DIY: Replacing driver side coolant flange on a MKIV Jetta 8v 2.o…
Ok, so if you notice that you are loosing coolant and you are seeing a small puddle of coolant in your regular parking spot, you may have a coolant leak. It turns out my problem was the infamous drivers side coolant flange leak.
(please excuse the filthy engine bay)
1. Red crusty residue near the transmission on the underside of the car:
2. Red crusty residue on the drivers side between the coolant flange and the engine block:
If you experience any of these symptoms you may have a leaky coolant flange.
Here are the steps I took to remedy the problem:
DISCLAIMER: This DIY is for a MKIV Jetta 2.o, and may be similar to other makes/models. This information only a guide and if you screw up do not blame me – I will not be held responsible for any mistake you do while you work on your car.
Notes: Get the OEM VW coolant flange- I noticed the OEM is much stronger and seals better than the aftermarket replacement. I got mine from my service shop for around $20. If you don't get the OEM part, you will be doing this again!!!
1. Drain your coolant. I blocked and raised the drivers side of the car a drained all of the old coolant into an old milk carton. It's not necessary to remove all the coolant, but you should drain a majority - it makes much less of a mess. And, don't reuse the coolant - please recycle it:
Raise vehicle and block the wheels:
Remove the coolant reservoir cap on the expansion tank to release the vacuum in the cooling system:
Using the coolant drain valve located on the underside of the radiator on the drivers side drain the coolant. Again, it's not necessary to remove all the coolant, but you should drain a majority:
2. Remove the engine cover (if applicable), remove your air box and the tubing that connects it to the throttle body and set it to the side.
3. Locate the coolant flange:
4. Begin by removing all the wiring, connectors and small hoses from around the flange. To make this easier I disconnected and removed the metal bracket from the top of the block this is optional:
5. Remove all the hoses from the coolant flange. There are three hoses that connect to the flange and they all need to be removed. It doesn’t matter in what order, but be prepared to have some coolant drain out because there will be some left over in the block and hoses. I used a pair of channel lock pliers to loosen and move the spring clamps and they slip off fairly easily.
6. Now you can remove the flange from the block by removing the two nuts, then the bolts holding the flange in place. There is one nut and one bolt behind the nut holding the flange in place. Using a 10mm socket, remove the bottom bolt:
The top nut is bolted on to a stud that screws into the block. Remove the nut but leave the stud in place:
7. You can then pull up on the black metal tubing (it will swing up towards the front of the car) and get to the bolt behind it. Once you remove bolt you can then remove the flange from the block. Make sure to clean up the dried up coolant and the surface of the block where the flange mounts.
Quote, originally posted by leokempf » OK. figured it out. I didn't realize it would pivot all the way over at the thermostat housing. Forward of the "bar" I loosened a nut pretty far down in there that holds a bracket for some wires. Then I gave the bar a tug and it pivoted. Thanks.
8. Now get the new flange and swap out the coolant sensor and O-ring.
Old VS. New:
Coolant flange part # from ECSTuning:
See my notes above step 1 about using an OEM part
Remove clip and O-ring from the old flange:
Replace clip and O-ring and insert it into the new coolant flange:
NOTE: Now would be a good time to replace that black top coolant sensor with the new green top. I did not replace mine as I have had no problems with it.
9. Prep your new coolant flange (optional). This is probably unnecessary, but I used a high temp copper gasket sealant to make sure the flange will not leak again.
10. Place your new coolant flange into the block:
11. Replace the bolt and nut to secure the flange – be careful not to over tighten!
NOTE: Thanks to TMTuned99.5Golf: bolt torque is 7ft/lbs or 10 Nm
12. Continue to replace all hoses, making sure to get the spring clamps back into the original place. Then replace the metal bracket and all wiring, connectors and small hoses.
13. Time to add coolant – NOTE: Remember to close the drain valve on the underside of the radiator, or you will drain the coolant you are about to put in. Mix 50/50 Pentosin G12 and Distilled water and fill the coolant reservoir. Start the car and turn the cabin temperature knob to full HOT and turn the blower to HIGH and let the car warm up while you continue to fill the coolant reservoir. Fill until the expansion tank is filled to just above the midpoint of the container. Coolant temp should reach the 190 degree point. You may have to replace the expansion tank cap for the coolant pressure to build – then just top it off as needed.
14. Replace the engine cover and test drive – you have just finished replacing your coolant flange!
NOTE: You may find that you need to check the level over the next few weeks to make sure the coolant level is at the correct level – based from my experience this seems normal and I have had no problems with my cooling system.
If anyone would like to add to this DIY please IM me – and if you have any questions please feel free to contact me. Thanks!