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Thread: How to prime the oil pump without starting the car

  1. #26
    Join Date
    Sep 2006
    Location
    Los Gatos CA
    Posts
    4,246
    My Cars
    1987 325is, e34, Z3, e39
    Quote Originally Posted by E39 Newbie View Post
    Even more so when the engine has hydraulic cam chain tensioners. Case in point - I did an engine swap, replacing a blown engine in an Audi A4(?) with a known good used unit. We did lots of work on the new engine, replacing all those leaky oil gaskets under the intake, etc. Plus the engine had been sitting for who knows how long. On the date appointed, I wanted to prime the engine, but my friend hopped in the car and fired it up. Major noise ensued until the adjusters pumped up. Annnddddd... one of the exhaust cams jumped a tooth. He was so da*n lucky that he didn't bend valves. All could have been avoided with a simple prime. I just miss the old days when you could put a tool down the distributor hole and prime the engine with a drill.
    How did it jump a tooth?
    Empty hydraulic lifters put a lower load on the camshaft.
    Hydraulic-assist tensioners (at least on BMWs) have a spring pre-load and are on the slack side.
    There is more of a risk with pre-filled lifters, which haven't had a chance to bleed down to the right level.

    I didn't worry at all about wear on the first start. I was much more concerned about wear during a zillion incremental checks during assembly, especially when verifying the cam timing. Every bearing surface was assembled with a drop of oil, and I repeatedly drizzled oil over the camshafts during checks.

    On a related note, assembly lube is often over-used. Regular oil is preferable if you are building the engine to use in the near future. Assembly lube should be used when the engine might not be used immediately, especially if your projects tend to confuse weeks and decades. Or very sparingly when you need to briefly hold a part in place.
    Last edited by djb2; 10-17-2020 at 02:38 PM.

  2. #27
    Join Date
    Nov 2018
    Location
    La Habra, CA
    Posts
    1,117
    My Cars
    2002 525i
    Quote Originally Posted by djb2 View Post
    How did it jump a tooth?
    Empty hydraulic lifters put a lower load on the camshaft.
    Hydraulic-assist tensioners (at least on BMWs) have a spring pre-load and are on the slack side.
    There is more of a risk with pre-filled lifters, which haven't had a chance to bleed down to the right level.

    I didn't worry at all about wear on the first start. I was much more concerned about wear during a zillion incremental checks during assembly, especially when verifying the cam timing. Every bearing surface was assembled with a drop of oil, and I repeatedly drizzled oil over the camshafts during checks.

    On a related note, assembly lube is often over-used. Regular oil is preferable if you are building the engine to use in the near future. Assembly lube should be used when the engine might not be used immediately, especially if your projects tend to confuse weeks and decades. Or very sparingly when you need to briefly hold a part in place.
    Apparently the cam chains on this Audi V6 (from an A5 Quattro) are relatively loose until the adjuster pumps up. The engine had sat for who knows how long in a warehouse, and I'd replaced all the leaky oil gaskets that reside under the intake. So, I'm sure the oil galleys were pretty empty. On startup there was a lot of cam chain noise for a few seconds until the adjusters pumped up, then it started throwing codes for timing, and running rough. Upon further examination the exhaust cam on the driver side had skipped a tooth.
    Current stable:
    2002 525i (Daily Driver)
    1994 SN95 Mustang 'Vert (The Bumblebee)
    2001 325i Convertible (Beach cruiser project)

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