timing belt wont go back on

Wed Jul 22, 2015 5:35 pm

hi im attempting a timing belt change..on an m20b25 prefacelift”¦got a continental kit along with new water pump..got the old belt off fine and the crank and cam lined up. i replaced the water pump and tensioner but when i came to put the new belt on it just wont go on, tried putting the old one back on to see if it was the teeth but the old one wont go back on either..any ideas??

Wed Jul 22, 2015 5:42 pm

Ensure tensioner pully spring is compressed as possible. When you put the belt on dont try to get it all the way onto one cog, just slip it on 5mm and move onto next cog. Start at the crank pully then intermediate then camshaft then tensioner works for me. Try to keep the belt square if you know what I mean â˜º

Wed Jul 22, 2015 5:48 pm

except for the crank im trying to keep it as far out as possible..also the intermediate cog has tippexed marks that i didn't notice before and are not lined up at all could this be the problem?

Wed Jul 22, 2015 6:01 pm

I don't think it matters where intermediate cog is cos it doesn't drive anything. I would have a practice with the old belt, for me it seemed like I had to force the belt on the crank, but there was just a little knack to bending it just right so it can sit just on the cog whilst still being square. the cogs won,t have moved in relation to each other, so it can only be either technique or tensioner pulley

Wed Jul 22, 2015 6:39 pm

Timing belts can be quite tight to put back on the pulleys. Have you got any slack anywhere on the belt anywhere? If so, you need to get rid of the slack.

Wed Jul 22, 2015 8:53 pm

Yes what he said, there should be zero slack between crank - intermediate - camshaft. Any slack should be on the tensioner run. Your post sounds like you removed the belt and then aligned the marks? If you did this then you may not be able to get rid of all the slack between crank and cam. Don't worry too much if the marks line up exactly with the teeth of the cog, as long as the tooth with the mark is the nearest, and you finish correctly with tensioning you will be fine. Just turn the crank over a good few times with a spanner when you have the belt tensioned to reassure you its pointing to the correct tooth!

Wed Jul 22, 2015 8:59 pm

I lined them up with the old belt on but to take all the slack out the belt kinda lies in between the teeth...

Sun Aug 02, 2015 1:18 pm

Sun Aug 02, 2015 5:22 pm

Back the cam half a tooth so that the belt slides on.

Release the tensioner,turn the crank(clockwise

)two full turns BY HAND...22mm spanner on the crank nose...and re-check the timing marks.
If the cam is one tooth out,try again,but move the cam forward half a tooth.

Sun Aug 02, 2015 7:57 pm

tips wrote:except for the crank im trying to keep it as far out as possible..also the intermediate cog has tippexed marks that i didn't notice before and are not lined up at all could this be the problem?

Does your engine have it's distributor under the front of the inlet manifold?

Tue Aug 04, 2015 5:59 pm

daimlerman wrote:
tips wrote:except for the crank im trying to keep it as far out as possible..also the intermediate cog has tippexed marks that i didn't notice before and are not lined up at all could this be the problem?
Does your engine have it's distributor under the front of the inlet manifold?

im not sure what you mean..it looks exactly like the prefacelift pic in this link save the battery is in the boot
http://www.e30zone.net/e30zonewiki/inde ... _Servicing

Wed Aug 05, 2015 7:54 am

Some early M20 engines have a 'proper' distributor mounted under the front of the inlet manifold.It's driven via a jack shaft from the belt pulley just above the crank and a little to the n/s of the engine.(the lower part of this shaft drives the oil pump,BTW)

Later engines use a h/t cap mounted on the front of the camshaft.

If you have the early set up,then those tippex marks need to line up properly to locate the distributor correctly.....

If you have the later set up,those tippex marks are not important,as it's 'only' the oil pump that gets it's drive via that pulley....

Wed Aug 05, 2015 9:02 pm

He said he couldn't get the old belt back on either. This is painful, I wish I lived next door to him so I could pop round and have a look.

Wed Aug 05, 2015 10:03 pm

Painful...yes also downright embarrassing

a job that was meant to take a few hours has turned into a few weeks!!

Thu Aug 06, 2015 4:26 pm

ok finally got it back on BUT its one tooth out!! what should i move the cam or the crank”¦??

Thu Aug 06, 2015 5:29 pm

Move the cam.

Engine will run at one or two teeth out,but it will run better with it right.

Wed Aug 12, 2015 2:55 pm

Hi tips! I did my timing belt for the first time on last december,so i still remember well what i did.

At the first attempt i was a tooth off exactly like you. But then i understand that when you release the tensioner the cam goes one tooth off. So i removed again the belt and i putted the cam a tooth back. Then belt on again and when i released the tensioner...yeah! Everything ok!