GUIDE : Changing your cam belt


SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
Your cam belt (or timing belt as it is also known) performs an important role - it basically keeps the top end of the engine in synch with the bottom. As the pistons are fired, they translate their movement through the rods to the crankshaft which rotates 2 complete revolutions for a combustion cycle (intake and compression are one revolution, combustion and exhaust are another).

The top end of the engine i.e. the cylinder head works twice as fast because valves may need to open for the rising stroke of a cycle then close again for the falling e.g. the exhaust valve will open on the exhaust stroke but then will need to close for the intake of fresh air. The cam belt maintains the precise timing required for the cylinder head and block to work in synch with each other.

The 7MGTE is a non-interference engine which means the valves can never normally hit the pistons. There are cut-outs in the piston crowns (top) which give enough clearance for a fully open valve to still avoid contact. This is great news in the case of a cam belt failure because it is very common for the valves and pistons to collide in other (interference) engines. Basically the Supra doesn't suffer any real side effects of a cam belt snap other than the need for a new belt.

The belt should be periodically renewed by either time or mileage. I believe the advised schedule is 60k miles or 4 years from Toyota.

NOTE: You will need to remove the crank pulley from the engine to do this so the crank pulley bolt will have to be removed too. This is VERY tight and I recommend you follow the instructions in the engine removal guide to crank this off with the starter motor before you do anything else - you have been warned!

Step 1 - Remove the spark plugs (see the guide for changing the plugs), this gets rid of a lot of pipework and also allows you to turn the engine over easily without pressure building in the cylinders

Step 2 - Sadly I'm working on an engine on a stand but for normal cam belt changes you need to remove the viscous fan, air con belt and fan belt. You will also need to remove the top hose to the radiator to reach the same stage my engine is at. There is also an air con bracket you may need to move as well as a power steering air pipe but nothing too dissimilar to the guide

Step 3 - You need to remove 'number 3' timing belt cover which is the top one at the front of the engine. The picture shows all the nuts you need to remove, they are all 10mm


Step 4 - Before the cover can come off you need to remove the water outlet / thermostat housing which is simply another 2 10mm bolts. Once removed you can pull the housing clear by hand



Step 5 - Now pull the timing belt cover clear of the engine. This may have sealant around it or a gasket, either way remove the cover and clean away any remnants of the previous seal


Step 6 - Now you should have a clear view of both cam shaft timing pulleys (cam pulleys). The inlet is the one on the right hand side as you face the engine (as if you didn't know!) and the exhaust is on the left. The pulley you can see underneath the two cam pulleys is the idler pulley which is used to tension the cam belt.


Step 7 - Fit a 19mm socket to the crankshaft and rotate it (clockwise) until all the notch on the pulley is at the 0 mark on the bottom (number 1) timing cover (top dead centre or tdc). The second picture shows the crank pulley aligned with the 0 mark - you will notice someone has put a dot of tipex/white paint on to make it clear where the mark on the pulley is, not a bad idea.

Note that at the start you were told to 'crack off' the crank pulley bolt, you should still be able to apply enough force to rotate the engine without tightening the bolt up much at all so don't worry about getting it off again



Step 8 - Check that the matchmarks on the cam pulleys are aligned. These are grooves in the pulleys which should be pointing straight up in alignment with the marking on the black metal backplate (timing belt cover #2 to give it the proper name!). If they are way out then you need to rotate the pulley a full 360 degrees because you are half way through the 4 stroke cycle


Step 9 - The belt is directional and usually has arrows on it. If you are removing it and for some reason will be refitting the belt then make sure you know the direction of rotation and mark it with a white pen/tipex to be sure.

Onto the lower (number 1) timing belt cover next. Again, this is just 10mm bolts although one is behind the crank pulley - you did crack this off earlier didn't you?


Step 10 - Remove the 19mm crank pulley bolt, this will be slightly tight after turning the engine using the pulley in step 7 but you should be able to just restrain the crank pulley in one hand and undo the nut with the other.


Step 11 - Now you have to get the pulley off. You can get special tools to remove this but with a bit of pulling (no puns!) you can remove it from the engine. It must come off square or you will stress the woodruff key that holds it on the crank (we'll look at that next so don't panic if you don't know what one is).


Step 12 - With the pulley removed you are looking at the nose of the crankshaft itself. You'll notice a funny piece of metal sticking out of the crank, this is the woodruff key. To ensure the pulley stays aligned with the crank and doesn't rotate at all, this very simple piece of metal is inserted. It's a semi-circle of metal that drops into a groove in the crank and then protrudes slightly as you can see from the first picture.

