Home » Posts tagged 'engine'

Tag Archives: engine


Spark Plug and Tube DIY for Porsche 996/997

Spark plugs in the M96 engine need to be replaced annually. While you’re there, you should change the spark plug tubes as well, especially if you have no record of them having been changed. You can do it without dropping the exhaust first, but it will take you twice as long, even accounting for the time it takes to drop and reinstall the exhaust. Wayne Dempsey has a good DIY for spark plug replacement so we don’t need to repeat it here. Having done it both ways, I will be dropping the exhaust from now on. Be sure that the engine is cold before you begin.

If you find oil on the inside of the tube when you remove the plugs, then the tubes have cracked. Why else change the tubes? If you find oil on the valve cover seal or what appears to be a head gasket leak without an identifiable source, then your tubes may be leaking due to worn seals. They are relatively inexpensive to replace, and can help prevent wasting money on a more expensive repair that doesn’t work. The part number for the tube is 996-105-325-52. (Be sure to get the O-rings as well.)

The trick to getting the tubes out is to find a Porsche plug tube puller tool (expensive) or use a (cheap) boat plug. Tighten the boat plug using pliers and pull the tube out. Lube the sealing rings with dielectric grease and just press them back in. Replace the spark plugs without anti-seize compound and away you go. This would also be a good time to replace the coil-packs if you have no record of their replacement (997-602-107-00).

New Exhaust for 996

Since we dropped the exhaust to work on the plugs, we decided to upgrade while we were there. (Caution: rationalization in progress). Besides, the stainless steel exhaust is a thing of beauty and quite a bit lighter than the stock exhaust it replaced, which had started to rattle in recent weeks. Installation is very simple provided that the exhaust flanges haven’t rusted too badly. We replaced the cuffs, bolts and nuts all around. When we got the old exhaust off the car, we found out the internals on the right side were just floating around in the can — there’s your rattle.

Codes P1688 and P0107, WTF? Replacing Broken MINI Crank Damper

I decided to take the MINI to work this morning to see if everything was back in order after recently replacing the motor mount. The engine seemed to be running a little rough, but I just figured the new motor mount was a little more firm than the old one. I got off the highway after one exit due to traffic and I got the dreaded CEL (Check Engine Light.) I hate that light. It might as well say, “Yo. Something’s wrong. I know what it is, but I’m not going to tell you. Here’s a hint: It’s under the hood….” And the car went into limp mode. Fortunately I still had my code scanner which told me it was code P1688. That’s handy. What does that mean? Ugh. I just turned around and headed home. I’d have to reset the ECU every 5 minutes, but it is a pretty hilly route so I could do lots of coasting. So what is P1688 you ask? Not what it seems.

P1688 is the code for “Electronic Throttle Control Monitor Level 2/3 Mass Air Flow Calculation”. Which would indicate a problem with the throttle body, but I also had code P0107 last week at the track which is “Manifold Absolute Pressure/Barometric Pressure Circuit Low Input”. With those two together, the car is saying that for a given amount of throttle, there just doesn’t seem to be enough boost going on. And on the R53 MINIs that usually means the crank pulley (or more accurately, harmonic balancer) is shot.

The stock part is about $200, but since this car gets lots of track time, better to upgrade to a more robust model. ATI Performance makes a Super Damper for about $350, which we also sell in the store. As the old damper started to disintegrate, it took a good amount of the old belt with it. The old belt has had one rib sliced off. These two belts should be the same width.
missing rib
Once you get the right front up on a jack-stand, remove the wheel and fender liner, and use a belt tensioner tool to remove the belt.
tensioner tool
You can’t tell if the damper has gone bad by viewing it from the front, but when you look at it from the side, you’ll see a gap developing as the belt pulley separates from the damper.
mind the gap
ATI includes basic instructions with the new super damper. Here are some tips to make it easier on you. (Use at your own risk.)

