Mazda 6 Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Had my 2007 Mazda 6 times but had trouble getting bolt out. So without thinking took all the timing stuff out and used air gun and took crank shaft pulley off without thinking. Put pulley back on tried returning it but the crank shaft does a half turn and stops. Before taking crankshaft pulley off I could turn it clock wise and it wouldn't get stuck at all. Anyone have any idea why this would happen? Or what to do about it?
 

·
Registered
Joined
·
3,080 Posts
Your engine is out-of-time with the valves.

That's very serious, especially if you put any sort of force behind trying to turn it once it locked up (or worse, if you used the starter.) Most of the time valve/piston collisions do critical damage instantly, although OFTEN it appears you got away with it and then 10k miles or so later a valve head breaks off and destroys the engine.

You need to re-establish the engine's basic mechanical timing and, I hate to say it and you're not going to like hearing it either, but if there was ANY material amount of force used (especially the starter!) to attempt to rotate the engine beyond where it stopped the head has to come off, the valves have to be removed and CLOSELY inspected for damage. It is not possible to do that with the valves IN the head (or the head on the engine, obviously.)
 

·
Registered
Joined
·
9 Posts
Discussion Starter #3
No force was put behind it. Only used a socket wrench to try and re established the timing. There is no way of unlocking it unless taking cams and valves off?
 

·
Registered
Joined
·
3,080 Posts
Figuring out which way you're off without having a reference is not easy -- there should be reference marks for TDC via some mechanism for the cams and the crank (e.g. at the flywheel) but each engine is difference on exactly how they're indexed. On VW TDIs, for example (which have a timing belt that requires routine replacement) there's a TDC mark on the flywheel visible once you remove the top inspection cover, and the cam is at TDC when the slot where the vacuum pump mounts (which you have to remove) is parallel to the head and both #1 lobes are pointed upward; to know you're EXACTLY on for the cam you need a lock plate that goes into the slot. If you lose the reference on a TDI the best option to recover from that is to remove the cam, set the crank to TDC and lock it, then re-install the cam in the correct position.

Most interference engines are quite-sensitive to this relationship being exactly correct; it's not uncommon for the maximum margin of error on the crank without a valve collision to be in the ~10 degrees of rotation range. That's not much....

If you can find the reference method for that engine then figuring out what's off its index and by which direction (and thus how to reset it without doing it the hard way) may be possible. I haven't had one of these engines valve timing apart personally so I'm not aware of how basic mechanical timing is established.

Most engine valve timing systems are negatively impacted, sometimes to the point of jumping time or doing severe damage to the tensioner(s), if turned in reverse. In general its never a good practice to bar an engine over opposite its normal rotation.

I wish I had a procedure for this one but I don't... maybe someone else here does and will pipe up.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #5
There is a lot of slack in the chain. Would I be okay to change all the timing components like, timing chain, oil chain guides, vvt and all other sprockets, oil pump, water pump, vvt solenoid. Then try and re astablish timing.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #6
Oil chain and oil guides just noticed I had them together which looks like I'm just changing oil chain guide but not oil chain lol. I am trying to change all timing components.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10
Sorry if I'm asking dumb questions.. so I am guessing the only way to unlock it from the half turn is to take it all apart? Cams and cylender head. Besides all the stuff that I listed above that I'm changing out and the heag gasket is there anything else I should buy?
 

·
Registered
Joined
·
3,080 Posts
There absolutely should NOT be slack in the timing chain. I would refresh ALL the components in there; either buy them all and replace them all or CAREFULLY inspect to find the ones that need to be changed. Try to figure out the reason for the failure as well; it's not all that common for timing chain systems to go bad and lubrication failures are often at the root of the cause when they do.

You can usually remove the cam(s) on an OHC engine with the head on the engine, then the crank can be freely rotated to TDC as all valves are closed, then reinstall the cam(s) in the correct location. Normally the head does not have to come off and unless you have some other reason to do it or suspect damage to the valves or cylinders/pistons I wouldn't. If you do remove the head you need a cylinder head gasket and all head bolts; they're nearly-always one-time (torque-to-yield) use, you need to properly clean both mating surfaces and the torque sequence must be adhered to EXACTLY on re-installation.

As noted you need the proper locking tool set; those relationships have to be EXACT on assembly.
 

·
Registered
Joined
·
1,036 Posts
There are some specific instructions on how to remove canshafts... loosening cap bolts in a specific order and by a specific amount at a time - to prevent thrust bearing damage. Heads-up!
 

