the cambelt has broken on my 1989 bmw 318i. i have taken the cylinder head off and all the valves are currently clear of the path of the pistons. i cannot turn the cam pully by hand, and im wondering if the cam, being so stiff could have stopped spinning immediatley when the belt broke? ( at about 1500-2000 revs.)
also, there is no markings on the carbon deposits on the pistons or valves. could i have damaged the valves without leaving any obvious signs?
any good input would be greatly appreciated!
2007-10-22 07:01:57 · 11 answers · asked by lestannard82 2 in Cars & Transportation ➔ Maintenance & Repairs
bring it into a macheme shop they can leak check it for you mill the head and check the cam bearings
2007-10-22 07:15:01 · answer #1 · answered by mobile auto repair (mr fix it) 7 · 0⤊ 1⤋
Unfortunately, you removed the head. It would have been easier to replace the belt (properly), then only remove the head if the car showed signs of a damaged valve.
Replacing the head requires a new head gasket, new heat bolts and a torque wrench. Make sure you follow the instructions carefully when to do this. Make sure you put the gasket on the right way, right side up.
Since you don't see any marks on the cylinders, it probably means that there was no collision between the valves and the pistons. A machine shop will be able to test the head for you, or you can put it back on (using the above), put on a new timing belt, then do a compression check. The service manual or a Haynes manual will tell you what compression is required. If the compression is not good, then you'd need to remove the head again to have a valve job done on it.
It's not surprising that you can't turn the cam. If the valves and rockers are still on the head (I hope they are), then there is a fair amount of torque required to turn the cam and open the valves.
I highly recommend you get a good service manual, such as a Haynes manual to help you learn the details the easy way. Also, check out the Autozone website. There is a "How to" section that you should find helpful. Even when the information is for a different vehicle, if the construction is similar (for example another overhead cam engine), then the techniques will very similar.
2007-10-22 14:19:43 · answer #2 · answered by snake_slinger 4 · 0⤊ 1⤋
Its possible that you have been very very lucky and not damaged either the piston crowns or the valves. There should be at least some tell tale marks in the carbon build up on the piston crowns, from what you say there is not so I would conclude that they has been no damage.
Not to sure about the cam being tight, obviously you need to over come the force of the valve springs etc, but that should be the same with all cars.
2007-10-23 05:52:59 · answer #3 · answered by Anonymous · 0⤊ 0⤋
many FSM manuals will say on interference engine how far the cam can move ( 90 deg. is common).
the Gates belt and hose main page has a link to a manual that tells you which are free running and which are not. check it.
id say it is ok if the pistons and valve look ok.
it is 1 in 10000 chance if belt snaps and valves dont hit.
for sure pistons are ok.
the valves could have been bent , but you'd see witness marks for sure !
put it together, time the cam, and do a compression test.
if it is perfect then all is well.
start it and run it easy.
if valves do act up then get a valve job. or an exchange. head. I dont think you have anything to loose but time.
(cept 1 gasket or 2)
2007-10-26 00:02:38 · answer #4 · answered by gearhead 2 · 0⤊ 0⤋
Yes you could have damaged the valves and since you already have the head removed its not a big job to remove and check them.With the valves removed you will have no spring pressure on the cam lobes and the cam pulley should move with ease.Unfortunately the valves normally touch on this engine i know you cant see any obvious signs work through it slowly and systematically .Take no notice of people that say buy another car etc they are morons.All mechanical things on a 318 can be fixed if in doubt go to your local library and check the Haynes manual for your vehicle any more help just ask regards Mick UK
2007-10-22 14:26:05 · answer #5 · answered by mick 6 · 0⤊ 0⤋
Turn the cylinder head upside down and pour a little petrol into the combustion chamber if you have a damaged valve that is jamming the cam fuel will run out off the port of the damaged valve
2007-10-23 06:24:49 · answer #6 · answered by Anonymous · 0⤊ 0⤋
Really you should have popped another cambelt on first and done a compression check.
You may have been extremley lucky but i doubt it.
Try removing the cam and turn the head upside down and put some WD40 into each pot, if the valves are'nt sealing it will seep through any damaged ones.
2007-10-22 14:24:55 · answer #7 · answered by Anonymous · 0⤊ 1⤋
it sounds like youve been lucky. make sure the cam turns through all the valves useing a ring spanner.
make sure all the valves close
you should be ok if it does
2007-10-22 14:57:22 · answer #8 · answered by pj 3 · 0⤊ 0⤋
Call the dealership and ask the service manager and hope that he will help you.Of course he will want to get the job.
2007-10-22 14:11:03 · answer #9 · answered by hdf69 5 · 0⤊ 1⤋
Oh dear this sounds VERY expensive sir. It will be cheaper for you just to bin it and buy a different car.
2007-10-22 14:06:16 · answer #10 · answered by Anonymous · 0⤊ 2⤋