Floorpans done but now the engine knocks :(

[superbenk]

Just ranting because I'm frustrated. Had the 124 up on jack stands all winter while I patched up the rust in the floor pans. Can't afford carpet for it right now so I thought I'd just throw the seats & trim back in with some floor mats & go drive it. Got the gas lines back in place with new hoses & got her started up only to hear this loud knocking noise. It runs great but the noise is extremely concerning.

Did the hose stethoscope thing all over the top of the engine & around all the spinning bits on the front but couldn't find it. Finally got under the car & I think it's coming from the crankshaft area so I'm assuming I have a bad rod bearing. So there she sits again. I guess the next step is to think about pulling the motor & doing a rebuild. I've never done an engine rebuild before so that'll take some time.

I'm certainly open to tips, advice, ideas. Maybe I'll get a video up on Youtube so you all can hear it & maybe have some ideas that don't involve a rebuild. It ran really well last summer. I put about 1000 miles on it and didn't have any problems. I did notice it was burning some oil on startup which leads me to think the valve seals are shot, but that's it.

Thanks in advance for any tips, advice, ideas or even condolences

[zachmac]

What is the idle and revving oil pressure?

I have a friend here in town who is still driving a 76 Fiat I bought and sold him that had a terrible knock when another forum member sold it to me. Would have sworn a rod was going to come out the side any minute. Instead it just went away and the car has run great ever since. Best speculation is that a chunk of carbon broke of in a cylinder and acted as an ignition source in that cylinder causing pre-ignition and the knock. Once the carbon burned up the knock went away. Not sure but it is the only thing that makes sense.

Not saying you'll be as lucky but? So again, what king of oil pressure are you seeing?

[superbenk]

I don't have an oil pressure gauge but I don't remember the oil light coming on when it was running. I'll have to check that again & think about adding an oil pressure gauge.

Any way to diagnose something like that without tearing the engine apart?

[vandor]

You did not change the timing belt, by any chance? The fuel pump lobe hitting the #2 conrod makes the same sound. This happens if the auxiliary shaft pulley is not timed correctly during a timing belt change.

If you want to drive it during the summer it may be simpler to drop the oil pan and replace the rod bearings, maybe main bearings.
Well, check them first to be sure that is what the problem is

[superbenk]

I didn't change the timing belt but I was fiddling around with a leak-down test & turning the engine with a wrench so maybe I caused something to skip a tooth. I like that theory because I imagine it'd run fine if just the accessory shaft skipped but the cams & crank were all still aligned. I'll check that out this weekend & hope for the best.

[DieselSpider]

Did you turn it by the crank shaft, aux shaft or cam shaft when you did the leak down test? As a general note turning an engine, especially one with compression, by anything but the crankshaft can ruin your timing belt. If there is any possibility that you stressed the timing belt and it skipped you should replace it sooner rather than later.

[superbenk]

I don't remember for sure, but I probably did use the accessory pulley because I don't have a socket big enough for the crank pulley (what size is that exactly?). I'll be sure to replace the belt before driving the car again regardless. It's been on my list to do since I don't know when it was done prior to me buying the car last year.

Thanks for the advice!

[superbenk]

vandor, I think you're on to something! I lined everything up at the timing marks & found that the accessory shaft pulley is way out of time. Check out this photo that shows the timing mark on the accessory pulley is at 10 o'clock when it should be at 1 o'clock in line with the tensioner spring mount bolt:



I'm going to order a new timing belt & tensioner pulley before doing anything else to see if that solves my problem. Also buying a 38mm socket for the crank nut.

[RRoller123]

Shouldn't the crank timing mark be way over on the left side? Or is it different on the '78 1800 engine? On the 2L TDC is over on the exhaust side.

[superbenk]

No, this is correct for the 1800. The timing marks for the crankshaft are on the right side of the yellow plastic shield & TDC lines up approximately where my mark is at in that picture.

This is what the timing marks should look like:

[RRoller123]

Got it. Different for the 2L!

[superbenk]

Just a follow-up to close this out. vandor was indeed correct about the timing. I re-aligned the accessory shaft the way it is supposed to be & ran the car briefly - everything worked perfectly! I'm still going to replace the timing belt, but it's good to know I don't need to tear the engine apart right now.

Thanks everyone for the help & support!