You can use a universal pulley removal tool if you’re careful. You will need to buy 3 M6 bolts that are long enough to work with your tool. Be sure to get the hardest bolts you can (10.9). First step is to remove the center bolt. Use some penetrating oil before you start. You may get lucky and be able to remove it just by putting the car in 6th gear and having someone stomp on the brakes. But for me, the crank still turned. I ended up using a brace to stop the crank from rotating. In this case, it’s a tool for removing a fan from an E30. Go figure.
hold it
Now the real fun begins. If your tool did not include an appropriately sized center pin, then put the bolt back in and tighten, leaving about a half inch of threads showing. Attach your pulley removal tool. Have a helper hold the bolt with a wrench as the pulley tool will be pushing against the bolt and it will try to screw back in. When the bolt makes contact with the damper, you have to back it out some more and adjust everything and go again. Make sure the M6 bolts are not twisting. You should be able to compare the location of the damper to the other pulleys on the front of the engine to judge if you’re making progress. I ended up having to replace the bolt with a longer one to get the last quarter of inch of travel needed to remove the damper.
Once it came off, you can see how badly damaged it really was. (Hint: this is supposed to be one piece, not two.)
With the damper removed, you can see where it scored the engine as it oscillated. I’m surprised that didn’t make more noise….
Installation is the revers of removal. No, not really. From the ATI instructions: Inspect the crank for any burrs or nicks. Blow out the threaded hole to free it of debris (and clean the engine before you start since you can’t really get to it once installed.)
Start the new super damper by hand. Heat it with a heat gun or hair dryer if it doesn’t start easily. Use the supplied long bolt and washer to grab enough threads to pull it on most of the way. Continue until it bottoms out, then remove the bolt.
first bolt
Use a new OEM bolt to finish installation. Apply blue loctite and torque to 85 lbs. Reinstall the belt, taking care to route it correctly.
slack belt
Carefully release the belt tension using tensioner tool. Start the engine to check if everything is OK and the belt alignment is straight. Then reinstall the fender liner and wheel. Torque wheel to 87 ft lbs.

So which crank pulley do you recommend? Like so many things in live, that depends on your application. If you’re happy with stock performance, and you think you’ll be selling your car soon, go with the factory damper.  MINI redesigned them in 2005 so they’re a bit lighter and a bit more robust. Just keep in mind they’re good for only 75-80K miles. If you have a modified engine AND you want to raise the Rev limit, then get the ATI super damper. If you are building a race motor and want to rev up to 8K, then this is the one you want. If you’re looking for performance on a budget, then get a light-weight crank pulley. We sell both the Alta and the Cravenspeed crank pulleys. We like the solid design of the Cravenspeed but ran the Alta one successfully for 10 years on our old car. 

Stock or 2% overdrive? We always recommend stock sized crank pulleys. Better to get power gains by under driving the supercharger pulley (spins faster) than over driving the crank pulley which spins both the supercharger, AC and the alternator faster. Recall that the water pump sits on the back of the supercharger. If you put a 2% OD crank pulley on a car with a 17% SC pulley, you’re effectively using a 19% SC pulley. At that speed, the water pump is likely to cavitate resulting in a decrease in cooling efficiency. Any gain in boost is lost to an increase in temperature. 

Throttle Body Cleaning DIY

Continuing our theme of making up for delayed maintenance tasks, today we tackle cleaning the throttle body. A dirty throttle body may affect throttle response and decrease gas mileage. For all 996s built after the 2000 model year with “e-gas” (throttle by wire) this task should take 30 minutes or less. For earlier cars with an actual throttle cable, the process isn’t really that much more complicated, but the throttle cable does have to be disconnected.

  1. Disconnect intake hose and remove the airbox. (If you haven’t changed or cleaned your air filter in a while, this is a good opportunity to inspect the air filter as well.)
    remove airbox
  2. Inspect the throttle body before removing it. Look especially along the leading edge of the butterfly valve for crud buildup and any evidence of scoring or foreign object damage. Remove the four bolts indicated by the red arrows and disconnect the electrical connector at the top.
    inspect throttle body
  3. Inspect and clean the intake plenum. Look for foreign objects and excessive sludge. Clean as necessary.
    clean intake plenum
  4. Put the throttle body on your workbench and inspect both sides for build-up and damage. Clean using carburetor cleaner. Carefully open the butterfly valve manually to get to all of the areas needing cleaning.
  5. Installation is the reverse of removal. Be sure to reconnect the electrical connector at the top. Clean throttle body looks almost brand new.
    clean throttle body reinstalled

Ready to Rock the BMW M20 Engine, Rocker Replacement DIY

Unlike other DIY projects for the E30, if you do a quick search on the internet for “BMW M20 replace rocker without removing head” you won’t find much in the way of quality advice. I found one lengthy writeup which may be the single most poorly written and profane set of DIY instructions I’ve ever seen. At least it provided some inspiration and I was able to figure it out myself. So the answer is yes, Virginia, you can replace a broken rocker on the BMW M20 engine without removing the head. Here’s how. (Disclaimer: Use at your own risk, your experience may vary.)

