Timing Belt Change

by Gary Fischman - gary@miata.net 

(For some additional information about timing belt and crankshaft problems, see Brian Bousman's Web page where he archived many of the Miata.net crankshaft discussions.)

Related Articles

• Radiator removal
• Water pump replacement
• Thermostat replacement 1 2
• Ignition and timing

Changing the Timing Belt (and front crankshaft seal)

The Miata timing belt must be changed every 60,000 miles. Although the California Owner's Manual says 105,000 miles, this is just to satisfy a state requirement that says timing belts should last 100,000 miles or more. Still, it should be done at 60,000 miles.

The Miata engine is a non-interference engine, meaning that the pistons will not crash into the valves.

WARNING: Changing your own timing belt is not for the faint of heart!

If you screw it up, your engine may not run! However, if you are confident in your abilities and generally do your own work, you should be able to handle it.

Special Tools

Changing the timing belt requires no special tools. You will probably want to have a 14mm deep well socket, a 3" extension for your 1/2" drive, and you may want a steering wheel puller to remove the crankshaft pulley. (It shouldn't be necessary) Also, you may want a second pair of hands to hold the camshaft pulleys steady while you install the new belt. You will also need something to drive the new crankshaft and camshaft seals in. An appropriate piece of pipe, covered with electrical tape to prevent cutting the seal worked well for me. A long breaker-bar will be needed to remove the crankshaft bolt.

Parts to buy in advance

• Timing Belt
• Valve Cover Gasket
  You may be able to get away with not replacing this, but its only a $20 part and isn't really worth taking the risk of a leak.
• Front Crankshaft Seal
• A tube of High Temperature Silicon Sealant
• Accessory Belts (optional)
  They need to be removed anyway, so it can't hurt to replace them now instead of waiting until they break.
• 1 gallon of Anti-Freeze (optional)
  You need to drain it anyway, so if you haven't replaced it in the last year, you might as well do it now.
• Woodruff Key (optional)
  Miq Millman recommends replacing the Woodruff key (about $5) as a precaution. I haven't done it myself, but it can't hurt to do so.
• Camshaft seals (optional)
  Check for leaks and replace them if necessary.
• Water pump (optional)
  You need to remove the timing belt to replace the water pump. A water pump may last anywhere from 70,000 to 170,000 miles. We waited - ours lasted a long time. You need to decide. You'll save a lot of labor if you do it now, and water pumps are under $100.

The Breakdown...

Before you begin - LABEL EVERYTHING!!!! Label each part as it is taken out and also label its bolt sizes and what the part was connected to/in/between. This aids in any confusion to the novice engine worker.

Drain the coolant Into a suitable container and save it for reuse or, if you plan to replace it, for recycling. Remove the large plastic air intake pipe Remove the hose clamps at each end and one bolt. Also take off the chrome air pipe that runs across and into the valve cover. Remove the upper radiator hose Remove the two water hoses connected to the thermostat housing.

Optional: Remove the cooling fans and the radiator. This will give you a lot more room to work. It isn't too hard. There is an electrical connector on each fan. Remove the 2 bolts at the top and bottom of each fan and lift them out. Disconnect the lower coolant hose from the radiator (accessible from the trap door on the debris shield underneath) and remove the two upper bolts holding the radiator in place. Lift out the radiator and carefully put it aside. Be careful not to damage the cooling fins on the radiator. The are easily distorted. Remove the A/C belt Loosen the tensioner bolt, pivot bolt, and lock bolt on the power steering pump housing until the belt can be slipped off.

• Disconnect the ignition wires from the plugs.
• Remove the spark plugs. This will make it easier to turn the engine later.
• Remove the Valve Cover
• Crack the 3 bolts holding the water pump pulley on before loosening the belt. If you do happen to remove the belts before loosening the water pump pulley bolts, you can hold the pulley in place by wrapping the belt back around the pulley and holding it tightly, as close to the pulley as possible.
• Remove the Alternator belt.
  Loosen the alternator tensioner bolts. The bottom bolt can be difficult to get to.
• Remove the water pump pulley.
• 1990 - 1991: Remove the accessory belt pulley from the crankshaft pulley.

This is easier if you put the car in gear to keep the engine from turning. Loosen the bolts holding the pulley in place. As you remove the outside plate, pulley, and timing belt guides, make a note of the order in which they came off and the direction they face. This is important.
1992 and later: Remove the 21mm crankshaft bolt. This will be difficult. Put the car in 5th gear and engage the parking brake. Using a long breaker bar, crack the bolt loose.

