Engine oil cooler line replacement DIY

Here's beautiful, detailed, downloadable DIY on replacing oil cooler lines on a Volvo 850. With pix. This DIY is likely applicable for any Volvo P80 model.

oil cooler line

MVS Forums Contributor Jason (jreed) blasts out a beautiful, detailed, downloadable DIY on replacing oil cooler lines on a Volvo 850. This DIY is likely applicable  for any Volvo P80 model.

“The lower cooler line (lower = the one that goes to the lower inlet on the radiator) had developed a very slow leak at the crimp nearest the radiator. It was leaking just enough to start to wet the hose above the crimp. Many other people have reported finding leaks here and replacing these lines so I wasn’t surprised to find a leak starting on my hose. I decided to replace both upper and lower hoses at the same time to avoid having to repeat parts of the work later if the upper hose developed a leak too.”

“There are already several excellent guides on this job that have been written up, so many in fact that I wondered if it would be worthwhile to offer my own contribution. In the end I decided to go for it because I generally take photos anyway as I’m taking things apart to make sure I put them back together the right way.”

Oil Cooler Line Replacement Preparations

  1. Remove hubcap and partly loosen the nuts on front passenger’s wheel (~1/2 turn to break torque)
  2. Chock rear driver’s side wheel
  3. Raise front passenger’s corner of car to lift wheel. Install jack stands.
  4. Remove the nuts and wheel.
  5. Remove the two 10mm nuts holding the splash guard in place and remove the splash guard. This allows access to the lower oil cooler line connection at the radiator.
  6. Loosen the plastic nut holding the wheel liner down
  7. Fold back the wheel liner and hold it up with a vise grip, other clamp or a cord
  8. (Optional) Drain the engine oil and remove the oil filter. Having the oil filter out of the way make snaking the lines and thermostat into position much easier.

Removing the Lines

Under the car, loosen the 10mm bolt on the brackets holding the oil lines. I used a 10mm open end wrench for this job, one partial turn at a time. Once the bolt is loose I could turn it out relatively easily with my finger tips. This only took about 5 minutes – not as bad as I was expecting. I have read how others used a flexible joint and socket to remove the bolt. I tried that but couldn’t get a good angle on the bolt due to interference from the AC compressor bolt. Depending on the car, you may have to try different approaches to loosening the bolt.

Since others have mentioned that this part of the job was extremely difficult or impossible, it’s probably worth taking a look for yourself and giving it a try before you start in on the job. If you can’t get the bolt loose, then you’ll have the opportunity to go out and get a better tool, or even make the call to take the car to a repair shop. Loosening the bolt up in advance won’t hurt anything – just tighten it back up again afterwards until you’re ready to start the job.

  1. Loosen the thermostat housing screws with a T40 bit on a ¼” drive with long extension, or else a long T40 bit.
  2. Pull thermostat away from engine slightly. Remove gasket if stuck to engine. Be prepared with a catch pan to catch the engine oil (~1/3 L) that will drain out of the thermostat and lines.
  3. Disconnect the upper and lower oil cooler lines at the radiator. I used a pair of circlip pliers to prise open the clamp far enough to allow the line to be pulled off the radiator. This was a bit of a change in procedure for me – I used to pry the clamp open wide enough to pull it off of the line entirely before trying to pull the line out of the radiator. But I found it’s easier to just pry it open enough to slide the clip and line out. On the lower cooler hose I could slide the clamp backwards away from the end of the line.
  4. Make a note of the positions and pathway of the upper and lower oil cooler lines so you can snake the new ones in the same way.
  5. Push the thermostat back towards the oil filter area and pull it down from the engine. The lines will come along but will likely hang up on components above. I had to go back and forth a couple times from below and above to lower the lines, free them from obstructions, and then lower the thermostat and lines all the way out.
  6. Make a note of the relationship between the lines and the thermostat so you can install the new lines in the correct holes and with the correct orientation. The lower oil line bracket is smaller than the upper and nestles on top of it. This is a good time to compare the new parts with the old parts to make sure that the new parts are a good match.
  7. Disconnect the T30 screw holding the flange to the side of the thermostat. This flange holds the two oil lines in place.
  8. Pull out the lines and remove the old o-rings from the thermostat if stuck inside.
  9. Clean up the old thermostat. My old thermostat makes the “moan” sound on startup in colder weather, whenever there is some throttle applied. It lasts for about 2 – 4 minutes and then the sound dies down. The thermostat mechanism has a plunger and internal spring that I cleaned with brake cleaner fluid (acetone / heptane). Hopefully this will help quiet the mechanism down.
  10. Clean up the thermostat mating surface on the engine block.

Engine oil cooler line replacement DIY guide

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