (Always replace)
14 - To expansion tank, lower part
15 - Bolt - 15 Nm (11 ft lb)
16 - From radiator, lower part
17 - Coolant thermostat
18 - Oil cooler
19 - Coolant or Water-pump
20 - Cooler For EGR
21 - To expansion tank, upper


Radiator Fan Diagrams



1 - Radiator
2 - O-ring (Always replace)
3 - Coolant hose, upper
4 - Connector
5 - Retaining clip
6 - A/C Cut-out Thermal Switch -F163-
7 - From connector on cylinder head
8 - From connector on cylinder head/connector
9 - From ATF cooler (Only for vehicles with automatic transmission)
10 - Electrical connector / Color: black
11 - Cap: Test pressure 1.4 to 1.6 bar
12 - Bolt: tighten to 10 Nm (7 ft lb)
13 - Coolant expansion tank
14 - From connector to radiator for EGR/connector
15 - To cylinder head
16 - Fan shroud
17 - Right coolant fan -V35-
18 - Fan bracket
19 - Retaining clip
20 - Coolant fan -V7-
21 - Bracket
22 - Coolant hose, lower
23 - Electrical connector / Black, 3-pin connector
24 - Coolant Fan Control (FC) Thermal Switch -F18-
* Stage 1. 0N: 92 to 97 C
* Stage 1. OFF: 84 to 91 C
* Stage 2. ON: 99 to 105 C
* Stage 2. OFF: 91 to 98 C
25 - Bracket


ALH Coolant Water-pump



1. Idler Pully Bolt
2. Idler Pully
3. Pump Housing Bolt
4. Coolant Water-pump
5. O-ring seal


Thermostat 195*F.



1. Mounting Bolt
2. Flange
3. O-ring
4. Thermostat


FYI - For draining G-12 coolant out of the cooling system, open the cooling system drain thumb screw (pictured below).

Much needed, thanks!
 

Indwelling

Veteran Member
Joined
Apr 2, 2011
Location
Knoxville
TDI
1999.5 Jetta Tdi 2005 Passat Wagon TDI
Is there a coolant drain plug on 05 passat tdi block?
Drained the radiator to remove the front cap and noticed the previouse owner and the green stuff in it. Or can i mix g12 with it?

THanks
 

RECCE-17

Veteran Member
Joined
Oct 3, 2010
Location
Pembroke, Ontario, Canada
TDI
current 2011 Jetta,(ret)01' Jetta TDI (ret) 92' Golf Diesel
Great post Turbo Steve! Since its on the topic of the cooling system I just had a quick question for anyone who wishes to answer.

The other day I replaced my turbo with a VNT 17 and in the process I re routed the coolant hose to the heater core hose and removed the EGR cooler. I was driving on the highway today and noticed that at 90 km/h (60Mph) @ approx 2000 Rpm, I was not reaching full temp. it was not far off but Ive never had this happen in the summer. I'm assuming that the EGR Cooler helps heat the coolant a bit and that is why I was not at full temp. Any thoughts?

After I finished re routing my hoses I topped up with about 1/2 liter of G12.
 

GRW

Active member
Joined
Apr 5, 2005
Location
Everett WA.
TDI
2011 Jetta Sportwagon TDI
Question on type G11 vs G12?

To set the stage so to speak, we have two TDI's a 96 & a 98.
I have Bentley manual for the Jetta (want one for the passat).
Anyway the manual specifies G11 for 96 & early 97 and G12 for from early 97.
It states that the G11 is Blue/Green and G12 is Red.

Now to the question, my 98 Jetta has Pink (red) and that sounds right.
When we got the Passat (only had it a short time) it has Blue/Green colored anti freeze in it. I was getting ready to change it and wanted to make sure we had enough to do the change over and make sure I got it drained right when I ran into the statement above.

So should I be running the green/blue or the pink/red in my 96 Passat TDI?

While I am at it my parts guy said us G-05?


