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Please read through all of the instructions here and make sure you understand them before attempting this procedure!

There are two oil check valves ("non return valves") in the middle of the engine that keep oil sitting at the top of the engine for times when the oil pressure is low but it shouldn't be (i.e. when starting the car or when it's at idle). If you have valve noise when you start your car, but it goes away while you're driving, you probably need to replace these valves. Appearances to the contrary notwithstanding, this job is relatively easy if you've got the time and patience.

Definitions and Acronyms:

  • MAF: Mass Air Flow sensor. The MAF sensor senses the amount of air moving through the intake to accurately meter fuel injection.
  • EGR: Exhaust Gas Recirculation. The EGR valve lets exhaust gasses back into the intake manifold under certain conditions to lower combustion temperature and NOx emissions.
  • NOx: Nitrous Oxide.
  • ISV: Idle Stabilizer Valve. An electric valve controlled by the ECU to allow extra air through the intake manifold under certain conditions, to keep the engine from stalling.


Tools Required:

  • Phillips head screwdriver
  • 6mm allen wrench socket
  • 8mm Allen wrench socket
  • 10mm open-ended wrench
  • 17mm open-ended wrench
  • 19mm open-ended wrench
  • 10mm 6-point socket
  • Assorted socket extensions and flex adapters
  • Long needlenose pliers, magnetic pick-up tools, and/or alligator forceps
  • Slip-joint pliers or Channel Locks
  • Razor Blade
  • Paper Towels
  • 2 Rubber bands (2"-4" or 5mm-10mm diameter)
  • Small jar or can (i.e. a jam jar)


Parts Required:

  • Head -> intake manifold gaskets (set of two)
  • EGR -> intake manifold gasket
  • Valley pan gasket
  • Check valves (2)
  • Throttle Body -> intake manifold gasket (optional)
  • 3/16" (~3mm) ID rubber vacuum tubing -- about 1 foot (30cm) should do


Procedure:

  1. Remove the plastic covers that are on the top of engine.
  2. Remove the large flexible hose that runs from the Mass Air Flow (MAF) sensor to the plastic manifold behind the throttle body. If your car does not have a MAF sensor , this is the large hose that runs from the airbox to the plastic manifold behind the throttle body.
  3. Remove the camshaft breather tubes (fairly large tubes that run from the top of each head to the plastic manifold behind the throttle body). In some cars, one or both of the tubes are hard plastic. These have something like a child-proof cap on each end; you squeeze the two sides of it and pull straight back. Be careful, though, because these are prone to cracking.
  4. Remove the black plastic tube that sticks out of the top passenger's side of the plastic manifold behind the throttle body.
  5. Remove the two 10mm bolts that connect the top of the plastic manifold to the intake manifold.
  6. Pull the plastic manifold straight back (towards the firewall) about 1 inch until it is free of two metal posts on the bottom of the throttle body. Beware that the manifold has a rubber grommet for each of these posts and the grommets might fall. Keep an eye on them so that you can catch or retrieve them if this happens. Actually, that's not true; if one of the grommets falls, you will probably never see it again because it will have somehow lodged itself into a tiny crevace near the transmission. Just be careful so that they don't fall.
  7. Remove the two 10mm bolts that hold the EGR valve onto the intake manifold. This could take some time -- as you work on it, you'll find yourself cursing and bleeding a lot, and your back will start to hurt from bending over the engine bay, and you'll try the open ended wrench and then the 10mm socket and then the socket with some combinations of adapters and extensions, and suddenly everything will fall into place and the bolts will come right out. Throw away the gasket.
  8. Now you need to disconnect the fuel supply and return lines. You'll note that they are different lengths, so you'll be able to tell later on which goes where. For each hose, one side needs the 17mm open-ended wrench and the other side needs the 19mm open-ended wrench. Usually there isn't much pressure here if the engine is cold, but beware that fuel may squirt out at you when you loosen one of the hoses! No smoking now or you'll be sorry. Remember that even if no fuel sprays out, vapors will and it's the vapors that catch fire. At any rate, when you disconnect each fuel line, have your jam jar ready and stick the end of the hose in the jar so that gas doesn't spill all over the engine. Resist the temptation to hold the hoses down to drain fuel out of them -- remember that you're going to have to start the car eventually, and the less air you have in the fuel system, the easier that will be.
  9. Wrap the ends of the fuel lines and fuel rail with 2-3 paper towels and secure the towels with a rubber band. This keeps gas from dribbling, and keeps dirt and other bad stuff from getting in the fuel system.
  10. Now disconnect the throttle cable. There are two little metal clips that hold the end of the cable onto a plastic banana-shaped arm -- make sure you catch them both. Beware that they would rather fly off into the distance than be put back on, so keep a good grip on them lest they liberate themselves. Follow the cable back to a rubber grommet near the passenger's side of the engine that's mounted on a metal bracket. It takes a bit of twisting but this will come off. Don't garbage up the rubber grommet!
  11. Near that grommet there's a ground point; it's a 10mm bolt with blue paint on it and several brown wires coming off connectors that are under it. Remove the bolt and free the wires.
  12. Unplug the green wiring harness that's near the cruise control vacuum ball.
  13. Disconnect the colored plastic tubes from the colored rubber hoses for the intake manifold changeover valve, the cruise control actuator, and the EGR valve. You'll note that these are color-coordinated so that it's easy to put them back on. Handy, huh? Well, forget it. Rip off the colored rubber tubes and replace them with new vacuum tubing. Then remember which color tube went where! Actually you may want to hold off on replacing these until the end, if you're worried that you won't remember which color goes to which vacuum assembly.
  14. Disconnect the two-wire harness connector that's plugged in to the top of the Idle Stabilizer Valve (ISV).
  15. Reach behind the throttle body and disconnect the wiring harness that's plugged into the bottom of it.
  16. Disconnect the vacuum hose that runs from the left side of the throttle body to the bunch of valves near the MAF sensor. Be careful with this hose because it's 1/4" ID on one side and 3/8" on the other, so if something happens you'll have to kludge something together to fix it.
  17. If your car has an automatic transmission, there's another vacuum hose that starts at a small flat valve strapped to one of the heater hoses that go through the firewall, and ends on the driver's side of the throttle body. Disconnect that. This hose is 1/4" on one side and 3/16" on the other, so be careful with it. If you break this hose (or the other funny one) you can buy adapters and spare hose at most auto parts stores.
  18. There are two long, thin, brass-colored plates that run along each side of the top of the intake manifold, just inside from the fuel rail. These have two phillips head screws each holding them to the intake manifold. Remove the screws and remove the brass plates. I say that like it's easy, but probably it's going to be very hard to break the screws free. Just keep at them...they're tight for a reason.
  19. Remove the 6mm allen head bolts that hold the intake manifold to the engine. There are 10 of them. Six of them are short bolts; there is one per cylinder right near each spark plug. Four of them are longer, and they'r eat the top of the intake manifold directly under where those two brass-colored plates were.
  20. Now screw the brass colored plates back in. This is important because these plates hold the fuel rail on to the manifold, and the fuel rail holds the fuel injectors in place. The rail is also a very nice handle and if it's secured, you'll be able to use it as such.
  21. Pull straight up on he intake manifold; it may take a bit of work to un-stick the gaskets, but keep at it. If it takes too much effort, you've missed something. Don't try to pry it off.
  22. DON'T PULL THE INTAKE MANIFOLD ALL THE WAY OFF YET! You just wanted to free it from the gaskets. If you pull it up about 2 or 3 inches, you'll see a thin, delicate wire that's attached to a sensor on the passenger's side of the intake manifold, near the throttle body. That's the EGR temperature sensor, and if you have a shop manual it probably doesn't mention it. Prop the intake manifold on something, or have an assistant hold in to it, and unscrew the sensor with a 10mm open-ended wrench. Don't worry about twisting the wire, it will untwist when you're done.
  23. NOW pull the manifold off. Hey, that wasn't so hard, was it?
  24. Too bad you aren't done. There are nine 10mm bolts that hold the valley pan on. Two or three of them sit under the power steering high pressure hose, and are hard to get at -- you can remove them without removing the hose. Resist the temptation to disconnect the hose, or you'll be sorry. Don't say I didn't warn you!
  25. You'll need to pry the plate a bit, since the gasket will have turned to glue (very leaky glue). When you get the valley pan off, you might need to CAREFULLY scrape the remaining bits of the gasket off the engine with your razor blade. Be careful not to scratch the engine surface or let bits of gasket fall into the engine.
  26. Now you'll see the two valves; they're big (about 1" in diameter) and have a 6mm hex (or Torx) head. Unscrew the old valves, and screw the new ones in. Tighten the new valves to 45Nm (33ft lbs).