Broken Rocker

I broke the intake rocker on the #6 cylinder. You will get a range of advice on replacing just one rocker. Some say just to be safe, replace them all. If you have the improved rocker from the later years of the series, you can probably get away with just replacing the broken one. That was my case.

Here’s what you need to consider before you begin: you will need to remove the camshaft gear to get to the rocker arm shaft. To get to the cam gear, you need to remove the radiator and the timing belt. If you replace the timing belt, you should replace the tensioner, and the two seals behind the cam gear. If you don’t remember the last time you replaced the water pump, you should replace it as well. I replaced my water pump recently so I just went for the seals, tensioner, pulley, and new hoses. You will also want to replace the valve cover seal as well. Since you’re going to pull the spark plugs to make turning the engine by hand easier, you may want to replace them as well. Since you’re going to drain the coolant, you need to buy a new supply of coolant. I also changed the oil while everything was apart just in case any bits of rocker fell into the oil. (Turns out it was a clean break.) Replace your AC, PS, and Alternator belts too if you can’t remember the last time you replaced them. And of course you’re going to need a new rocker, eccentric, washer, bolt, nut and clamp.

Since these parts are relatively cheap, pick up a couple of spares in case you get into the project and realize any more rockers are cracked. Of course, having your trusty Bentley Manual is a must. Now you’re ready to start. Give yourself at least twelve hours of work time to do this if you’ve never done it before. You will also need an assistant once you get to step 29.

