Odd engine knock
 

Hi guys, I just joined this forum and want to ask a question. I just picked up a low mileage (150,000) 1991 Accord for my daughters first car knowing that there was an engine problem. I already have a donor car in the driveway to swap engines but I am not sure that will be nessasary. Okay, here's the scoop... the engine knocks with what sounds just like a bad rod bearing...but when you drop the auto trans into gear it goes silent. I have lost rod bearings in the past and they never did that. So I am wonering, is it common for honda automatics to have flex plate issues? I am kinda thinking it might be loose torque converter bolts to the flex plate or even a cracked flex plate. I have not torn into this project at all but I will have some time to work on it this weekend and have just been thinking it thru so far. Is there anything else that would manifest itself with the same type of heavy mechanical knocking that a rod bearing would exhibit? What do you think?
Thanks for reading.
Mike

You could put a load on the engine then pull a spark plug wire with the plastic pliers they make to do that and if it starts knocking you will know it is in the engine and general location. You can have someone with their foot on brake in reverse while you do the work. Reverse to be a little safer. I am not familiar with any problems with flex plates. The thrust bearing on the crank may have something to do with the noise going away under load as if it is worn the crank will move around.

Thanks Chris, pulling the plug wires one by one was on my list of diognostics for this weekend...finally off work and will have some time to mess with it.

Well I guess it looks like the engine comes out...#4 rod bearing is the culprit:( Time for some surgery on the donor car.

why take out engine if only rod bearing is bad??

remove the oil pan and inspect the crankshaft ,, if only the bearings are bad install new rod and main bearings ,, you can do all this without removing the engine
if it needs a crank it is a different story

I used to work for a garage that did a lot of changing main and rod bearings in the car and most didn’t last a year. I guess it depends on the general condition of the motor other than the one bearing. It is worth a look compared to changing motors. I think a piston pin could also be the noise.

I guess it wouldn't hurt to drop the pan and have a look, to make that much noise I would think it can't be good...but it does go silent with either the spark plug wire removed or dropping into gear and putting a load on the engine. Since I just got the car I don't know if the previous owner let it run low on oil or how long they drove it that way. Could be more bearings on the death march but haven't got bad enough to make noise yet.

Okay, got the bottom end apart and #4 rod bearing spun. Crank journal looks pretty good but I will mic it to be sure it is still round. The bearing shells had not climed over each other yet but it couldn't have been far off so every thing was still riding on bearing material. Looks like the previous owner ran it low on oil based on the massive leak by the oil filter and wet undercarriage behind that point. I don't know for sure but it looks like #4 is last in line for oil in the galley so it makes sense that it gave up if there was a shortage of oil.

When obtaining replacement rod bearings is the number stamped across the parting line on the connecting rod the identifying number for the correct bearing? I have not been into a Honda this far before and I read somewhere that there are different bearings used on assembly of these and there are no identifying marks left on the bearing shell I just pulled out. Also are all of the rod bearings matched in case I decide to replace the others, if one is a 2 then will they all be 2's in the same engine? Oh one other thing, is the oil pan gasket on these a reusable style...it looks like the reusable valve cover gaskets. Just wondering:rolleyes:

Regards, Mike

Rubber gaskets for oilpan and valvecover. Heat & age make them hardened, so they're only kinda re-usable if they're fairly new. I bet if you re-use the pan gasket, it'll leak.

my car has a knocking noise but it only happens when im on the gas pretty hard and let go right away. it only knocks once. is this the same thing or is yours a continuos knocking?

h2oskibum:
I sent you a PM with a website that has a chart of the bearings which are by color

if crank is ok,,,,,,install all green bearing get them from an part store that sells parts for import cars.....green is the middle of the colors .. i have done it like this many, many ,many times with no problems ,,you can always get some plastic gauge if you want , if you do so , make sure to properly clean all the plastic gauge before final assembly and torque the bearings properly ( 34 ft lb , do it in 2 separate stages),,also make sure to put some grease on the bearings on final assembly before torquing them

if you want to use factory bearings for the rods,,,,,,,,you read the letter or bar ( 1 bar =a 2 bars =b etc etc ) from the crank at each journal and the number or bar from the connecting rod......then you match letter and #( bar) and you get the colors

since Kris sent you a chart i won't post the colors here

I would also remove the oil pick up screen and clean it real good
yell if you need help

The one I'm working on the knock is...or was continuous, sounds like you might have something else going on. Maybe something is loose and when you load and then unload the drivetrain you are getting a clunk or possibly ignition related??? Someone else on here might be more help than I am, I haven't owned a Honda since I sold my 86 Prelude in 89.

Regards, Mike

Well many thanks for all the advice to those that offered, but the rod journal is .023 out of round:eek: that wont cut it. So it looks like I will be pulling the motor out of the donor car after all. I may put this one on the back burner for now and put a crank kit in it later for a back up motor, with only 150,000 miles on it...it should have a lot of life left in it. The donor car has 260,000 miles on it and although it runs good and doesn't smoke I don't know how much longer it might last. What does a crank kit go for on one of these...ballpark of course;)

Regards, Mike