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Replaced heater core on 2001 1.8T - notes from the job

205 Views 2 Replies 3 Participants Last post by  Urlik
This week I replaced the heater core on my 2001 Passat 1.8T. I followed the Mr. B video, and overall the process went smoothly. Posting some notes below in case they are helpful to others. Comments below assume all the interior trim panels are off and the glove box is out.

Electrical connections - Molex connectors on each side need to be disconnected and free. When reconnecting them a bit of pressure is sometimes needed, or moving one of the side clips a bit to let the connectors seat fully.

Yellow ABS connector - use a pick to go behind it and release the narrow center tab. Then it slides off and can be disconnected.

Full bolt list to remove to free up the dash - here are all the bolts to remove to free up the dash. This assumes all of the panels, the glove box, and the center console have been removed first.
  • (2) 16mm bolts on DS
  • (1) 16mm bolt on PS
  • (4) bolts on center console (two on each side)
  • (1) hex bolt up under dash on DS
  • (2) bolts on L-bracket under dash on PS
Engine side disassembly - here are the things to disconnect on the engine bay side:
  • A/C hex bolt (evacuate the A/C first obviously)
  • Wiper arm (to get to the back ECM cover bolt)
  • Back ECM bolt going through hole in cowl (drop the hood, go in on an angle with the socket, then straight down)
  • ECM bolts (all the other ones)
  • ECM clip
  • Molex connectors
One tip here is to pull the ECM and connectors away and put them in a plastic bag. When I got everything back together the white Molex connector was stuck under the ECM housing, so I had to unbolt that thing and fish it back out. The plastic bag was for the big flush I did on the coolant - just wanted the ECM area to stay dry.

Shifter protection - put something THICK over the shifter. I used a towel, and my shifter got a bit scuffed up, so good protection is needed. The dash absolutely has to come up and over the shifter to get enough room to swap the heater core. Main challenge is with the tubes - too close and they will hit the windshield and not allow the right angle to get the heater core in.

Center console bolts - when putting the four bolts back in there is a sliding silver plate on each side. At first I thought one side wasn't lined up because I could not see the bolt holes, but it was because of the position of the plate. Pulled the carpet back, slid the plate, and all good getting things lined up.

Bus wiring on DS - with the two ground lugs and the wiring bus (all the red wires) I created a diagram and used zip ties to hold the wires together. All the wires have closed connectors, so it is easy to zip them together and then put a tape label on each one. Makes it much less stressful putting the wiring back in place.

Steering column - this part of the work was a headache. I figured out that the trick is to turn the steering wheel to expose the 16mm bolt so that you can get a socket on it. Once that bolt was off I had to fight with the Torx head because the area was slightly rusty, and I had to pound a screwdriver under the Torx head to free it up. Once the bolt was loose I turned the wheel straight and THEN taped up the steering wheel. Previously I was taping up the wheel first, but there is no way to access the steering column bolts if you don't turn the wheel. Also with the steering column - probably good to tape it or hold it in place once it is disconnected. With the dash pulled back it will slide out, which happened to me, and luckily there were paint marker lines on the column so that I could get it back in the exact same spot.

Angle of the heater core tubes when putting the dash back - my daughter helped me slide the dash back into place, and the one challenge was tilting the dash a bit so that the heater core tubes cleared the firewall. She watched from the engine side until I worked the dash into the right spot, and after that it was fairly easy to slide the dash all the way home.

Ducts to the rear floor in the center console - a good idea to just pull the white/black ducts on each side of the center console before lifting the dash back. They are easy enough to get back into place and will just bang into everything when lifting the dash back over the shifter.

When I was done I sawed the old heater core in half and pulled out the inner coils. It was loaded up with sludge and gunk, and that was after hours of flushing with an aquarium pump and CLR last fall.

Plant Wood Twig Font Woody plant

Hope this helps others!
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Wow! Great post.
Moving this to the B5 Garage. Great post!
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