The crank pulley also has a groove cut out of it, this is shown in the second picture. The woodruff key slides into this groove and is locked in position.

Remove the woodruff key and place it somewhere safe - do not lose it!



Step 13 - Now you can get that final 10mm bolt for the lower cover and remove it (no gasket on this one)




SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
Step 14 - For reference, here's a picture of the routing of the cam belt. It's dead easy, only one adjuster and two cams - count yourself lucky it's not a V8 etc :)


Step 15 - Time to get to work on the belt itself, loosen the 14mm nut on the idler pulley and the pulley will release the tension on the belt


Step 16 - I popped the water pump pulley off at this stage because I was going to take an elaborate photo (was going to show the idler retracted, the bolt being tightened and hold a camera all at the same time!) which didn't come out in the end, if you should so choose you can do it this way or just push the idler with your fingers. My route was to remove the pulley (picture 1) and use mole grips to lock the cam belt idler pulley to one of the nuts on the water pump (picture 2). Once all the slack was removed I tightened the 14mm up so it didn't move.




Step 17 - The belt will simply slide off now. Admire the belt.

If you have any signs of cracks or cuts or oil renew the belt. Spin the idler pulley and if it isn't smooth replace it.



Step 18 - At this point I could have thrown the belt in the bin and continue stripping down the engine but I figure you might want to know how to put it back together so I refitted the original belt. First, work it over the crank pulley teeth (be careful with your belt, don't bend it unnecessarily or catch it on anything sharp).

Refitting should be done on a cold engine but I assume you've done all of this on a cold engine seeing as it involves removing the cooling system's top hose.

Note: There are often markers on the belt with a double white line for the crank pulley and two single white lines for the cam pulley markers. You can use these if you like but tbh there's no real need. Just make sure the directional arrow is correct (the engine turns clockwise as you face it)


Step 19 - Now run the belt over the right hand side of the oil pump pulley (the toothed wheel on the right), ensuring it's not really slack. The left hand side of the belt goes around the crank pulley and up on the right hand side of the tensioner


Step 20 - Reinstall the number 1 timing belt cover


Step 21 - Refit the woodruff key to the crank and slide the pulley over the key ensuring the cut out is aligned with the key



Step 22 - Tighten up the crank pulley bolt so that you can turn the engine over, you can torque it up to the full 195 ft/lbs if you have a method of locking it but if not then just do it when everything's back together


Step 23 - Now nudge the pulley (if required) to ensure the notch on the crank pulley is still aligned perfectly with the zero marker


Step 24 - With the cover fitted and the pulley aligned, run the belt up the right hand side of the engine, keeping it nice and tight


Step 25 - If you need to tweak the alignment of the cam pulleys slightly to get the belt teeth to sit properly then you can but this should only be a very small amount (you're talking about a mm or 2 not a lot). If you do need to nudge it then hold a 14mm socket on and then wrap the belt over the pulley


Step 26 - Run the belt over the top of the intake cam pulley but don't go over the exhaust side yet


Step 27 - Check how taut the belt is. There should be very little movement in it or you haven't gone tight enough. You don't want to be even 1 tooth out so try again. Sadly the first picture didn't come out very well showing you what it looks like when wrong so I lightened it a lot and you can just make out how much deflection there is in the belt. The second picture shows you how it should be so this is the one to follow anyway




SM Official Expert: Guide Author
SM Expert
May 26, 2009
Derbyshire, UK
Step 28 - Now run the belt over the exhaust cam pulley too, tweak the alignment by a tiny amount if required again


Step 29 - Check again for deflection, there shouldn't be a lot of play as shown in the picture


Step 30 - Ensure the matchmarks for the camp pulleys haven't moved from the marks. If they have, take the belt off and try again


Step 31 - Loosen the idler pulley bolt and it will spring out and push against the belt. Nip this 14mm up again where it lands


Step 32 - Now you need to put the 19mm socket back on the crank and rotate fully 2 revolutions clockwise. This is to complete one cycle of the engine and check everything is aligned


Step 33 - After turning the engine, loosten the idler pulley's 14mm bolt again and it will spring out a bit more. Tighten it up to the full 36 ft/lb and you're done.

You can now rotate the engine a few more times and make sure everything's perfect but it should stay perfect from this point. To complete, just refit your timing belt cover (number 3 - the top one!) and then the thermostat housing.

Take your time and ensure you get the alignment marks spot on when you refit and it's not a difficult job, good luck.