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The car has been running very smoothly indeed for the past few weeks. Starting problem eliminated by properly adjusting the choke, and everything was fine.
This evening on the way home from work I was idling when all of a sudden a very knocking sound began suddenly. It was so loud, it was almost a constant banging.
After calming down and looking at the engine, I decided to drive the few blocks home. On the way, the knock get a bit better, but it is still definitely there, and definitly coming from the engine.
What am I looking at? Basically, what do I now have to learn about? Will I need to take the head off to see if there is something rattling around on top of the pistons? Or something else in that area?
Greg
'73 144, B20B, SU HIF6
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In addition to what has already been mentioned, i just went through something of the same sort... There are other threads on it if you just look a little more in the past month's threads. Turns out the screw from my weber went into the third cylinder and stuff. Hope your's turns out to be something not too bad. Good luck!
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Kyle - '68 Volvo 142 w/71 b20b and m40...
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I hate to ask, but... you got oil in there? What about the oil pressure light... does it work? That is to say, it should come on with the ignition, then immediately go out as soon as it starts.
Could be a timing gear, but could also be a rod knock, which is a bit more serious. IN any case, I wouldn't be driving it until you at least diagnose the problem. And if it is a timing gear or a rod knock, dont' run it till you fix it!
-Matt
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-Matt '70 145s, '65 1800s, '66 122s wagon, others inc. '53 XK120 FHC
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All of this is a great help. I will proceed cautiously and keep posting progress.
About the oil. Yes, my first panic was that I had somehow let all the engine leak out of the engine. But no, it is still above minimum on the dipstick, so I know at least it wasn't my carelessness in that manner anyhow. Glad you brought it up, though. It isn't outside the realm of possibilities.
Greg
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engine = oil --> I have a bad problem with word juxtapositions
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From my experience, the two can make very similar sounds. But:
1) Rod knock - more prevalent at higher rpms, especially on the overrun (rev it up, close the throttle - the rod will tend to knock worse as the compression slows the engine down). Often at idle they won't make much noise at all Recently, I was able to tell my PV's motor had a bad rod by pulling the plug wires (whoich would have no effect on a bad timing gear). 1,3,4 made no difference, pulling #2 would make the knock appear. When disassembled, yep - spund bearing on #2.
2) Timing gear woes of various sorts - more prevalent at idle and low rpms, and often fading completely away at higher rpms. At low speeds the oil pump is placing very little load on the cam, and once the lobes go past 'TDC' the lifter pushes the cam forward until the next lobe hits. This back and forth torque on the cam exacerbates any slack in the gear or thrust washer which creates the clatter. When revved up, however, the oil pump and lessened rebound tension on the springs places the cam under a constant pull, so the slack isn't slopping back and forth, and it gets quiet. On my PV's original B18 I had the hub come loose from the fiber gear. It made a *horrible* noise at idle, like an old diesel engine just started up. Rev it up past 2000 or so and it got completely quiet, sounded 100% normal. When I took the timing cover off the fiber portion fell right off.
Also - I was certain I had a rod knock on my 1800E once, it turned out to be the heavy cast iron double pulley on the front of the engine coming loose. Sounded and acted just like a rod knock. I was actually going to pull the timing cover off just to see what the timing gears looked like when I found the bolt on the pulley loose. Tightened it back up - no more nasty knocking.
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I'm JohnMc, and I approved this message.
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Yea... I'd go along with that, but I felt there wasn't enough information to really distinguish twixt the two...
Usually a timing gear knock would be half speed too. either way, best to figure it out before deciding it isn't serious...
-Matt
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-Matt '70 145s, '65 1800s, '66 122s wagon, others inc. '53 XK120 FHC
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I agree with Phil. Probably the fiber timing gear coming loose from the
knurled steel hub. They get very noisy but are unlikely to do any serious
damage other than keep the engine from operating. Engine may suddenly quit
and not start. If so pop the distributor cap and watch while cranking.
If the rotor doesn't turn, that's the timing gear. They all give out
eventually.
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George Downs, Bartlesville, Oklahoma, Central US
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My first suspect would be the cam timing gear coming loose, or the retainer plate behind it. See if you can narrow the noise down to the timing cover at the front of the engine -- listen through a length of hose or something.
Not difficult to fix if it doesn't come completely apart. Don't run it any more than you have to to locate the noise.
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I will listen with the hose as you suggest. I would be surprised, however, because I had the timing gears replaced last fall. But of course, it is possible they did a bad job of it.
Greg
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