rod bearing wear pattern - please help - long but urgent

hi guys,

got a nasty knock out of my 91 @ 215.000 km. sound is less loud when in gear but doesn't completely go away. it got louder each day. it wasn't as precise as clockwork - it felt like it was fading out and in from time to time but you could hear it most of the time... it appeared to be the loudest around the bellhousing

my oil pressure is always above the center mark and when revving just slightly under the maximum. oil is standard weight...

the knock getting less loud pointed me towards the rods. so did a few other people hearing the car. i checked the valvetrain nonetheless and the pushrods are straight.

the rod bearings don't have the excessive play they should have. i plastic gauged them and they seem to be borderline all right (1-2 thau' clearance)
the wear pattern on the lower bearing shows only the slightest wear in the center (circlewise, that is the outside is not worn and the center is worn 180 dg.). the top bearings show different wear - the middle of the bearing, on its full width shows signs of wear. the sides (from 0-45 dg. and from 135-180 dg. ) show no sign of wear.

i never looked at rod bearings before and therefore can't tell how they should look.
i checked to of the mains as well to rule out the crank. very even pattern, within specs, no scoring etc...

how should the bearing shells look, do the upper ones usually differ from the lower ones and what else could cause the constant knocking?

i want to get this done, right now the car is sitting in the garage wit the guts open and i need it back as soon as possible.
any help is greatly appreciated,

michael

If it's an auto trans. check your flexplate. E-1 told me I had bad bearings, turned out to be the flexplate, quite common on these to loosen up and or crack. If you already have the oil pan out you might as well replace the rod bearings, w/that milage they are going to wear out eventually

Interesting! I have the same problem with my 92. it has over 207K MI. I replaced the con rod bearings without a change in the knock. Mine doesn't come until after the engine warms up. It is quite until then. I will do a search on flexplate to find out how to check it out.

what would i look for to check the flexplate? how to go about it?
i have the inspection cover open but can't see much through it.
will i have to pull the tranny for that?

i will change the rod bearings anyway, for sure.

anybody who did the bearings so far - do they have different wear patterns?

With the inspection plate off, rotate the engine with a wrench on the front crankshaft bolt. Check that all the torque converter bolts are torqued and don't have any damage to the heads. Check for any cracking on the plate, especially around the bolt holes. Use a ruler and measure at various points to see if the plate is warped or skewed.

thanks, mate

will do so right away!

Rod knock.
With engine warm and running pull 1 plug wire at a time, when you pull the wire on the bad one it will knock.
Main bearing knock.
Knock is quite when under heavy load and gets louder when off the gas.
In every case you will have low oil pressure when warm.

ok, the problem IS the flexplate. the bolts holding the t.c. were slightly loose. around one bolt there is a crack, about .5 inch long.

do i have to change the flexplate or would washers under the bolts be a good enough fix?

what kind of money should i expect the flexplate to cost me?

thanks for all your help so far guys,

michael

I sort of remember paying $65 for a Crown flexplate a couple of years back.

The rod bearings normally wear much more on the upper half. That's the half that does the work -- when the cylinder fires, it pushes down on the piston, which puts all the load on the upper bearing shell as it's pushing the crankshaft.

Think peddling a bicycle uphill -- the foot that's pushing down does the work. How much load is there in the opposite peddle?

Micha said:

ok, the problem IS the flexplate. the bolts holding the t.c. were slightly loose. around one bolt there is a crack, about .5 inch long.

do i have to change the flexplate or would washers under the bolts be a good enough fix?

what kind of money should i expect the flexplate to cost me?

thanks for all your help so far guys,

michael

Click to expand...

You will need to replace it and the bolts.

thanks, eagle

i checked some of the flexplate related threads and it seems to crack around the crank mounting. if i 'just' have a little (contained) crack around one of the bolt holes - probably due to driving around with the bolts banging in the holes - will i just be able to tighten the bolts and be all right?

with washers: i can't imagine the crack growing further with the bolts locked down again...

langer1 : you're just too fast for me

trust me it will grow.....replace it.