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TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

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Old January 22nd, 2001, 18:40   #1
Turbo Steve
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Default Cooling System 101

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 ]
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Old January 22nd, 2001, 18:42   #2
Turbo Steve
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Default Re: Cooling System 101

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).

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Old January 22nd, 2001, 19:03   #3
Drivbiwire
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Join Date: Oct 1998
Location: Boise, Idaho
Default Re: Cooling System 101

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
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Old January 22nd, 2001, 19:25   #4
Turbo Steve
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Default Re: Cooling System 101

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/For...ML/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).]
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Old January 23rd, 2001, 07:14   #5
Drivbiwire
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Join Date: Oct 1998
Location: Boise, Idaho
Default Re: Cooling System 101

Here are some pictures of my Auto TDI, I did not take off the engine cover cause somebody was in a hurry to go to work. I'll try and get some better photos later.


These are 128kb files, I kept them large to improve the quality in case you want to zoom in on the details:
http://tdipics.mmcorp.net/members/Dr...3_074836AA.JPG
http://tdipics.mmcorp.net/members/Dr...3_074916AA.JPG
http://tdipics.mmcorp.net/members/Dr...3_074942AA.JPG
http://tdipics.mmcorp.net/members/Dr...3_075011AA.JPG
http://tdipics.mmcorp.net/members/Dr...3_075031AA.JPG
http://tdipics.mmcorp.net/members/Dr...3_075055AA.JPG

DB
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Old January 23rd, 2001, 07:25   #6
Ric Woodruff
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Join Date: Feb 1999
Default Re: Cooling System 101

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
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Old January 23rd, 2001, 07:26   #7
Drivbiwire
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Join Date: Oct 1998
Location: Boise, Idaho
Default Re: Cooling System 101



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).]
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Old January 23rd, 2001, 08:08   #8
SoTxBill
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Location: its not the base, its the additives!!
Default Re: Cooling System 101

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).]
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Old January 23rd, 2001, 10:31   #9
gardentender
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Join Date: Feb 2000
Location: Dullest Texxus
Fuel Economy: 53+/46/41
Default Re: Cooling System 101

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
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Old January 24th, 2001, 01:30   #10
Drivbiwire
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Location: Boise, Idaho
Default Re: Cooling System 101

Yes the coolant is extended drain, the coolant is a VW specific number otherwise the same as other extended drain antifreezes.

DB
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Old January 24th, 2001, 01:33   #11
vwnut84
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Default Re: Cooling System 101

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...
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Old February 3rd, 2001, 18:58   #12
Turbo Steve
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Default Re: Cooling System 101

Jed:

This thread should give you a good overview of our TDI's Cooling System.
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Old June 16th, 2001, 16:19   #13
Turbo Steve
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Default Re: Cooling System 101

Time for a refresher course! [img]images/icons/grin.gif[/img]
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Old June 16th, 2001, 18:58   #14
tadc
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Default Re: Cooling System 101

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.
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Old June 16th, 2001, 20:28   #15
NYTDI
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Default Re: Cooling System 101

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...EZECOOLANT.pdf

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