1. Place your car on jack stands and remove the front wheels, plastic under-tray, and hood. Take the transmission out of gear.
2. Drain the coolant out of your radiator using the drain screw at the bottom of your radiator and the 19mm screw plug on the block. You will make a mess so be prepared. The M20 engine holds about 3 gallons of coolant.
3. Remove the hoses to the radiator and remove the radiator by removing the bracket that holds it at the top and lift it out of the car. There will be some coolant left in the radiator so be sure to drain that too. If you are replacing all of the hoses, remove the rest of the hoses that go to the water pump as well. At a minimum you will need to remove the metal pipe that crosses in front of the waterpump and attaches to the timing belt cover.
4. Remove the mechanical fan using a long thin 32 mm wrench and fan pulley holder.
5. Remove the distributor and the rotor using a 3mm allen key.
6. Cut you belts or loosen the brackets for your AC (if you have one, I don’t), power steering pump, and alternator and remove your belts.
7. Remove the pulleys from your water pump and vibration damper.
8. Remove the cover that protects the position transmitter wire that crosses the timing belt cover.
9. Remove the timing belt cover, both halves.
10. Remove your spark plugs. (Optional, I found it easier to rotate the engine manually with them removed.)
11. Remove your valve cover and gasket.
12. Remove the oil pipe that runs the length of the head so you don’t damage it.
13. Note which rocker is broken. (I’m describing what worked for me with intake #6 rocker.)
14. Using a 22 mm socket, rotate the engine clockwise until it reaches Top Dead Center (TDC). This will be marked on both the cam gear and the crank. On the cam gear there will be a line on the head and a mark on the cam gear indicating TDC. On the crank, there is notch on the crank gear wheel. These two marks should both line up, otherwise your timing belt is installed wrong (not uncommon to be off by one tooth.) Freshen the markings so you can be sure you can find TDC again.
15. Rotate the engine manually in the clockwise direction until the pressure is relieved on the remaining 5 intake rockers. This will occur when the cam lob for the broke rocker is at its highest. Rotate until you are just ahead or just past the peak, but the other 5 rockers remain without tension. This will make replacement easier as you’ll see later.
16. Using a different color paint, mark this point on your cam gear and your crank gear wheel at the same line on the engine as TDC. Once we remove the timing belt, you want to be sure neither the crank nor the camshaft has turned while there is no tension between them so you don’t bend a valve.
17. Relieve pressure on the timing belt tensioner and remove the spring.
18. Remove the timing belt.
19. If you’re replacing your water pump, follow the instructions in the Bentley manual and replace the water pump now.
20. Remove the cam gear using a Torx socket. The Torx bolt is a T50. The corresponding socket is an E12. (Older cars may have an allen head bolt.)
21. Remove the bracket that locks down the two rocker arm shafts at the font of the cylinder head.
22. Remove the blind plug closest to the front (cam gear end) of the cylinder head. Use a screw driver to carefully pry it out and discard it. You’ll want to replace all four plugs while you have the valve cover off.
23. Remove the clamps that go over the rockers on each of the intake rockers.
24. All six rockers (including the broken one) should be loose on the rocker arm. Slide them off the valve perch toward the back of the engine. They should slide freely on the rocker arm shaft. You may need to lube to get them moving. Loosen the eccentrics if you don’t have enough play.
25. Lube the rocker arm shaft and see if it spins freely. Try to move it forward without prying. You are trying to slide it out the front of the engine far enough to reach the broken rocker. If you can’t get a good grip on it, wrap a piece of brass around it (or split a small piece of copper pipe) and use vice grips to get it to move. You want to be sure not to damage the surface of the rocker arm shaft.
26. Replace the blind plug at back end of the cylinder head.
27. Place your new eccentric into your new rocker along with the bolt, washer and nut. Be sure to put it in correctly so the adjusting hole is up and away from the rocker arm. Spin the eccentric so it creates the largest gap to the valve perch when installed. It will be adjusted later.
28. Slide the new rocker on the end of the rocker arm shaft.
29. Have a helper climb up in the engine bay with a large screw driver and press down on the valve spring of the rocker you are replacing. Remember that since the lob is up, the piston is down in the cylinder so you won’t damage the valve. You need to apply quite a bit of down ward pressure to free up the rocker on the rocker arm so you can move it back into position. Once the rocker is fully on the shaft and while keeping the pressure on the spring, use a rubber mallet to move the rocker shaft back into position. Be sure to align the rocker in the correct position so you can reinstall the clamp.
30. Spin the rocker arm shaft so the indentations are parallel for the bracket to be replaced that holds the arms in position. Reinstall the bracket.
31. Move the 5 loose rockers into the correct position above their valves and reinstall the clamps on each rocker.
32. Put a new blind plug at the front of the rocker arm shaft. (Replace the two plugs on the exhaust rocker arm while you’re at it.)
33. Before you reinstall the cam gear, you should replace the two seals behind it. Pull the guide cover off. Discard the o-ring and replace it with a new one. Pound out your old shaft seal, clean up the guide cover, and use the old seal to press in the new one. Lube it up along with the new o-ring and replace. You’ll be thankful you did this when your new timing belt puts additional tension on your old cam gear seal and you’re taking all of the timing belt parts off again next weekend because your cylinder head is leaking oil after you put on your new timing belt. (Don’t ask me how I know this….)
34. Reinstall the cam gear. Tighten it but don’t torque to spec until you have the timing belt back on. Check that the timing lines (the one you painted, not TDC) still line up.
35. Follow the instructions in the Bentley Manual to install your new timing belt tensioner and timing belt. Torque the cam gear nut. Verify your marks line up for TDC. Rotate the engine clockwise 4 cycles to make sure they still line up.
36. Follow the instructions in the Bentley Manual to adjust your valves.
37. Put the oil pipe back on the top of the cylinder head.
38. Put a little RTV Black on the Rocker Arm Shaft bracket as well as along the tops of the four blind plugs. Put on a new valve cover seal, and reinstall your valve cover.
39. For the rest, as they say in the Bentley manual, installation is the reverse of removal…

All Done

Screamin’ Demon

I finished the ignition upgrade last night. The latest performance project for the MINI was to improve the ignition system to match the improvements in airflow in and out of the engine. Because the smaller pulley produces more boost, the induction air is a bit hotter than stock. Since the air is hotter, the spark plug is one step cooler. Because the air/fuel mixture has more potential energy, the coil is upgraded to produce a stronger spark. To get that stronger spark to the cooler plug more efficiently, a plug-wire with lower resistance is used. This all doesn’t add up to more horesepower directly, but should reduce horsepower loss due to system inefficiencies, if that makes sense. The net result is a smoother running engine and actually better fuel economy.

The combination I used included MSD 8.5mm wires and a Screamin’ Demon Coilpack (like the MSD coilpack) and NGK Iridium Plugs.

stock MINI plugs

I was actually surprised by the condition of the old plugs. My MINI now has over 60,000 miles in less than 3 years of motoring. These are the original plugs. They’re rated to 100,000 miles and would probably make it. (An even tan color is good.) I’m used to plugs that wouldn’t last 10,000 miles let alone 60. Interesting to note that this is only the second part (after the brake caliper) that I’ve found that says “BMW” on it.