Thanks Gary :confused:
 
Last edited:

TonyJetta

Top Post Dawg
Joined
Sep 15, 2005
Location
Tucson, Az
TDI
'15 Jetta TDI SE / '06 Jetta TDI DSG Pkg0 / '96 Passat TDI
Anyway the manual specifies G11 for 96 & early 97 and G12 for from early 97.
It states that the G11 is Blue/Green and G12 is Red.
Factory fill for the '96 and early '97s was G11 - Blue/Green
Factory fill for late '97 and on is G12 - pink (Red)

Now to the question, my 98 Jetta has Pink (red) and that sounds right.
When we got the Passat (only had it a short time) it has Blue/Green colored anti freeze in it. I was getting ready to change it and wanted to make sure we had enough to do the change over and make sure I got it drained right when I ran into the statement above.
G12 replaces G11. It sounds like they are supposed to be compatible, but I prefer to flush. Make sure you do a thorough flush. Most of us flush with distilled water. Make sure the water you get out is as clear as possible; this indicates the system is cleaned of the G11.

So should I be running the green/blue or the pink/red in my 96 Passat TDI?
G12 is compatible with all materials used in the '96 engine.

While I am at it my parts guy said us G-05?
Nope! I think he was referring to Zerex G-05, which is used in Cummins...I just changed the coolant in my truck.

Tony
 

dieselfuel

Veteran Member
Joined
Dec 28, 2008
Location
ohio
TDI
2003 Jetta TDI
Am I the only one running Evans HDTC waterless coolant in an ALH? I'm also running a hybrid thermostat that will reach 107.1 C in the engine block (measured with VCDS).

I like the fact that there's no water in the coolant, so it should prevent corrosion of the heatercore and the radiator. Wish I'd know about this waterless coolant 2-3 years ago. Hopefully there's not much corrosion in my hc and rad after 8 yrs and 156,600 miles.

fwiw,



df
 
Last edited:

A_Shifter

Veteran Member
Joined
May 20, 2006
Location
Clarkdale, AZ
TDI
2003 Jetta Wagon TDI
Alright...I'm going to ask.

Would somebody mind pointing out the obvious?
2003 ALH Wagon.
After successfully draining my cooling system, installing Frost Heater, Race Pipe & EGR delete kit, upgrading my turbo, and searching the Forums, Google etc...I'm unable to find info on how to refill my cooling system. :eek:
Yep. I'm prepared for some ribbing.
 

TonyJetta

Top Post Dawg
Joined
Sep 15, 2005
Location
Tucson, Az
TDI
'15 Jetta TDI SE / '06 Jetta TDI DSG Pkg0 / '96 Passat TDI
Ummm...through the coolant bottle?

You can fill faster if you remove the upper radiator hose from the engine side. I've done that just about every time to refill the coolant system.

You will always get the system to a full level, then it will 'burp' several times, requiring small additions of coolant. Just be careful if you are opening a hot cap: Do it very slowly, or wait untilt eh engine is cool, then add more coolant.

Tony
 

A_Shifter

Veteran Member
Joined
May 20, 2006
Location
Clarkdale, AZ
TDI
2003 Jetta Wagon TDI
Ummm...through the coolant bottle?

You can fill faster if you remove the upper radiator hose from the engine side. I've done that just about every time to refill the coolant system.

You will always get the system to a full level, then it will 'burp' several times, requiring small additions of coolant. Just be careful if you are opening a hot cap: Do it very slowly, or wait untilt eh engine is cool, then add more coolant.

Tony
Yeh, coolant bottle's taking for-EVER. Knew there was a better way :)
So I'll do the upper hose thing.
The drain cock was obvious enough - thought I mighta missed something equally obvious for re-filling.
Thanks for taking the time to reply!
 

A_Shifter

Veteran Member
Joined
May 20, 2006
Location
Clarkdale, AZ
TDI
2003 Jetta Wagon TDI
Ummm...through the coolant bottle?

You can fill faster if you remove the upper radiator hose from the engine side. I've done that just about every time to refill the coolant system.

You will always get the system to a full level, then it will 'burp' several times, requiring small additions of coolant. Just be careful if you are opening a hot cap: Do it very slowly, or wait untilt eh engine is cool, then add more coolant.

Tony
Yeh, coolant bottle's taking for-EVER. Knew there was a better way :)
So I'll do the upper hose thing.
The drain cock was obvious enough - thought I mighta missed something equally obvious for re-filling.
Thanks for taking the time to reply!
 
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