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Saturday, January 27, 2007 11:41:22 PM - Views Technotes :: Coolant System

This is a HUGE combination technote with content from some technotes as well.

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[Buying Parts] [Thermostat] [Hoses] [Water Pump *NEW*] [Heater Core] [Expansion Tank] [Radiator Fans] [Oil Cooler] [Troubleshooting the cooling system]

Buy Coolant Parts (links)
To buy some of the rarer hoses, try TT tuning's page.

How to replace the Thermostat...
If you have power steering - There's a lot more involved here - basically, remove your belts - then remove your power steering pump and set it aside.

1. After Removing the power steering pump here is the location of the thermostat housing. This picture shows the coolant drained. 4. This shows where the rubber seal sits on the elbow of the housing.
2. Move aside the coolant hose, and loosen the two bolts that hold the housing to the water pump. Remove the housing, take the thermostat out (just pull it out), then clean the housing. 5. Put the new thermostat in - noting the coolant flow (there's usually an arrow - make it point to the lower hose to the radiator). Put the elbow back in place with the rubber gasket, and reconnect the hose.
3. Clean out the inside of where the thermostat sits in the pump.

Here is the cleaned out housing mouth...

  6. Refill the coolant - and start your engine up, filling up the coolant level as the air escapes the system. once the coolant levels off close the cap and let run for 10 minutes.


Go up to step 4...

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Replacing the Hoses
You can buy the upper, lower, and bypass hoses at most auto parts stores - but to get some of the weird hoses (like the oil cooler T hose, or the 16v bypass hose) - you must order them from online.

1. This picture shows the Upper radiator hose and Lower radiator hose, to change hoses you will need to empty your coolant from your car - loosen the lower radiator hose and drain into a bucket. Once it is drained, loosen the upper hose and replace it. 5. In this picture you can clearly see the T hose for the water pump, this is part of the Oil cooler system, it is a little bit difficult to remove, if you look carefully there is a bolt to loosen the metal pipe that goes up to the heater core.
2. Continue in the same manner changing the lower radiator hose, attached to the thermostat. 6. If you have a rusted clamp on your hands, cut it. GET NEW CLAMPS!!
3. This shows the hoses where they go into the head. The one that goes down to the left is the bypass hose. 7. If an old hose won't pull off - cut it. Be careful not to damage the flange.
4. This shows the bottom of the bypass hose. Loosen and replace it. 8. Rotten hose. Fun, Huh?

Go up to step 5...

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Water Pump

This details replacing the waterpump in the Early style factory A1 cars. It is FAR easier in a Non-A/C car, and fairly easy in a newer style A/C car. The Old style can be identified by the square compressor on top.

Extra special thanks to VWVortex user petebee (Peter Brown) who provided the pictures and notes!!

Click to Enlarge The culprit.
Click to Enlarge First we have to remove el gordo alternator. It's held in place by a lower mounting allen bolt (6mm) that is a pain to get at, plus the bolt/nut that attach to the adjuster bracket on top. My alternator is a big sucka. To get at the lower bolt remove your horn first:
Click to Enlarge Now you'll have a bit more room. Looking up from underneath, find the small triangular opening in the A/C bracketry, this is where you'll gain access to the lower mounting allen bolt:
Click to Enlarge Now loosen the top nut/bolt on the adjuster bracket. Bentley says to move towards the engine to loosen the belt...ha. Check the available room that the fatty alternator affords (that's the WP that we're bumpin' up against):
Click to Enlarge

I just loosened everything up, wiggled the alternator around with the lower mounting bolt very loose, and finally was able to free the belt. Fatty alternator had to stay under there because I couldn't work it out with A/C bracketry in the way.

Next you have to remove the timing belt covers (I was lazy and didn't take pics of this):

1. Remove two nuts on the valve cover that hold the upper t-belt cover in place, then remove the funny 6mm allen bolt in the middle of the cover. Remove upper cover.

2. Remove pulleys on the crank and WP. For the crank I held the pulley in place with a socket wrench on the center bolt, and was able to crack the pulley bolts. This is actually a dual pulley (one for WP, one for A/C). Once you remove the bolts the pulleys pull apart, and there are quite a few shims that are located in between the two pieces. For the WP, I held the pulley in place with a large pipe wrench (the strap kind) and was able to break free the allen bolts on the pulley.

3. Remove the hub on the crank. This was a bit tricky, but used the same approach as the pulley (wrench on center bolt). The hub is held in place by 6mm allen bolts..and guess what happened to one:

Click to Enlarge

4. Now you need to remove the bolt, nut and allen bolt that are holding the lower timing belt cover in place.

Next we'll remove the A/C compressor. This is documented in the Bentley under the engine removal section. Basically you will need to remove the following bolts that hold the A/C brackets onto the engine.