Note: Archie Glasgow sent in this photo of a homemade tool that keeps the engine from turning while removing the bolt. We haven't tried it, but we see no reason why it wouldn't work.

• Remove the 3 timing belt cover plates.
  These are easy to remove. First remove the upper plate, then the middle plate, and finally the lower plate. Be sure to make a note of the various pieces being held by these bolts so you know where to replace them.

• Mark positions!
  Using a suitable socket, rotate the crankshaft pully clockwise two complete turns. (The transmission should be in neutral for this.) Continue rotating until the "E" mark on the left camshaft pulley lines up with the "E" mark engraved on the head and the "I" mark on the right camshaft pulley lines up with the "I" mark on the head. If the marks don't line up exactly, but are only off by half a tooth, use some chalk to mark the positions. If the marks don't line up and are off by a full tooth or more, your timing belt may have slipped. If this is the case, you may want to seek professional advice before continuing. (If the car was running fine, the belt most likely didn't slip and the marks are simply off for some other reason. If the car was running like crap, then the belt probably did slip.)
  Dave Streib suggests:
  Before removing the old belt, count the teeth/spaces between all the points that the belt touches on the 3 wheels. Next, mark the starting "space", and ending space on both the belt and cams. This is easily done with some WhiteOut. Remove the belt. Transpose the marks from the old belt onto the new belt, and count the spaces to make sure that they are correct. Finally, match the new marks on the new belt with the marks on the cams/crankshaft.
• Loosen the timing belt tensioner lock bolt.
  Temporarily secure the tensioner with the spring fully extended.
• Remove the timing belt.
  Once the belt has been removed, do not rotate either the crankshaft pulley or the camshaft pulleys. If you do, you will not be able to figure out the proper rotational alignment.

TIP: Sean Archer and Vic Harder from the Canadian Rockies Chapter of MCA offered this great tip. We haven't tried it, so we're not sure what kind of caveats might be attached to it, but its sure worth a try! If you're replacing the camshaft seals or water pump as well, you won't be able to do this.

When you are ready to remove the old timing belt and apply the new one, cut the old belt in half for its entire length. That leaves lots of room to push on the new belt. Push the old belt back as far as it will go on the crank and cam sprockets, leaving approximately a 1/4" to slide the new belt over. Once the new belt is on and lined up correctly, simply cut the old one off and push the new one into place.

Inspect and Replace the Front Crankshaft Oil Seal

This step is optional. If the seal is leaking, definitely replace it. If not, you may want to let it go until next time. Especially if you have an early model with a "questionable" crankshaft.

• 1990-'91: Remove the 21mm crankshaft bolt. This will be difficult. Put the car in 5th gear and engage the parking brake. Using a long breaker bar, crack the bolt loose. 
• Remove the Woodruff key.
• Remove the timing belt pulley.
  You may require a wheel puller to get this off.
• Remove the oil seal.
  Be extremely careful not to score the crankshaft during the removal. This can cause leaks. The oil seal is a steel ring covered with plastic and rubber. The best way to remove it is to carefully cut the plastic and rubber and pry out the seal with a screwdriver. Be sure to put a piece of cloth between the screwdriver and the metal areas so you don't score anything. This takes a bit of work.
• Install the new seal
  Coat the new seal with a bit of oil and press it firmly into place with your hands.
• Seat the seal
  You need to drive the seal flush with the oil pump body. A large socket or pipe is good for this. I use a piece of pipe covered with tape to prevent damage to the seal. Drive the pipe against the seal with a hammer until it is seated flush.
• 1990-91: Replace the timing belt pulley.
• 1990-91: Install the Woodruff key.
• 1990-91: Tighten the crankshaft lockbolt to 80-87 foot-pounds. 
• 1992 & later: Install the woodruff key and timing belt pulley. 
• 1992 & later: You will need to install and remove the crankshaft bolt and pulley a couple of times, so install it, but do not torque it down.

