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K7M engine (Renault Sandero)

During a timing-belt and tensioner change, I used a locking-pin(an 8mm bolt) to hold the engine while breaking loose the crank-pulley bolt.

Not being an experienced mech', I'm concerned I may have inserted the locking pin at the wrong phase in the 4-stroke cycle(*), and was wondering whether that might have damaged any of the internal moving engine parts e.g. piston, valve, cylinder.

I had to apply quite a bit of force to get it loose and at some point I noticed the bolt I used as a locking pin was slightly bent.

  • I noticed the pin would go in to varying degrees/at varying lengths depending on the current phase. I since found what I think is the best position in the cycle to insert the locking-pin i.e. just before TDC on cam-gear.
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Basically, no. With the pin in place, the pistons are going to be in the exact same place no matter what. It is the cam which makes the difference which stroke any given cylinder is at.

To hopefully better explain, when the piston is at top dead center (TDC), it can be at TDC on either the compression or exhaust stroke: the piston doesn't care. When it's at bottom dead center (BDC), it can be at the end of the intake or the power stroke. It doesn't matter. And the pin will still pin the crankshaft because there's only one place where the pin lines up.

Since the cam spins at 1/2 the speed of the crankshaft, it's position is what matters. If, once you've put cam belt back on, as long as the alignment marks are in the right spots, everything should be good to go. In your case, 12 o'clock position for the cam and 6 o'clock for the crankshaft.

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  • I had to try several iterations of putting the pin in to find out where the deepest point was. So that's why I thought perhaps I had put it in at the wrong point in the cycle. It did lock the engine but when I later found the deepest insertion point, it got me thinking I hope I didn't do damage because it didn't go in as deep before... and before was when I put the crank bolt under the most strain. I was under the impression I could insert it wherever I stopped to make my markings, which from previous questions I knew could be anywhere i.e. not necessarily at TDC.
    – Jim
    Commented Jan 10, 2023 at 14:37
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    @Jim - I was using TDC as an example, not specifically for your engine. I'm just saying, the pin is only used to keep the crank in place. As long as it goes through the crank pin hole into the block hole, you can't really do it wrong. Ultimately, you need to use the cam and crank gear alignment marks to get everything timed correctly.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jan 10, 2023 at 14:44
  • Not sure I was clear enough. I'll try to phrase question. Is there a single point in the 4-stroke cycle for the locking pin to be inserted? Or can it do it's job even if it doesn't go in as far as another point in the cycle?
    – Jim
    Commented Jan 10, 2023 at 14:52
  • Not sure I was clear enough. It's a bit tricky to explain. Does the locking-pin go into the crank shaft itself? Or does it just protrude deep enough to catch on to any part connected to the shaft, to stop the shaft rotating? See page 7 of the k7m timing-belt manual you posted.
    – Jim
    Commented Jan 10, 2023 at 15:00
  • I have just read the manual @Pᴀᴜʟsᴛᴇʀ2 posted. I believe that you were not meant to use the locking pin to undo the crankshaft bolt. The manual talks about locking the flywheel with a screwdriver when undoing the crankshaft pulley bolt.
    – HandyHowie
    Commented Jan 11, 2023 at 10:32

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