Thermostat Replacement / Radiator Cleaning / Coolant Change

(by Dave Kraige, with tips from Bernie Benz and Peter Kirby)

Tools needed:

Supplies needed:


  1. Remove cover under engine, 4 nuts, 3 screws.

  2. While under the car, remove the screw that holds the rear and driver side radiator cowls together (Fig 7, right-hand arrow). This will provide slightly more room to get to the lower radiator hose fitting.

  3. Remove 4 screws holding down upper radiator cowl, remove cowl.

  4.       -- If you are not replacing your thermostat, skip to step 14. --

  5. Remove 10mm bolt holding upper passenger side radiator support to body. (Fig 1)

  6. Remove 10mm nut holding radiator support to radiator (Fig 2), and remove radiator support. This allows the passenger side radiator cowl to move a little more, providing more room to work on the power steering pump and thermostat. You may also want to remove the screw that secures the right end of this cowl (Fig 2a), in order to allow a little more play.

  7. Take note of how tight your power steering pump belt is.

  8. Using a 13mm open-end wrench, loosen, but do not remove nut for power steering pump belt tensioner (Fig 3). Space is tight, you may have to lean on the radiator cowl a little bit, but you will get it eventually.

  9. Loosen, but do not remove the two 13mm power steering pump mounting bolts (Fig 4).

  10. Remove the 13mm power steering pump belt tensioner bolt (Fig 5).

  11. Remove nut and bolt for power steering pump belt tensioner (Fig 3).

  12. Remove the two 13mm mounting bolts (Fig 4).

  13. Remove belt from power steering pump pulley. You may have to push the pump down a bit to get enough slack.

  14. Carefully pull up on power steering pump, maneuvering the mounting tabs around the engine lift point. The pump can be rotated out of the way and propped against the fuel rail (Fig 6). You can now clearly see the thermostat cover (Maybe not in the photo, but you can in real life).

  15. Place a large pan or bucket under lower radiator hose.

  16. Remove coolant expansion tank cap.

  17. Loosen clamp on lower radiator hose (Fig 7) and pull it back several inches out of the way of the fitting.

  18. Carefully rotate and pull on the radiator hose until it comes loose. Remember that the fittings are plastic, so avoid putting too much stress on them. Try to pull the lower cowl toward the rear of the car, otherwise the coolant will dump right onto it and splash everywhere.

  19. Several liters of old fluid will come out, hopefully it will hit your strategically-placed bucket. When it comes out green, grumble curses about previous owner.

  20. Reattach lower radiator hose. If you plan to do the thorough cleaning, there is no need to get it extremely tight, as you will be removing it again later. If you are just doing a routing flush and refill, go ahead and tighten appropriately.

  21.       -- If you are not replacing your thermostat, skip to step 34. --

  22. Loosen clamp on the other end of the lower radiator hose, where it connects to the thermostat cover, and pull the hose loose (Fig 8).

  23. Use a closed-end wrench to remove the two 10mm bolts holding down the thermostat cover (Fig 9). A ratcheting combination wrench makes this part much easier. Pull thermostat cover away from housing, and remove it from the car. Clean the surface that mates to the thermostat housing and o-ring, and set it aside.

  24. Move your bucket or pan under the thermostat.

  25. Carefully use a flat screwdriver to pry the thermostat out of its housing. Be gentle and take your time, it may seem like it is stuck in extremely tight but it will eventually come out. Try prying both from above and through the hole where the thermostat cover used to be. Once it comes loose you will get a good deal more old fluid, hopefully you will catch most of it. One option is to push the thermostat open while it is still in place. this way you can control the fluid coming out, rather than having a huge gush when the thermostat finally breaks free.

  26. Clean the thermostat housing to prepare it for the new thermostat.

  27. Install new thermostat. The gold bridge should be vertical (don't know what difference this makes). Install new o-ring, and be sure that entire unit is nicely seated all the way around.