Whew. OK, now you're halfway done, so take a break. Drink a non-alcoholic beverage and gather your wits for the rest of the procedure. Basically it's the opposite of what you just finished, so I'll just mention a few important points:
  • Put the valley pan cover on a flat surface and make sure that it isn't warped before you put it back on the car.
  • When you re-torque the valley pan cover, don't just tighten the screws around in a circle. Cross the pan with every screw. Get them finger tight at first, and then torque them to 10Nm (7ft lbs) with your torque wrench.
  • Remember to counter-twist the wires for the EGR temp sensor before you screw it in, so the wires aren't twisted when you're done.
  • The EGR valve -> intake manifold gasket is more important than it looks. Use the new one, and make sure it's tight!
  • Torque the intake manifold bolts to 20Nm (15ft lbs).
  • Tighten the fuel rail connectors well! Just be careful not to twist anything off. Use two wrenches.
  • Don't forget the ground wires!
  • Once you've put everything back together, and you start the car, it will run like crap for 10-20 seconds while air gets out of the fuel lines. Just grit your teeth and put your foot on the gas pedal until it smoothes out (don't put the pedal to the floor; hold it down just enough to keep the car from stalling). It might still cough every once in a while for a mile or so, but don't worry unless it continues for days.
  • Make sure that the phillips head screws that hold those two brass colored plates down are very tight! Otherwise the injectors will leak fuel onto the engine, and you don't want that.
  • It's a good idea to have an assistant sit in the car and rev the engine for a bit while you look for fuel and vacuum leaks. Do this before you take your test drive!


Now that we've worked ourselves into such a fever pitch of excitement, I'll declare us done. It's a good idea to change your oil and oil filter now, and then again after 1000 miles or so to make sure that anything that might have fallen into the engine while you were working gets removed. Also keep an eye (nose?) out for leaking fuel or oil.


I've tried to make this procedure as complete as possible. However, if you notice any ommissions, or something I've gotten wrong, or have good quality pictures of your engine while you're in the midst of this procedure that I can use to replace the illustrations I've got here, please send me an e-mail. My e-mail address is noted on the main page.


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