advice needed on bush and thrust washer
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  1. #1
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    Default advice needed on bush and thrust washer

    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.


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    Nice set of pictures and good explanation.
    I'd probably just make a bushing with an integral flange to take up the wear space on the cap. Machine the cap a bit in the center area to true it up for a nice smooth running face. The larger groove, don't worry about that, the gear OD should not be making any contact when you have the spacer/flange in place.
    I'd use 660 bearing bronze, or an aluminum bronze for that repair.

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    Is the idler shaft machined out of the cap or is it a pressed in hardened piece?Pretty much agree with Hu except I would clean up the small groove and insert a bronze washer pinned with bronze pins and face to original height.
    The bushing may be a standard 25x22x(width) available from INA or Garlock.It looks like a steel backed clad bearing like the mains.
    The thrust faces have plenty of bearing area and appear to be pressure lubed so I wonder if lube was lost;blockage, or maybe the bush wore out first and starved the thrust face?
    Your right the larger gear would have more thrust than the smaller and control the direction unless they had different helix angles to counter act it.Who knows maybe it was just a 100k mile design.

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    You can replace main caps,its done often.....providing the Manuf .sells one.Ive replaced many main caps by selective fitting ,but theoretically,you should use an undersize cap and have the bore line bored.

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    Thanks for the advice HuFlung Dung and ratbldr427, I am going for the bush with flange, pinning a washer securely is probably belt and braces and probably less chance of bearing spin happening but with my level of skill and experience I am less confident I can do it right. I phoned around suppliers but none could help with small quantities but I did find the existing bush is called a 'clinch lock bi metal bush, have not tried INA or Garlock yet but will tommorow. The idler shaft is a pressed in hardened insert with an oil hole in the middle of the cylinder fed from the No 1 main bearing. The idler pin is measuring round throughout its length with no wear apparent other than appears scuffed in a very small area. The engine is a Kia and used in the Sedona/Carnival and Hyundai Teracan and maybe a few others. Kia do not have a fix for this problem, its endemic in these engines and probably the main reason for them siezing, they replaced the 2.9 diesel around 2010 so they are not likely to be interested now. I have caught this one at an early stage, the next stage is the idler gear jams against the crank mounted drive gear and both gears have teeth sheared off, drive is lost to the oil pump and balance shafts, the oil pump stops followed by seized engine. john.k I checked with Kia, they will not supply main caps for the reason you state but they offered to supply a complete new block and caps and as you can imagine thats three times what the car is worth. Thanks again for the advice.

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    Even the ultra reliable perkins motors have oil pumps driven by idlers mounted on the front main cap.And they sometimes fail when the idler bush gets worn badly.......Of course with balance shafts ,they can often be eliminated by some judicious plugging of oilways,if thats where the problem lies..

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    John, the balance shaft assembly on these engines is in a self contained housing with two shafts mounted on the engine block in the sump, it would be easy to leave it out with no detriment to the workings and re assemble the engine without it but I would imagine the resulting vibration might wear out the engine faster ? I believe some race enthusiasts remove balance shafts from their engines but is there any benefit ? I had a Perkins diesel in the 1980s, the clatter the Kia makes with this problem reminded me of that engine, it was very loud on tickover sounded more like a HGV truck engine than a car and I think Perkins did not use balance shafts at the time. The Kia Sedona was a cheap car compared to similar GM and Fords so I suppose its inevitable costs were kept down.


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