What causes Cam bearings to melt?
03-07-2015, 11:19 AM
#17
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Year: 1998
Engine: 4.0L 162,000
For others information, This problem can occur due to a few things, mostly engine builder related.
Did the builder use a high pressure or high volume oil pump?
Did the builder inspect and set the spring and pin correctly? Forgot the pin or spring.
This cam bearing problem is related to CAM WALK.
This can be caused by the oil pump putting too much pressure on the gears and causing the cam to move back and forth.
It can also be cause by too weak or poorly adjusted pin/spring at the front of the cam to control cam movement.
Solution is- use the stock oil pump. Do NOT use the HP or HV oil pump.
Do NOT use the pin/spring method to control the cam movement, but instead use a longer pin(no spring) or bolt and carefully measure and adjust the length so that the cam has about 0.004" movement/play.
Better yet, use a '99 block with the cam retainer plate instead of the pin/spring method.
Did the builder use a high pressure or high volume oil pump?
Did the builder inspect and set the spring and pin correctly? Forgot the pin or spring.
This cam bearing problem is related to CAM WALK.
This can be caused by the oil pump putting too much pressure on the gears and causing the cam to move back and forth.
It can also be cause by too weak or poorly adjusted pin/spring at the front of the cam to control cam movement.
Solution is- use the stock oil pump. Do NOT use the HP or HV oil pump.
Do NOT use the pin/spring method to control the cam movement, but instead use a longer pin(no spring) or bolt and carefully measure and adjust the length so that the cam has about 0.004" movement/play.
Better yet, use a '99 block with the cam retainer plate instead of the pin/spring method.
03-07-2015, 05:41 PM
#19
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Year: 1995
Model: Grand Cherokee
Engine: 4.0 with all of the noise and clatter
The zinc isn't for the cam bearings, it's for the cam lobes and lifters. Lack of zinc won't cause the bearings to mushroom out like that.
03-07-2015, 06:30 PM
#20
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Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
I'm a little toasted, but curious. What would happen if the oil pressure relief valve was clogged? One might wonder what would "give" without that.
MMMM. But if the drive gears striped it shouldn't run long enough to mess up the cam bearings...
MMMM. But if the drive gears striped it shouldn't run long enough to mess up the cam bearings...
03-08-2015, 08:50 AM
#21
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Year: 1999
Model: Cherokee
Engine: 4.0
My uneducated guess would be it ended up being the installers error or he would have been back. Many yrs. ago I worked in a engine rebuilders shop and the cost of the rebuilt engine was based on how many new parts were used.
Cheapest ones used all the old parts possible highest price (same engine) used mostly new parts and the better the parts the higher the cost. This was a 3 man shop I worked in so we did things differently. I have been around the large rebuilders and saw how they did things with one person doing one or two things at a time many of them knowing very little about engines as a whole. Scary at the very least I personally would not buy one but....
From what was shown in the photos no way to really tell who may have been at fault except that there was a lot of it.
Cheapest ones used all the old parts possible highest price (same engine) used mostly new parts and the better the parts the higher the cost. This was a 3 man shop I worked in so we did things differently. I have been around the large rebuilders and saw how they did things with one person doing one or two things at a time many of them knowing very little about engines as a whole. Scary at the very least I personally would not buy one but....
From what was shown in the photos no way to really tell who may have been at fault except that there was a lot of it.
03-09-2015, 07:04 AM
#23
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Model: Cherokee
ASE Master Tech here
I'm mostly an engine tech. I've worked in BIG rebuilding plants years ago.
My best guess is it's the builder's fault, not you or the oil. These folks buy the very cheapest replacement parts they can find on the international market. If you buy bearings like Federal Mogal etc. they are multi-layer with different metals for size stability, heat trasnfer, wear properties etc.. If you took out one of those bearings I'd bet you'd find it to be a single soft alloy all the way through.
This accounts for the applecore dist. gear as well. Anytime you change to a roller cam you must use a bronze gear or this will happen. I'm sure the gear on this dist is sub-standard material. How can anyone produce a NEW dist. and sell it for under $200. ?
Though your cam isn't roller it may have been heat treated in the wear areas which made it harden in those areas. It's cheaper than heat treating the whole thing. Most likely it's a re-grind (I've done that operation) and it might have had spot heat treatment which causes hard spots. Of course the dist gear is soft so it acts like running a stock gear against a roller cam in a V-8.
Bearings that wear fast from oil issues don't usually "squish out" like that, they gall and spin.
I'm guessing the dist gear was the main failure and the bearings would have gone alot longer before failure but you were smart enough to look and see what was wrong. They might have made it past the warranty period.
Like the other posts mentioned, incorrect valve spring pressure would do this as well, especially combined with cheap bearings.
I was going to buy a rebuild for my own xj to save time but I'm pretty certain I'll do it myself. I need to know what quality parts I have.
In case I go rebuilt I'd appreciate a PM to steer me away from the rebuilder you used.
Best of luck you you with this,
Dan
2001 XJ unmolested (So Far) 240k. miles
My best guess is it's the builder's fault, not you or the oil. These folks buy the very cheapest replacement parts they can find on the international market. If you buy bearings like Federal Mogal etc. they are multi-layer with different metals for size stability, heat trasnfer, wear properties etc.. If you took out one of those bearings I'd bet you'd find it to be a single soft alloy all the way through.
This accounts for the applecore dist. gear as well. Anytime you change to a roller cam you must use a bronze gear or this will happen. I'm sure the gear on this dist is sub-standard material. How can anyone produce a NEW dist. and sell it for under $200. ?
Though your cam isn't roller it may have been heat treated in the wear areas which made it harden in those areas. It's cheaper than heat treating the whole thing. Most likely it's a re-grind (I've done that operation) and it might have had spot heat treatment which causes hard spots. Of course the dist gear is soft so it acts like running a stock gear against a roller cam in a V-8.
Bearings that wear fast from oil issues don't usually "squish out" like that, they gall and spin.
I'm guessing the dist gear was the main failure and the bearings would have gone alot longer before failure but you were smart enough to look and see what was wrong. They might have made it past the warranty period.
Like the other posts mentioned, incorrect valve spring pressure would do this as well, especially combined with cheap bearings.
I was going to buy a rebuild for my own xj to save time but I'm pretty certain I'll do it myself. I need to know what quality parts I have.
In case I go rebuilt I'd appreciate a PM to steer me away from the rebuilder you used.
Best of luck you you with this,
Dan
2001 XJ unmolested (So Far) 240k. miles
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