cAUSE OF BIGEND BEARING FALIURE. THOUGHTS PLEASE.

[jonnaz]

im curreently rebuilding a 3b engine as it seized solid about a month ago because a bigend bearing spun and welded the conrod to the crank. i was in the process of getting the car back on the road as it has been sat in previous owners garden for 3 years. now the engine is stripped and gettinbg a forged bottom end

the oil pressure guage was unredable as it was peeling so didnt work therfore i dont know if the oil pressure dopped. the bearing spun on number 3 conrod the others look fine.

anyone got any ideas of what culd have cause it?

[BW2309]

I can say through experience of many S2 engines that it's almost certainly oil. As these engines get older slightly higher piston ring wear allows more fuel to get into the oil than normal. Couple this with usually low annual mileage which aloows the oil to carbon up - this is called tea-leafing. These flakes can block the oil pump and oil ways. Was it big end on cyl 5 by any chance??? As the oil pump is right at the front of the block (it's a radial rather than usual gear type) #5 suffers first.
Once the sump is removed you can see a bad build up of carbon on the sump walls. A good flush, using only Genuine Synta 10/40 or Synta gold will keep it healthy.

Luckily, in most cases the engines are that strong that all's needed is new big end and main shells.

First sign of this issue is a knocking under load at about 2500-4000rpm (that's when torque at its best). This sounds a bit like pinking so don't just think the timing's out!!!

The guage rarely reads low as it's the oil flow that is reduced and the actual pressure stays high and certainly high enough to never distrub the oil warning light!!

[AUDIS2avant]

An baring that seases is always an oil related issue, either lost pressure, or bad oil

[jonnaz]

bearing failure

I can say through experience of many S2 engines that it's almost certainly oil. As these engines get older slightly higher piston ring wear allows more fuel to get into the oil than normal. Couple this with usually low annual mileage which aloows the oil to carbon up - this is called tea-leafing. These flakes can block the oil pump and oil ways. Was it big end on cyl 5 by any chance??? As the oil pump is right at the front of the block (it's a radial rather than usual gear type) #5 suffers first.
Once the sump is removed you can see a bad build up of carbon on the sump walls. A good flush, using only Genuine Synta 10/40 or Synta gold will keep it healthy.

Luckily, in most cases the engines are that strong that all's needed is new big end and main shells.

First sign of this issue is a knocking under load at about 2500-4000rpm (that's when torque at its best). This sounds a bit like pinking so don't just think the timing's out!!!

The guage rarely reads low as it's the oil flow that is reduced and the actual pressure stays high and certainly high enough to never distrub the oil warning light!!

it was the bigend on cyl #3 it happend without warning no knocking engine sounded sweet. drove down the road pressed the clutch the it just stopped and wouldnt turn over. there is a little bit of carbon on the walls of the sump but not a huge ammount. i didnt change the oil which is stupid as it should have been the first thing done
there is some wear on the bottom of the top piston ring.

[BW2309]

it was the bigend on cyl #3 it happend without warning no knocking engine sounded sweet. drove down the road pressed the clutch the it just stopped and wouldnt turn over. there is a little bit of carbon on the walls of the sump but not a huge ammount. i didnt change the oil which is stupid as it should have been the first thing done
there is some wear on the bottom of the top piston ring.

I wish I'd not deleted the pics I had on my lap top

Will def be due to carbon deposits in the oil mate. When u rebuild it make sure u give all accessible oil ways a good clear out. Best to clean off the sump thoroughly too as that carbon can break off in chunks when the engine gets hot again too. Make sure you blow an air line through the oil ways in the crank too - it's those that get most badly clogged as the port is very small in diameter, and they obviosuly feed the big ends!
If you're having the pistons out I am assuming you're having new rings anyway?? - Also, make sure the oil feed pipes for the piston crown cooling are free.These jets unscrew from underneath. U can then make sure the pathways and the jets themselves are clear.
They only have an internal diameter of about 1mm and they spray oil under the piston.
I bet the bores are OK though, they're a good block!!!! You can usually still see the honing marks, even at 150k plus!

[jonnaz]

be bearng

I wish I'd not deleted the pics I had on my lap top

Will def be due to carbon deposits in the oil mate. When u rebuild it make sure u give all accessible oil ways a good clear out. Best to clean off the sump thoroughly too as that carbon can break off in chunks when the engine gets hot again too. Make sure you blow an air line through the oil ways in the crank too - it's those that get most badly clogged as the port is very small in diameter, and they obviosuly feed the big ends!
If you're having the pistons out I am assuming you're having new rings anyway?? - Also, make sure the oil feed pipes for the piston crown cooling are free.These jets unscrew from underneath. U can then make sure the pathways and the jets themselves are clear.
They only have an internal diameter of about 1mm and they spray oil under the piston.
I bet the bores are OK though, they're a good block!!!! You can usually still see the honing marks, even at 150k plus!

thanks for the info. its getting forged pistons and conrods with glyco bearings as its apart might as well build it proplerly. should be running 400bhp+ when done.
i hve got the crown sprayers out they lookok but i will give everything a blast with air and clean the sump of carbon deposits. i'll replace the oil pump as it is probs shot. where can i get a new one from?

[BW2309]

To be honest, I would buy engine parts like an oil pump from the dealer. The warrenty is more than worth the little bit extra you pay!

Should be a nice lump when done!!
Even at 400bhp the engine's not over stressed. It should be reliable. Just make sure even if it only covers a few K-miles each year change the oil every 8-12months. Then it'll be fine.

[220bhp]

I had a bearing failure on no 5 ,it did not seize but just disintegrated.the cause was the oil pump, some how through ware and tare the impeller chipped a little piece of the casing which intern caused the return valve on the oil pump to stick open hence no oil pressure and bearing failure.

[JP]

Big end bearing failure can happen for a number of reasons but the one you describe is from oil starvation. Either through blocked galleries or failed pump. There will be no warning in the form of knocking or anything it will literally pick up on the bearing from heat and seize the engine solid.

Both the big end and crank journal will look burned black when this happens and the engine will be impossible to turn over.

Other bearing failure is much more gradual like that caused from running too rich or worn rings where the fuel gets into the oil and makes the bearings go brittle.

As for the rebuild use genuine big end bearings as these are sputter bearings on the upper shell whereas the glyco ones are not.

[repo]

Broken damper causes bearings to die as well. In this case You can see worn spots/polished lines on all the bearings parallel to the crank.

Pump may have got jammed because of long period of not running, and the little gear ring on the nose of the crank may have gotten loose because of that. Check that. I have seen the pump to produce some oil pressure on low revs, but still the gear started to slip on higher revs, causing the oil pressure to drop.

Also, if Your head loses oil somewhere (loose/worn out cam cap, broken tappets), the first bearings that suffer from oil starvation are the conrod bearings 2 and 3.

If engine has been overrevving heavily, a conrod bolt may have stretched a bit, and the bearing play got crooked.

Since You did not change the oil, there are lot of possibilities. Most likely water in the sump, stuck oil filter or oil simply turned to mud. Still, check all the issues mentioned on this post to prevent this from happening again.