No compression - wtf?

[whiskychaser]

I am confused... even if you did compression test before changing chain and tensioner. It wouldn't read anything if you are lucky.

The fact you got zero compression on all 6 means timing is all wrong. With first cylinder all the way up as in compression with both valves closed... the timing mark should be zero at the harmonic balancer.

The lobes on no 1 cylinder were pointing up and towards each other. The two dots on the flats at the back end of the cams were facing up and flats were in a horizontal line. Valves on no.1 cylinder were def. closed. I made a physical and visual check that no.1 piston was at TDC. I lined up the timing mark on the timing chain housing with the mark between the O and T marks on the crankshaft pulley. (As the pulley is in two parts, I made sure the lug from the back section was in the hole of the front before bolting it together)

I dont know what the harmonic balancer or how you mean the mark is zero but I'm very keen to learn!!

[yaofeng]

Your first pic is the chain tensioner. Like you, I cut mine in half to save removing the head. On my car this pivots on a dowel. I removed the dowel, poked the end of the new tensioner up through the head and tapped in a new dowel and fitted a new circlip at the end.

Your second pic looks like the pin that you push the chain guide on to. It was one of these pins that sheared and I found it in the sump. On my car these pins have threads. I fitted two new pins and a new guide. (I also fitted the other guide that bolts on top of the head and two new chains)

I'm not sure what your third pic is I can only guess this is what the chain tensioner pivots on in your car?

After 9/94 BMW replaced the aluminum chain guide (BMW call this chain tensioner, I am used to the SAAB convention calling it the chain guide. But tensioner it is.) with one plastic. My 525i was a 5/94 production. It came with an aluminum tensioner. I cut it in half to remove it like you did so I did not have to remove the head. The only way I can fit the chain tensioner back was to use the plastic one because I can snap it in place. It is not possible to reinstall the aluminum tensioner back with the head in place. Since I didn't know how to remove the old tensioner pivot pin to install the new one which works with the plastic tensioner, I had to make use of the old pin. The plastic tensioner has a shorter width then the aluminum tensioner at the pivot. (Fortunately the pin diameter is the same.) To make it work I need to make up the difference in width. So I cut a piece from the discarded aluminum tensioner pivot to slip onto the old tensioner pin and reused the snap ring. The new plastic tensioner doesn't require a snap ring if fitted with the new guide. It just snaps in. I had to reuse the metal snap ring with the new tensioner, old tensioner pin combination.

[yaofeng]

The lobes on no 1 cylinder were pointing up and towards each other. The two dots on the flats at the back end of the cams were facing up and flats were in a horizontal line. Valves on no.1 cylinder were def. closed. I made a physical and visual check that no.1 piston was at TDC. I lined up the timing mark on the timing chain housing with the mark between the O and T marks on the crankshaft pulley. (As the pulley is in two parts, I made sure the lug from the back section was in the hole of the front before bolting it together)

I dont know what the harmonic balancer or how you mean the mark is zero but I'm very keen to learn!!

The picture below is what he meant. But I think your timing set at No. 1 piston TDC was dead on except it was set on one with bent valves.

[whiskychaser]

[QUOTE=yaofeng]The picture below is what he meant. But I think your timing set at No. 1 piston TDC was dead on except it was set on one with bent valves.

I have to agree :-( The only thing I WAS slightly unhappy about was that I coudnt get the left side of the slots in the main chain sprocket to line up with the bolt holes in the end of the exhaust cam. They are to the left, but not as far over as I wanted. But if the crank and cams are fixed, that position is dictated by the length of the chain which of course I pulled tight. Either way, the marks tally in practise.

I dont know exactly how hydraulic cam followers work, but even with a cold engine I dont expect to find 25 thou between the follower and the cam.

Will have to either take the head off or pop down the local hospital and see if I can borrow an endoscope :-)

[grave77]

when u heard that sound, you have bent some valves, broke some maybe, a dead chain with an engine running = dead engine. I have seen an engine trashed cuz of that while driving at 50m/h M20 engine lost the timing belt and grind all the valves into the pistons.

better now you remove the head, and see what the damage you have, also check the oil pan for any metal fragments this would tell you if you smashed any of the pistons with a broken valve fragments.

[632 Regal]

I dont know exactly how hydraulic cam followers work, but even with a cold engine I dont expect to find 25 thou between the follower and the cam.

there is only a certain amout of interferance between the valves and pistons which would explain the .025 clearance on all the intake valves. There should be NO clearance weather the engine is cold or warm or running with hydraulics.

new head time

[whiskychaser]

when u heard that sound, you have bent some valves, broke some maybe, a dead chain with an engine running = dead engine. I have seen an engine trashed cuz of that while driving at 50m/h M20 engine lost the timing belt and grind all the valves into the pistons.

better now you remove the head, and see what the damage you have, also check the oil pan for any metal fragments this would tell you if you smashed any of the pistons with a broken valve fragments.

Some years ago I had a timing belt go on a Honda 16 valve doing 85mph in the fast last of the motorway. Did no damage to pistons/valves. Two miracles is too much to expect. I better read up on how to take the cams off without snapping them

[whiskychaser]

there is only a certain amout of interferance between the valves and pistons which would explain the .025 clearance on all the intake valves. There should be NO clearance weather the engine is cold or warm or running with hydraulics.

new head time

Thanks for clearing that up. My guess is the inlet valve heads are larger and they took a hit whereas the exhausts may have escaped.

[632 Regal]

correct, pull the head and make sure before you buy a new one.

Thanks for clearing that up. My guess is the inlet valve heads are larger and they took a hit whereas the exhausts may have escaped.

[Paul in NZ]

my old toyota broke the belt and did no damage...a non intereference engine i think,tow to shop,new belt,drive home