These tips regarding the seals  were sent in by Joe Heagney ( jheagney@micromatter.com ):

Belt had obviously been changed recently, almost no gaskets   on belt covers, got the seal out and discovered that the crank nose was  ok, but the sealing surface had been gouged in several places by some  cretin trying to remove the seal, probably at timing belt change time.  After much soul searching and not a little deliberation on the familial  heritage of the cretin, I cleaned up the sealing surface by filing and  grinding with a Craytex rubber/abrasive wheel on a cordless Dremel tool,  and changed the seal. Then I thought, what about the camshaft seals? By  this time I had realized that removing these seals was a real pain in the   posterior and had discussed the problem with a friend who had taught   motorcycle repair in a former life. He suggested (here's tip number one)  that you can drill the seal with a small drill and screw in a sheet metal  screw and pull on the screw to remove the seal. He had a minerature slide  hammer puller for this, but vise grips and a hammer work since they  aren't very tight. Next he said that he had had cretin gouged motorcycle  cranks to repair and had smoothed the crank and then cleaned the gouge  and filled it with epoxy (tip number two). When I pulled the seals from  the camshafts it was obvious that the same cretin had been there as well.   To make it easy to work on the camshafts I pulled the bearing caps and  filed the sealing surface smooth and then cleaned and filled the gouges.  I used J.B. Weld, which has a long cure time, but it made a very smooth  surface when sanded with 600 wet or dry.

Inspect and replace the camshaft seals if required

• To remove the sprocket, you need to secure the camshaft with a crescent wrench at the bolt-shaped section of the cam between the #1 and #2 lobes. Loosen the 14mm cam sprocket bolt, taking care when it breaks loose not to let the wrench on the cam shaft smash into the side of the head. (The enthusiasts manual says this area is relatively soft and easily damaged.)
• The sprocket just pulls off once the bolt is free.
• Remove the seal by carefully cutting it away and pulling it free. Take care not to gall the metal. Replace like the crank seal: oil it up and press it into place. (A 34mm socket works great!)

Replace the Water Pump

If you plan to replace the water pump, now is the time. When you're done, come back here.

• To replace the sprocket, the dowel pin on the cam shaft should be vertical. The appropriate mark on the pulley - I for intake, E for exhaust, should be facing up when the pulley goes back on.
• Torque the bolt to 36-45 ft.lb., holding the cam shaft with the crescent wrench as before.

Replace the Timing Belt

Verify that the timing belt pulley mark is aligned with the v-shaped timing mark on the front of the engine.
Verify that the camshaft pulley marks are aligned with the marks on the seal plate. Install the timing belt. CAUTION: Do not rotate the belt counterclockwise. Someone recently did and managed to shear the exhaust cam pulley. You'll require some help installing the belt. Someone will have to hold the camshaft pulleys steady while you thread the belt on. This will take a couple of tries to get it right. Turn crankshaft 2 turns clockwise Align the timing belt pulley mark with the timing mark.
Verify alignment of camshaft pulleys. Be sure the marks on the pulleys are still aligned with the marks on the seal plate. If not, remove the belt and repeat from the beginning of the Replace the Timing Belt section.

• Turn the crankshaft 1 5/6 turns clockwise
  And align the timing belt pulley with the tension set mark.
• Tension the belt
  Loosen the tensioner bolt to apply tension to the belt. Tighten the tensioner bolt to 37-52 Newton Meters.
• Turn the crankshaft 2 1/6 turns clockwise
  Verify the timing marks are still correctly aligned.
• Check belt deflection
  Apply about 22 pounds of pressure to the center of the belt between the camshaft pulleys. The deflection should be 9-11.5mm. If not, repeat from the tension setting.

Putting it back together...

• '90-'91:Install the timing belt inner guide plate.
• Install the lower, middle and upper timing belt covers.
• Install the valve cover
  Apply silicone sealant in the corners where the rounded areas are by the camshafts.
• '90-'91: Install the timing belt outer guide plate.
• '90-'91:Install the crankshaft pulley and the plate.
• '92 and later: Replace the timing belt pulley and crankshaft bolt. Torque to  116-122 foot-pounds.
• Reinstall the spark plugs and wires. Torque spark plugs to 11 - 17 ft. lbs.
• Reinstall the water pump pulley and the belts. Tighten pulley to 69-95 inch-lbs.
• Adjust tension on the two accessory belts.
• Reinstall the coolant hoses.
• Reinstall the air intake.
• Fill the radiator.
• Say a prayer and start it up!

At this point its a good idea to check the ignition timing and idle speed. If everything was done correctly, it should not have changed, but it can't hurt to check.