On the underside right above where the alternator sits ( fatty alt was still stuck in there. Just push it to the side). Here are the two bolts covered with gunk that require removal:

Click to Enlarge Here's a wrench on one for better reference:
Click to Enlarge Next remove the two bolts that are along the side of the compressor:
Click to Enlarge Then remove the two bolts that hold the bracket to the block. They flank the warm up regulator:
Click to Enlarge Then remove the two bolts that attach to the support rod:
Click to Enlarge There are two more that we need to remove that were covered by the timing belt cover. They are both located above the intermediate shaft. One is a 10mm bolt, the other is a nut/stud. Remove these two, wiggle the compressor with one hand...reach down and grab fatty alternator with the other so it doesn't fall into the bucket of coolant...and flip the whole compressor and bracket unit onto the front radiator support:
Click to Enlarge Look how my 1/2" breaker socket is dwarfed in comparison to the ginourmous alternator that I just extricated:
Click to Enlarge Now you can remove your WP. First I took off the t-stat cover (see the backed out bolt for reference). It is held in by two of these:
Click to Enlarge Now pull out the t-stat, but have the bucket ready!!! Loosen the two rubber hoses that are located on the right side of the WP. Remove the four bolts holding in the WP (mine only had the upper two in place, but you can see from the picture where the other two should be):
Click to Enlarge Here's a shot of the Bentley just for good measure:
Click to Enlarge After removing the mounting bolts, twist the WP off the two hoses, and here's what it looks like. So much room I could hold a square dance in there
Click to Enlarge And here is the nasty, leaky culprit that I spent four hours gettin' out


Heater Core
This is a really good time to replace your heater valve - even if you don't need it - it's still a good idea.
You have to drain the cooling system before doing this - you'll want to have a bucket handy inside the car too!
If you don't have A/C - then this is a joke. It's really easy to do the heater core. Just snap off the cover on the driver's side. Unclamp the hoses, slide out the heater core.

If you have A/C - Then it sucks to be you! - Just kidding - Here's the technote - based on the technote from the Drivers Found Website

1. First Step is to remove the top and bottom of your console, seeing on this picture, the arrows indicate the first set of screws to remove. 7. gently pull the plastic cut out and bend at bottom of box. The heater core is ready to be removed. Remember - it still has coolant in it. Slide it gently out.

2. Pull out the 2 heater control handles and the speed control of the fan and pop out the heater control panel out. 2 screws that hold the controls to the console need to come out.

The second picture shows the next 2 screws that need to come out before you can start removing the top console part - I you can't get the console off - this is probably what's holding it back.

8. This shows the area clear of the heater core, clean it out - it will have gunk in it (especially if your heater core leaked a lot like mine did. once done slide the replacement heater core in place.
3. Unplug your stereo and gauges and stuff. Unscrew the shifter ball, and remove the shifter boot. 9. Reconnect the hoses and screw the clamps down. Refill your loss coolant, and start the engine, let it run until it is warm and the coolant is circulating - making sure you check your hoses for leakage. (you need to have the heater set to HOT for the circulation to occur)
4. It's easier to get the console off with the parking brake down, the seats slid all the way back and the shifter in 4th gear.



10. Next remember the plastic cover that was such a pain in the butt to remove first few steps ago? Here's how you modify it. You will loose a little bit of air pressure in the vents - but it all goes to your feet - so It's not so bad.

Here is the modified cover, I used the hack saw blade again and cut a slide through slots for the hoses. Now you can just slide the cover back on the hoses. This works - that is all that counts.

5. The heater core will be reached from the driver side of the box, you will notice a box screwed in with 4 screws, 3 of which are easy enough to reach, but the fourth one is located at the rear, at the top of the box (the picture shows the location and what tool to use to reach it)  I used a 3/8" ratchet with an 1/4" short socket using an extension magnetic tip of a screwdriver with a #2 Phillips head. 11. The Flap we cut out is held in place by the cover we screwed back unto the heater exchange box. now we are left with 2 cut outs in the air box... I used some black caulking and filled the cracks showing. You can also use a soldering iron to melt the plastic back into place. Be careful not to burn the heater core.
6. Get yourself a lot of paper towels, a bucket, maybe a trash bag to protect your floor. Unscrew the clamps on the hoses and disconnect them, slide the panel covering them off. (It's a real pain - See below how to modify it to be easier) Next, you will notice the plastic marked in 2 parallel lines the width of the heater core, grab a thin hacksaw blade and cut away 2 lines from below the head of the heater core to the bottom of the box. 12. Here's the final product. Looks funny - but it works. And that's what counts!

Reassemble your dash and enjoy the warm air you deserve so much in the winter time.

Go up to step 7...

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Move the Coolant Expansion Tank
Replace that ugly brown and green expansion tank. This is easy...

