Arthur Whitlock
Plastic
- Joined
- Sep 28, 2019
I hope someone on here can give me some advice, the photos show No 1 bearing cap on a 2.9L 183 bhp diesel engine, the caps are jig bored at the factory so replacing the cap is not an option and its not the main bearings or crankshaft thats the problem. The car maker thought it ok to mount the balance shaft/oil pump idler gear onto the main bearing cap which maybe is normal, I don't know much about engines. All was ok for 100000 miles then a loud clanking sound was heard, so loud it sounded like the main bearings had failed. The main engine appears to be ok except the turbo may possibly have been starved of oil so its whining loud, the duplex idler gear bush spigot is 21.96 mm diameter and although scuffed is not showing full on destruction, what remains of the gear bush measures 22.39 mm to 23.44 inside diameter and as you can see from the photos its almost hanging off its that worn out. The idler gear has milled its way into the bearing cap, the two circular grooves are not meant to be there so the lateral movement on its spigot is now about 1/8 inch, hard to believe but the main crank gear and oil pump and balance shaft gears are all ok. Thanks to the oil filtration system it seems the main bearing journals are also ok even though the cast steel swarf off the cap and the existing bush has fragmented into the sump. Having read up on duplex helical gears it seems there is a lateral force which theoretically cancels out as the teeth have opposing slant but in this case they are different sizes and much different stress on each so I can see why its eating into the cap as for some reason there is no thrust spacer or washer between the gear and the bearing cap which seems wrong to me but this is the way the engine was made. The idler gear will do 6000 rpm max but mainly run at 3000 to 4000 rpm when the crank is at 2000 rpm. I want to make a new bush to fit the idler gear and a 40mmx1/8 inch thrust washer and machine the bearing cap flat and fit a new spigot. What material might be ok for the new bush and thrust washer bearing in mind the bush wall thickness will be 1.5mm ( inside diameter of idler with old bush removed is 25mm ) and there was an oil groove in the middle and lubricated under pressure from the spigot, I searched for ready made bushes but cannot find anything so will probably have to make something.