Oil Discussion - Timing Chain Guides & high Si

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I just had a thought but can't seem to dig up any information on it and thought I would post it here.

As many manufacturers are using plastic type timing chain guides and from what I can find this is impregnated with glass media for durability, I was wondering if some UOA's that are high in Si could be caused by excessive guide wear and not necessarily an unfiltered air leak or leaking gasket sealant that also contains Si, into the oil.

Could this be another possible consideration when looking at UOA's and seeing elevated Si levels?

Thoughts?
 
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Great question. I only have experience with one manufacturer (BMW). Wear is viewed as tiny bits of plastic which are too large for a UOA to pick up. The scuttlebutt is that the chains elongates and the spring in the tensioner is weak so guides take a beating from the now elongated chain.
 
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I suspect that the tiny bits of plastic show up as insolubles in the UOA maybe? But I thought the chain rubbing up against the guide repeatedly and breaking loose some of the microscopic glass that it these guides might generate higher Si levels in the UOA.

It's an interesting though I think.
 
Originally Posted by StevieC
I suspect that the tiny bits of plastic show up as insolubles in the UOA maybe? But I thought the chain rubbing up against the guide repeatedly and breaking loose some of the microscopic glass that it these guides might generate higher Si levels in the UOA.

It's an interesting though I think.


My understanding is that it doesn't wear, it just snaps into large pieces which fall down into the oil pan. These are large pieces are clearly visible. Think plastic spoon size. Telltale sign of pending failure is made by sound.

https://www.e90post.com/forums/attachment.php?attachmentid=912305&stc=1&d=1378982230
 
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The '07 4Runner I bought at 164K miles of ~22K mile OCIs and a stretched timing chain had remarkably low wear at the 2 lower guides and 2 upper dampers. The upper dampers appeared to be phenolic resin blocks, the lower guides were metal backing plates with brown-colored composite sliding surfaces. Could barely make out the travel path of the chain across their surfaces...amazing given the poor oil change history and high mileage.
 
We did a head gasket on a 2.4L Chrysler for a friend of my dads and we had a look at the guides while we were in there since we had the engine apart anyway and they looked worn slightly but for the most part really good. We were surprised because the vehicle has 180,000km on it. The 2.4's are good engines normally but to see something that looks plastic rubbing against a metal chain for that long and still in excellent shape is a testament to quality materials being used today and the extent of how far engineering has come from even 30 years ago.
 
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I could see the possibility in this. I have done a couple of Timing chain jobs that showed excessive guide wear. These were used cars with unknown OCI or types. All had extreme wear to the point of wearing through the guides. No breaking of them, just what looked like cutting wear. Both early Ford Modular V8's. My presumption was using conventional oil in a oem speced syn blend app.
 
I don't think any early ford modular V8s spec synthetic or even synthetic blend. I was working at a ford dealer in parts around 2003-2004 when the early ones were popular.
 
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