  28. Reinstall thermostat cover.

  29. Reattach lower radiator hose to thermostat cover.

  30. Drop power steering pump back into place, pull belt back onto pulley.

  31. Reinstall 13mm mounting bolts (Fig 4), but leave fairly loose.

  32. Reinstall nut and bolt for belt tensioner (Fig 3), but leave fairly loose. Be careful not to drop the nut. You'd think it would fall right out and hit the ground, but trust me, it doesn't. It doesn't the second time you drop it, either.

  33. Reinstall tensioner bolt (Fig 5). Be careful not to cross-thread it, I imagine the part it goes into is expensive.

  34. Tension belt to your heart's desire. Refer back to step 6. You should probably be able to push it about 10mm in the middle of a span.

  35. Tighten 13mm nut (Fig 3) and mounting bolts (Fig 4).

  36. Reinstall upper radiator cowl.

  37. Move your pan underneath the center of the firewall.

  38. To get as much of the remaining fluid out as possible, remove the driver side heater hose at one end. The engine end is the low end, but it is much easier to get to the firewall end (Fig 10, A) and just carefully bend the hose down so that fluid will flow out of the motor. Since most of the fluid came out through the thermostat housing, not much should come out here.

  39. Reattach heater hose.

  40. On the passenger side heater hose, there is a vent screw (Fig 10, B) which will overflow when you have filled your system completely. If yours works, open it. I found mine to be absurdly tight and was afraid to work it any harder, so I simply loosened the hose clamp right behind it and pulled the hose almost off, so that the bottom was still connected but there was an open crack at the top to allow venting.

  41. Loosen clamp on upper radiator hose and pull hose loose (Fig 11). Again, remember, plastic fittings. Be gentle.

  42. Pour water down the upper radiator hose so that there will be something in the engine when you start it. Once the hose is full, reattach it and tighten the clamp. Not too tight if you're doing the thorough cleaning, you're just going to take it off again anyway.

  43.        -- If you are just flushing and refilling, and not doing the thorough cleaning, skip to step 50. --

  44. Measure out 1/2 cup trisodium phosphate powder. Put a funnel in the expansion tank, and start pouring in water. Add the TSP as you are pouring water. Continue adding water until you get a little above the "minimum" mark on the expansion tank.

  45. Reinstall expansion tank cap.

  46. Start the engine and watch. As it warms up, some of the water will drain out of the expansion tank, just keep replenishing it to keep it over the "minimum" mark. When water starts to flow out of the vent (or loosened hose) in the heater hose, you're done. Close up the vent (or re-tighten the hose, again no need to overdo it since you will be doing this again).

  47. Drive around for a while. Enjoy the fact that the new thermostat actually allows the engine to get reasonably hot. Get 'er good and hot, let that cleaner do its job.

  48. Return to base and park. Go inside and watch some baseball or something while it cools off. You don't want to drain the fluid again while it is hot, because you risk burning yourself severely, or, worse (depending on how you look at it), warping something in your engine. Best to let it cool.

  49. Once cool, repeat steps 14-19 and 35-45, except during step 41 replace the TSP with 1/4 cup of crystalline oxalic acid.

  50. Time for the final dump and refill. Repeat steps 14-19, this time snugging the lower radiator hose clamp for good. Also replace the screw in the driver's side cowling (Fig 7).

  51. Reinstall under-engine cover.

  52. Repeat steps 39-40, but this time use distilled water and go ahead and tighten the upper radiator hose completely.

  53. Put your funnel in the expansion tank. Pour in 3 liters of Pentosin phosphate-free good stuff (I used blue because I thought red coolant was like asking for trouble), along with some more distilled water. Keep adding water until you get above the "minimum" mark.

  54. Repeat step 43, this time seal everything up for good. You'll probably want to drive around for a while and check to make sure everything runs okay.

  55. All done! I can't believe it took 51 steps. A fairly easy afternoon job, though. Do it, make a note of it, and then forget about it for two years. Enjoy!