·
Registered
Joined
·
1,036 Posts
You can usually remove the cam(s) on an OHC engine with the head on the engine, then the crank can be freely rotated to TDC as all valves are closed, then reinstall the cam(s) in the correct location.
With this, for Reinstallation of the Cams: the cams have to be placed in the bearings (with their correct TDC-related rotational position) and then the bearing caps tightened with the cams not being rotated much at all from that point... because rotating them (much) would cause valve-to-piston contact... potentially damaging / bending valve stem(s).

One thought I had is that the instructions on exactly how to remove the cams from the head (i.e. which bearing caps to slacken and by how) much MAY NOT work with the cam(s) in a random (i.e. not TDC related) position. Then damage to the camshaft thrust bearing can occur. Comments?
 

·
Rally Racer
Joined
·
2,648 Posts
I think you will have to disconnect the timing components and reset everything to TDC. There are special tools for this but aside from disassembling everything it is the only thing I can see now. Even if you do dissamble it all you will still needed the tools to set up your timing. Perhaps a metal bar and 6mm bolt?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #16
I have the timing tools. Just trying to get the easiest way to unlock crank pulley from the half turn. Try and figure out why it's jamming up in the first place.
 

·
Registered
Joined
·
3,080 Posts
With this, for Reinstallation of the Cams: the cams have to be placed in the bearings (with their correct TDC-related rotational position) and then the bearing caps tightened with the cams not being rotated much at all from that point... because rotating them (much) would cause valve-to-piston contact... potentially damaging / bending valve stem(s).

One thought I had is that the instructions on exactly how to remove the cams from the head (i.e. which bearing caps to slacken and by how) much MAY NOT work with the cam(s) in a random (i.e. not TDC related) position. Then damage to the camshaft thrust bearing can occur. Comments?
Good question -- I'm not familiar with this SPECIFIC engine's setup.

The other alternative is to remove the chain and, with plugs OUT (so there's no resistance against compression) SLOWLY work all the components to the correct TDC positions. It should be possible to do this without unbolting the camshafts; you can figure out where each piston is and whether it's rising or falling where the crank is right now with a rod down the plug hole (carefully!) and can see the cam position (and thus which valves are being opened at what time) with the valve cover off. Once you get everything to TDC you can then lock all components.

My concern with an engine that has run into any sort of "lock-up" situation like this is whether there has been valve train damage already done. If there has then the risk of a dropped valve down the road is very real and that event quite-reliably destroys engines when it happens.
 

·
Rally Racer
Joined
·
2,648 Posts
I have the timing tools. Just trying to get the easiest way to unlock crank pulley from the half turn. Try and figure out why it's jamming up in the first place.
So I understand the crank will not turn either direction and you have the timing chain disconnected?
If it does not move at all I believe something to be bamaged. If it is moving but not much then what @tickerguy said is likely happening. Pistons and valves are not making space for each other (improper social distancing).
 

·
Registered
Joined
·
9 Posts
Discussion Starter #19
Tickerguy: when it locked up I was re establishing the timing so everything was done by hand with no force, but with that said ur saying I would be better off changing the valves? If I change the valves what else should I be changing out? Mise well I'm already pretty deep with everything disconnected and taken apart.... Want to say thank thank you to everyone who's been taken the time to help me.
 

·
Registered
Joined
·
3,080 Posts
You don't know about actual valve damage without disassembly which means the head has to come off. If you were using only hand force and stopped when it locked you're probably ok.

Most OHV engines are easy enough to get the cam out so you can have a look at the top of the lifters. If any impact that occurred was bad enough to do damage it USUALLY leaves visible evidence that looks sort of like a "spider web" on the lifter. If there's no evidence of trouble then you've got reasonable confirmation (not proof, but best you're going to do without a big bill and a bunch more work) that you're ok. Just be really careful about getting any sort of grit or debris in there, and pay particular attention to the journals, torque specs and sequence on replacement. It also gives you a "free" opportunity to see if any of the lifters appear to be frozen (this usually looks sort of like a "bow-tie" pattern on the top) or any other indications of abnormal wear. Since you're already doing major work this is low-effort for high-return, especially if you find evidence of something bad that would have nailed you soon down the road. If you don't have assembly lube use a small amount of engine oil on the journals and tops of the lifters during reassembly so the surfaces are not dry on initial start until oil gets up there.
 
1 - 20 of 22 Posts
Top