1. This is where the bottle is moving to. 10. The new location being prepped.
2. Here's the old Location 11. Screw or rivet the plates in place.
3. Drain the coolant bottle, and remove the overflow hose. 12. Place the bottles back on their brackets.
4. After it's empty, disconnect the bottom hose from the system - remember where this is for later. 13. Now you have to reconnect it to the system. Get some coolant hose (Auto parts store) and get some 90' pressure hose angles that fit the hose, 6 clamps and a tube of hose sealant, and some hose insulation to protect the fuel lines and spark plug wires.

Just run the pipe across the engine to where the bottom hose was connected to.

6. Remove the tank, and get a cold chisel, and gently tap in between body and bracket until the 4 weld points are cut. Bend the bracket back to normal after you are done. 14. This shows the connection to the system
7. Drill four holes in the bracket and mark the spots on the new location. You have to move the windshield washer bottle bracket about 1" forward too. 15. Slide the hose insulation across the tubing that runs across the engine, and refill the bottle.
8. Make sure the back is flat, grind it, metal brush it clean, prime it, paint it... 16. start the engine - check for leaks. You can lift the bottle to get the air out of the system.
9. Meanwhile back in the engine, the sidewalls have been prepped for a nice coat of primer... 17. Done

Go up to step 10...

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Upgraded Radiator Fans
You can find the Flex-a-lite Scirocco twin Radiator fan here - or on ebay...

1. Disconnect your battery and take it out of the car. The picture shows the location of the connector to the radiator fan, unplug that bugger. 7. This is where I hid my relays, Get your relays down here.
2. Driver side of the radiator , these bolts need to be removed. 8. Here's a picture of the way it's wired.
3. Passenger side 9. This shows how I passed the tie wrap through the shroud, buy drilling 2 1/8" holes in the shroud. Just run the wires to the temp sensor and power.
4. Here we have the Flex-a-lite "Scirocco" fan, the brackets are included in the price and make the mounting of the fan on your radiator simple. Just bolt it back on the opposite way you unbolted the original radiator fan. 6. Look at all the new space!
5. Wire the new fan up - Check the polarity to make the fans pull air toward the engine. Make sure you use heat shrink wrap or waterproof connectors 7. Another view.

6. I take no credit for this part of the mod, it took it from someone else's web page. I just constructed the tech note for it... this diagram is plain and simple, easy to read.. if you're not color blind you can do this.

*Added February 11, 2005 - Updated diagram for multiple speeds.

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Up to step 7


Buy Relays and sockets for the fan...

$2.19 EA Bosch 30A Automotive Relay $1.19 EA 30A Automotive Relay
$1.50 EA Relay Socket $1.90 EA 2 place Relay socket

Back to top or Back to the Fan Section

Fixing the Oil cooler
Shown here is how to replace the rings on the oil cooler. You must drain the oil to do this. If you replace the oil cooler with a new one - you have to drain the oil and the coolant. DO NOT RE-USE THE OIL OR THE COOLANT!!!

1. Drain the oil, remove oil filter, take this nice big nut off of the shaft here... 4. Replace the o-ring. Put the cooler back on the flange
2. Slowly slide the cooler off of the flange. Remember to be careful of the hoses. 5. Tighten the big nut back down. Put on a filter and finish changing your oil...
3. Here is the oil cooler removed from the flange shaft, CLEAN IT!

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Cooling system Troubleshooting chart
From the Bentley Manual...

Problem Cause What to do
  1. No Coolant
  2. Burst hose
  3. Weak hose blocking flow at high speeds
  4. V-belt slipping or broken
  5. Thermostat stuck shut
  6. Bad Coolant cap
  7. Clogged Radiator
  8. Incorrect timing - or running lean
  9. Coolant pump broken
  10. Something's funky with the head gasket - letting water in and boiling it - If you have white smoke in the exhaust check this.
  1. Fill It!
  2. Replace it - Refill the system
  3. Replace the old hose
  4. Replace the belt or tighten it.
  5. Replace it!
  6. Replace it with another cap
  7. Get a new one...
  8. Fix your timing/mixture
  9. Get a new one - $50
  10. Replace head gasket
The heater doesn't work well, temp gauge low or none
  1. Thermostat stuck open
  2. Fan stuck on (this almost never happens)
  1. Replace it!
  2. Get a new Temp sensor for the corner of the radiator
The heater doesn't work well, temp gauge is normal
  1. Heater core clogged
  2. Heater core hoses blocked
  3. Heater hoses Reversed
  4. Heater valve dead
  1. Replace it!
  2. Replace it!
  3. Reverse them
  4. Replace it!
The heater works fine, temp gauge reads low or none
  1. Faulty gauge or sender
  1. Replace the sender first, then test the gauge

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